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MS C 6.0 Run-Time Library Reference
The following document is from the Microsoft Programmer’s Library 1.3 CD-ROM.
Microsoft C - RUN-TIME LIBRARY REFERENCE
────────────────────────────────────────────────────────────────────────────
Microsoft (R) C - RUN-TIME LIBRARY REFERENCE
FOR THE MS-DOS (R)
OPERATING SYSTEM
────────────────────────────────────────────────────────────────────────────
MICROSOFT CORPORATION
PUBLISHED BY
Microsoft Press
A Division of Microsoft Corporation
One Microsoft Way, Redmond, Washington 98052-6399
Copyright (C) 1990 by Microsoft Press
All rights reserved. No part of the contents of this book may be reproduced
or transmitted in any form or by any means without the written permission of
the publisher.
Library of Congress Cataloging-in-Publication Data
Microsoft C run-time library reference.
Includes index.
1. C (Computer program language) 2. Microsoft C
(Computer program) 3. Macro instructions (Electronic
computers) I. Microsoft.
QA76.73.C15M52 1990 005.13'3 89-12240
ISBN 1-55615-225-6
Printed and bound in the United States of America.
1 2 3 4 5 6 7 8 9 HCHC 3 2 1 0 9
Distributed to the book trade in Canada by General Publishing Company, Ltd.
Distributed to the book trade outside the United States and Canada by
Penguin
Books Ltd.
Penguin Books Ltd., Harmondsworth, Middlesex, England
Penguin Books Australia Ltd., Ringwood, Victoria, Australia
Penguin Books N.Z. Ltd., 182-190 Wairau Road, Auckland 10, New Zealand
British Cataloging in Publication Data available.
Sample
Writers: Editors: Programs:
Phil Nelson Amanda Clark Bruce McKinney
Terry Ward Moira Macdonald
Marjorie Manwaring
Bill Nolan
Microsoft, the Microsoft logo, MS-DOS, QuickC, and XENIX are
registered trademarks and Windows is a trademark of Microsoft Corporation.
AT&T and UNIX are registered trademarks of American Telephone
and Telegraph Company.
Hercules is a registered trademark of Hercules Computer
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Olivetti is a registered trademark of Ing. C. Olivetti.
Document No. 410840021-520-R00-1088
Part No. 04412
Table of Contents
────────────────────────────────────────────────────────────────────────────
Introduction
About the C Run-Time Library
ANSI C Compatibility
OS/2 and XENIX(R) Programming
Expanded Graphics Library
About This Book
Other Books of Interest
Document Conventions
PART I Overview
────────────────────────────────────────────────────────────────────────────
Chapter 1 Using C Library Routines
1.1 Calling Library Routines
1.2 Using Header Files
1.2.1 Including Necessary Definitions
1.2.2 Including Function Declarations
1.3 File Names and Path Names
1.4 Choosing Between Functions and Macros
1.5 Stack Checking on Entry
1.6 Handling Errors
1.7 Operating-System Considerations
1.8 Floating-Point Support
1.9 Using Huge Arrays with Library Functions
Chapter 2 Run-Time Routines by Category
2.1 Buffer Manipulation
2.2 Character Classification and Conversion
2.3 Data Conversion
2.4 Directory Control
2.5 File Handling
2.6 Graphics
2.6.1 Low-Level Graphics and Character-Font Functions
2.6.2 Presentation-Graphics Functions
2.7 Input and Output
2.7.1 Text and Binary Modes
2.7.2 Stream Routines
2.7.3 Low-Level Routines
2.7.4 Console and Port I/O
2.8 Internationalization
2.9 Math
2.10 Memory Allocation
2.10.1 Near and Far Heaps
2.10.2 Based Heaps
2.11 Process and Environment Control
2.12 Searching and Sorting
2.13 String Manipulation
2.14 System Calls
2.14.1 BIOS Interface
2.14.2 DOS Interface
2.15 Time
2.16 Variable-Length Argument Lists
Chapter 3 Global Variables and Standard Types
3.1 _amblksiz
3.2 daylight, timezone, tzname
3.3 _doserrno, errno, sys_errlist, sys_nerr
3.4 _fmode
3.5 _osmajor, _osminor, _osmode, _osversion
3.6 environ
3.7 _psp
3.8 Standard Types
PART II Run-Time Functions
────────────────────────────────────────────────────────────────────────────
About the Run-Time Reference
abort
abs
access
acos Functions
alloca
_arc Functions
asctime
asin Functions
assert
atan Functions
atexit
atof, atoi, atol, _atold
bdos
_beginthread
Bessel Functions
_bfreeseg
_bheapseg
_bios_disk
_bios_equiplist
_bios_keybrd
_bios_memsize
_bios_printer
_bios_serialcom
_bios_timeofday
bsearch
cabs, cabsl
calloc Functions
ceil, ceill
_cexit, _c_exit
cgets
_chain_intr
chdir
_chdrive
chmod
chsize
_clear87
clearerr
_clearscreen
clock
close
_control87
cos Functions
cprintf
cputs
creat
cscanf
ctime
cwait
dieeetomsbin, dmsbintoieee
difftime
_displaycursor
div
_dos_allocmem
_dos_close
_dos_creat Functions
_dos_find Functions
_dos_freemem
_dos_getdate
_dos_getdiskfree
_dos_getdrive
_dos_getfileattr
_dos_getftime
_dos_gettime
_dos_getvect
_dos_keep
_dos_open
_dos_read
_dos_setblock
_dos_setdate
_dos_setdrive
_dos_setfileattr
_dos_setftime
_dos_settime
_dos_setvect
_dos_write
dosexterr
dup, dup2
ecvt
_ellipse Functions
_enable
_endthread
eof
exec Functions
exit, _exit
exp, expl
_expand Functions
fabs, fabsl
fclose, fcloseall
fcvt
fdopen
feof
ferror
fflush
fgetc, fgetchar
fgetpos
fgets
fieeetomsbin, fmsbintoieee
filelength
fileno
_floodfill, _floodfill_w
floor, floorl
flushall
fmod, fmodl
fopen
FP_OFF, FP_SEG
_fpreset
fprintf
fputc, fputchar
fputs
fread
free Functions
_freect
freopen
frexp, frexpl
fscanf
fseek
fsetpos
_fsopen
fstat
ftell
ftime
_fullpath
fwrite
gcvt
_getactivepage
_getarcinfo
_getbkcolor
getc, getchar
getch, getche
_getcolor
_getcurrentposition Functions
getcwd
_getdcwd
_getdrive
getenv
_getfillmask
_getfontinfo
_getgtextextent
_getimage Functions
_getlinestyle
_getphyscoord
getpid
_getpixel Functions
gets
_gettextcolor
_gettextcursor
_gettextposition
_gettextwindow
_getvideoconfig
_getviewcoord Functions
_getvisualpage
getw
_getwindowcoord
_getwritemode
gmtime
_grstatus
halloc
_hard Functions
_heapadd Functions
_heapchk Functions
_heapmin Functions
_heapset Functions
_heapwalk Functions
hfree
hypot, hypotl
_imagesize Functions
inp, inpw
int86
int86x
intdos
intdosx
is Functions
isatty
itoa
kbhit
labs
ldexp, ldexpl
ldiv
lfind
_lineto Functions
localeconv
localtime
locking
log Functions
long double Functions
longjmp
_lrotl, _lrotr
lsearch
lseek
ltoa
_makepath
malloc Functions
matherr, _matherrl
max
_memavl
memccpy, _fmemccpy
memchr, _fmemchr
memcmp, _fmemcmp
memcpy, _fmemcpy
memicmp, _fmemicmp
_memmax
memmove, _fmemmove
memset, _fmemset
min
mkdir
mktemp
mktime
modf, modfl
movedata
_moveto Functions
_msize Functions
onexit
open
_outgtext
_outmem
outp, outpw
_outtext
_pclose
perror
_pg_analyzechart Functions
_pg_analyzepie
_pg_analyzescatter Functions
_pg_chart Functions
_pg_chartscatter Functions
_pg_chartpie
_pg_defaultchart
_pg_getchardef
_pg_getpalette
_pg_getstyleset
_pg_hlabelchart
_pg_initchart
_pg_resetpalette
_pg_resetstyleset
_pg_setchardef
_pg_setpalette
_pg_setstyleset
_pg_vlabelchart
_pie Functions
_pipe
_polygon Functions
_popen
pow Functions
printf
putc, putchar
putch
putenv
_putimage Functions
puts
putw
qsort
raise
rand
read
realloc Functions
_rectangle Functions
_registerfonts
_remapallpalette, _remappalette
remove
rename
rewind
rmdir
rmtmp
_rotl, _rotr
scanf
_scrolltextwindow
_searchenv
segread
_selectpalette
_setactivepage
_setbkcolor
setbuf
_setcliprgn
_setcolor
_setfillmask
_setfont
_setgtextvector
setjmp
_setlinestyle
setlocale
setmode
_setpixel Functions
_settextcolor
_settextcursor
_settextposition
_settextrows
_settextwindow
setvbuf
_setvideomode
_setvideomoderows
_setvieworg
_setviewport
_setvisualpage
_setwindow
_setwritemode
signal
sin Functions
sopen
spawn Functions
_splitpath
sprintf
sqrt, sqrtl
srand
sscanf
stackavail
stat
_status87
strcat, _fstrcat
strchr, _fstrchr
strcmp, _fstrcmp
strcmpi
strcoll
strcpy, _fstrcpy
strcspn, _fstrcspn
_strdate
strdup Functions
strerror, _strerror
strftime
stricmp, _fstricmp
strlen, _fstrlen
strlwr, _fstrlwr
strncat, _fstrncat
strncmp, _fstrncmp
strncpy, _fstrncpy
strnicmp, _fstrnicmp
strnset, _fstrnset
strpbrk, _fstrpbrk
strrchr, _fstrrchr
strrev, _fstrrev
strset, _fstrset
strspn, _fstrspn
strstr, _fstrstr
_strtime
strtod, strtol, _strtold, strtoul
strtok, _fstrtok
strupr, _fstrupr
strxfrm
swab
system
tan Functions
tell
tempnam, tmpnam
time
tmpfile
toascii, tolower, toupper Functions
tzset
ultoa
umask
ungetc
ungetch
unlink
_unregisterfonts
utime
va_arg, va_end, va_start
vfprintf, vprintf, vsprintf
wait
_wrapon
write
Index
Introduction
────────────────────────────────────────────────────────────────────────────
The Microsoft(R) C Run-Time Library is a set of over 500 ready-to-use
functions and macros designed for use in C programs. The run-time library
makes programming easier by providing
■ Fast and efficient routines to perform common programming tasks (such
as string manipulation), sparing you the time and effort needed to
write such routines
■ Reliable methods of performing operating-system functions (such as
opening and closing files)
The C run-time library is important because it provides basic functions not
provided by the C language itself. These functions include input and output,
memory allocation, process control, graphics, and many others.
This book describes the Microsoft C run-time library routines included with
the Microsoft Professional Development System version 6.0. These comprise
all of the routines included with earlier versions of Microsoft C, as well
as many new routines.
────────────────────────────────────────────────────────────────────────────
NOTE
Microsoft documentation uses the term "OS/2" to refer to the OS/2
systems─Microsoft Operating System/2 (MS(R) OS/2) and IBM(R) OS/2.
Similarly, the term "DOS" refers to both the MS-DOS(R) and IBM Personal
Computer DOS operating systems. The name of a specific operating system is
used when it is necessary to note features that are unique to that system.
────────────────────────────────────────────────────────────────────────────
About the C Run-Time Library
The Microsoft C run-time library contains a number of new routines and
features which support American National Standards Institute (ANSI) C
compatibility, OS/2 and XENIX(R) programming, and sophisticated graphics
programming.
To ease the task of transporting programs from one operating system to
another, the description of each library routine includes compatibility
boxes, which show at a glance whether the routine is compatible with ANSI C,
MS-DOS, OS/2, UNIX(R), and XENIX. (In this book, references to XENIX systems
also encompass UNIX and other UNIX-like systems.)
ANSI C Compatibility
The C run-time library routines are designed for compatibility with the ANSI
C standard, which Microsoft C compilers support. The major innovation of
ANSI C is to permit argument-type lists in function prototypes
(declarations). Given the information in the function prototype, the
compiler can check later references to the function to make sure that the
references use the correct number and type of arguments and the correct
return value.
To take advantage of the compiler's type-checking ability, the include files
that accompany the C run-time library have been expanded. In addition to the
definitions and declarations required by library routines, the include files
now contain function declarations with argument-type lists. Several new
include files have also been added. The names of these files are chosen to
maximize compatibility with the ANSI C standard and with XENIX and UNIX
names.
OS/2 and XENIX(R) Programming
Microsoft C run-time library routines are designed to maintain maximum
compatibility between MS-DOS, OS/2, and XENIX or UNIX systems. The library
offers a number of operating-system interface routines that allow you to
take advantage of specific DOS and OS/2 features.
Most of the functions in the C library for DOS and OS/2 are compatible with
like-named routines in the C library for XENIX. For additional
compatibility, the math library functions have been extended to provide
exception handling in the same manner as the UNIX System V math functions.
Expanded Graphics Library
The Microsoft C run-time library now contains over one hundred graphics
routines. The core of this library consists of several dozen low-level
graphics routines, which allow your programs to select video modes, set
points, draw lines, change colors, and draw shapes such as rectangles and
ellipses. You can display real-valued data, such as floating-point values,
within windows of different sizes by using various coordinate systems.
Recent additions to the graphics library include presentation graphics and
fonts. The presentation-graphics library provides powerful tools for adding
presentation-quality graphics to your programs. These routines can display
data as a variety of graphs, including pie charts, bar and column charts,
line graphs, and scatter diagrams.
The fonts library allows your programs to display various styles and sizes
of text in graphics images or charts. You can use font-manipulation routines
with any graphics routines that display text, including presentation
graphics.
About This Book
This book assumes that you understand the C language and know how to compile
and link programs. If you have questions about these subjects, consult your
compiler documentation.
This book has two parts. Part 1, "Overview," introduces the Microsoft C
library. It describes general rules for using the library and summarizes the
main categories of library routines. Part 1 contains the following chapters:
■ Chapter 1, "Using C Library Routines," gives general rules for
understanding and using C library routines and mentions special
considerations that apply to certain routines. It is recommended that
you read this chapter before using the run-time library; you may also
want to turn to Chapter 1 when you have questions about library
procedures.
■ Chapter 2, "Run-Time Routines by Category," lists the C library
routines by category and discusses considerations that apply to each
category. This chapter makes it easy to locate routines by task. Once
you find the routine you want, turn to the reference page in Part 2
for a detailed description.
■ Chapter 3, "Global Variables and Standard Types," describes variables
and types that are used by library routines. Global variables and
standard types are also described in the reference descriptions of the
routines that use them.
Part 2, "Run-Time Functions," describes the library routines in alphabetical
order. Once you are familiar with the C library rules and procedures, you
will probably use this part most often.
Other Books of Interest
This book provides a guide to the C run-time library provided with the
Microsoft C Professional Development System version 6.0.
The following books cover a variety of topics that you may find useful. They
are listed only for your convenience. With the exception of its own
publications, Microsoft does not endorse these books or recommend them over
others on the same subject.
■ Barkakati, Nabajyoti. The Waite Group's Microsoft C Bible.
Indianapolis, IN: Howard W. Sams, 1988.
A topical guide to the Microsoft C run-time library. A similar volume
is available for the Microsoft QuickC(R) product.
■ Campbell, Joe. C Programmer's Guide to Serial Communications.
Indianapolis, IN: Howard W. Sams & Company, 1987.
A comprehensive guide to the specialized area of serial communication
programming in C.
■ Hansen, Augie. Proficient C: The Microsoft Guide to Intermediate &
Advanced C Programming. Redmond, WA: Microsoft Press, 1987.
An intermediate-level guide to C programming.
■ Harbison, Samuel P., and Guy L. Steele, Jr. C: A Reference Manual, 2d
ed. Englewood Cliffs, NJ: Prentice Hall, 1987.
A comprehensive guide to the C language and the standard library.
■ Kernighan, Brian W., and Dennis M. Ritchie. The C Programming
Language, 2d ed. Englewood Cliffs, NJ: Prentice Hall, 1988.
The first edition of this book is the classic definition of the C
language. The second edition includes new information on the proposed
ANSI C standard.
■ Lafore, Robert. Microsoft C Programming for the IBM. Indianapolis, IN:
Howard W. Sams & Company, 1987.
The first half of this book teaches C. The second half concentrates on
specifics of the PC environment, such as BIOS calls, memory, and video
displays.
■ Mark Williams Company. ANSI C: A Lexical Guide. Englewood Cliffs, NJ:
Prentice Hall, 1988.
A dictionary-style guide to the ANSI C standard.
■ Plauger, P. J., and Jim Brodie. Standard C. Redmond, WA: Microsoft
Press, 1989.
A quick reference guide to the ANSI C implementation by the secretary
and chairman of the ANSI-authorized C Programming Language Standards
Committee.
■ Plum, Thomas. Reliable Data Structures in C. Cardiff, NJ: Plum Hall,
1985.
An intermediate-level look at data structures using the C language.
■ Plum, Thomas, and Jim Brodie. Efficient C. Cardiff, NJ: Plum Hall,
1985.
A guide to techniques for increasing the efficiency of C programs.
■ Press, William H., Brian P. Flannery, Saul A. Teukolsky, and William
T. Vetterling. Numerical Recipes in C: The Art of Scientific
Computing. New York: Cambridge University Press, 1988.
A comprehensive look at numerical techniques using the C language.
■ Schustack, Steve. Variations in C: Programming Techniques for
Developing Efficient Professional Applications. Redmond, WA: Microsoft
Press, 1985.
An intermediate-level guide to developing business applications in C.
■ Ward, Robert. Debugging C. Indianapolis, IN: Que Corporation, 1986.
An advanced guide to the theory and practice of debugging C programs.
■ Wilton, Richard. Programmer's Guide to PC and PS/2 Video
Systems:Maximum Video Performance from the EGA, VGA, HGC, & MCGA.
Redmond, WA: Microsoft Press, 1987.
An advanced guide to all the PC and PS/2 video modes.
Document Conventions
This book uses the following document conventions :
Example Description
────────────────────────────────────────────────────────────────────────────
STDIO.H Uppercase letters indicate file names,
segment names, registers, and terms used
at the operating-system command level.
_far Boldface letters indicate C keywords,
operators, language-specific characters,
and library routines. Within discussions
of syntax, bold type indicates that the
text must be entered exactly as shown.
expression Words in italics indicate placeholders
for information you must supply, such as
a file name. Italics are also
occasionally used for emphasis in the
text.
[[option]] Items inside double square brackets are
optional.
#pragma pack {1|2} Braces and a vertical bar indicate a
choice among two or more items. You must
choose one of these items unless double
square brackets surround the braces.
#include <io.h> This font is used for examples, user
input, program output, and error
messages in text.
CL options [[files...]] Three dots following an item indicate
that more items having the same form may
appear.
while() A column of three dots tells you that
{ part of the example program has been
. intentionally omitted.
.
.
}
CTRL+ENTER Small capital letters are used for the
names of keys on the keyboard. When you
see a plus sign (+) between two key
names, you should hold down the first
key while pressing the second.
The carriage-return key, sometimes
marked as a bent arrow on the keyboard,
is called ENTER.
"argument" Quotation marks enclose a new term the
first time it is defined in text.
"C string" Some C constructs, such as strings,
require quotation marks. Quotation marks
required by the language have the form "
" and ' ' rather than " " and ' '.
Color Graphics Adapter (CGA) The first time an acronym is used, it is
often spelled out.
PART I Overview
────────────────────────────────────────────────────────────────────────────
The first part of this book provides an overview of the run-time library
provided with the Microsoft C Professional Development System.
Chapter 1 is a general guide to the use of the run-time library routines.
Chapter 2 lists the routines by category.
Chapter 3 tells how to access global variables and types defined in the
run-time library.
Chapter 1 Using C Library Routines
────────────────────────────────────────────────────────────────────────────
This chapter provides basic information about how to use Microsoft C library
routines. It also describes some special rules, such as file- and path-name
conventions, that apply to particular routines. You should read this chapter
before you begin to use C library routines, and you may also want to refer
back to it if you have questions about library procedures.
1.1 Calling Library Routines
To use a C library routine, simply call it in your program, just as if it is
defined there. For instance, suppose you write the following program and
name it SAMPLE.C:
#include <stdio.h>
main()
{
printf( "Microsoft C" );
}
The program prints Microsoft C by calling the printf routine, which is
part of the standard C library. Calling a library routine normally involves
two groups of files:
1. Header ("include") files that contain declarations and type
definitions required by library routines
2. Library files that contain the library routines in compiled form
Header files and library files are both included with Microsoft C. Header
files are used when compiling, and library files are used when linking.
You include the necessary header files in your program source code with
#include directives. The description of each library routine in Part 2,
"Reference," tells you what header file the routine requires. Since printf
requires the STDIO.H header file, the SAMPLE.C program contains the
following line:
#include <stdio.h>
This line causes the compiler to insert the contents of STDIO.H into the
source file SAMPLE.C.
After you compile the source file, you link the resulting object (.OBJ) file
with the appropriate library (.LIB) file to create an executable (.EXE)
file. Your object file contains the name of every routine that your program
calls, including library routines. If a routine is not defined in your
program, the linker searches for its code in a library file and includes
that code in the executable file.
Normally, the code for standard library routines is contained in the
"default library" that you create when installing Microsoft C. Since the
linker automatically searches the default library, you do not need to
specify that library's name when linking your program. The following command
links the example program with the default library:
link sample,,,;
If you call a library routine that is not contained in the default library,
you must give the linker the name of the library file that contains the
routine. For instance, suppose your program uses a Microsoft C graphics
routine and you did not make GRAPHICS.LIB part of your default library when
installing Microsoft C. You would then link the program using a line like
the following:
link sample,,, graphics.lib;
For more information about libraries and linking, consult the installation
documentation for your compiler.
1.2 Using Header Files
As stated in the previous section, you should include C header files when
using library routines. This section describes particular reasons why header
files are required.
1.2.1 Including Necessary Definitions
Many C library routines use constants, type definitions, or macros defined
in a header file. To use the routine, you must include the header file
containing the needed definition(s). The following list gives examples:
Definition Example
────────────────────────────────────────────────────────────────────────────
Macro If a library routine is implemented as a
macro, the macro definition appears in a
header file. For instance, the toupper
macro is defined in the header file
CTYPE.H.
Manifest constant Many library routines refer to constants
that are defined in header files. For
instance, the open routine uses
constants such as O_CREAT, which is
defined in the header file FCNTL.H.
Type definition Some library routines return a structure
or take a structure as an argument. For
example, stream input/output routines
use a structure of type FILE, which is
defined in STDIO.H.
1.2.2 Including Function Declarations
The Microsoft C header files also contain function declarations for every
function in the C library. These declarations are in the style recommended
by the ANSI C standard. Given these declarations, the compiler can perform
"type checking" on every reference to a library function, making sure that
you have used the correct return type and arguments. Function declarations
are sometimes called "prototypes," since the declaration serves as a
prototype or template for every subsequent reference to the function.
A function declaration lists the name of the function, its return type, and
the number and type of its arguments. For instance, below is the declaration
of the pow library function from the header file MATH.H:
double pow( double x, double y );
The example declares that pow returns a value of type double and takes two
arguments of type double. Given this declaration, the compiler can check
every reference to pow in your program to ensure that the reference passes
two double arguments to pow and takes a return value of type double.
The compiler can perform type checking only for function references that
appear after the function declaration. Because of this, function
declarations normally appear near the beginning of the source file, prior to
any use of the functions they declare.
Function declarations are especially important for functions that return a
value of some type other than int, which is the default. For example, the
pow function returns a double value. If you do not declare such a function,
the compiler treats its return value as int, which can cause unexpected
results.
It is also a good practice to provide declarations for functions that you
write. If you do not want to type the declarations by hand, you can generate
them automatically by using the /Zg compiler option. This option causes the
compiler to generate ANSI-standard function declarations for every function
defined in the current source file. Redirect this output to a file, then
insert the file near the beginning of your source file.
Your program can contain more than one declaration of the same function, as
long as the declarations do not conflict. This is important if you have old
programs whose function declarations do not contain argument-type lists. For
instance, if your program contains the declaration
char *calloc( );
you can later include the following declaration:
char *calloc(unsigned, unsigned);
Because the two declarations are compatible, even though they are not
identical, no conflict occurs. The second declaration simply gives more
information about function arguments than the second. A conflict would
arise, however, if the declarations gave a different number of arguments or
gave arguments of different types.
Some library functions can take a variable number of arguments. For
instance, the printf function can take one argument or several. The compiler
can perform only limited type checking on such functions, a factor that
affects the following library functions:
■ In calls to cprintf, cscanf, printf, and scanf, only the first
argument (the format string) is type checked.
■ In calls to fprintf, fscanf, sprintf, and sscanf, only the first two
arguments (the file or buffer and the format string) are type checked.
■ In calls to open, only the first two arguments (the path name and the
open flag) are type checked.
■ In calls to sopen, only the first three arguments (the path name, the
open flag, and the sharing mode) are type checked.
■ In calls to execl, execle, execlp, and execlpe, only the first two
arguments (the path name and the first argument pointer) are type
checked.
■ In calls to spawnl, spawnle, spawnlp, and spawnlpe, only the first
three arguments (the mode flag, the path name, and the first argument
pointer) are type checked.
1.3 File Names and Path Names
Many library routines take strings representing paths and file names as
arguments. If you plan to transport your programs to the XENIX operating
system, you should remember that XENIX uses file- and path-name conventions
that are different from those used by DOS and OS/2. If you do not plan to
transport your programs to XENIX, you can skip this section.
Case Sensitivity
The DOS and OS/2 operating systems are not case sensitive (they do not
distinguish between uppercase and lowercase letters). Thus, SAMPLE.C and
Sample.C refer to the same file in DOS and OS/2. However, the XENIX
operating system is case sensitive. In XENIX, SAMPLE.C and Sample.C refer to
different files. To transport programs to XENIX, choose file and path names
that work correctly in XENIX, since either case works in DOS and OS/2. For
instance, the following directives are identical in DOS and OS/2, but only
the second works in XENIX:
#include <STDIO.H>
#include <stdio.h>
Subdirectory Conventions
Under XENIX, certain header files are normally placed in a subdirectory
named SYS. Microsoft C follows this convention to ease the process of
transporting programs to XENIX. If you do not plan to transport your
programs, you can place the SYS header files elsewhere.
Path-Name Delimiters
XENIX uses the slash (/) in path names, while DOS and OS/2 use the backslash
(\). To transport programs to XENIX, it is advantageous to use path-name
delimiters that are compatible with XENIX whenever possible.
1.4 Choosing Between Functions and Macros
This book uses the words "routine" and "function" interchangeably. However,
the term "routine" actually encompasses both functions and macros. Because
functions and macros have different properties, you should pay attention to
which form you are using. The descriptions in the reference section indicate
whether routines are implemented as functions or as macros.
Most routines in the Microsoft C library are functions. They consist of
compiled C code or assembled Microsoft Macro Assembler (MASM) code. However,
a few library routines are implemented as macros that behave like functions.
You can pass arguments to library macros and invoke them in the same way you
invoke functions.
The main benefit of using macros is faster execution time. A macro is
expanded (replaced by its definition) during preprocessing, creating in-line
code. Thus, macros do not have the overhead associated with function calls.
On the other hand, each use of a macro inserts the same code in your
program, whereas a function definition occurs only once regardless of how
many times it is called. Functions and macros thus offer a trade-off between
speed and size.
Apart from speed and size issues, macros and functions have some other
important differences:
■ Some macros treat arguments with side effects incorrectly when the
macro evaluates its arguments more than once (see the example that
follows this list). Not every macro has this effect. To determine if a
macro handles side effects as desired, examine its definition in the
appropriate header file.
■ A function name evaluates to an address, but a macro name does not.
Thus, you cannot use a macro name in contexts requiring a function
pointer. For instance, you can declare a pointer to a function, but
you cannot declare a pointer to a macro.
■ You can declare functions, but you cannot declare macros. Thus, the
compiler cannot perform type checking of macro arguments as it does of
function arguments. However, the compiler can detect when you pass the
wrong number of arguments to a macro.
■ You must always include the appropriate header file when using a
library macro. Every library macro is defined with a #define directive
in a header file. If you do not include the header file, the macro is
undefined.
The following example demonstrates how some macros can produce unwanted side
effects. It uses the toupper routine from the standard C library.
#include <ctype.h>
int a = 'm';
a = toupper(a++);
The example increments a when passing it as an argument to the toupper
routine, which is implemented as a macro. It is defined in CTYPE.H:
#define toupper(c) ( (islower(c)) ? _toupper(c) : (c) )
The definition uses the conditional operator (? :). The conditional
expression evaluates the argument c twice: once to check if it is
lowercase and again to create the result. This macro evaluates the argument
a++ twice, increasing a by 2 instead of 1. As a result, the value
operated on by islower differs from the value operated on by _toupper.
Like some other library routines, toupper is provided in both macro and
function versions. The header file CTYPE.H not only declares the toupper
function but also defines the toupper macro.
Choosing between the macro version and function version of such routines is
easy. If you wish to use the macro version, you can simply include the
header file that contains the macro definition. Because the macro definition
of the routine always appears after the function declaration, the macro
definition normally takes precedence. Thus, if your program includes CTYPE.H
and then calls toupper, the compiler uses the toupper macro:
#include <ctype.h>
int a = 'm';
a = toupper(a);
You can force the compiler to use the function version of a routine by
enclosing the routine's name in parentheses:
#include <ctype.h>
int a = 'm';
a = (toupper) (a);
Because the name toupper is not immediately followed by a left parenthesis,
the compiler cannot interpret it as a macro name. It must use the toupper
function.
A second way to do this is to "undefine" the macro definition with the
#undef directive:
#include <ctype.h>
#undef toupper
Since the macro definition no longer exists, subsequent references to
toupper use the function version.
A third way to make sure the compiler uses the function version is to
declare the function explicitly:
#include <ctype.h>
int toupper(int _c);
Since this function declaration appears after the macro definition in
CTYPE.H, it causes the compiler to use the toupper function.
1.5 Stack Checking on Entry
For certain library routines, the compiler performs stack checking on entry.
(The "stack" is a memory area used for temporary storage.) Upon entry to
such a routine, the stack is checked to determine if it has enough room for
the local variables used by that routine. If it does, space is allocated by
adjusting the stack pointer. Otherwise, a "stack overflow" run-time error
occurs. If stack checking is disabled, the compiler assumes there is enough
stack space; if there is not, you might overwrite memory locations in the
data segment and receive no warning.
Typically, stack checking is enabled only for functions with large
local-variable requirements (more than about 150 bytes), since there is
enough free space between the stack and data segments to handle functions
with smaller requirements. If the function is called many times, stack
checking slows execution slightly.
Stack checking is enabled for the following library functions:
execvp printf spawnvpe system
execvpe scanf sprintf vprintf
fprintf spawnvp sscanf write
fscanf
1.6 Handling Errors
Many library routines return a value that indicates an error condition. To
avoid unexpected results, your code should always check such error values
and handle all of the possible error conditions. The description of each
library routine in the reference section lists the routine's return
value(s).
Some library functions do not have a set error return. These include
functions that return nothing and functions whose range of return values
makes it impossible to return a unique error value. To aid in error
handling, some functions in this category set the value of a global variable
named errno.
If the reference description of a routine states that it sets the errno
variable, you can use errno in two ways:
1. Compare errno to the values defined in the header file ERRNO.H.
2. Handle errno with the perror or strerror library routines. The perror
routine prints a system error message to the standard error (stderr).
The strerror routine stores the same information in a string for later
use.
When you use errno, perror, and strerror, remember that the value of errno
reflects the error value for the last call that set errno. To avoid
confusion, you should always test the return value to verify that an error
actually occurred. Once you determine that an error has occurred, use errno
or perror immediately. Otherwise, the value of errno may be changed by
intervening calls.
Library math routines set errno by calling the matherr or _matherrl library
routines, which are described in the reference section. If you wish to
handle math errors differently from these routines, you can write your own
routine and name it matherr or _matherrl. Your routine must follow the rules
listed in the matherr reference description.
The ferror library routine allows you to check for errors in stream
input/output operations. This routine checks if an error indicator has been
set for a given stream. Closing or rewinding the stream automatically clears
the error indicator. You can also reset the error indicator by calling the
clearerr library routine.
The feof library routine tests for end-of-file on a given stream. An
end-of-file condition in low-level input and output can be detected with the
eof routine or when a read operation returns 0 as the number of bytes read.
The _grstatus library routine allows you to check for errors after calling
certain graphics library operations. See the reference page on the _grstatus
function for details.
1.7 Operating-System Considerations
The library routines listed in this section behave differently under
different operating system versions. For more information on an individual
routine, see the description of that routine in the reference section.
Routine Restrictions
────────────────────────────────────────────────────────────────────────────
locking These routines are effective only in
sopen OS/2 and in DOS versions 3.0 and later.
_fsopen
dosexterr The dosexterr routine provides error
handling for system call 0x59 (get
extended error) in DOS versions 3.0 and
later.
dup The dup and dup2 routines can cause
dup2 unexpected results in DOS versions
earlier than 3.0. If you use dup or dup2
to create a duplicate file handle for
stdin, stdout, stderr, stdaux, or stdprn
, calling the close function with one
handle causes errors in later I/O
operations that use the other handle.
This anomaly does not occur in OS/2 or
in DOS versions 3.0 and later.
exec When using the exec and spawn families
spawn of functions under DOS versions earlier
than 3.0, the value of the arg0 argument
(or argv[0] to the child process) is not
available to the user; a null string (""
) is stored in that position instead. In
OS/2, the arg0 argument contains the
command name; in DOS versions 3.0 and
later, it contains the complete command
path.
Microsoft C defines global variables that indicate the version of the
current operating system. You can use these to determine the
operating-system version in which a program is executing. See Chapter 3,
"Global Variables and Standard Types," for more information.
1.8 Floating-Point Support
Microsoft math library routines require floating-point support to perform
calculations with real numbers (numbers that can contain fractions). This
support can be provided by the floating-point libraries that accompany your
compiler software or by an 8087, 80287, or 80387 coprocessor. The names of
the functions that require floating-point support are listed below:
acos cos fmod modfl
acosl cosl fmodl pow
asin cosh fmsbintoieee powl
asinl coshl _fpreset sin
atan dieeetomsbin frexp sinl
atanl difftime frexpl sinh
atan2 dmsbintoieee gcvt sinhl
atan2l ecvt hypot sqrt
atof exp hypotl sqrtl
_atold expl ldexp _status87
bessel fabs ldexpl strtod
cabs fabsl log _strtold
cabsl fcvt logl tan
ceil fieeetomsbin log10 tanl
ceill floor log10l tanh
_clear87 floorl modf tanhl
_control87
Note that the bessel routine does not correspond to a single function, but
to twelve functions named j0, j1, jn, y0, y1, yn, _j0l, _j1l, _jnl, _y0l,
_y1l, and _ynl. Also note that the _clear87 and _control87 functions are not
available with the /FPa compiler option.
Also requiring floating-point support is the printf family of functions
(cprintf, fprintf, printf, sprintf, vfprintf, vprintf, and vsprintf). These
functions require support for floating-point input and output if used to
print floating-point values.
The C compiler tries to detect whether floating-point values are used in a
program so that supporting functions are loaded only if required. This
behavior saves a considerable amount of space for programs that do not
require floating-point support.
When you use a floating-point type specifier in the format string for a
printf or scanf call, make sure you specify floating-point values or
pointers to floating-point values in the argument list. These must
correspond to any floating-point
type specifiers in the format string. The presence of floating-point
arguments allows the compiler to detect that floating-point support code is
required. If a floating-point type specifier is used to print an integer
argument, for example, floating-point values will not be detected because
the compiler does not actually read the format string used in the printf and
scanf functions. For instance, the following program produces an error at
run time:
main( ) /* This example causes an error */
{
long f = 10L;
printf("%f", f);
}
In the preceding example, the functions for floating-point support are not
loaded because
■ No floating-point arguments are given in the call to printf.
■ No floating-point values are used elsewhere in the program.
As a result, the following error occurs:
Floating point not loaded
Here is a corrected version of the above call to printf in which the long
integer value is cast to double:
main( ) /* This example works correctly */
{
long f = 10L;
printf("%f", (double) f);
}
1.9 Using Huge Arrays with Library Functions
In programs that use small, compact, medium, and large memory models,
Microsoft C allows you to use arrays exceeding the 64K (kilobyte) limit of
physical memory in these models by explicitly declaring the arrays as _huge.
However, generally, you cannot pass _huge data items as arguments to C
library functions. In the compact-model library used by compact-model
programs and in the large-model library used by both large-model and
huge-model programs, only the functions listed below use argument arithmetic
that works with _huge items:
bsearch _fmemcmp _fmemset lsearch
fread _fmemcpy halloc memccpy
fwrite _fmemicmp hfree memchr
_fmemccpy _fmemmove lfind
_fmemchr
With this set of functions, you can read from, write to, search, sort, copy,
initialize, compare, or dynamically allocate and free _huge arrays; the
_huge array can be passed without difficulty to any of these functions in a
compact-, large-, or huge-model program. The model-independent routines in
the above list (those beginning with _f) are available in all memory models.
The memset, memcpy, and memcmplibrary routines are available in two
versions: as C functions and as intrinsic (in-line) code. The function
versions of these routines support huge pointers in compact and large memory
models, but the intrinsic versions do not support huge pointers. (The
function version of such routines generates a call to a library function,
whereas the intrinsic version inserts in-line code into your program. Your
compiler documentation explains how to select the intrinsic versions of
library routines.)
Chapter 2 Run-Time Routines by Category
────────────────────────────────────────────────────────────────────────────
Microsoft C library routines handle various kinds of tasks. If you know the
type of task you need done, but don't know exactly which routine to use, the
categorized lists of routines in this chapter can help.
The descriptions here are intended only to give you a brief overview of the
capabilities of the run-time library. For a complete description of the
behavior, syntax, and use of each routine, see Part 2, "Run-Time Functions."
The main categories of library routines are
■ Buffer manipulation
■ Character classification and conversion
■ Data conversion
■ Directory control
■ File handling
■ Graphics
■ Input and output
■ Internationalization
■ Math
■ Memory allocation
■ Process and environment control
■ Searching and sorting
■ String manipulation
■ System calls
■ Time
■ Variable-length argument lists
2.1 Buffer Manipulation
The buffer-manipulation routines are useful for working with areas of memory
on a character-by-character basis. A "buffer" is an array of characters,
similar to a character string. However, unlike strings, buffers are not
usually terminated with a null character ('\0'). Therefore, the
buffer-manipulation routines always take a length or count argument.
Function declarations for the buffermanipulation routines are given in the
include files MEMORY.H and STRING.H, with an exception being the swab
function, which appears in STDLIB.H.
Routines beginning with _f are model independent; the _f stands for far.
These routines are useful in writing mixed-model programs because they can
be called from any program, regardless of the memory model being used.
Routine Use
────────────────────────────────────────────────────────────────────────────
memccpy, _fmemccpy Copy characters from one buffer to
another until a given character or a
given number of characters has been
copied
memchr, _fmemchr Return a pointer to the first
occurrence, within a specified number of
characters, of a given character in the
buffer
memcmp, _fmemcmp Compare a specified number of characters
from two buffers
memcpy, _fmemcpy Copy a specified number of characters
from one buffer to another
memicmp, _fmemicmp Compare a specified number of characters
from two buffers without regard to the
case of the letters (uppercase and
lowercase treated as equivalent)
memmove, Copy a specified number of characters
_fmemmove from one buffer to another
memset, _fmemset Use a given character to initialize a
specified number of bytes in the buffer
swab Swaps bytes of data and stores them at
the specified location
When the source and target areas overlap, only the memmove and _fmemmove
functions are guaranteed to copy the full source properly. (The memcpy and
_fmemcpy routines do not always copy the full source in such cases.)
2.2 Character Classification and Conversion
The character classification and conversion routines allow you to test
individual characters in a variety of ways and to convert between uppercase
and lowercase characters.
Routine Use
────────────────────────────────────────────────────────────────────────────
isalnum Tests for alphanumeric character
isalpha Tests for alphabetic character
isascii Tests for ASCII character
iscntrl Tests for control character
isdigit Tests for decimal digit
isgraph Tests for printable character except
space
islower Tests for lowercase character
isprint Tests for printable character
ispunct Tests for punctuation character
isspace Tests for white-space character
isupper Tests for uppercase character
isxdigit Tests for hexadecimal digit
toascii Converts character to ASCII code
tolower Tests character and converts to
lowercase if uppercase
_tolower Converts character to lowercase
(unconditional)
toupper Tests character and converts to
uppercase if
lowercase
_toupper Converts character to uppercase
(unconditional)
The classification routines identify characters by finding them in a table
of classification codes. Using these routines to classify characters is
generally faster than writing a test expression such as the following:
if ((c >= 0) || c <= 0x7f))
All of these routines are implemented in two versions: as functions and as
macros. The function prototypes and macro definitions appear in CTYPE.H.
Section 1.4, "Choosing Between Functions and Macros," explains how to choose
the appropriate version. The toupper and tolower functions are also declared
in the STDLIB.H header file.
2.3 Data Conversion
The data-conversion routines convert numbers to strings of ASCII characters
and vice versa. These routines are implemented as functions, all of which
are declared in the include file STDLIB.H. The atof function, which converts
a string to a floating-point value, is also declared in MATH.H.
Routine Use
────────────────────────────────────────────────────────────────────────────
abs Finds absolute value of integer
atof Converts string to float
atoi Converts string to int
atol Converts string to long
_atold Converts string to long double
ecvt Converts double to string
fcvt Converts double to string
gcvt Converts double to string
itoa Converts int to string
labs Finds absolute value of long integer
ltoa Converts long to string
strtod Converts string to double
strtol Converts string to a long integer
_strtold Converts string to long double
strtoul Converts string to an unsigned long
integer
ultoa Converts unsigned long to string
2.4 Directory Control
The directory-control routines let a program access, modify, and obtain
information about the directory structure. These routines are functions and
are declared in DIRECT.H.
Routine Use
────────────────────────────────────────────────────────────────────────────
chdir Changes current working directory
_chdrive Changes current drive
getcwd Gets current working directory
_getdcwd Gets current working directory for the
specified drive
_getdrive Gets the current disk drive
mkdir Makes a new directory
rmdir Removes a directory
_searchenv Searches for a given file on specified
paths
2.5 File Handling
The file-handling routines let you create, manipulate, and delete files.
They also set and check file-access permissions.
File-handling routines work on a file designated by a path name or by a
"file handle," an integer assigned by the operating system that identifies
an open file. These routines modify or give information about the designated
file. Most of them are declared in the include file IO.H, with the
exceptions being the fstat and stat functions (declared in SYS\STAT.H), the
_fullpath routine (declared in DIRECT.H), and the remove and rename
functions (also declared in STDIO.H).
Routine Use
────────────────────────────────────────────────────────────────────────────
access Checks file-permission setting
chmod Changes file-permission setting
chsize Changes file size
filelength Gets file length
fstat Gets file-status information on handle
_fullpath Makes an absolute path name from a
relative path name
isatty Checks for character device
locking Locks areas of file (available with OS/2
and
DOS versions 3.0 and later)
_makepath Merges path-name components into a
single, full path name
mktemp Creates unique file name
remove Deletes file
rename Renames file
setmode Sets file-translation mode
_splitpath Splits a path name into component pieces
stat Gets file-status information on named
file
umask Sets default-permission mask
unlink Deletes file
The access, chmod, _fullpath, _makepath, remove, rename, _splitpath, stat,
and unlink routines operate on files specified by a path name or file name.
The chsize, filelength, fstat, isatty, locking, and setmode routines work
with files designated by a file handle.
The mktemp and umask routines have functions that are slightly different
from the other routines. The mktemp routine creates a unique file name, and
the programmer can use mktemp to create unique file names that do not
conflict with the names of existing files. The umask routine sets the
default permission mask for any new files created in a program. The mask can
override the permission setting given in the open or creat call for the new
file.
2.6 Graphics
Microsoft C graphics routines offer a wide variety of graphics functions,
low-level graphics primitives, font functions, and presentation graphics
(displays such as graphs and pie charts).
Graphics functions are supplied in two libraries that must be explicitly
linked with your program. The GRAPHICS.LIB library provides support for
low-level graphics and character-font routines. The library PGCHART.LIB
supports presentation-graphics routines.
2.6.1 Low-Level Graphics and Character-Font Functions
The low-level graphics and font functions are declared in the include file
GRAPH.H.
The library can be divided into the eight categories listed below, which
correspond to the different tasks involved in creating and manipulating
graphic objects.
Most graphics routines work only in DOS. Two categories of routines
("configuring mode and environment" and "creating text output") work in OS/2
as well as DOS.
Category Task
────────────────────────────────────────────────────────────────────────────
Configuring mode and environment Select the proper display mode for the
(OS/2 and DOS) hardware and establish memory areas for
writing and displaying of images
Setting coordinates Specify the logical origin and the
active display area within the screen
Setting low-level graphics Specify a palette mapping for low-level
palettes graphics routines
Setting attributes Specify background and foreground
colors, fill masks, and line styles for
low-level graphics routines
Creating graphics Draw and fill figures
output
Creating text output (OS/2 and Write text on the screen
DOS)
Transferring images Store images in memory and retrieve them
Displaying fonts Display text in character fonts
compatible with Microsoft Windows(tm)
The following sections explain each of these categories.
2.6.1.1 Configuring Mode and Environment
Routines that configure the mode and environment establish the graphics or
text mode of operation, determine the current graphics environment, and
control the display of the cursor.
All of the routines listed in this section are available in OS/2 as well as
DOS.
Routine Use
────────────────────────────────────────────────────────────────────────────
_clearscreen Erases the screen and fills it with the
current background color
_getactivepage Gets the current active page number
_getbkcolor Returns the current background color
_getvideoconfig Obtains status of current graphics
environment
_getvisualpage Gets the current visual page number
_grstatus Returns the status of the most recent
graphics function call
_setactivepage Sets memory area for the active page for
writing
images
_setbkcolor Sets the current background color
_settextrows Sets the number of text rows
_setvideomode Selects an operating mode for the
display screen
_setvideomoderows Sets the video mode and the number of
rows for text operations
_setvisualpage Sets memory area for the current visual
page
2.6.1.2 Setting Coordinates
The "set coordinates" routines set the current text or graphics position and
convert pixel coordinates between the various graphic coordinate systems.
The Microsoft C graphics functions recognize three sets of coordinates:
1. Fixed physical coordinates
2. View coordinates defined by the application
3. Window coordinates that can include floating-point values
The functions in this category establish window and view coordinate systems
and translate between physical, view, and window coordinate systems.
Routine Use
────────────────────────────────────────────────────────────────────────────
_getcurrentposition Determines current position in view
coordinates
_getcurrentposition_w Determines current position in window
coordinates
_getphyscoord Converts view coordinates to physical
coordinates
_getviewcoord Converts physical coordinates to view
coordinates
_getviewcoord_w Converts window coordinates to view
coordinates
_getviewcoord_wxy Converts window coordinates in _wxycoord
structure to view coordinates
_getwindowcoord Converts view coordinates to window
coordinates
_setcliprgn Limits graphic output to a region of the
screen
_setvieworg Positions the view-coordinate origin
_setviewport Limits graphics output to a region of
the screen and positions the
view-coordinate origin to the upper-left
corner of that region
_setwindow Defines a floating-point window
coordinate system
The default view coordinate system is identical to the physical screen
coordinate system. The physical origin (0, 0) is always in the upper-left
corner of the display. The x axis extends in the positive direction left to
right, while the y axis extends in the positive direction top to bottom.
The physical horizontal and vertical dimensions depend on the hardware
display configuration and the selected mode. These values are accessible at
run time by examining the numxpixels and numypixels fields of the
videoconfig structure returned by _getvideoconfig. (The _getvideoconfig
routine is listed in the previous section.)
The _setvieworg function allows you to move the viewport origin to a new
position relative to the physical screen.
Routines that refer to coordinates on the physical screen or viewport
require integer values. However, in real-world graphing applications, you
might wish to use floating-point values, such as stock prices or average
rainfall. The window coordinate system allows you to display graphics using
floating-point values instead of integers.
The _getcurrentposition and _getcurrentposition_w routines allow you to
determine the location of the current graphics-output point.
The _setcliprgn function defines a restricted active display area on the
screen. The _setviewport function does the same thing and also resets the
viewport origin to the upper-left corner of the restricted active display
area.
The physical coordinates of any view-coordinate point can be determined with
the _getphyscoord function, and the view coordinates of any physical point
can be determined with the _getviewcoord function.
The view coordinates of any window coordinate can be determined with the
_getviewcoord_w and _getviewcoord_wxy functions. The window coordinates of
any view coordinate can be determined with the _getwindowcoord function.
The _setwindow function defines the current viewport as a real-coordinate
window bound by the specified floating-point values.
2.6.1.3 Setting Low-Level Graphics Palettes
Use the low-level palette routines to select or remap color palettes.
Routine Use
────────────────────────────────────────────────────────────────────────────
_remapallpalette Changes all color indexes in the current
palette
_remappalette Changes a single color index in the
current palette
_selectpalette Selects a predefined palette
Some video modes support a "color palette," which is a table of the color
values that can be displayed together on the screen at any given time. A
"color value" is a long integer representing a color that can be displayed
on your system.
In CGA color graphics modes, you can use the _selectpalette routine to
choose one of several predefined palettes.
On EGA and VGA video systems, you can "remap" (change) the palette using the
_remappalette or _remapallpalette routines. For instance, the EGA _ERESCOLOR
mode offers a total of 64 color values, of which 16 can be displayed at a
time. In this mode, the palette contains 16 "color indices," or slots to
which you can assign color values.
The _remappalette routine changes a single color index to a specified color
value. The _remapallpalette routine changes all of the available palette
entries simultaneously.
2.6.1.4 Setting Attributes
The low-level output functions that draw lines, arcs, ellipses, and other
basic figures do not specify color or line-style information. Instead, the
low-level graphics functions rely on a set of attributes that are set
independently by the following functions:
Routine Use
────────────────────────────────────────────────────────────────────────────
_getarcinfo Determines the endpoints in viewport
coordinates of the most recently drawn
arc or pie
_getcolor Gets the current color
_getfillmask Gets the current fill mask
_getlinestyle Gets the current line-style mask
_getwritemode Gets the current logical write mode
_setcolor Sets the current color
_setfillmask Sets the current fill mask
_setlinestyle Sets the current line-style mask
_setwritemode Sets logical write mode for line drawing
The _getcolor and _setcolor functions get or set the current color index for
graphics and font output. The _getbkcolor and _setbkcolor functions get or
set the current background color.
The _getfillmask and _setfillmask functions get or set the current fill
mask. The mask is an 8-by-8-bit template array, with each bit representing a
pixel. If a bit is 0, the pixel in memory is left untouched, as the mask is
transparent to that pixel. If a bit is 1, the pixel is assigned the current
color value. The template is repeated as necessary over the entire fill
area.
The _getlinestyle and _setlinestyle functions get or set the current line
style. The line style is determined by a 16-bit template buffer with each
bit corresponding to a pixel. If a bit is 1, the pixel is set to the current
color. If a bit is 0, the pixel is not changed. The template is repeated for
the length of the line.
The _getwritemode and _setwritemode functions get or set the logical write
mode for straight line drawing. The default mode, _GPSET, causes lines to be
drawn in the current graphics color. Other modes combine the current
graphics color and the original screen image using various logical
operations.
2.6.1.5 Creating Graphics Output
The graphics output functions use a set of specified coordinates and draw
various figures. They use the current or default attributes for line-style
mask, fill mask, write mode, background color, and foreground color.
The name of each function announces its task or the figure it draws, as the
following list indicates:
Routine Use
────────────────────────────────────────────────────────────────────────────
_arc, _arc_w, _arc_wxy Draw an arc
_ellipse, _ellipse_w, Draw an ellipse or circle
_ellipse_wxy
_floodfill, _floodfill_w Flood-fill an area of the screen with
the current color
_getcurrentposition, Obtain the current graphic-output
_getcurrentposition_w position used by _lineto and _outgtext
_getpixel, _getpixel_w Obtain a pixel's color
_lineto, _lineto_w Draw a line from the current graphic
output position to a specified point
_moveto, _moveto_w Move the current graphic-output position
to a specified point
_pie, _pie_w, _pie_wxy Draw a pie-slice-shaped figure
_polygon, _polygon_w, Draw or scan-fill a polygon
_polygon_wxy
_rectangle, _rectangle_w, Draw or scan-fill a rectangle
_rectangle_wxy
_setpixel, _setpixel_w Set a pixel's color
Most of these routines are available in several forms, which are indicated
by their names. Output functions without a suffix use the view coordinate
system. Functions that end with _w take double values as arguments and use
the window coordinate system. Functions that end with _wxy use _wxycoord
structures to define the coordinates and use the window coordinate system.
Circular figures, such as arcs and ellipses, are centered within a "bounding
rectangle" specified by two points that define the diagonally opposed
corners of the rectangle. The center of the rectangle becomes the center of
the figure, and the rectangle's borders determine the size of the figure.
2.6.1.6 Creating Text Output
The next group of routines provides text output in both graphics and text
modes. Unlike the standard console I/O library routines, these functions
recognize text-window boundaries and use the current text color.
All of the routines listed in this section work in OS/2 as well as DOS.
Routine Use
────────────────────────────────────────────────────────────────────────────
_displaycursor Sets the cursor on or off upon exit from
a graphics routine
_gettextcolor Obtains the current text color
_gettextcursor Returns the current cursor attribute
(text modes only)
_gettextposition Obtains the current text-output position
_gettextwindow Gets the current text window boundaries
_outmem Prints text of a specified length from a
memory
buffer
_outtext Outputs a text string to the screen at
the current text position
_scrolltextwindow Scrolls the current text window up or
down
_settextcolor Sets the current text color
_settextcursor Sets the current cursor attribute (text
modes only)
_settextposition Relocates the current text position
_settextwindow Defines the current text-display window
_wrapon Enables or disables line wrap
The _outtext and _outmem routines provide no formatting. If you want to
output integer or floating-point values, you must convert the values into a
string variable (using the sprintf function) before calling these routines.
The _outtext routine recognizes the \n (newline character) and \r (carriage
return) sequences. The _outmem routine treats these sequences as printable
graphics characters.
2.6.1.7 Transferring Images
The functions in this category transfer screen images between memory and the
display, using a buffer allocated by the application, or determine the size
in bytes of the buffer needed to store a given image.
The functions that end with _w or _wxy use window coordinates; the other
functions in this set use view coordinates.
Routine Use
────────────────────────────────────────────────────────────────────────────
_getimage, Store a screen image in memory
_getimage_w,
_getimage_wxy
_imagesize, Return the size (in bytes) of the buffer
_imagesize_w, needed to store the image
_imagesize_wxy
_putimage, Retrieve an image from memory and
_putimage_w display it
In some cases, the buffer needed to store an image with the _getimage
functions must be larger than 64K (65,535) bytes. Use the halloc routine to
allocate a buffer larger than 64K.
2.6.1.8 Displaying Fonts
The functions listed in this section control the display of font-based
characters on the screen.
Routine Use
────────────────────────────────────────────────────────────────────────────
_getfontinfo Obtains the current font characteristics
_getgtextextent Determines the width in pixels of
specified text in the current font
_getgtextvector Gets orientation of font text output
_outgtext Outputs text in the current font to the
screen at the specified pixel position
_registerfonts Initializes font library
_setfont Finds a single font that matches a
specified set of characteristics and
makes this font the current font for use
by the _outgtext function
_setgtextvector Sets the current orientation for font
text output
_unregisterfonts Frees memory allocated by _registerfonts
2.6.2 Presentation-Graphics Functions
The presentation-graphics functions are declared in the PGCHART.H include
file. The library can be divided into the three categories listed below,
corresponding to the different tasks involved in creating and manipulating
graphic objects:
Category Task
────────────────────────────────────────────────────────────────────────────
Displaying presentation graphics Initialize video structures for
presentation graphics and establishes
the default chart type. Display
presentation-graphics chart: bar,
column, pie, scatter, or line chart.
Analyzing Analyze data (does not display chart).
presentation-graphics data
Manipulating Modify basic chart structures (e.g.,
presentation-graphics structures palettes, cross-hatching styles).
2.6.2.1 Displaying Presentation Graphics
The functions listed in this section initialize the presentation-graphics
library and display the specified graph type.
Because the _pg_initchart routine initializes the presentation-graphics
library, it must be called before any other function in the
presentation-graphics library. The _pg_defaultchart function initializes the
variables in the chart environment.
The other routines in this category display the specified graph. The
single-series versions plot one set of data, and the multiseries versions
(those ending with an ms suffix) plot several sets of data in the same chart
style.
Presentation-graphics programs can display text in different font sizes by
taking advantage of font-based characters (see Section 2.6.1.8, "Displaying
Fonts.") Call the _registerfonts and _setfont routines to select a font
before calling the _pginitchart routine. Subsequent charts use the selected
font. You can later call the _unregisterfonts routine to restore the default
character font and free the memory previously allocated for fonts.
Routine Use
────────────────────────────────────────────────────────────────────────────
_pg_chart Displays a single-series bar, column, or
line chart
_pg_chartms Displays a multiseries bar, column, or
line chart
_pg_chartpie Displays a pie chart
_pg_chartscatter Displays a scatter diagram for a single
series of data
_pg_chartscatterms Displays a scatter diagram for more than
one series of data
_pg_defaultchart Initializes all necessary variables in
the chart environment for a specified
chart type
_pg_initchart Initializes the presentation-graphics
library
2.6.2.2 Analyzing Presentation-Graphics Charts
These routines calculate default values for the specified graph type but do
not display the chart. The single-series versions analyze one set of data,
and the multiseries versions analyze several sets of data in the same chart
style.
Routine Use
────────────────────────────────────────────────────────────────────────────
_pg_analyzechart Analyzes a single series of data for a
bar, column, or line chart
_pg_analyzechartms Analyzes a multiseries of data for a
bar, column, or line chart
_pg_analyzepie Analyzes data for a pie chart
_pg_analyzescatter Analyzes a single series of data for a
scatter diagram
_pg_analyzescatterms Analyzes a multiseries of data for a
scatter diagram
2.6.2.3 Manipulating Presentation-Graphics Structures
These functions control low-level aspects of the presentation-graphics
package.
Routine Use
────────────────────────────────────────────────────────────────────────────
_pg_hlabelchart Writes text horizontally on the screen
_pg_vlabelchart Writes text vertically on the screen
_pg_getpalette Retrieves current colors, line styles,
fill patterns, and plot characters for
all presentation-graphics palettes
_pg_setpalette Sets current colors, line styles, fill
patterns, and plot characters for all
presentation-graphics palettes
_pg_resetpalette Sets current colors, line styles, fill
patterns, and plot characters to the
default values for the current screen
mode
_pg_getstyleset Retrieves the contents of the current
styleset
_pg_setstyleset Sets the contents of the current
styleset
_pg_resetstyleset Resets the contents of the current
styleset to the default value for the
current screen mode
_pg_getchardef Retrieves the current 8-by-8-pixel bit
map for a specified character
_pg_setchardef Sets the 8-by-8-pixel bit map for a
specified
character
2.7 Input and Output
The input and output (I/O) routines of the standard C library allow you to
read and write data to and from files and devices. In C, there are no
predefined file structures; all data items are treated as sequences of
bytes. The following three types of I/O functions are available:
1. Stream
2. Low-level
3. Console and port
The "stream" I/O functions treat data as a stream of individual characters.
By choosing among the many stream functions available, you can process data
in different sizes and formats, from single characters to large data
structures. Stream I/O also provides buffering, which can significantly
improve performance.
The "low-level" I/O routines do not perform buffering and formatting.
Instead, they invoke the operating system's input and output capabilities
directly. These routines let you access files and peripheral devices at a
more basic level than the stream functions.
The "console and port" I/O routines allow you to read or write directly to a
console (keyboard and screen) or an I/O port (such as a printer port). The
port I/O routines simply read and write data in bytes. With console I/O
routines, some additional options are available, such as detecting whether a
character has been typed at the console. You can also choose between echoing
characters to the screen as they are read or reading characters without
echoing.
The C library also provides a number of direct DOS I/O system call routines.
These are described in Section 2.14, "System Calls."
File I/O operations can be performed in two modes: text or binary. The
following section describes these modes and their use.
────────────────────────────────────────────────────────────────────────────
WARNING
Because stream routines are buffered and low-level routines are not, the two
types of routines are generally incompatible. You should use either stream
or low-level routines consistently for processing a given file.
────────────────────────────────────────────────────────────────────────────
2.7.1 Text and Binary Modes
Many C programs use data files for input and output. Under DOS and OS/2,
data files are normally processed in text mode. In this mode, each
carriage-return-line-feed (CR-LF) combination is translated into a single
line-feed character during input. During output, each line-feed character is
translated into a CR-LF combination.
Sometimes you may want to process a file without making those translations.
In these cases you use binary mode, which suppresses CR-LF translations.
You can control the file translation mode in the following ways:
■ To process a few selected files in binary mode, while retaining the
default text mode for most files, you can specify binary mode when you
open the selected files. The fopen routine opens a file in binary mode
when you specify the letter b in the access-mode string for the file.
The open routine opens a file in binary mode when you specify the
O_BINARY flag in the oflag argument. For more information about fopen
and open, see the reference description of each routine.
■ To process most or all files in binary mode, you can change the
default mode to binary. The global variable _fmode controls the
default translation mode, which is normally text. If you set _fmode to
O_BINARY, the default mode is binary except for stdaux and stdprn,
which are opened in binary mode by default.
You can change the value of _fmode in two ways:
1. Link with the file BINMODE.OBJ (supplied with Microsoft C). This
changes the initial setting of _fmode to the O_BINARY flag, causing
all files except stdin, stdout, and stderr to be opened in binary
mode.
2. Change the value of _fmode directly by setting it to the O_BINARY flag
in your program. This has the same effect as linking with BINMODE.OBJ.
You can still override the default mode (now binary) for a particular file
by opening it in text mode. Specify the letter t when using fopen, or
specify the O_TEXT flag when using open.
By default, the stdin, stdout, and stderr files are opened in text mode, and
the stdaux and stdprn files are opened in binary mode. The setmode routine
allows you to change these defaults or change the mode of a file after it
has been opened. See the reference description of setmode for details.
2.7.2 Stream Routines
Stream I/O functions handle data as a continuous stream of characters. To
use the stream functions, you must include the file STDIO.H in your program.
This file defines constants, types, and structures used in the stream
functions, and contains function declarations and macro definitions for the
stream routines.
When a file is opened for I/O using the stream functions, the opened file is
associated with a structure of type FILE (defined in STDIO.H) containing
basic information about the file. A pointer to the FILE structure is
returned when the stream is opened. Subsequent operations use this pointer
(also called the "stream pointer," or just "stream") to refer to the file.
The stream functions provide for buffered, formatted, or unformatted input
and output. When a stream is buffered, data that is read from or written to
the stream is collected in an intermediate storage location called a
"buffer". In write operations, the output buffer's contents are written to
the appropriate final location when the buffer is full, the stream is
closed, or the program terminates normally. The buffer is said to be
"flushed" when this occurs. In read operations, a block of data is placed in
the input buffer read from the buffer; when the input buffer is empty, the
next block of data is transferred into the buffer.
Buffering produces efficient I/O because the system can transfer a large
block of data in a single operation rather than performing an I/O operation
each time a data item is read from or written to a stream. However, if a
program terminates abnormally, output buffers may not be flushed, resulting
in loss of data.
Some of the constants defined in STDIO.H may be useful in your program. The
manifest constant EOF is defined to be the value returned at end-of-file.
NULL is the null pointer. FILE is the structure that maintains information
about a stream. BUFSIZ defines the default size of stream buffers, in bytes.
Routine Use
────────────────────────────────────────────────────────────────────────────
clearerr Clears the error indicator for a stream
fclose Closes a stream
fcloseall Closes all open streams
fdopen Associates a stream with an open file
handle
feof Tests for end-of-file on a stream
ferror Tests for error on a stream
fflush Flushes a stream
fgetc Reads a character from a stream
(function version)
fgetchar Reads a character from stdin (function
version)
fgetpos Gets the position indicator of a stream
fgets Reads a string from a stream
fileno Gets the file handle associated with a
stream
flushall Flushes all streams
fopen Opens a stream
fprintf Writes formatted data to a stream
fputc Writes a character to a stream (function
version)
fputchar Writes a character to stdout (function
version)
fputs Writes a string to a stream
fread Reads unformatted data from a stream
freopen Reassigns a FILE pointer to a new file
fscanf Reads formatted data from a stream
fseek Moves file position to a given location
fsetpos Sets the position indicator of a stream
_fsopen Opens a stream with file sharing
ftell Gets current file position
fwrite Writes unformatted data items to a
stream
getc Reads a character from a stream
getchar Reads a character from stdin
gets Reads a line from stdin
getw Reads a binary int item from a stream
printf Writes formatted data to stdout
putc Writes a character to a stream
putchar Writes a character to stdout
puts Writes a line to a stream
putw Writes a binary int item to a stream
rewind Moves file position to beginning of a
stream
rmtmp Removes temporary files created by
tmpfile
scanf Reads formatted data from stdin
setbuf Controls stream buffering
setvbuf Controls stream buffering and buffer
size
sprintf Writes formatted data to a string
sscanf Reads formatted data from a string
tempnam Generates a temporary file name in given
directory
tmpfile Creates a temporary file
tmpnam Generates a temporary file name
ungetc Places a character in the buffer
vfprintf Writes formatted data to a stream
vprintf Writes formatted data to stdout
vsprintf Writes formatted data to a string
2.7.2.1 Opening a Stream
A stream must be opened using the fdopen, fopen, freopen, or _fsopen
function before input and output can be performed on that stream. When
opening a stream, the named stream can be opened for reading, writing, or
both, and can be opened in either text or binary mode.
The fdopen, fopen, freopen, and _fsopen functions return a FILE pointer. You
normally assign the pointer value to a variable and use the variable to
refer to the opened stream. For instance, if your program contains the lines
FILE *infile
infile = fopen ("test.dat", "r");
you can use the FILE pointer variable infile to refer to the stream.
2.7.2.2 Using Predefined Stream Pointers
When a program begins execution, the C start-up code automatically opens
several streams: standard input, standard output, and standard error. By
default, the standard input, standard output, and standard error streams are
directed to the console (keyboard and screen). This means that when a
program expects input from the "standard input," it receives that input from
the console. Similarly, a program that writes to the "standard output"
prints its data to the console. Error messages generated by the library
routines are sent to the "standard error," meaning that error messages
appear on the user's console.
Under DOS, two additional streams are opened: standard auxiliary and
standard print. (These streams are not available in OS/2.) The assignment of
standard auxiliary and standard print depends on the machine configuration.
These streams usually refer to the first serial port and a printer port, but
those ports may not be available on some systems. Be sure to check your
machine configuration before using these streams.
You can refer to the standard streams with the following predefined stream
pointers:
Pointer Stream
────────────────────────────────────────────────────────────────────────────
stdin Standard input
stdout Standard output
stderr Standard error
stdaux Standard auxiliary (DOS only)
stdprn Standard print (DOS only)
You can use these pointers in any function that requires a stream pointer as
an argument. Some functions, such as getchar and putchar, are designed to
use stdin or stdout automatically. The pointers stdin, stdout, stderr,
stdaux, and stdprn are constants, not variables; do not try to assign them a
new stream pointer value.
DOS and OS/2 allow you to redirect a program's standard input and standard
output at the operating-system command level. OS/2 also allows you to
redirect a program's standard error. See your operating system user's manual
for a complete discussion of redirection.
Within your program, you can use freopen to redirect stdin, stdout, stderr,
stdaux, or stdprn so that it refers to a disk file or to a device. See the
reference description of freopen for more details.
2.7.2.3 Controlling Stream Buffering
As mentioned earlier, stream routines can use in-memory buffers to speed I/O
operations. Files opened using the stream routines are buffered by default,
except for stdaux and stdprn, which are normally unbuffered. The stdout and
stderr streams are flushed whenever they are full or (if you are writing to
a character device) after each library call.
By using the setbuf or setvbuf function, you can cause a stream to be
unbuffered, or you can associate a buffer with an unbuffered stream. Buffers
allocated by the system are not accessible to you, but buffers allocated
with setbuf or setvbuf refer to arrays in your program and can be
manipulated. Buffers can be any size up to 32,767 bytes. This size is set by
the manifest constant BUFSIZ in STDIO.H if you use seftbuf; if you use
setvbuf, you can set the size of the buffer yourself. (See the descriptions
of setbuf and setvbuf in the reference section for more details.)
────────────────────────────────────────────────────────────────────────────
NOTE
These routines affect only buffers created by C library routines. They have
no effect on buffers created by the operating system.
────────────────────────────────────────────────────────────────────────────
2.7.2.4 Closing Streams
The fclose and fcloseall functions close a stream or streams. The fclose
routine closes a single specified stream; fcloseall closes all open streams
except stdin, stdout, stderr, stdaux, and stdprn. If your program does not
explicitly close a stream, the stream is automatically closed when the
program terminates. How-ever, it is a good practice to close a stream when
your program is finished with it, as the number of streams that can be open
at a given time is limited.
2.7.2.5 Reading and Writing Data
The stream functions allow you to transfer data in a variety of ways. You
can read and write binary data (a sequence of bytes), or specify reading and
writing by characters, lines, or more complicated formats.
Reading and writing operations on streams always begin at the current
position of the stream, known as the "file pointer" for the stream. The file
pointer is changed to reflect the new position after a read or write
operation takes place. For example, if you read a single character from a
stream, the file pointer is increased by one byte so that the next operation
begins with the first unread character. If a stream is opened for appending,
the file pointer is automatically positioned at the end of the file before
each write operation.
The fseek and fsetpos functions allow you to position the file pointer
anywhere in a file. The next operation occurs at the position you specified.
The rewind routine positions the file pointer at the beginning of the file.
Use the ftell or fgetpos routine to determine the current position of the
file pointer.
The feof macro detects an end-of-file condition on a stream. Once the
end-of-file indicator is set, it remains set until the file is closed, or
until clearerr, fseek, fsetpos, or rewind is called.
Streams associated with a character-oriented device (such as a console) do
not have file pointers. Data coming from or going to a console cannot be
accessed randomly. Routines that set or get the file-pointer position (such
as fseek, fgetpos, fsetpos, ftell, or rewind) have undefined results if used
on a stream associated with a character-oriented device.
2.7.2.6 Detecting Errors
When an error occurs in a stream operation, an error indicator for the
stream is set. You can use the ferror macro to test the error indicator and
determine whether an error has occurred. Once an error has occurred, the
error indicator for the stream remains set until the stream is closed, or
until you explicitly clear the error indicator by calling clearerr or
rewind.
2.7.3 Low-Level Routines
Low-level input and output calls do not buffer or format data. Declarations
for the low-level functions are given in the include files IO.H, FCNTL.H,
SYS\TYPES.H, and SYS\STAT.H. Unlike the stream functions, low-level
functions do not require the include file STDIO.H. However, some common
constants are defined in STDIO.H; for example, the end-of-file indicator
(EOF) may be useful. If your program requires these constants, you must
include STDIO.H.
Routine Use
────────────────────────────────────────────────────────────────────────────
close Closes a file
creat Creates a file
dup Creates a second handle for a file
dup2 Reassigns a handle to a file
eof Tests for end-of-file
lseek Repositions file pointer to a given
location
open Opens a file
read Reads data from a file
sopen Opens a file for file sharing
tell Gets current file-pointer position
umask Sets default file-permission mask
write Writes data to a file
2.7.3.1 Opening a File
You must open a file before performing I/O functions on it. The open
function opens a file; it can also create the file when opening it. In OS/2
and DOS versions 3.0 and later, you can use sopen to open a file with
file-sharing attributes. The creat function can create and open a file.
The file can be opened for reading, writing, or both, and opened in either
text or binary mode (see Section 2.7.1, "Text and Binary Modes"). The
include file FCNTL.H must be included when opening a file, as it contains
definitions for flags used in open. In some cases, the files SYS\TYPES.H and
SYS\STAT.H must also be included; for more information, see the reference
description for the open function.
These functions return a file handle, which is normally assigned to an
integer variable. You use the variable to refer to the opened file.
2.7.3.2 Reading and Writing Data
Use the read and write routines to read and write to files. These operations
begin at the current position in the file. The current position is updated
each time a read or write operation occurs.
The lseek function allows you to place the file pointer anywhere in the
file. The next operation occurs at the position you specified. The tell
function indicates the current position of the file pointer. The eof routine
tests for the end of the file.
Low-level I/O routines set the errno variable when an error occurs. Chapter
3, "Global Variables and Standard Types," describes errno.
Character-oriented devices, such as the console, do not have file pointers.
The lseek and tell routines have undefined results if used on a handle
associated with a device.
2.7.3.3 Closing Files
The close function closes an open file. Open files are automatically closed
when a program terminates. However, it is a good practice to close a file
when your program is finished with it, as there is a limit to the number of
files that can be open at one time.
2.7.3.4 Using Predefined Handles
When a program begins execution, three files are automatically opened:
standard input, standard output, and standard error. In DOS, two additional
files are opened: standard auxiliary and standard print. (These files are
not available in OS/2.)
Low-level routines can access these files using the following predefined
handles:
Stream Handle
────────────────────────────────────────────────────────────────────────────
stdin 0
stdout 1
stderr 2
stdaux (DOS only) 3
stdprn (DOS only) 4
You can use these file handles without previously opening the files. The
files are opened and the handles are assigned when the program starts.
The dup and dup2 functions allow you to assign multiple handles for the same
file. These functions are typically used to associate the predefined file
handles with different files.
In DOS and OS/2, you can redirect the standard input and standard output at
the operating-system command level. OS/2 also allows you to redirect the
standard error. See your operating system user's manual for a complete
discussion of redirection.
2.7.4 Console and Port I/O
The console and port I/O routines are implemented as functions and are
declared in the include file CONIO.H. These functions perform reading and
writing operations on your console or on the specified port. The cgets,
cscanf, getch, getche, and kbhit routines take input from the console, while
cprintf, cputs, putch, and ungetch write to the console. The input or output
of these functions can be redirected.
Routine Use
────────────────────────────────────────────────────────────────────────────
cgets Reads a string from the console
cprintf Writes formatted data to the console
cputs Writes a string to the console
cscanf Reads formatted data from the console
getch Reads a character from the console
getche Reads a character from the console and
echoes it
inp Reads one byte from the specified I/O
port
inpw Reads a two-byte word from the specified
I/O port
kbhit Checks for a keystroke at the console
outp Writes one byte to the specified I/O
port
outpw Writes a two-byte word to the specified
I/O port
putch Writes a character to the console
ungetch "Ungets" the last character read from
the console so that it becomes the next
character read
────────────────────────────────────────────────────────────────────────────
NOTE
Programs that need only run under DOS can also use a number of direct DOS
I/O system calls ( _dos_open, _dos_read, _dos_close, etc.) These are
described in detail in Section 2.14, "System Calls."
────────────────────────────────────────────────────────────────────────────
The console or port does not have to be opened or closed before I/O is
performed, so there are no open or close routines in this category. The port
I/O routines inp and outp read or write one byte at a time from the
specified port. The inpw and outpw routines read and write two-byte words,
respectively.
The console I/O routines allow reading and writing of strings (cgets and
cputs), formatted data (cscanf and cprintf), and characters. Several options
are available when reading and writing characters.
The putch routine writes a single character to the console. The getch and
getche routines read a single character from the console; getche echoes the
character back to the console, while getch does not. The ungetch routine
"ungets" the last character read; the next read operation on the console
begins with the "ungotten" character.
The kbhit routine determines whether a key has been struck at the console.
This routine allows you to test for keyboard input before you attempt to
read from the console.
────────────────────────────────────────────────────────────────────────────
NOTE
The console I/O routines are not compatible with stream or low-level library
routines and should not be used with them.
────────────────────────────────────────────────────────────────────────────
2.8 Internationalization
Internationalization routines are useful for creating different versions of
a program for international markets. These routines are declared in the
header file LOCALE.H, except for strftime, which is declared in TIME.H.
Routine Use
────────────────────────────────────────────────────────────────────────────
localeconv Sets a structure with appropriate values
for formatting numeric quantities
setlocale Selects the appropriate locale for the
program
strcoll Compares strings using locale-specific
information
strftime Formats a date and time string
strxfrm Transforms a string based on
locale-specific
information
2.9 Math
The math routines allow you to perform common mathematical calculations. All
math routines work with floating-point values and therefore require
floating-point support (see Section 1.8, "Floating-Point Support").
The math library provides two versions of some routines. The first version
of the routine supports double arguments and return values. The second
version supports an 80-bit data type, allowing the routine to take long
double arguments and return a long double value. The second version usually
has the same name with the suffix l. For instance, the acos routine supports
double arguments and return values, while acosl supports long double
arguments and return values.
Routines which support long double values are not available when you compile
with the /Fpa (alternate math) compiler option. The same is true of the
_clear 87, _control87, and _status87 routines.
Most math declarations are in the include file MATH.H. However, the
_clear87, _control87, _fpreset, and _status87 routines are defined in
FLOAT.H, the abs and labs functions are defined in MATH.H and STDLIB.H, and
the div and ldiv routines are declared in STDLIB.H.
Routine Use
────────────────────────────────────────────────────────────────────────────
acos, acosl Calculate the arccosine
asin, asinl Calculate the arcsine
atan, atanl Calculate the arctangent
atan2, atan2l Calculate the arctangent
bessel Calculates Bessel functions
cabs, cabsl Find the absolute value of a complex
number
ceil, ceill Find the integer ceiling
_clear87 Gets and clears the floating-point
status word
_control87 Gets the old floating-point control word
and sets a new control-word value
cos, cosl Calculate the cosine
cosh, coshl Calculate the hyperbolic cosine
dieeetomsbin Converts IEEE double-precision number to
Microsoft (MS) binary format
div Divides one integer by another,
returning the quotient and remainder
dmsbintoieee Converts Microsoft binary
double-precision number to IEEE format
exp, expl Calculate the exponential function
fabs, fabsl Find the absolute value
fieeetomsbin Converts IEEE single-precision number to
Microsoft binary format
floor, floorl Find the largest integer less than or
equal to the
argument
fmod, fmodl Find the floating-point remainder
fmsbintoieee Converts Microsoft binary
single-precision number to IEEE format
_fpreset Reinitializes the floating-point-math
package
frexp, frexpl Calculate an exponential value
hypot, hypotl Calculate the hypotenuse of right
triangle
ldexp, ldexpl Calculate the product of the argument
and 2exp
ldiv Divides one long integer by another,
returning the quotient and remainder
log, logl Calculate the natural logarithm
log10, log10l Calculate the base-10 logarithm
_lrotl, _lrotr Shift an unsigned long int item left (
_lrotl) or right ( _lrotr)
matherr, _matherrl Handle math errors
max, min Return the larger or smaller of two
values
modf, modfl Break down the argument into integer and
fractional parts
pow, powl Calculate a value raised to a power
rand Gets a pseudorandom number
_rotl, _rotr Shift an unsigned int item left ( _rotl)
or right
( _rotr)
sin, sinl Calculate the sine
sinh, sinhl Calculate the hyperbolic sine
sqrt, sqrtl Find the square root
srand Initializes a pseudorandom series
_status87 Gets the floating-point status word
tan, tanl Calculate the tangent
tanh, tanhl Calculate the hyperbolic tangent
The bessel routine does not correspond to a single function, but to twelve
functions named j0, j1, jn, y0, y1, yn, _j0l, _j1l, _jnl, _y0l, _y1l,
and _ynl.
The matherr and _matherrl routines are invoked by the math functions when
errors occur. The matherr routine handles functions that return a double
value and _matherrl handles routines that return a long double.
These routines are defined in the library, but you can redefine them for
different error-handling. The user-defined function, if given, must follow
the rules given in the reference description of matherr and _matherrl.
You are not required to supply a definition for the matherr routines. If no
definition is present, the default error returns for each routine are used.
The reference description of each routine describes that routine's error
returns.
2.10 Memory Allocation
The memory-allocation routines allow you to allocate, free, and reallocate
blocks of memory. Memory-allocation routines are declared in the include
file MALLOC.H.
Routine Use
────────────────────────────────────────────────────────────────────────────
alloca Allocates a block of memory from the
program's stack
_bfreeseg Frees a based heap
_bheapseg Allocates a based heap
calloc, _bcalloc, _fcalloc, Allocate storage for an array
_ncalloc
_expand, _bexpand, _fexpand, Expand or shrink a block of memory
_nexpand without moving its location
free, _bfree, _ffree, _nfree Free an allocated block
_freect Returns approximate number of items of
given size that could be allocated in
the near heap
halloc Allocates storage for huge array
_heapadd, _bheapadd Add memory to a heap
_heapchk, _bheapchk, _fheapchk Check a heap for consistency
, _nheapchk
_heapmin, _bheapmin, Release unused memory in a heap
_fheapmin, _nheapmin
_heapset, _bheapset, _fheapset Fill free heap entries with a specified
, _nheapset value
_heapwalk, _bheapwalk, Return information about each entry in a
_fheapwalk, _nheapwalk heap
hfree Frees a block allocated by halloc
malloc, _bmalloc, _fmalloc, Allocate a block of memory
_nmalloc
_memavl Returns approximate number of bytes
available for allocation in the near
heap
_memmax Returns size of largest contiguous free
block in the near heap
_msize, _bmsize, _fmsize, Return size of an allocated block
_nmsize
realloc, _brealloc, _frealloc, Reallocate a block to a new size
_nrealloc
stackavail Returns size of stack space available
for allocation with alloca
Some memory-management routines, such as malloc, are available in different
versions that begin with _b, _f, or _n. These variations are described in
the following section.
The malloc and free routines allocate and free memory space, respectively,
while a program runs. The malloc routine allocates memory from the "heap,"
which is a pool of memory not otherwise used by your program. In tiny-,
small-, and medium-model programs, the heap consists of unused memory in
your program's default data segment. In compact-, large-, and huge-model
programs, it is unused memory outside the default data segment.
The malloc and free routines satisfy the memory-allocation requirements of
most programs. More specialized memory-management routines are discussed
below.
The realloc and _expand routines can expand or shrink an allocated memory
block. They behave differently in cases in which there is not enough room to
expand the block in its current location. In this case, realloc moves the
block as needed, but _expand does not.
The calloc routine allocates memory for an array and initializes every byte
in the allocated block to 0.
The halloc routine is similar to calloc, except that it can allocate memory
for a huge array (one that exceeds 64K in size). This routine is useful when
you need a very large data object, or if you need to return allocated memory
to the operating system for subsequent calls to the spawn family of
functions.
2.10.1 Near and Far Heaps
As mentioned in the previous section, heap memory can reside inside or
outside your program's default data segment, depending on what memory model
your program uses. When it lies inside the default data segment, the heap is
called the "near heap," since it can be accessed with near pointers. The
"far heap" is memory that spans one or more segments outside the default
data segment. The far heap can be accessed only with far pointers.
In various memory models, malloc automatically allocates memory from the
near heap or far heap, as appropriate. The C library also includes near and
far versions of malloc, free, and other memory-management routines, which
allow you to specify the near and far heaps explicitly. These have the same
names as standard memory routines, but are preceded by _n (for near) or _f
(for far).
For instance, the _nmalloc routine always allocates memory from the near
heap and returns a near pointer, no matter which memory model your program
uses. Use _nfree to release memory allocated with _nmalloc.
Similarly, _fmalloc always allocates memory from the far heap and returns a
far pointer, regardless of memory model. Use the _ffree routine to release
memory allocated with _fmalloc.
2.10.2 Based Heaps
You can also allocate memory from a "based heap," which is a single segment
that lies outside the default data segment. Based-heap routines generally
use the same names as standard memory routines, but begin with _b. For
instance, _bmalloc allocates a memory block from the based heap and _bfree
frees the block.
Based heaps offer the following advantages:
■ Localized data. Based heaps allow you to group related data in a
single segment. This can simplify the management of related data. In
OS/2, based heaps can also minimize the risk of general protection
faults and improve performance.
■ Faster pointer arithmetic. Although the based heap lies in the far
data segment, pointers to its data items are the same size as near
pointers. Thus, pointer arithmetic on items in a based heap is faster
than pointer arithmetic on items in the far heap.
The _bheapseg routine allocates a based heap segment, from which you can
then allocate blocks of memory. You can call _bheapseg more than once to
allocate as many based-heap segments as needed (within the confines of
available memory).
The _bfreeseg routine frees a based-heap segment. This routine frees every
block in the based-heap segment, whether or not you previously freed the
blocks individually.
────────────────────────────────────────────────────────────────────────────
NOTE
Near- , far- , and based-heap calls are not ANSI compatible and will make
your program less portable.
────────────────────────────────────────────────────────────────────────────
2.11 Process and Environment Control
The process-control routines allow you to start, stop, and manage processes
from within a program. Environment-control routines allow you to get and
change information about the operating-system environment.
A "process" is a program being executed by the operating system. It consists
of the program's code and data, plus information about the process, such as
the number of open files. Whenever you execute a program at the
operating-system level, you start a process.
All process-control functions except signal are declared in the include file
PROCESS.H. The signal function is declared in SIGNAL.H. The abort, exit, and
system functions are also declared in the STDLIB.H include file. The
environment-control routines (getenv and putenv) are declared in STDLIB.H.
Routine Use
────────────────────────────────────────────────────────────────────────────
abort Aborts a process without flushing
buffers or calling functions registered
by atexit and onexit
assert Tests for logic error
atexit Schedules routines for execution at
program
termination
_beginthread Creates an execution thread (OS/2 only)
_cexit Performs the exit termination procedures
(such as flushing buffers) and returns
control to the calling program
_c_exit Performs the _exit termination
procedures and returns control to the
calling program
cwait Suspends the calling process until a
specified child process terminates (OS/2
only)
_endthread Terminates an execution thread (OS/2
only)
execl Executes child process with argument
list
execle Executes child process with argument
list and given environment
execlp Executes child process using PATH
variable and argument list
execlpe Executes child process using PATH
variable, given environment, and
argument list
execv Executes child process with argument
array
execve Executes child process with argument
array and given environment
execvp Executes child process using PATH
variable and argument array
execvpe Executes child process using PATH
variable, given environment, and
argument array
exit Calls functions registered by atexit and
onexit, then flushes all buffers and
closes all open files before terminating
the process
_exit Terminates process without processing
atexit or onexit functions or flushing
buffers
getenv Gets the value of an environment
variable
getpid Gets process ID number
longjmp Restores a saved stack environment
onexit Schedules routines for execution at
program
termination
_pclose Waits for a child command and closes a
pipe on the associated stream
perror Prints error message
_pipe Creates a pipe
_popen Creates a pipe and asynchronously
executes a child copy of the command
processor
putenv Adds or changes the value of an
environment
variable
raise Sends a signal to the calling process
setjmp Saves a stack environment
signal Handles an interrupt signal
spawnl Executes child process with argument
list
spawnle Executes child process with argument
list and given environment
spawnlp Executes child process using PATH
variable and argument list
spawnlpe Executes child process using PATH
variable, given environment, and
argument list
spawnv Executes child process with argument
array
spawnve Executes child process with argument
array and given environment
spawnvp Executes child process using PATH
variable and argument array
spawnvpe Executes child process using PATH
variable, given environment, and
argument array
system Executes an operating system command
wait Suspends the calling process until any
of the caller's immediate child
processes terminate (OS/2 only)
The atexit and onexit routines create a list of functions to be executed
when the calling program terminates. The only difference between the two is
that atexit is part of the ANSI standard. The onexit function is offered for
compatibility with previous versions of Microsoft C.
The _exit routine terminates a process immediately, whereas exit terminates
the process only after flushing buffers and calling any functions previously
registered by atexit and onexit. The _cexit and _c_exit routines are
identical to exit and _exit, respectively, except that they return control
to the calling program without terminating the process.
The setjmp and longjmp routines save and restore a stack environment. These
allow you to execute a nonlocal goto.
The exec and spawn routines start a new process called the "child" process.
The difference between the exec and spawn routines is that the spawn
routines are capable of returning control from the child process to its
caller (the "parent" process). Both the parent process and the child process
are present in memory (unless P_OVERLAY is specified). In the exec routines,
the child process overlays the parent process, so returning control to the
parent process is impossible (unless an error occurs when attempting to
start execution of the child process).
There are eight forms each of the spawn and exec routines (see Table 2.1).
The differences among the forms involve the method of locating the file to
be executed as the child process, the method for passing arguments to the
child process, and the method of setting the environment.
Passing an argument list means that the arguments to the child process are
listed separately in the exec or spawn call. Passing an argument array means
that the arguments are stored in an array, and a pointer to the array is
passed to the child process. The argument-list method is typically used when
the number of arguments is constant or is known at compile time. The
argument-array method is useful when the number of arguments must be
determined at run time.
Several process-control routines take advantage of the multitasking
capability of OS/2. The _beginthread and _endthread routines create and
terminate execution threads. The cwait and wait routines suspend the calling
process until one child process terminates. The _pipe, _popen, and _pclose
routines create and manipulate pipes, which link processes for sequential
execution.
Table 2.1 Forms of the spawn and exec Routines
╓┌───────────────────┌──────────────────┌────────────────────┌───────────────►
Argument-Passing
Routines Locating the File Convention Environment
Settings
─────────────────────────────────────────────────────────────────────────────
execl, spawnl Do not use PATH Argument list Inherited from
parent
execle, spawnle Do not use PATH Argument list Pointer to
environment table
for child process
passed as last
argument
execlp, spawnlp Use PATH Argument list Inherited from
parent
Argument-Passing
Routines Locating the File Convention Environment
Settings
parent
execlpe, spawnlpe Use PATH Argument list Pointer to
environment table
for child process
passed as last
argument
execv, spawnv Do not use PATH Argument array Inherited from
parent
execve, spawnve Do not use PATH Argument array Pointer to
environment table
for child process
passed as last
argument
execvp, spawnvp Use PATH Argument array Inherited from
Argument-Passing
Routines Locating the File Convention Environment
Settings
execvp, spawnvp Use PATH Argument array Inherited from
parent
execvpe, spawnvpe Use PATH Argument array Pointer to
environment table
for child process
passed as last
argument
─────────────────────────────────────────────────────────────────────────────
The assert macro is typically used to test for logic errors. It prints a
message when a given "assertion" fails to hold true. Defining the identifier
NDEBUG to any value causes occurrences of assert to be removed from the
source file, thus allowing you to turn off assertion checking without
modifying the source file.
2.12 Searching and Sorting
Search and sort routines provide binary-search, linear-search, and
quick-sort capabilities. They are all declared in SEARCH.H.
Routine Use
────────────────────────────────────────────────────────────────────────────
bsearch Performs binary search
lfind Performs linear search for given value
lsearch Performs linear search for given value,
which is added to array if not found
qsort Performs quick sort
2.13 String Manipulation
The string functions are declared in the include file STRING.H. They allow
you to compare strings, copy them, search for strings and characters, and
perform various other operations.
Routines beginning with _f are model-independent versions of the
corresponding routines and are useful in mixed-model programs. These
routines can be called from any point in the program, regardless of which
model is being used.
Routine Use
────────────────────────────────────────────────────────────────────────────
strcat, _fstrcat Append one string to another
strchr, _fstrchr Find first occurrence of a given
character in a string
strcmp, _fstrcmp Compare two strings
strcpy, _fstrcpy Copy one string to another
strcspn, _fstrcspn Find first occurrence of a character
from a given character set in a string
strdup, _fstrdup, _nstrdup Duplicate a string
strerror Maps an error number to a message string
_strerror Maps a user-defined error message to a
string
stricmp, _fstricmp Compare two strings without regard to
case
strlen, _fstrlen Find length of string
strlwr, _fstrlwr Convert string to lowercase
strncat, _fstrncat Append characters of a string
strncmp, _fstrncmp Compare characters of two strings
strncpy, _fstrncpy Copy characters of one string to another
strnicmp, _fstrnicmp Compare characters of two strings
without regard
to case
strnset, _fstrnset Set characters of a string to a given
character
strpbrk, _fstrpbrk Find first occurrence of a character
from one string in another
strrchr, _fstrrchr Find last occurrence of a given
character in string
strrev, _fstrrev Reverse string
strset, _fstrset Set all characters of a string to a
given character
strspn, _fstrspn Find first substring from a given
character set in a string
strstr, _fstrstr Find first occurrence of a given string
in another string
strtok, _fstrtok Find next token in a string
strupr, _fstrupr Convert a string to uppercase
All string functions work on null-terminated character strings. When working
with character arrays that do not end with a null character, you can use the
buffer-manipulation routines, described in Section 2.1.
2.14 System Calls
The following routines give access to IBM-PC BIOS interrupts and DOS system
calls. Except for the FP_OFF, FP_SEG, and segread routines, these routines
are for DOS application programs only; they do not work under OS/2.
2.14.1 BIOS Interface
The functions in this category provide direct access to the BIOS interrupt
services. They are all declared in BIOS.H.
Routine Use
────────────────────────────────────────────────────────────────────────────
_bios_disk Issues service requests for both hard
and floppy disks, using INT 0x13
_bios_equiplist Performs an equipment check, using INT
0x11
_bios_keybrd Provides access to keyboard services,
using
INT 0x16
_bios_memsize Obtains information about available
memory, using INT 0x12
_bios_printer Performs printer output services, using
INT 0x17
_bios_serialcom Performs serial communications tasks,
using
INT 0x14
_bios_timeofday Provides access to system clock, using
INT 0x1A
────────────────────────────────────────────────────────────────────────────
NOTE
BIOS routines are hardware dependent. Some of them may not work as expected
on machines whose hardware differs from the IBM PC.
────────────────────────────────────────────────────────────────────────────
2.14.2 DOS Interface
These routines are implemented as functions and declared in DOS.H.
Routine Use
────────────────────────────────────────────────────────────────────────────
bdos Invokes DOS system call; uses only DX
and AL registers
_chain_intr Chains one interrupt handler to another
_disable Disables interrupts
_dos_allocmem Allocates a block of memory, using DOS
system call 0x48
_dos_close Closes a file, using DOS system call
0x3E
_dos_creat Creates a new file and erases any
existing file having the same name,
using DOS system call 0x3C
_dos_creatnew Creates a new file and returns an error
if a file having the same name exists,
using DOS system
call 0x5B
_dos_findfirst Finds first occurrence of a given file,
using DOS system call 0x4E
_dos_findnext Finds subsequent occurrences of a given
file, using DOS system call 0x4F
_dos_freemem Frees a block of memory, using DOS
system
call 0x49
_dos_getdate Gets the system date, using DOS system
call 0x2A
_dos_getdiskfree Gets information on a disk volume, using
DOS system call 0x36
_dos_getdrive Gets the current default drive, using
DOS system call 0x19
_dos_getfileattr Gets current attributes of a file or
directory, using DOS system call 0x43
_dos_getftime Gets the date and time a file was last
written, using DOS system call 0x57
_dos_gettime Gets the current system time, using DOS
system
call 0x2C
_dos_getvect Gets the current value of a specified
interrupt vector, using DOS system call
0x35
_dos_keep Installs terminate-and-stay-resident
(TSR) programs using DOS system call
0x31
_dos_open Opens an existing file, using DOS system
call 0x3D
_dos_read Reads a file, using DOS system call 0x3F
_dos_setblock Changes the size of a previously
allocated block, using DOS system call
0x4A
_dos_setdate Sets the current system date, using DOS
system
call 0x2B
_dos_setdrive Sets the default disk drive, using DOS
system
call 0x0E
_dos_setfileattr Sets the current attributes of a file,
using DOS system call 0x43
_dos_setftime Sets the date and time that the
specified file was last written, using
DOS system call 0x57
_dos_settime Sets the system time, using DOS system
call 0x2D
_dos_setvect Sets a new value for the specified
interrupt vector, using DOS system call
0x25
_dos_write Sends output to a file, using DOS system
call 0x40
dosexterr Obtains in-depth error information from
DOS system call 0x59
_enable Enables interrupts
FP_OFF Returns offset portion of a far pointer
(OS/2
and DOS)
FP_SEG Returns segment portion of a far pointer
(OS/2
and DOS)
_harderr Establishes a hardware error handler
_hardresume Returns to DOS after a hardware error
_hardretn Returns to the application after a
hardware error
int86 Invokes DOS interrupts
int86x Invokes DOS interrupts with segment
register values
intdos Invokes DOS system call using registers
other than DX and AL
intdosx Invokes DOS system call using registers
other than DX and AL with segment
register values
segread Returns current values of segment
registers (OS/2 and DOS)
The _harderr routine is used to define a hardware-error interrupt handler.
The _hardresume and _hardretn routines are used within a hardware error
handler to define the return from the error.
The dosexterr function obtains and stores the error information returned by
DOS system call 0x59 (extended error handling). This function is provided
for use with DOS versions 3.0 and later.
The bdos routine is useful for invoking DOS calls that use either or both of
the DX (DH/DL) and AL registers for arguments. However, bdos should not be
used to invoke system calls that return an error code in AX if the carry
flag is set; since your program cannot detect whether the carry flag is set,
it cannot determine whether the value in AX is a legitimate value or an
error value. In this case, the intdos routine should be used instead, since
it allows the program to detect whether the carry flag is set. The intdos
routine can also be used to invoke DOS calls that use registers other than
DX and AL.
The intdosx routine is similar to the intdos routine, but is used when ES is
required by the system call, when DS must contain a value other than the
default data segment (for instance, when a far pointer is used), or when
making the system call in a large-model program. When calling intdosx, give
an argument that specifies the segment values to be used in the call.
The int86 routine can be used to invoke any interrupt. The int86x routine is
similar; however, like the intdosx routine, it is designed to work with
large-model programs and far items, as described in the preceding paragraph.
The FP_OFF and FP_SEG routines allow easy access to the segment and offset
portions of a far pointer value. FP_OFF and FP_SEG are implemented as macros
and defined in DOS.H. You can use these macros in OS/2 as well as DOS.
The segread routine returns the current values of the segment registers.
This routine is typically used with the intdosx and int86x routines to
obtain the correct segment values.
The _chain_intr routine is useful for chaining interrupt handlers together.
The _enable routine enables interrupts, while the _disable routine disables
interrupts.
The routines prefixed with _dos_ are all direct system interfaces that use
the system calls noted above. More detailed information on these system
calls can be found in the MS-DOS Encyclopedia (Duncan, ed.; Redmond, WA:
Microsoft Press, 1988)or the Programmer's PC Sourcebook (Hogan; Redmond, WA:
Microsoft Press, 1988).
────────────────────────────────────────────────────────────────────────────
NOTE
The DOS interface I/O routines are generally incompatible with console,
low-level, and stream I/O routines. Do not mix different types of I/O
routines in the same source file.
────────────────────────────────────────────────────────────────────────────
2.15 Time
The time functions allow you to obtain the current time, then convert and
store it according to your particular needs. The current time is always
taken from the system time.
Routine Use
────────────────────────────────────────────────────────────────────────────
asctime Converts time from type struct tm to a
character string
clock Returns the elapsed CPU time for a
process
ctime Converts time from a long integer to a
character string
difftime Computes the difference between two
times
ftime Puts current system time in variable of
type
struct tm
gmtime Converts time from integer to struct tm
localtime Converts time from integer to struct tm
with local correction
mktime Converts time to a calendar value
_strdate Returns the current system date as a
string
strftime Formats a date and time string
_strtime Returns the current system time as a
string
time Gets current system time as a long
integer
tzset Sets external time variables from the
environment time variable
utime Sets file-modification time
The time and ftime functions return the current time as the number of
seconds elapsed since midnight Universal Coordinated Time (UTC) on January
1, 1970. This value can be converted, adjusted, and stored in a variety of
ways by using the asctime, ctime, gmtime, localtime, and mktime functions.
The utime function sets the modification time for a specified file, using
either the current time or a time value stored in a structure.
The clock function returns the elapsed CPU time for the calling process.
The ftime function requires two files: SYS\TYPES.H and SYS\TIMEB.H. It is
declared in SYS\TIMEB.H. The utime function also requires two include files:
SYS\TYPES.H and SYS\UTIME.H. It is declared in SYS\UTIME.H. The remainder of
the time functions are declared in the include file TIME.H.
When you want to use ftime or localtime to make adjustments for local time,
you must define an environment variable named TZ. Section 3.2, which
describes the global variables daylight, timezone, and tzname, includes a
discussion of the TZ variable. TZ is also described on the tzset reference
page in Part 2 of this book.
The _strdate and _strtime routines return strings containing the current
date and time, respectively, in the DOS and OS/2 date and time format rather
than in the XENIX-style formats.
The stfrtime function is useful for creating international versions of a
program. See Section 2.8, "Internationalization."
2.16 Variable-Length Argument Lists
The va_arg, va_end, and va_start routines are macros that provide a portable
way to access the arguments to a function when the function takes a variable
number of arguments. Two versions of the macros are available: the macros
defined in the VARARG.H include file, which are compatible with the UNIX
System V definition, and the macros defined in STDARG.H, which conform to
the ANSI C standard.
Routine Use
────────────────────────────────────────────────────────────────────────────
va_arg Retrieves argument from list
va_end Resets pointer
va_start Sets pointer to beginning of argument
list
For more information on the differences between the two versions and for an
explanation of how to use the macros, see their descriptions in Part 2 of
this book.
Chapter 3 Global Variables and Standard Types
────────────────────────────────────────────────────────────────────────────
The Microsoft C Run-Time Library contains definitions for a number of
variables and standard types used by library routines. You can access these
variables and types by including in your program the files in which they are
declared, or by giving appropriate declarations in your program, as shown in
the following sections.
3.1 _amblksiz
The _amblksiz variable controls memory heap granularity.
It is declared in the MALLOC.H include file as follows:
extern unsigned int _amblksiz;
The _amblksiz variable controls the amount of memory used in the heap for
dynamic memory allocation.
Memory space is always requested from the operating system in blocks
containing _amblksiz bytes. The first time a program calls a
memory-allocation function such as malloc, the operating system allocates a
block of heap memory. The size of this block is defined by _amblksiz, which
has a default value of 8K (8,192 bytes).
Later memory requests are satisfied from the original block. When that block
is exhausted, another block of _amblksiz bytes is allocated. If your C
program allocates a block larger than _amblksiz, multiple blocks that are
each of size _amblksiz are allocated until the request is satisfied.
To change the size of the default memory block, assign the desired size to
the _amblksiz variable, as in the following example:
_amblksiz = 2048;
The heap allocator always rounds the operating-system request to the nearest
power of 2 greater than or equal to _amblksiz. The above statement allocates
memory in multiples of 2K (2,048 bytes).
Fewer system calls are required if you set _amblksiz to a large value, but
your program may use more memory than needed. If program speed is important,
set _amblksiz to a large value. If size is important, set _amblksiz to a
smaller value.
Note that adjusting the value of _amblksiz affects allocation in the near,
far, and based heaps. The value of _amblksiz has no effect on huge memory
blocks (those allocated with halloc and similar functions).
3.2 daylight, timezone, tzname
The daylight, timezone, and tzname variables are global timezone variables
used in time functions.
They are declared in the TIME.H include files as follows:
extern int daylight;
extern long timezone;
extern char *tzname [2];
Some time and date routines use the daylight, timezone, and tzname variables
to make local-time adjustments. Whenever a program calls the ftime,
localtime, or tzset function, the value of daylight, timezone, and tzname is
determined from the value of the TZ environment variable. If you do not
explicitly set the value of TZ, the default value of PST8PDT is used. The
following list shows each variable and its value:
Variable Value
────────────────────────────────────────────────────────────────────────────
daylight Nonzero if a daylight-saving-time zone
(DST) is specified in TZ; otherwise
zero. Default value is one.
timezone Difference in seconds between Greenwich
mean time and the local time. Default
value is 28,800.
tzname[0] Three-letter time zone name derived from
the TZ environment variable. Default
value is "PST" (Pacific standard time).
tzname[1] Three-letter daylight-saving-time zone
name derived from the TZ environment
variable. Default value is PDT. If the
DST zone is omitted from TZ, tzname[1]
is an empty string.
3.3 _doserrno, errno, sys_errlist, sys_nerr
The _doserrno, errno, sys_errlist, and sys_nerr variables contain error
codes, and are used by the perror and _strerror routines to print error
information.
These variables are declared in the STDLIB.H include file. Manifest
constants for the errno variables are declared in the ERRNO.H include file.
The declarations are as follows:
extern int _doserrno;
extern int errno;
extern char *sys_errlist[ ];
extern int sys_nerr;
The errno variable is set to an integer value to reflect the type of error
that has occurred in a system-level call. Each errno value is associated
with an error message, which can be printed with the perror routine or
stored in a string with the strerror routine.
Note that only some routines set the errno variable. If a routine sets
errno, the description of the routine in the reference section says so
explicitly.
The value of errno reflects the error value for the last call that set
errno. However, this value is not necessarily reset by later successful
calls. To avoid confusion, test for errors immediately after a call.
The include file ERRNO.H contains the definitions of the errno values.
However, not all of the definitions given in ERRNO.H are used in DOS and
OS/2. Some of the values in ERRNO.H are present to maintain compatibility
with XENIX and UNIX operating systems.
The errno values in DOS and OS/2 are a subset of the values for errno in
XENIX systems. Thus, the errno value is not necessarily the same as the
actual error code returned by a DOS or OS/2 system call. To access the
actual DOS and OS/2 error code, use the _doserrno variable, which contains
this value.
In general, you should use _doserrno only for error detection in operations
involving input and output, since the errno values for input and output
errors have DOS and OS/2 error-code equivalents. In other cases, the value
of _doserrno is undefined.
The syserrlist variable is an array; the perror and strerror routines use it
to process error information. The sys_nerr variable tells how many elements
the sys_errlist array contains.
Table 3.1 gives the errno values for DOS and OS/2, the system error message
for each value, and the value of each constant. Note that only the ERANGE
and EDOM constants are specified in the ANSI standard.
Table 3.1 errno Values and Their Meanings
╓┌───────────┌──────────────────────────────────────────────────────────┌────►
Constant Meaning Value
─────────────────────────────────────────────────────────────────────────────
E2BIG Argument list too long 7
Constant Meaning Value
─────────────────────────────────────────────────────────────────────────────
E2BIG Argument list too long 7
EACCES Permission denied 13
EBADF Bad file number 9
EDEADLOCK Resource deadlock would occur 36
EDOM Math argument 33
EEXIST File exists 17
EINVAL Invalid argument 22
EMFILE Too many open files 24
ENOENT No such file or directory 2
ENOEXEC Exec format error 8
Constant Meaning Value
─────────────────────────────────────────────────────────────────────────────
ENOEXEC Exec format error 8
ENOMEM Not enough memory 12
ENOSPC No space left on device 28
ERANGE Result too large 34
EXDEV Cross-device link 18
─────────────────────────────────────────────────────────────────────────────
3.4 _fmode
The _fmode variable controls the default file-translation mode.
It is declared in the STDLIB.H include file as follows:
extern int _fmode;
By default, the value of _fmode is O_TEXT, causing files to be translated in
text mode (unless specifically opened or set to binary mode). When _fmode is
set to O_BINARY, the default mode is binary. You can set _fmode to the flag
O_BINARY by linking with BINMODE.OBJ or by assigning it the O_BINARY value.
3.5 _osmajor, _osminor, _osmode, _osversion
The _osmajor, _osminor, _osmode, and _osversion variables specify the
version number of the operating system or the current mode of operation.
They are declared in the STDLIB.H include file as follows:
extern unsigned char _osmajor;
extern unsigned char _osminor;
extern unsigned char _osmode;
extern unsigned char _osversion;
The _osmajor, _osminor, and _osversion variables specify the version number
of DOS or OS/2 currently in use. The _osmajor variable holds the "major"
version number and the _osminor variable stores the "minor" version number.
Thus, under DOS version 3.20, _osmajor is 3 and _osminor is 20. The
_osversion variable holds both values; its low byte contains the major
version number and its high byte the minor version number.
These variables are useful for creating programs that run in different
versions of DOS and OS/2. For example, you can test the _osmajor variable
before making a call to sopen; if the major version number is earlier (less)
than 3, open should be used instead of sopen.
The _osmode variable indicates whether the program is in OS/2 protected mode
or in real mode (DOS or OS/2 real mode). An _osmode value of DOS_MODE
indicates real mode operation and a value of OS2_MODE indicates protected
operation.
3.6 environ
The environ variable is a pointer to the strings in the process environment.
It is declared in the STDLIB.H include file as follows:
extern char *environ [ ];
The environ variable provides access to memory areas containing
process-specific information.
The environ variable is an array of pointers to the strings that constitute
the process environment. The environment consists of one or more entries of
the form
NAME=string
where NAME is the name of an environment variable and string is the value of
that variable. The string may be empty. The initial environment settings are
taken from the operating-system environment at the time of program
execution.
The getenv and putenv routines use the environ variable to access and modify
the environment table. When putenv is called to add or delete environment
settings, the environment table changes size; its location in memory may
also change, depending on the program's memory requirements. The environ
variable is adjusted in these cases and always points to the correct table
location.
3.7 _psp
The _psp variable contains the segment address of the program segment prefix
(PSP) for the process.
It is declared in the STDLIB.H include file as follows:
extern unsigned int _psp;
The PSP contains execution information about the process, such as a copy of
the command line that invoked the process and the return address on process
termination or interrupt. The _psp variable can be used to form a long
pointer to the PSP, where _psp is the segment value and 0 is the offset
value.
Note that the _psp variable is supported only in DOS.
3.8 Standard Types
A number of library routines use values whose types are defined in include
files. In the following list, these types are described, and the include
file defining each type is given.
Standard Type Description
────────────────────────────────────────────────────────────────────────────
clock_t The clock_t type, defined in TIME.H,
stores time values. It is used by the
clock function.
complex The complex structure, defined in
MATH.H, stores the real and imaginary
parts of complex numbers. It is used by
the cabs function.
diskfree_t The diskfree_t structure, defined in
DOS.H, stores disk information used by
the _dos_getdiskfree routine.
diskinfo_t The diskinfo_t structure, defined in
BIOS.H, records information about disk
drives returned by the _bios_disk
routine.
div_t, ldiv_t The div_t and ldiv_t structures, defined
in STDLIB.H, store the values returned
by the div and ldiv functions,
respectively.
dosdate_t The dosdate_t structure, defined in
DOS.H, records the current system date
used in the _dos_getdate and
_dos_setdate routines.
dostime_t The dostime_t structure, defined in
DOS.H, records the current system time
used in the _dos_gettime and
_dos_settime routines.
DOSERROR The DOSERROR structure, defined in
DOS.H, stores values returned by DOS
system call 59H (available under DOS
versions 3.0 and later).
exception The exception structure, defined in
MATH.H, stores error information for
math routines. It is used by the matherr
routine.
FILE The FILE structure, defined in STDIO.H,
is the structure used in all stream
input and output operations. The fields
of the FILE structure store information
about the current state of the stream.
find_t The find_t structure, defined in DOS.H,
stores file-attribute information
returned by the _dos_findfirst and
_dos_findnext routines.
fpos_t The fgetpos and fsetpos functions use
the fpos_t object type, defined in
STDIO.H, to record all the information
necessary to uniquely specify every
position within the file.
jmp_buf The jmp_buf type, defined in SETJMP.H,
is an array type rather than a structure
type. A buffer of this type is used by
the setjmp and longjmp routines to save
and restore the program
environment.
lconv The lconv type is a structure containing
formatting rules for numeric values in
different countries. It is defined in
LOCALE.H.
onexit_t The onexit routine is declared as an
onexit_t pointer type, which is defined
in STDLIB.H.
ptrdiff_t The ptrdiff_t type is used for the
signed integral result of the
subtraction of two pointers.
REGS The REGS union, defined in DOS.H, stores
byte and word register values to be
passed to and returned from calls to the
DOS interface functions.
sig_atomic_t The sig_atomic_t type, defined in
SIGNAL.H, is the integral type of an
object that can be modified as an atomic
entity, even in the presence of
asynchronous interrupts. It is used in
conjunction with the signal routine.
size_t The size_t type, defined in STDDEF.H and
several other include files, is the
unsigned integral result of the sizeof
operator.
SREGS The SREGS structure, defined in DOS.H,
stores the values of the ES, CS, SS, and
DS registers. This structure is used by
the DOS interface functions that require
segment register values (int86x, intdosx
, and segread).
stat The stat structure, defined in
SYS\STAT.H, contains file-status
information returned by the stat and
fstat routines.
time_t The time_t type, defined in TIME.H,
represents time values in the mktime and
time routines.
timeb The timeb structure, defined in
SYS\TIMEB.H, is used by the ftime
routine to store the current system
time.
tm The tm structure, defined in TIME.H, is
used by the asctime, gmtime, and
localtime functions to store and
retrieve time information.
utimbuf The utimbuf structure, defined in
SYS\UTIME.H, stores file access and
modification times used by the utime
function to change file-modification
dates.
va_list The va_list array type, defined in
STDARG.H, is used to hold information
needed by the va_arg macro and the
va_end routine. The called function
declares a variable of type va_list,
which may be passed as an argument to
another function.
PART II Run-Time Functions
────────────────────────────────────────────────────────────────────────────
The second part of this book is the reference section. It describes, in
alphabetical order, each function of the run-time library provided with the
Microsoft C Professional Development System.
Each reference entry gives syntax, return values, and other useful
information about the library functions. Information on compatibility is
supplied to assist you in writing portable programs.
About the Run-Time Reference
The following pages describe, in alphabetical order, the more than 400
functions in the Microsoft run-time library. In some cases, related routines
are clustered in the same description. For example, the based, near, and far
versions of _heapwalk are in the same discussion, as are the regular and
long double versions of the math functions, such as acos and atan.
Differences are noted where appropriate. Refer to Chapter 2, "Run-Time
Routines by Category," or to the index to locate any function that does not
appear in the expected position within the alphabetical reference.
The discussion of each function (or group of functions) is divided into the
following sections:
■ Description. Summarizes the routine's effect, names the include
file(s) containing its declaration, illustrates the syntax, and
briefly describes the arguments.
■ Remarks. Gives a more detailed description of the routine and how it
is used.
■ Return Value. Describes the value returned by the routine.
■ Compatibility. Tells whether the routine is compatible with ANSI C,
MS-DOS, OS/2, UNIX, and XENIX.
■ See Also. Names related routines.
■ Example. Gives a complete program showing the use of the routine.
abort
────────────────────────────────────────────────────────────────────────────
Description
Aborts the current process and returns an error code.
#include <process.h> Required only for function declarations;
#include <stdlib.h> use either PROCESS.H or STDLIB.H
void abort( void );
Remarks
The abort function prints the message
abnormal program termination
to stderr, then calls raise(SIGABRT). The action taken in response to the
SIGABRT signal depends on what action has been defined for that signal in a
prior call to the signal function. The default SIGABRT action is for the
calling process to terminate with exit code 3, returning control to the
parent process or operating system.
The abort function does not flush stream buffers or do atexit/onexit
processing.
Return Value
The abort function does not return control to the caller. Rather, it
terminates the process and, by default, returns an exit code of 3 to the
parent process.
Compatibility
ANSI DOS OS/2 UNIX XENIX
In multithread libraries, the abort function does not call raise(SIGABRT).
Instead, it simply terminates the process with exit code 3.
See Also
exec functions, exit, _exit, raise, signal, spawn functions
Example
/* ABORT.C: This tries to open a file and aborts if the attempt fails. */
#include <stdio.h>
#include <stdlib.h>
void main()
{
FILE *stream;
if( (stream = fopen( "NOSUCHF.ILE", "r" )) == NULL )
{
perror( "Couldn't open file" );
abort();
}
else
fclose( stream );
}
Output
Couldn't open file: No such file or directory
abnormal program termination
abs
────────────────────────────────────────────────────────────────────────────
Description
Calculates the absolute value.
#include <stdlib.h> Required only for function declarations;
#include <math.h> use either STDLIB.H or MATH.H
int abs( int n );
n Integer value
Remarks
The abs function returns the absolute value of its integer argument n.
Return Value
The abs function returns the absolute value of its argument. There is no
error return.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
cabs, fabs, labs
Example
/* ABS.C: This program computes and displays the absolute values of
* several numbers.
*/
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
void main()
{
int ix = -4, iy;
long lx = -41567L, ly;
double dx = -3.141593, dy;
iy = abs( ix );
printf( "The absolute value of %d is %d\n", ix, iy);
ly = labs( lx );
printf( "The absolute value of %ld is %ld\n", lx, ly);
dy = fabs( dx );
printf( "The absolute value of %f is %f\n", dx, dy );
}
Output
The absolute value of -4 is 4
The absolute value of -41567 is 41567
The absolute value of -3.141593 is 3.141593
access
────────────────────────────────────────────────────────────────────────────
Description
Determines file-access permission.
#include <io.h> Required only for function declarations
#include <errno.h> Required for definition of errno
constants
int access( char *pathname, int mode );
pathname File or directory path name
mode Permission setting
Remarks
With files, the access function determines whether the specified file exists
and can be accessed in mode. The possible mode values and their meanings in
the access call are as follows:
Value Meaning
────────────────────────────────────────────────────────────────────────────
00 Check for existence only
02 Check for write permission
04 Check for read permission
06 Check for read and write permission
With directories, access determines only whether the specified directory
exists; under DOS and OS/2, all directories have read and write access.
Return Value
The access function returns the value 0 if the file has the given mode. A
return value of -1 indicates that the named file does not exist or is not
accessible in the given mode, and errno is set to one of the following
values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
EACCES Access denied: the file's permission
setting does not allow the specified
access.
ENOENT File or path name not found.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
chmod, fstat, open, stat
Example
/* ACCESS.C: This example uses access to check the file named "data"
* to see if it exists and if writing is allowed.
*/
#include <io.h>
#include <stdio.h>
#include <stdlib.h>
void main()
{
/* Check for existence */
if( (access( "access.c", 0 )) != -1 )
{
printf( "File exists\n" );
/* Check for write permission */
if( (access( "access.c", 2 )) != -1 )
printf( "File has write permission\n" );
}
}
Output
File exists
File has write permission
acos Functions
────────────────────────────────────────────────────────────────────────────
Description
Calculate the arccosine.
#include <math.h>
#include <errno.h> Required for definition of errno
constant
double acos( double x );
long double acosl( long double x );
x Value whose arccosine is to be
calculated
Remarks
The acos functions return the arccosine of x in the range 0 to π radians.
The value of x must be between -1 and 1. The acosl function is the 80-bit
counterpart, which uses an 80-bit, 10-byte coprocessor form of arguments and
return values. See the reference page on the long double functions for more
details on this data type.
Return Value
The acos functions return the arccosine result. If x is less than -1 or
greater than 1, the function sets errno to EDOM, prints a DOMAIN error
message to stderr, and returns 0. Error handling can be modified with the
matherr (or _matherrl) routine.
Compatibility
acos
ANSI DOS OS/2 UNIX XENIX
acosl
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
asin functions, atan functions, cos functions, matherr, sin functions, tan
functions
Example
/* ASINCOS.C: This program prompts for a value in the range -1 to 1.
* Input values outside this range will produce DOMAIN error messages.
* If a valid value is entered, the program prints the arcsine and the
* arccosine of that value.
*/
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
void main()
{
double x, y;
printf( "Enter a real number between -1 and 1: " );
scanf( "%lf", &x );
y = asin( x );
printf( "Arcsine of %f = %f\n", x, y );
y = acos( x );
printf( "Arccosine of %f = %f\n", x, y );
}
Output
Enter a real number between -1 and 1: .32696
Arcsine of 0.326960 = 0.333085
Arccosine of 0.326960 = 1.237711
alloca
────────────────────────────────────────────────────────────────────────────
Description
Allocates memory on the stack.
#include <malloc.h> Required only for function declarations
void *alloca( size_t size );
size Bytes to be allocated from stack
Remarks
The alloca routine allocates size bytes from the program's stack. The
allocated space is automatically freed when the calling function is exited.
When you compile with optimization on (either by default or by using one of
the /O options), the stack pointer may not be restored properly in functions
that have no local variables and that also reference the alloca function.
The following program demonstrates the problem:
/* Compile with CL /Lp /AM /Ox /Fc */
#include <malloc.h>
void main( void )
{
func( 10 );
}
void func( register int i )
{
alloca( i );
}
To ensure that the stack pointer is properly restored, make sure that any
function referencing alloca declares at least one local variable.
The pointer value returned by alloca should never be passed as an argument
to free, nor should alloca be used in an expression that is an argument to a
function.
Return Value
The alloca routine returns a void pointer to the allocated space, which is
guaranteed to be suitably aligned for storage of any type of object. To get
a pointer to a type other than char, use a type cast on the return value.
The return value is NULL if the space cannot be allocated.
Compatibility
▼ ANSI DOS OS/2 UNIX ▼ XENIX
See Also
calloc functions, malloc functions, realloc functions
Example
/* ALLOCA.C: This program checks the stack space available before
* and after using the alloca function to allocate space on the stack.
*/
#include <malloc.h>
#include <stdio.h>
void main()
{
char *buffer;
printf( "Bytes available on stack: %u\n", stackavail() );
/* Allocate memory for string. */
buffer = alloca( 120 * sizeof( char ) );
printf( "Enter a string: " );
gets( buffer );
printf( "You entered: %s\n", buffer );
printf( "Bytes available on stack: %u\n", stackavail() );
}
Output
Bytes available on stack: 2028
Enter a string: How much stack space will this string take?
You entered: How much stack space will this string take?
Bytes available on stack: 1902
_arc Functions
────────────────────────────────────────────────────────────────────────────
Description
Draw elliptical arcs.
#include <graph.h>
short _far _arc( short x1, short y1, short x2, short y2, short x3,
short y3, short x4, short y4 );
short _far _arc_w( double x1, double y1, double x2, double y2, double x3,
double y3, double x4, double y4 );
short _far _arc_wxy( struct _wxycoord _far *pwxy1,
struct _wxycoord _far *pwxy2,
struct _wxycoord _far *pwxy3, struct _wxycoord _far *pwxy4);
x1, y1 Upper-left corner of bounding rectangle
x2, y2 Lower-right corner of bounding rectangle
x3, y3 Second point of start vector (center of
bounding rectangle is first point)
x4, y4 Second point of end vector (center of
bounding rectangle is first point)
pwxy1 Upper-left corner of bounding rectangle
pwxy2 Lower-right corner of bounding rectangle
pwxy3 Second point of start vector (center of
bounding rectangle is first point)
pwxy4 Second point of end vector (center of
bounding rectangle is first point)
Remarks
The _arc functions draw elliptical arcs. The center of the arc is the center
of the bounding rectangle, which is defined by points (x1, y1) and (x2, y2)
for _arc and _arc_w and by points pwxy1 and pwxy2 for _arc_wxy. The arc
starts where it intersects an imaginary line extending from the center of
the arc through (x3, y3) for _arc and _arc_w and through pwxy3 for _arc_wxy.
It is drawn counterclockwise about the center of the arc, ending where it
intersects an imaginary line extending from the center of the arc through
(x4, y4) for _arc and _arc_w and through pwxy4 for _arc_wxy.
The _arc routine uses the view coordinate system. The _arc_w and _arc_wxy
functions use the real-valued window coordinate system.
In each case, the arc is drawn using the current color. Since an arc does
not define a closed area, it is not filled.
Return Value
These functions return a nonzero value if the arc is successfully drawn;
otherwise, they return 0.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_ellipse functions, _lineto functions, _pie functions, _rectangle
functions, _setcolor
Example
/* ARC.C: This program draws a simple arc. */
#include <graph.h>
#include <stdlib.h>
#include <conio.h>
void main()
{
short x, y;
struct xycoord xystart, xyend, xyfill;
/* Find a valid graphics mode */
if( !_setvideomode( _MAXRESMODE ) )
exit( 1 );
/* Draw arcs */
x = 100; y = 100;
_arc( x - 60, y - 60, x, y, x - 30, y - 60, x - 60, y - 30 );
_arc( x + 60, y + 60, x, y, x, y + 30, x + 30, y );
/* Get endpoints of second arc and enclose the figure, then fill it. */
_getarcinfo( &xystart, &xyend, &xyfill );
_moveto( xystart.xcoord, xystart.ycoord );
_lineto( xyend.xcoord, xyend.ycoord );
_floodfill( xyfill.xcoord, xyfill.ycoord, _getcolor() );
getch();
_setvideomode( _DEFAULTMODE );
}
asctime
────────────────────────────────────────────────────────────────────────────
Description
Converts a tm time structure to a character string.
#include <time.h>
char *asctime( const struct tm *timeptr );
timeptr Time/date structure
Remarks
The asctime function converts a time stored as a structure to a character
string. The timeptr value is usually obtained from a call to gmtime or
localtime, both of which return a pointer to a tm structure, defined in
TIME.H. (See gmtime for a complete description of the tm structure fields.)
The tm structure contains the following elements:
Element Description
────────────────────────────────────────────────────────────────────────────
int tm_sec Seconds after the minute (0 -59)
int tm_min Minutes after the hour (0 -59)
int tm_hour Hours since midnight (0 -23)
int tm_mday Day of the month (0 -31)
int tm_mon Months since January (0 -11)
int tm_year Years since 1900
int tm_wday Days since Sunday (0 - 6)
int tm_yday Days since January 1 (0 -365)
int tm_isdst Daylight-saving-time flag
The string result produced by asctime contains exactly 26 characters and has
the form of the following example:
Wed Jan 02 02:03:55 1980\n\0
A 24-hour clock is used. All fields have a constant width. The newline
character (\n) and the null character ('\0') occupy the last two positions
of the string. The asctime function uses a single statically allocated
buffer to hold the return string. Each call to this routine destroys the
result of the previous call.
Return Value
The asctime function returns a pointer to the character string result. There
is no error return.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
ctime, ftime, gmtime, localtime, time, tzset
Example
/* ASCTIME.C: This program places the system time in the long integer
aclock,
* translates it into the structure newtime and then converts it to
* string form for output, using the asctime function.
*/
#include <time.h>
#include <stdio.h>
struct tm *newtime;
time_t aclock;
void main()
{
time( &aclock ); /* Get time in seconds */
newtime = localtime( &aclock ); /* Convert time to struct tm form
*/
/* Print local time as a string */
printf( "The current date and time are: %s\n", asctime( newtime ) );
}
Output
The current date and time are: Thu Jun 15 06:57:59 1989
asin Functions
────────────────────────────────────────────────────────────────────────────
Description
Calculate the arcsine.
#include <math.h>
#include <errno.h>
double asin( double x );
long double asinl( long double x );
x Value whose arcsine is to be calculated
Remarks
The asin functions calculate the arcsine of x in the range -π/2 to π/2
radians. The value of x must be between -1 and 1. The asinl function is the
80-bit counterpart, which uses an 80-bit, 10-byte coprocessor form of
arguments and return values. See the reference page on the long double
functions for more details on this data type.
Return Value
The asin functions return the arcsine result. If x is less than -1 or
greater than 1, asin sets errno to EDOM, prints a DOMAIN error message to
stderr, and returns 0.
Error handling can be modified by using the matherr (or _matherrl) routine.
Compatibility
asin
ANSI DOS OS/2 UNIX XENIX
asinl
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
acos functions, atan functions, cos functions, matherr, sin functions, tan
functions
Example
/* ASINCOS.C: This program prompts for a value in the range -1 to 1.
* Input values outside this range will produce DOMAIN error messages.
* If a valid value is entered, the program prints the arcsine and the
* arccosine of that value.
*/
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
void main()
{
double x, y;
printf( "Enter a real number between -1 and 1: " );
scanf( "%lf", &x );
y = asin( x );
printf( "Arcsine of %f = %f\n", x, y );
y = acos( x );
printf( "Arccosine of %f = %f\n", x, y );
}
Output
Enter a real number between -1 and 1: .32696
Arcsine of 0.326960 = 0.333085
Arccosine of 0.326960 = 1.237711
assert
────────────────────────────────────────────────────────────────────────────
Description
Prints an error message and aborts the program.
#include <assert.h>
#include <stdio.h>
void assert( int expression );
expression C expression specifying assertion being
tested
Remarks
The assert routine prints a diagnostic message and calls the abort routine
if expression is false (0). The diagnostic message has the form
Assertion failed: expression, file filename, line linenumber
where filename is the name of the source file and linenumber is the line
number of the assertion that failed in the source file. No action is taken
if expression is true (nonzero).
The assert routine is typically used in program development to identify
program logic errors. The given expression should be chosen so that it holds
true only if the program is operating as intended. After a program has been
debugged, the special "no debug" identifier NDEBUG can be used to remove
assert calls from the program. If NDEBUG is defined (by any value) with a /D
command-line option or with a #define directive, the C preprocessor removes
all assert calls from the program source.
The assert routine is implemented as a macro.
Return Value
None.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
abort, raise, signal
Example
/* ASSERT.C: In this program, the analyze_string function uses the
* assert function to test several conditions related to string and
* length. If any of the conditions fails, the program prints a
* message indicating what caused the failure.
*/
#include <stdio.h>
#include <assert.h>
#include <string.h>
void analyze_string( char *string ); /* Prototype */
void main()
{
char test1[] = "abc", *test2 = NULL, test3[] = "";
printf ( "Analyzing string '%s'\n", test1 );
analyze_string( test1 );
printf ( "Analyzing string '%s'\n", test2 );
analyze_string( test2 );
printf ( "Analyzing string '%s'\n", test3 );
analyze_string( test3 );
}
/* Tests a string to see if it is NULL, empty, or longer than 0 characters
*/
void analyze_string( char * string )
{
assert( string != NULL ); /* Cannot be NULL */
assert( *string != '\0' ); /* Cannot be empty */
assert( strlen( string ) > 2 ); /* Length must be greater than 2 */
}
Output
Analyzing string 'abc'
Analyzing string '(null)'
Assertion failed: string != NULL, file assert.c, line 28
abnormal program termination
atan Functions
────────────────────────────────────────────────────────────────────────────
Description
Calculate the arctangent of x (atan and atanl) and the arctangent of y/x
(atan2 and atan2l).
#include <math.h>
double atan( double x );
double atan2( double y, double x );
long double atanl( long double x );
long double atan2l( long double y, long double x );
x, y Any number
Remarks
The atan family of functions calculates the arctangent of x, and the atan2
family of functions calculates the arctangent of y/x. The atan group returns
a value in the range -π/2 to π/2 radians, and the atan2 group returns a
value in the range -π toπ radians. The atan2 functions use the signs of both
arguments to determine the quadrant of the return value.
Return Value
The atan family of functions returns the arctangent result. If both
arguments of atan2 or atan2l are 0, the function sets errno to EDOM, prints
a DOMAIN error message to stderr, and returns 0.
Error handling can be modified by using the matherr (or _matherrl) routine.
Compatibility
atan, atan2
ANSI DOS OS/2 UNIX XENIX
atanl, atan2l
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
acos functions, asin functions, cos functions, matherr, sin functions, tan
functions
Example
/* ATAN.C: This program calculates the arctangent of 1 and -1. */
#include <math.h>
#include <stdio.h>
#include <errno.h>
void main()
{
double x1, x2, y;
printf( "Enter a real number: " );
scanf( "%lf", &x1 );
y = atan( x1 );
printf( "Arctangent of %f: %f\n", x1, y );
printf( "Enter a second real number: " );
scanf( "%lf", &x2 );
y = atan2( x1, x2 );
printf( "Arctangent of %f / %f: %f\n", x1, x2, y );
}
Output
Enter a real number: -862.42
Arctangent of -862.420000: -1.569637
Enter a second real number: 78.5149
Arctangent of -862.420000 / 78.514900: -1.480006
atexit
────────────────────────────────────────────────────────────────────────────
Description
Processes the specified function at exit.
#include <stdlib.h> Required only for function declarations
int atexit( void ( *func )( void ) );
func Function to be called
Remarks
The atexit function is passed the address of a function (func) to be called
when the program terminates normally. Successive calls to atexit create a
register of functions that are executed in LIFO (last-in-first-out) order.
No more than 32 functions can be registered with atexit or onexit. The
functions passed to atexit cannot take parameters.
All routines passed to atexit should have the _loadds attribute if used in
multithread dynamic-link libraries.
Return Value
The atexit function returns 0 if it is successful, or a nonzero value if an
error occurs (e.g., if there are already 32 exit functions defined).
Compatibility
ANSI DOS OS/2 ▼ UNIX ▼ XENIX
Use the ANSI-standard atexit function (rather than the similar onexit
function) whenever ANSI portability is desired.
In the OS/2 environment, the atexit function calls the OS/2 function
DosExitList.
See Also
abort, exit, _exit, onexit
Example
/* ATEXIT.C: This program pushes four functions onto the stack of
functions
* to be executed when atexit is called. When the program exits, these
* programs are executed on a "last in, first out" basis.
*/
#include <stdlib.h>
#include <stdio.h>
void fn1( void ), fn2( void ), fn3( void ), fn4( void );
void main()
{
atexit( fn1 );
atexit( fn2 );
atexit( fn3 );
atexit( fn4 );
printf( "This is executed first.\n" );
}
void fn1()
{
printf( "next.\n" );
}
void fn2()
{
printf( "executed " );
}
void fn3()
{
printf( "is " );
}
void fn4()
{
printf( "This " );
}
Output
This is executed first.
This is executed next.
atof, atoi, atol, _atold
────────────────────────────────────────────────────────────────────────────
Description
Convert strings to double (atof), long double (_atold) integer (atoi), or
long (atol).
#include <math.h> atof, _atold
#include <stdlib.h> atof, _atold, atoi, atol
double atof( const char *string );
long double _atold( const char *string );
int atoi( const char *string );
long atol( const char *string );
string String to be converted
Remarks
These functions convert a character string to a double-precision
floating-point value (atof), an integer value (atoi), a long integer value
(atol), or a long double value (_atold). The input string is a sequence of
characters that can be interpreted as a numerical value of the specified
type.
The string size that can be handled by the atof or _atold function is
limited to 100 characters.
The function stops reading the input string at the first character that it
cannot recognize as part of a number. This character may be the null
character ('\0') terminating the string.
The atof and _atold functions expect string to have the following form:
[[whitespace]] [[{sign}]] [[ IK0digits]] [[.digits]]
[[{d| D | e | E}[[sign]digits]]
A whitespace consists of space and/or tab characters, which are ignored;
sign is either plus (+) or minus (-); and digits are one or more decimal
digits. If no digits appear before the decimal point, at least one must
appear after the decimal point. The decimal digits may be followed by an
exponent, which consists of an introductory letter (d, D, e, or E) and an
optionally signed decimal integer.
The atoi and atol functions do not recognize decimal points or exponents.
The string argument for these functions has the form
[[whitespace]] [[sign]]digits
where whitespace, sign, and digits are exactly as described above for atof.
Return Value
Each function returns the double, long double, int, or long value produced
by interpreting the input characters as a number. The return value is 0 (for
atoi), 0L (for atol), and 0.0 (for atof and _atold) if the input cannot be
converted to a value of that type. The return value is undefined in case of
overflow.
Compatibility
atof, atoi, atol
ANSI DOS OS/2 UNIX XENIX
_atold
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
ecvt, fcvt, gcvt
Example
/* ATOF.C: This program shows how numbers stored as strings can be
* converted to numeric values using the atof, atoi, and atol functions.
*/
#include <stdlib.h>
#include <stdio.h>
void main()
{
char *s; double x; int i; long l;
s = " -2309.12E-15"; /* Test of atof */
x = atof( s );
printf( "atof test: ASCII string: %s\tfloat: %e\n", s, x );
s = "7.8912654773d210"; /* Test of atof */
x = atof( s );
printf( "atof test: ASCII string: %s\tfloat: %e\n", s, x );
s = " -9885 pigs"; /* Test of atoi */
i = atoi( s );
printf( "atoi test: ASCII string: %s\t\tinteger: %d\n", s, i );
s = "98854 dollars"; /* Test of atol */
l = atol( s );
printf( "atol test: ASCII string: %s\t\tlong: %ld\n", s, l );
}
Output
atof test: ASCII string: -2309.12E-15 float: -2.309120e-012
atof test: ASCII string: 7.8912654773d210 float: 7.891265e+210
atoi test: ASCII string: -9885 pigs integer: -9885
atol test: ASCII string: 98854 dollars long: 98854
bdos
────────────────────────────────────────────────────────────────────────────
Description
Invokes the DOS system call.
#include <dos.h>
int bdos( int dosfunc, unsigned int dosdx, unsigned int dosal );
dosfunc Function number
dosdx DX register value
dosal AL register value
Remarks
The bdos function invokes the DOS system call specified by dosfunc after
placing the values specified by dosdx and dosal in the DX and AL registers,
respectively. The bdos function executes an INT 21H instruction to invoke
the system call. When the system call is complete, bdos returns the contents
of the AX register.
The bdos function is intended to be used to invoke DOS system calls that
either take no arguments or take arguments only in the DX (DH, DL) and/or AL
registers.
Do not use the bdos function to call interrupts that modify the DS register.
Instead, use the intdosx or int86x function. The intdosx and int86x
functions load the DS and ES registers from the segregs parameter and also
store the DS and ES registers into segregs after the function call.
This call should not be used to invoke system calls that indicate errors by
setting the carry flag. Since C programs do not have access to this flag,
your program cannot determine whether the return value is an error code. The
intdos function should be used in these cases.
Return Value
The bdos function returns the value of the AX register after the system call
has completed.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
intdos, intdosx
Example
/* BDOS.C: This example calls DOS function 0x9 (display string)
* to display a $-terminated string.
*/
#include <dos.h>
/* Function 0x09 assumes that DS will contain segment of the string.
* This will be true for all memory models if the string is declared near.
*/
char _near str[] = "Hello world!\r\n$";
void main()
{
/* Offset of string must be in DX, segment in DS. AL is not needed,
* so 0 is used.
*/
bdos( 0x09, (int)str, 0 );
}
Output
Hello world!
_beginthread
────────────────────────────────────────────────────────────────────────────
Description
Begins thread in OS/2 process.
#include <process.h> Multithread version of PROCESS.H
#include <stddef.h> Declaration of threadid variable
int _far _beginthread( void( _far *start_address )( void _far * ),
void _far *stack_bottom, unsigned stack_size, void _far *arglist );
start_address Starting address
stack_bottom Address of the thread stack
stack_size Stack size for thread
arglist Argument list for thread
Remarks
The _beginthread function creates a thread that begins execution of a far
routine at start_address. When the thread returns from that far routine, it
is terminated automatically. The user can also terminate the thread by
calling _endthread.
The address of the thread stack is given by stack_bottom. If stack_bottom is
set to NULL, the run-time library code will allocate and deallocate the
thread stack as needed. Since the _beginthread function can determine the
current status of all thread IDs, it can free the old stack and allocate a
new stack whenever a thread is reused.
If it is not NULL, the stack_bottom argument must specify a word address,
and the stack must be at least as long as specified by the stack_size
argument. Usually this memory is either a global array or memory returned by
malloc or _fmalloc.
The stack_size argument must be even and nonzero.
If you are writing multithread programs that make C run-time calls from
child threads, be sure to allocate a sufficiently large stack. For example,
the C function printf requires more than 500 bytes of stack space. To be
safe, allocate at least 2,048 bytes for a thread's stack. (If your child
thread makes no run-time calls, stack space is generally not a problem.)
As a general rule, you should have 2K of stack space free when calling any
API (Applications Program Interface) routine (e.g., OS/2 system calls).
The arglist is a parameter, the size of a far pointer, to be passed to the
newly created thread. Typically it is the address of a data item, such as a
character string, to be passed to the new thread. The arglist may be NULL if
not needed, but _beginthread should be provided with some value to pass to
the child thread.
All threads will be terminated if any thread calls abort, exit, _exit, or
DosExit. A good practice in multithread programming is to make the first
thread the main thread and wait until other threads have terminated before
exiting the program.
The OS/2 function DosCreateThread should not be called directly to create
threads. The _beginthread function performs initialization procedures
required to call other C run-time library functions safely.
Return Value
The function returns the thread identification number of the new thread, if
successful. A return value of -1 indicates an error, and errno is set to one
of the following values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
EAGAIN Too many threads
EINVAL Invalid argument, "bad stack"
Compatibility
▼ ANSI ▼ DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_endthread
Example
/* BEGTHRD.C illustrates multiple threads using functions:
* _beginthread _endthread
*
* Also the global variable:
* _threadid
*
* This program requires the multithread library. For example, compile
* with the following command line:
* CL /MT THREADS.C
*/
#define INCL_NOCOMMON
#define INCL_NOPM
#define INCL_DOSPROCESS
#define INCL_VIO
#include <os2.h>
#include <process.h> /* _beginthread, _endthread */
#include <stddef.h> /* _threadid */
#include <stdlib.h>
#include <conio.h>
void Bounce( int c ); /* Prototypes */
void CheckKey( void *dummy );
/* GetRandom returns a random integer between min and max. */
#define GetRandom( min, max ) ((rand() % (int)(((max) + 1) - (min))) +
(min))
#define STACK_SIZE 4096
BOOL repeat = TRUE; /* Global repeat flag and video variable */
VIOMODEINFO vmi = { sizeof( VIOMODEINFO ) };
void main()
{
PCHAR stack;
CHAR ch = 'A';
/* Get display screen's text row and column information. */
VioGetMode( &vmi, 0 );
/* Launch CheckKey thread to check for terminating keystroke. */
_beginthread( CheckKey, NULL, STACK_SIZE, NULL );
/* Loop until CheckKey terminates program. */
while( repeat )
{
/* On first loops, launch character threads. */
_beginthread( Bounce, NULL, STACK_SIZE, (void *)ch++ );
/* Wait one second between loops. */
DosSleep( 1000L );
}
}
/* CheckKey - Thread to wait for a keystroke, then clear repeat flag. */
void CheckKey( void *dummy )
{
getch();
repeat = 0; /* _endthread implied */
}
/* Bounce - Thread to create and control a colored letter that moves
* around on the screen.
*
* Params: ch - the letter to be moved
*/
void Bounce( int ch )
{
/* Generate letter and color attribute from thread argument. */
char blankcell[2] = { 0x20, 0x07 };
char blockcell[2] = { ch , (ch % 16) + 1 };
int xold, xcur, yold, ycur;
BOOL first = TRUE;
/* Seed random number generator and get initial location. */
srand( *_threadid );
xcur = GetRandom( 0, vmi.col - 1 );
ycur = GetRandom( 0, vmi.row - 1 );
while( repeat )
{
/* Pause between loops. */
DosSleep( 100L );
/* Blank out our old position on the screen, and draw new letter.
*/
if( first )
first = FALSE;
else
VioWrtCellStr( blankcell, 2, yold, xold, 0 );
VioWrtCellStr( blockcell, 2, ycur, xcur, 0 );
/* Increment the coordinate for next placement of the block. */
xold = xcur;
yold = ycur;
xcur += GetRandom( -1, 1 );
ycur += GetRandom( -1, 1 );
/* Correct placement (and beep) if about to go off the screen. */
if( xcur < 0 )
xcur = 1;
else if( xcur == vmi.col )
xcur = vmi.col - 2;
else if( ycur < 0 )
ycur = 1;
else if( ycur == vmi.row )
ycur = vmi.row - 2;
/* If not at screen border, continue, otherwise beep. */
else
continue;
DosBeep( (ch - 'A') * 100, 175 );
}
/* _endthread given (but not really needed) to terminate. */
_endthread();
}
Bessel Functions
────────────────────────────────────────────────────────────────────────────
Description
Compute the Bessel function.
#include <math.h>
double j0( double x );
double j1( double x );
double jn( int n, double x );
double y0( double x );
double y1( double x );
double yn( int n, double x );
long double _j0l( long double x );
long double _jnl( int n, long double x );
long double _j1l( long double x );
long double _y0l( long double x );
long double _y1l( long double x );
long double _ynl( int n, long double x );
x Floating-point value
n Integer order
Remarks
The j0, j1, and jn routines return Bessel functions of the first kind─orders
0, 1, and n, respectively.
The y0, y1, and yn routines return Bessel functions of the second
kind─orders 0, 1, and n, respectively. The argument x must be positive.
The long double versions of these functions are the 80-bit counterparts and
use the 80-bit, 10-byte coprocessor form of arguments and return values. See
the reference page on the long double functions for more details on this
data type.
The Bessel functions are explained more fully in most mathematics reference
books, such as the Handbook of Mathematical Functions (Abramowitz and
Stegun; Washington: U.S. Government Printing Office, 1964). These functions
are commonly used in the mathematics of electromagnetic wave theory.
Return Value
These functions return the result of a Bessel function of x.
For y0, y1, or yn, if x is negative, the routine sets errno to EDOM, prints
a DOMAIN error message to stderr, and returns -HUGE_VAL.
Error handling can be modified by using the matherr (or _matherrl) routine.
Compatibility
j0, j1, jn, y0, y1, yn
▼ ANSI DOS OS/2 UNIX XENIX
_j0l, _j1l, _jnl, _y0l, _y1l, _ynl
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
matherr
Example
/* BESSEL.C: This program illustrates Bessel functions, including:
* j0 j1 jn y0 y1 yn
*/
#include <math.h>
#include <stdio.h>
void main()
{
double x = 2.387;
int n = 3, c;
printf( "Bessel functions for x = %f:\n", x );
printf( " Kind\t\tOrder\t\Function\tResult\n\n" );
printf( " First\t\t0\tj0( x )\t\t%f\n", j0( x ) );
printf( " First\t\t1\tj1( x )\t\t%f\n", j1( x ) );
for( c = 2; c < 5; c++ )
printf( " First\t\t%d\tjn( n, x )\t%f\n", c, jn( c, x ) );
printf( " Second\t0\ty0( x )\t\t%f\n", y0( x ) );
printf( " Second\t1\ty1( x )\t\t%f\n", y1( x ) );
for( c = 2; c < 5; c++ )
printf( " Second\t%d\tyn( n, x )\t%f\n", c, yn( c, x ) );
}
Output
Bessel functions for x = 2.387000:
Kind Order Function Result
First 0 j0( x ) 0.009288
First 1 j1( x ) 0.522941
First 2 jn( n, x ) 0.428870
First 3 jn( n, x ) 0.195734
First 4 jn( n, x ) 0.063131
Second 0 y0( x ) 0.511681
Second 1 y1( x ) 0.094374
Second 2 yn( n, x ) -0.432608
Second 3 yn( n, x ) -0.819314
Second 4 yn( n, x ) -1.626833
_bfreeseg
────────────────────────────────────────────────────────────────────────────
Description
Frees a specified based heap.
#include <malloc.h> Required only for function declarations
int _bfreeseg( _segment seg );
seg Segment selected
Remarks
The _bfreeseg function frees a based heap. The seg argument is a based heap
returned by an earlier call to _bheapseg. It specifies the based heap to be
freed.
The number of bytes freed is the number of bytes specified when the block
was allocated. After the call, the freed heap is again available for
allocation.
Return Value
The _bfreeseg function returns 0 if successful and -1 in the case of an
error.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_bheapseg, calloc functions, free functions, malloc functions, realloc
functions
Example
/* BHEAPSEG.C: This program C illustrates dynamic allocation of based
* memory using functions _bheapseg, _bfreeseg, _bmalloc, and _bfree.
*/
#include <stdio.h>
#include <malloc.h>
#include <stdlib.h>
#include <string.h>
void main()
{
_segment seg;
char _based( seg ) *outstr, _based( seg ) *instr;
char _based( seg ) *pout, _based( seg ) *pin;
char tmpstr[80];
int len;
printf( "Enter a string: " );
gets( tmpstr );
/* Request a based heap. Use based so that memory won't be taken from
* near heap.
*/
if( (seg = _bheapseg( 1000 )) == _NULLSEG )
exit( 1 );
/* Allocate based memory for two strings. */
len = strlen( tmpstr );
if( ((instr = _bmalloc( seg, len + 1 )) == _NULLOFF) ||
((outstr = _bmalloc( seg, len + 1 )) == _NULLOFF) )
exit( 1 );
/* Copy a lowercased string to dynamic memory. The based memory is
* far when addressed as a whole.
*/
_fstrlwr( _fstrcpy( (char _far *)instr, (char _far *)tmpstr ) );
/* Copy input string to output string in reversed order. When reading
* and writing individual characters from a based heap, the compiler
will
* try to process them as near, thus speeding up the processing.
*/
for( pin = instr + len - 1, pout = outstr;
pout < outstr + len; pin--, pout++ )
*pout = *pin;
*pout = '\0';
/* Display strings. Again strings as a whole are far. */
printf( "Input: %Fs\n", (char _far *)instr );
printf( "Output: %Fs\n", (char _far *)outstr );
/* Free blocks and release based heap. */
_bfree( seg, instr );
_bfree( seg, outstr );
_bfreeseg( seg );
}
Output
Enter a string: Was I god
Input: was i god
Output: dog i saw
_bheapseg
────────────────────────────────────────────────────────────────────────────
Description
Allocates a based heap.
#include <malloc.h> Required only for function declarations
_segment _bheapseg( size_t size );
size Segment size to allocate
Remarks
The _bheapseg function allocates a based-heap segment of at least size
bytes. (The block may be larger than size bytes because of space required
for alignment and for maintenance information.)
The heap code will try to enlarge the heap as necessary. If the original
block of memory is depleted (e.g., by calls to _bmalloc and _brealloc), the
run-time code will try to enlarge the heap as necessary.
The value returned by _bheapseg is the identifier of the based-heap segment.
This value should be saved and used in subsequent calls to other based-heap
functions.
The _bheapseg function can be called repeatedly. For each call, the C
library will allocate a new based-heap segment.
Return Value
The _bheapseg function returns the newly allocated segment selector that the
user must save for use in subsequent based-heap functions. A return value of
-1 indicates failure.
Always check the return from the _bheapseg function (especially when it is
used in real mode), even if the amount of memory requested is small.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
calloc functions, free functions, malloc functions, realloc functions
Example
/* BHEAPSEG.C: This program C illustrates dynamic allocation of based
* memory using functions _bheapseg, _bfreeseg, _bmalloc, and _bfree.
*/
#include <stdio.h>
#include <malloc.h>
#include <stdlib.h>
#include <string.h>
void main()
{
_segment seg;
char _based( seg ) *outstr, _based( seg ) *instr;
char _based( seg ) *pout, _based( seg ) *pin;
char tmpstr[80];
int len;
printf( "Enter a string: " );
gets( tmpstr );
/* Request a based heap. Use based so that memory won't be taken from
* near heap.
*/
if( (seg = _bheapseg( 1000 )) == _NULLSEG )
exit( 1 );
/* Allocate based memory for two strings. */
len = strlen( tmpstr );
if( ((instr = _bmalloc( seg, len + 1 )) == _NULLOFF) ||
((outstr = _bmalloc( seg, len + 1 )) == _NULLOFF) )
exit( 1 );
/* Copy a lowercased string to dynamic memory. The based memory is
* far when addressed as a whole.
*/
_fstrlwr( _fstrcpy( (char _far *)instr, (char _far *)tmpstr ) );
/* Copy input string to output string in reversed order. When reading
* and writing individual characters from a based heap, the compiler
will
* try to process them as near, thus speeding up the processing.
*/
for( pin = instr + len - 1, pout = outstr;
pout < outstr + len; pin--, pout++ )
*pout = *pin;
*pout = '\0';
/* Display strings. Again, strings as a whole are far. */
printf( "Input: %Fs\n", (char _far *)instr );
printf( "Output: %Fs\n", (char _far *)outstr );
/* Free blocks and release based heap. */
_bfree( seg, instr );
_bfree( seg, outstr );
_bfreeseg( seg );
}
Output
Enter a string: Was I god
Input: was i god
Output: dog i saw
_bios_disk
────────────────────────────────────────────────────────────────────────────
Description
Calls BIOS disk services using system call INT 0x13.
#include <bios.h>
unsigned _bios_disk( unsigned service, struct diskinfo_t *diskinfo );
service Disk function desired
diskinfo Disk parameters
Remarks
The _bios_disk routine uses system call INT 0x13 to provide several
disk-access functions. The service parameter selects the function desired,
while the diskinfo structure provides the necessary parameters. Note that
the low-level disk operations allowed by the _bios_disk routine are very
dangerous to use because they allow direct manipulation of the disk.
The diskinfo structure provides the following parameters:
Element Description
────────────────────────────────────────────────────────────────────────────
unsigned drive Drive number
unsigned head Head number
unsigned track Track number
unsigned sector Starting sector number
unsigned nsectors Number of sectors to read, write, or
compare
void far *buffer Memory location to write to, read from,
or compare
The service argument can be set to one of the following manifest constants:
Constant Function
────────────────────────────────────────────────────────────────────────────
_DISK_FORMAT Formats the track specified by diskinfo.
The head and track fields indicate the
track to format. Only one track can be
formatted in a single call. The buffer
field points to a set of sector markers.
The format of the markers depends on the
type of disk drive; see a technical
reference to the PC BIOS to determine
the marker format. There is no return
value.
_DISK_READ Reads one or more disk sectors into
memory. This service uses all fields of
the structure pointed to by diskinfo, as
defined earlier in this section. If no
error occurs, the function returns 0 in
the high-order byte and the number of
sectors read in the low-order byte. If
there is an error, the high-order byte
will contain a set of status flags. If
there is an error, the high-order byte
will contain a set of status flags, as
defined under _DISK_READ. Status is
returned in the 8 high-order bits of the
return value, as listed below:
Bits Meaning
────────────────────────────────────────────────────────────────────────────
0x01** Invalid request or a bad
command
0x02** Address mark not found
0x04** Sector not found
0x05** Reset failed
0x07** Drive parameter activity
failed
0x09** Direct Memory Access (DMA)
overrun
0x0A** Bad sector flag detected
0x10** Data read (ECC) error
0x11** Corrected data read (ECC)
error
0x20** Controller failure
0x40** Seek error
0x80** Disk timed out or failed
to respond
0xAA** Drive not ready
0xBB** Undefined error
0xCC** Write fault on drive
0xE0** Status error
_DISK_RESET Forces the disk controller to do a hard
reset, preparing for floppy-disk I/O.
This is useful after an error occurs in
another operation, such as a read. If
this service is specified, the
diskinfo argument is ignored.
_DISK_STATUS Obtains the status of the last disk
operation. If this service is specified,
the diskinfo argument is ignored.
_DISK_VERIFY Checks the disk to be sure the specified
sectors exist and can be read. It also
runs a CRC (cyclic redundancy check)
test. This service uses all fields
(except buffer) of the structure pointed
to by diskinfo, as defined earlier in
this section. If no error occurs, the
function returns 0 in the high-order
byte and the number of sectors compared
in the low-order byte. If there is an
error, the high-order byte will contain
a set of status flags, as defined under
_DISK_READ (above).
_DISK_WRITE Writes data from memory to one or more
disk sectors. This service uses all
fields of the structure pointed to by
diskinfo, as defined earlier in this
section. If no error occurs, the
function returns 0 in the high-order
byte and the number of sectors written
in the low-order byte. If there is an
error, the high-order byte will contain
a set of status flags, as defined under
_DISK_READ (above).
Return Value
The _bios_disk function returns the value in the AX register after the BIOS
interrupt.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
Example
/* BDISK.C: This program first attempts to verify a disk by using an
* invalid disk head number. After printing the return value error code,
* the program verifies the disk by using a valid disk head code.
*/
#include <conio.h>
#include <stdio.h>
#include <bios.h>
void main()
{
unsigned status = 0;
struct diskinfo_t disk_info;
disk_info.drive = 0;
disk_info.head = 10; /* Invalid head number */
disk_info.track = 1;
disk_info.sector = 2;
disk_info.nsectors = 8;
printf( "Insert disk in drive A: and press any key\n" );
getch();
status = _bios_disk( _DISK_VERIFY, &disk_info );
printf( "Return value: 0x%.4x\n", status );
if( status & 0xff00 ) /* Error if high byte is 0 */
printf( "Seek error\n" );
else
printf( "No seek error\n" );
printf( "Press any key\n" );
getch();
disk_info.head = 0; /* Valid head number */
status = _bios_disk( _DISK_VERIFY, &disk_info );
printf( "Return value: 0x%.4x\n", status );
if( status & 0xff00 ) /* Error if high byte is 0 */
printf( "Seek error\n" );
else
printf( "No seek error\n" );
}
Output
Insert disk in drive A: and press any key
Return value: 0x0400
Seek error
Press any key
Return value: 0x0008
No seek error
_bios_equiplist
────────────────────────────────────────────────────────────────────────────
Description
Calls BIOS equipment-list service, using system call INT 0x11.
#include <bios.h>
unsigned _bios_equiplist( void );
Remarks
The _bios_equiplist routine uses system call INT 0x11 to determine what
hardware and peripherals are currently installed on the machine.
Return Value
The function returns a set of bits indicating what is installed, as defined
below:
Bits Meaning
────────────────────────────────────────────────────────────────────────────
0 Any disk drive installed if true
1 True (1) if math coprocessor installed
2 -3 System RAM in 16K blocks (16-64K)
4 -5 Initial video mode
6 -7 Number of floppy-disk drives installed
(00 = 1, 01 = 2, etc.)
8 False (0) if and only if a Direct Memory
Access (DMA) chip is installed
9 -11 Number of RS232 serial ports installed
12 True (1) if and only if a game adapter
is installed
13 True (1) if and only if an internal
modem is installed
14 -15 Number of printers installed
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
Example
/* BEQUIPLI.C: This program checks for the presence of diskettes. */
#include <bios.h>
#include <stdio.h>
void main()
{
unsigned equipment;
equipment = _bios_equiplist();
printf( "Equipment bits: 0x%.4x\n", equipment );
if( equipment & 0x1000 ) /* Check for game adapter bit */
printf( "Game adapter installed\n" );
else
printf( "No game adapter installed\n" );
}
Output
Equipment bits: 0x4061
No game adapter installed
_bios_keybrd
────────────────────────────────────────────────────────────────────────────
Description
Calls BIOS keyboard services, using INT 0x16.
#include <bios.h>
unsigned _bios_keybrd( unsigned service );
service Keyboard function desired
Remarks
The _bios_keybrd routine uses system call INT 0x16 to access the keyboard
services. The service argument can be any of the following manifest
constants:
Constant Meaning
────────────────────────────────────────────────────────────────────────────
_KEYBRD_READ, Reads the next character from the
_NKEYBRD_READ keyboard. If no character has been
typed, the call will wait for one. If
the low-order byte of the return value
is nonzero, the call contains the ASCII
value of the character typed. The
high-order byte contains the keyboard
scan code for the character. The
_NKEYBRD_READ constant is used with
enhanced keyboards to obtain the scan
codes for function keys F11 and F12 and
the cursor control keys.
_KEYBRD_READY, Checks whether a keystroke is waiting to
_NKEYBRD_READY be read and, if so, reads it. The return
value is 0 if no keystroke is waiting,
or it is the character waiting to be
read, in the same format as the
_KEYBRD_READ or _NKEYBRD_READY return.
This service does not remove the waiting
character from the input buffer, as does
the _KEYBRD_READ or _NKEYBRD_READ
service. The _NKEYBRD_READY constant is
used with enhanced keyboards to obtain
the scan codes for function keys F11 and
F12 and the cursor control keys.
_KEYBRD_SHIFTSTATUS, Returns the current SHIFT-key status.
_NKEYBRD_SHIFTSTATUS Only the low-order byte of the return
value is affected. The
_NKEYBRD_SHIFTSTATUS constant is used to
get a full 16-bit status value. Any
combination of the following bits may be
set:
Bit Meaning if True
────────────────────────────────────────────────────────────────────────────
00H Rightmost SHIFT key pressed
01H Leftmost SHIFT key pressed
02H Either CTRL key pressed
3H Either ALT key pressed
04H SCROLL LOCK on
05H NUM LOCK on
06H CAPS LOCK on
07H In insert mode (INS)
08H Left CTRL key pressed
09H Left ALT key pressed
0AH Right CTRL key pressed
0BH Right ALT key pressed
0CH SCROLL LOCK key pressed
0DH NUM LOCK key pressed
0EH CAPS LOCK key pressed
0FH SYS REQ key pressed
Return Value
With the ...READ and ...SHIFTSTATUS arguments, the _bios_keybrd function
returns the contents of the AX register after the BIOS call.
With the ...READY argument, _bios_keybrd returns 0 if there is no key. If
there is a key, _bios_keybrd returns the key waiting to be read (i.e. the
same value as _KEYBRD_READ).
With the ...READ and the ...READY arguments, the _bios_keybrd function
returns -1 if CTRL+BREAK has been pressed and is the next keystroke to be
read.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
Example
/* BKEYBRD.C: This program prints a message on the screen until the
* right SHIFT key is pressed.
*/
#include <bios.h>
#include <stdio.h>
void main()
{
while( !(_bios_keybrd( _KEYBRD_SHIFTSTATUS ) & 0001) )
printf( "Use the right SHIFT key to stop this message\n" );
printf( "Right SHIFT key pressed\n" );
}
Output
Use the right SHIFT key to stop this message
Use the right SHIFT key to stop this message
Use the right SHIFT key to stop this message
Use the right SHIFT key to stop this message
Right SHIFT key pressed
_bios_memsize
────────────────────────────────────────────────────────────────────────────
Description
Calls the BIOS memory-size service, using system call INT 0x12.
#include <bios.h>
unsigned _bios_memsize( void );
Remarks
The _bios_memsize routine uses system call INT 0x12 to determine the total
amount of main memory installed.
Return Value
The routine returns the total amount of installed memory in 1K blocks. The
maximum return value is 640, representing 640K of main memory.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
Example
/* BMEMSIZE.C: This program displays the amount of memory installed. */
#include <bios.h>
#include <stdio.h>
void main()
{
unsigned memory;
memory = _bios_memsize();
printf ( "The amount of memory installed is: %dK\n", memory );
}
Output
The amount of memory installed is: 639K
_bios_printer
────────────────────────────────────────────────────────────────────────────
Description
Calls BIOS printer services using system call INT 0x17.
#include <bios.h>
unsigned _bios_printer( unsigned service, unsigned printer, unsigned data
);
service Printer function desired
printer Target printer port
data Output data
Remarks
The _bios_printer routine uses system call INT 0x17 to perform printer
output services for parallel printers. The printer argument specifies the
affected printer, where 0 is LPT1, 1 is LPT2, and so forth.
Some printers do not support the full set of signals. As a result, the "Out
of Paper" condition, for example, may not be returned to your program.
The service argument can be any of the following manifest constants:
Constant Meaning
────────────────────────────────────────────────────────────────────────────
_PRINTER_INIT Initializes the selected printer. The
data argument is ignored. The return
value is the low-order status byte
defined below.
_PRINTER_STATUS Returns the printer status in the
low-order status byte defined below. The
data argument is ignored.
_PRINTER_WRITE Sends the low-order byte of data to the
printer specified by printer. The
low-order byte of the return value
indicates the printer status after the
operation, as defined below:
Bit Meaning if True
────────────────────────────────────────────────────────────────────────────
0 Printer timed out
1 Not used
2 Not used
3 I/O error
4 Printer selected
5 Out of paper
6 Acknowledge
7 Printer not busy
Return Value
The _bios_printer function returns the value in the AX register after the
BIOS interrupt.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
Example
/* BPRINTER.C: This program checks the status of the printer attached to
* LPT1 when it is off line, then initializes the printer.
*/
#include <bios.h>
#include <conio.h>
#include <stdio.h>
#define LPT1 0
void main()
{
unsigned status;
printf ( "Place printer off line and press any key\n" );
getch();
status = _bios_printer( _PRINTER_STATUS, LPT1, 0 );
printf( "Status with printer off line: 0x%.4x\n\n", status );
printf( "Put the printer on line and then\n" );
printf( "Press any key to initialize printer\n" );
getch();
status = _bios_printer( _PRINTER_INIT, LPT1, 0 );
printf( "Status after printer initialized: 0x%.4x\n", status );
}
Output
Place printer off line and press any key
Status with printer off line: 0x0018
Put the printer on line and then
Press any key to initialize printer
Status after printer initialized: 0x0090
_bios_serialcom
────────────────────────────────────────────────────────────────────────────
Description
Calls BIOS communications services, using system call INT 0x14.
#include <bios.h>
unsigned _bios_serialcom( unsigned service, unsigned serial_port, unsigned
data );
service Communications service
serial_port Serial port to use
data Port configuration bits
Remarks
The _bios_serialcom routine uses system call INT 0x14 to provide serial
communications services. The serial_port argument is set to 0 for COM1, to 1
for COM2, and so on.
The _bios_serialcom routine may not be able to establish reliable
communications at baud rates in excess of 1,200 baud ( _COM_1200) due to the
overhead associated with servicing computer interrupts. Faster data
communication rates are possible with more direct programming of serial-port
controllers. See C Programmer's Guide to Serial Communications for more
details on serial-communications programming in C.
The service argument can be set to one of the following manifest constants:
Constant Service
────────────────────────────────────────────────────────────────────────────
_COM_INIT Sets the port to the parameters
specified in the data argument
_COM_SEND Transmits the data characters over the
selected serial port
_COM_RECEIVE Accepts an input character from the
selected serial port
_COM_STATUS Returns the current status of the
selected serial port
The data argument is ignored if service is set to _COM_RECEIVE or
_COM_STATUS. The data argument for _COM_INIT is created by combining (with
the OR operator) one or more of the following constants:
Constant Meaning
────────────────────────────────────────────────────────────────────────────
_COM_CHR7 7 data bits
_COM_CHR8 8 data bits
_COM_STOP1 1 stop bit
_COM_STOP2 2 stop bits
_COM_NOPARITY No parity
_COM_EVENPARITY Even parity
_COM_ODDPARITY Odd parity
_COM_110 110 baud
_COM_150 150 baud
_COM_300 300 baud
_COM_600 600 baud
_COM_1200 1,200 baud
_COM_2400 2,400 baud
_COM_4800 4,800 baud
_COM_9600 9,600 baud
The default value of data is 1 stop bit, no parity, and 110 baud.
Return Value
The function returns a 16-bit integer whose high-order byte contains status
bits. The meaning of the low-order byte varies, depending on the service
value. The high-order bits have the following meanings:
Bit Meaning if Set
────────────────────────────────────────────────────────────────────────────
15 Timed out
14 Transmission-shift register empty
13 Transmission-hold register empty
12 Break detected
11 Framing error
10 Parity error
9 Overrun error
8 Data ready
When service is _COM_SEND, bit 15 will be set if data could not be sent.
When service is _COM_RECEIVE, the byte read will be returned in the
low-order bits if the call is successful. If an error occurs, any of the
bits 9, 10, 11, or 15 will be set.
When service is _COM_INIT or _COM_STATUS, the low-order bits are defined as
follows:
Bit Meaning if Set
────────────────────────────────────────────────────────────────────────────
7 Receive-line signal detected
6 Ring indicator
5 Data set ready
4 Clear to send
3 Change in receive-line signal detected
2 Trailing-edge ring indicator
1 Change in data-set-ready status
0 Change in clear-to-send status
Note that this function works only with IBM personal computers and true
compatibles.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
Example
/* BSERIALC.C: This program checks the status of serial port COM1. */
#include <bios.h>
#include <stdio.h>
void main()
{
unsigned com1_status;
com1_status = _bios_serialcom( _COM_STATUS, 0, 0 );
printf ( "COM1 status: 0x%.4x\n", com1_status );
}
Output
COM1 status: 0x6000
_bios_timeofday
────────────────────────────────────────────────────────────────────────────
Description
Calls BIOS time and date services, using system call INT 0x1A.
#include <bios.h>
unsigned _bios_timeofday( unsigned service, long *timeval );
service Time function desired
timeval Clock count
Remarks
The _bios_timeofday routine uses system call INT 0x1A to get or set the
clock count. The service argument can be either of the following manifest
constants:
Constant Meaning
────────────────────────────────────────────────────────────────────────────
_TIME_GETCLOCK Copies the current value of the clock
count to the location pointed to by
timeval. If midnight has not passed
since the last time the system clock was
read or set, the function returns 0;
otherwise, the function returns 1.
_TIME_SETCLOCK Sets the current value of the system
clock to the value in the location
pointed to by timeval. There is no
return value.
Return Value
The _bios_timeofday function returns the value in the AX register after the
BIOS interrupt.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
Example
/* BTIMEOFD.C: This program gets the current system clock count before and
after
* a "do-nothing" loop and displays the difference.
*/
#include <bios.h>
#include <stdio.h>
void main()
{
long i, begin_tick, end_tick;
_bios_timeofday( _TIME_GETCLOCK, &begin_tick );
printf( "Beginning tick count: %lu\n", begin_tick );
for( i = 1; i <= 900000; i++ )
;
_bios_timeofday( _TIME_GETCLOCK, &end_tick );
printf( "Ending tick count: %lu\n", end_tick );
printf( "Elapsed ticks: %lu\n", end_tick - begin_tick );
}
Output
Beginning tick count: 1114255
Ending tick count: 1114287
Elapsed ticks: 32
bsearch
────────────────────────────────────────────────────────────────────────────
Description
Performs binary search of a sorted array.
#include <stdlib.h> Required for ANSI compatibility
#include <search.h> Required only for function declarations
void *bsearch( const void *key, const void *base, size_t num, size_t
width,
int ( *compare )( const void *elem1, const void *elem2 ) );
key Object to search for
base Pointer to base of search data
num Number of elements
width Width of elements
compare Function that compares two elements:
elem1 and elem2
elem1 Pointer to the key for the search
elem2 Pointer to the array element to be
compared with the key
Remarks
The bsearch function performs a binary search of a sorted array of num
elements, each of width bytes in size. The base value is a pointer to the
base of the array to be searched, and key is the value being sought.
The compare argument is a pointer to a user-supplied routine that compares
two array elements and returns a value specifying their relationship. The
bsearch function calls the compare routine one or more times during the
search, passing pointers to two array elements on each call. The routine
compares the elements, then returns one of the following values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
< 0 elem1 less than elem2
= 0 elem1 identical to elem2
> 0 elem1 greater than elem2
If the array you are searching is not in ascending sort order, bsearch does
not work properly. If the array contains duplicate records with identical
keys, there is no way to predict which of the duplicate records will be
located by bsearch.
Return Value
The bsearch function returns a pointer to the first occurrence of key in the
array pointed to by base. If key is not found, the function returns NULL.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
lfind, lsearch, qsort
Example
/* BSEARCH.C: This program reads the command-line arguments, sorting them
* with qsort, and then uses bsearch to find the word "cat."
*/
#include <search.h>
#include <string.h>
#include <stdio.h>
int compare( char **arg1, char **arg2 ); /* Declare a function for
compare */
void main( int argc, char **argv )
{
char **result;
char *key = "cat";
int i;
/* Sort using Quicksort algorithm: */
qsort( (char *)argv, argc, sizeof( char * ), compare );
for( i = 0; i < argc; ++i ) /* Output sorted list */
printf( "%s ", argv[i] );
/* Find the word "cat" using a binary search algorithm: */
result = (char **)bsearch( (char *) &key, (char *)argv, argc,
sizeof( char * ), compare );
if( result )
printf( "\n%s found at %Fp\n", *result, result );
else
printf( "\nCat not found!\n" );
}
int compare( char **arg1, char **arg2 )
{
/* Compare all of both strings: */
return strcmpi( *arg1, *arg2 );
}
Output
[C:\LIBREF] bsearch dog pig horse cat human rat cow goat
bsearch cat cow dog goat horse human pig rat
cat found at 0292:0FD0
cabs, cabsl
────────────────────────────────────────────────────────────────────────────
Description
Calculate absolute value of a complex number.
#include <math.h>
double cabs( struct complex z );
long double cabsl( struct _complexl z );
z Complex number
Remarks
The cabs and cabsl functions calculate the absolute value of a complex
number, which must be a structure of type complex (or _complexl). The
structure z is composed of a real component x and an imaginary component y.
A call to one of the cabs routines is equivalent to the following:
sqrt( z.x*z.x + z.y*z.y )
The cabsl function is the 80-bit counterpart and it uses the 80-bit, 10-byte
coprocessor form of arguments and return values. See the reference page on
the long double functions for more details on this data type.
Return Value
On overflow, these functions call matherr or _matherrl, return HUGE_VAL, and
set errno to ERANGE.
Compatibility
cabs
▼ ANSI DOS OS/2 UNIX XENIX
cabsl
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
abs, fabs, labs
Example
/* CABS.C: Using cabs, this program calculates the absolute value of
* a complex number.
*/
#include <math.h>
#include <stdio.h>
void main()
{
struct complex number = { 3.0, 4.0 };
double d;
d = cabs( number );
printf( "The absolute value of %f + %fi is %f\n",
number.x, number.y, d );
}
Output
The absolute value of 3.000000 + 4.000000i is 5.000000
calloc Functions
────────────────────────────────────────────────────────────────────────────
Description
Allocate an array in memory with elements initialized to 0.
#include <stdlib.h> For ANSI compatibility (calloc only)
#include <malloc.h> Required only for function declarations
void *calloc( size_t num, size_t size );
void _based( void ) *_bcalloc( _segment seg, size_t num, size_t size );
void _far *_fcalloc( size_t num, size_t size );
void _near *_ncalloc( size_t num, size_t size );
num Number of elements
size Length in bytes of each element
seg Segment selector
Remarks
The calloc family of functions allocates storage space for an array of num
elements, each of length size bytes. Each element is initialized to 0.
In large data models (compact-, large-, and huge-model programs), calloc
maps to _fcalloc. In small data models (tiny-, small-, and medium-model
programs), calloc maps to _ncalloc.
The various calloc functions allocate storage space in the data segments
shown in the list below:
Function Data Segment
────────────────────────────────────────────────────────────────────────────
calloc Depends on data model of program
_bcalloc Based heap, specified by seg segment
selector
_fcalloc Far heap (outside default data segment)
_ncalloc Near heap (inside default data segment)
Return Value
The calloc functions return a pointer to the allocated space. The storage
space pointed to by the return value is guaranteed to be suitably aligned
for storage of any type of object. To get a pointer to a type other than
void, use a type cast on the return value.
The _fcalloc and _ncalloc functions return NULL if there is insufficient
memory available or if num or size is 0. The _bcalloc function returns
_NULLOFF in this case.
Compatibility
calloc
ANSI DOS OS/2 UNIX XENIX
_bcalloc, _fcalloc, _ncalloc
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
free functions, halloc, hfree, malloc functions, realloc functions
Example
/* CALLOC.C: This program uses calloc to allocate space for 40 long
integers.
* It initializes each element to zero.
*/
#include <stdio.h>
#include <malloc.h>
void main()
{
long *buffer;
buffer = (long *)calloc( 40, sizeof( long ) );
if( buffer != NULL )
printf( "Allocated 40 long integers\n" );
else
printf( "Can't allocate memory\n" );
free( buffer );
}
Output
Allocated 40 long integers
ceil, ceill
────────────────────────────────────────────────────────────────────────────
Description
Calculate the ceiling of a value.
#include <math.h>
double ceil( double x );
long double ceill( long double x );
x Floating-point value
Remarks
The ceil and ceill functions return a double (or long double) value
representing the smallest integer that is greater than or equal to x.
The ceill function is the 80-bit counterpart and it uses the 80-bit, 10-byte
coprocessor form of arguments and return values. See the reference page on
the long double functions for more details on this data type.
Return Value
These functions return the double or long double result. There is no error
return.
Compatibility
ceil
ANSI DOS OS/2 UNIX XENIX
ceill
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
floor, fmod
Example
/* FLOOR.C: This example displays the largest integers less than or equal
* to the floating-point values 2.8 and -2.8. It then shows the smallest
* integers greater than or equal to 2.8 and -2.8.
*/
#include <math.h>
#include <stdio.h>
void main()
{
double y;
y = floor( 2.8 );
printf( "The floor of 2.8 is %f\n", y );
y = floor( -2.8 );
printf( "The floor of -2.8 is %f\n", y );
y = ceil( 2.8 );
printf( "The ceil of 2.8 is %f\n", y );
y = ceil( -2.8 );
printf( "The ceil of -2.8 is %f\n", y );
}
Output
The floor of 2.8 is 2.000000
The floor of -2.8 is -3.000000
The ceil of 2.8 is 3.000000
The ceil of -2.8 is -2.000000
_cexit, _c_exit
────────────────────────────────────────────────────────────────────────────
Description
Perform clean-up operations and return without terminating the process.
#include <process.h>
void _cexit( void );
void _c_exit( void );
Remarks
The _cexit function calls, in LIFO ("last in, first out") order, the
functions registered by atexit and onexit. Then the _cexit function flushes
all I/O buffers and closes all open files before returning.
The _c_exit function returns to the calling process without processing
atexit or onexit functions or flushing stream buffers.
The behavior of the exit, _exit, _cexit, and _c_exit functions is described
in the following list:
Function Action
────────────────────────────────────────────────────────────────────────────
exit Performs complete C library termination
procedures, terminates the process, and
exits with the supplied status code
_exit Performs "quick" C library termination
procedures, terminates the process, and
exits with the supplied status code
_cexit Performs complete C library termination
procedures and returns to caller, but
does not terminate the process
_c_exit Performs "quick" C library termination
procedures and returns to caller, but
does not terminate the process
Return Value
None.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
abort, atexit, exec functions, exit, onexit, spawn functions, system
cgets
────────────────────────────────────────────────────────────────────────────
Description
Gets a character string from the console.
#include <conio.h> Required only for function declarations
char *cgets( char *buffer );
buffer Storage location for data
Remarks
The cgets function reads a string of characters directly from the console
and stores the string and its length in the location pointed to by buffer.
The buffer argument must be a pointer to a character array. The first
element of the array, buffer[0], must contain the maximum length (in
characters) of the string to be read. The array must contain enough elements
to hold the string, a terminating null character ('\0'), and two additional
bytes.
The cgets function continues to read characters until a
carriage-return-line-feed (CR-LF) combination is read, or the specified
number of characters is read. The string is stored starting at str[2]. If a
CR-LF combination is read, it is replaced with a null character ('\0')
before being stored. The cgets function then stores the actual length of the
string in the second array element, buffer[1].
Because all DOS editing keys are active when you call cgets, pressing F3
repeats the last entry.
Return Value
The cgets function returns a pointer to the start of the string, at
buffer[2]. There is no error return.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
getch, getche
Example
/* CGETS.C: This program creates a buffer and initializes the first byte
* to the size of the buffer - 2. Next, the program accepts an input
string
* using cgets and displays the size and text of that string.
*/
#include <conio.h>
#include <stdio.h>
void main()
{
char buffer[82] = { 80 }; /* Maximum characters in first byte */
char *result;
printf( "Input line of text, followed by carriage return:\n");
result = cgets( buffer ); /* Input a line of text */
printf( "\nLine length = %d\nText = %s\n", buffer[1], result );
}
Output
Input line of text, followed by carriage return:
This is some text
Line length = 17
Text = This is some text
_chain_intr
────────────────────────────────────────────────────────────────────────────
Description
Chains an interrupt from one handler to another.
#include <dos.h>
void _chain_intr( void( _interrupt _far *target )());
target Target interrupt routine
Remarks
The _chain_intr routine passes control from one interrupt handler to
another. The stack and the registers of the first routine are passed to the
second, allowing the second routine to return as if it had been called
directly.
The _chain_intr routine is generally used when a user-defined interrupt
handler begins processing, then chains to the original interrupt handler to
finish processing.
Chaining is one of two techniques, listed below, that can be used to
transfer control from a new interrupt routine to an old one:
1. Call _chain_intr with the interrupt routine as an argument. Do this if
your routine is finished and you want the second interrupt routine to
terminate the interrupt call.
void _interrupt new_int( unsigned _es, unsigned _ds,
unsigned _di, unsigned _si,... )
{
++_di; /* Initial processing here */
_chain_intr( old_int ); /* New DI passed to old_int */
--_di; /* This is never executed */
}
2. Call the interrupt routine (after casting it to an interrupt function
if necessary). Do this if you need to do further processing after the
second interrupt routine finishes.
void _interrupt new_int( unsigned _es, unsigned _ds,
unsigned _di, unsigned _si,... )
{
++_di; /* Initial processing here */
(*old_int)(); /* New DI passed to old_int */
_asm mov _di, di /* Put real DI from old_int */
/* into _di for return */
}
Note that the real registers set by the old interrupt function are not
automatically set to the pseudoregisters of the new routine.
Use the _chain_intr function when you do not want to replace the default
interrupt handler, but you do need to see its input. An example is a TSR
(terminate-and-stay-resident) program that checks all keyboard input for a
particular "hot key" sequence.
The _chain_intr function should be used only with C functions that have been
declared with type _interrupt. The _interrupt declaration ensures that the
procedure's entry/exit sequence is appropriate for an interrupt handler.
Return Value
The _chain_intr function does not return to the caller.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_dos_getvect, _dos_keep, _dos_setvect
chdir
────────────────────────────────────────────────────────────────────────────
Description
Changes the current working directory.
#include <direct.h> Required only for function declarations
#include <errno.h> Required for errno constants
int chdir( char *dirname );
dirname Path name of new working directory
Remarks
The chdir function changes the current working directory to the directory
specified by dirname. The dirname argument must refer to an existing
directory.
This function can change the current working directory on any drive; it
cannot be used to change the default drive itself. For example, if A: is the
default drive and \BIN is the current working directory, the following call
changes the current working directory for drive C:
chdir("c:\\temp");
Notice that you must place two backslashes ( \\ ) in a C string in order to
represent a single backslash ( \ ); the backslash is the escape character
for C strings and therefore requires special handling.
This function call has no apparent immediate effect. However, when the
_chdrive function is called to change the default drive to C:, the current
working directory becomes C:\TEMP.
In OS/2 protected mode, the current working directory is local to a process
rather than system-wide. When a process terminates, the current working
directory is restored to its original value. Under DOS, the new directory
set by the program becomes the new current working directory.
Return Value
The chdir function returns a value of 0 if the working directory is
successfully changed. A return value of -1 indicates an error, in which case
errno is set to ENOENT, indicating that the specified path name could not be
found.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
_dos_setdrive, mkdir, rmdir, system
Example
/* CHGDIR.C: This program uses the chdir function to verify that a
* given directory exists. Under real mode that directory also becomes
* the current directory. Under protected mode, it is only the default
* directory for the current process.
*/
#include <direct.h>
#include <stdio.h>
#include <stdlib.h>
void main( int argc, char *argv[] )
{
if( chdir( argv[1] ) )
printf( "Unable to locate the directory: %s\n", argv[1] );
else
system( "dir *.c" );
}
Output
[C:\LIBREF] chgdir \tmp
The volume label in drive C is OS2.
Directory of C:\TMP
DUP C 232 4-18-89 11:18a
TEST C 713 4-07-88 2:49p
2 File(s) 14155776 bytes free
_chdrive
────────────────────────────────────────────────────────────────────────────
Description
Changes the current working drive.
#include <direct.h> Required only for function declarations
int _chdrive( int drive );
drive Number of new working drive
Remarks
The _chdrive function changes the current working drive to the drive
specified by drive. The drive argument uses an integer to specify the new
working drive (1=A, 2=B, etc.).
This function changes only the working drive; the chdir function changes the
working directory.
In OS/2 protected mode, the working drive is local to a process rather than
system-wide. When a process terminates, the working drive is restored to its
original value. Under DOS, the new drive set by the program becomes the new
working drive.
Return Value
The _chdrive function returns a value of 0 if the working drive is
successfully changed. A return value of -1 indicates an error.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
chdir, _dos_setdrive, _fullpath, _getcwd, _getdrive, mkdir, rmdir,
system
Example
/* GETDRIVE.C illustrates drive functions including:
* _getdrive _chdrive _getdcwd
*/
#include <stdio.h>
#include <conio.h>
#include <direct.h>
#include <stdlib.h>
void main()
{
int ch, drive, curdrive;
static char path[_MAX_PATH];
/* Save current drive. */
curdrive = _getdrive();
printf( "Available drives are: \n" );
/* If we can switch to the drive, it exists. */
for( drive = 1; drive <= 26; drive++ )
if( !_chdrive( drive ) )
printf( "%c: ", drive + 'A' - 1 );
while( 1 )
{
printf( "\nType drive letter to check or ESC to quit: " );
ch = getch();
if( ch == 27 )
break;
if( isalpha( ch ) )
putch( ch );
if( _getdcwd( toupper( ch ) - 'A' + 1, path, _MAX_PATH ) != NULL )
printf( "\nCurrent directory on that drive is %s\n", path );
}
/* Restore original drive. This is only necessary for DOS. Under OS/2
* the current drive of the calling process is always restored.
*/
_chdrive( curdrive );
printf( "\n" );
}
Output
Available drives are:
A: B: C:
Type drive letter to check or ESC to quit: q
Type drive letter to check or ESC to quit: a
Current directory on that drive is A:\
Type drive letter to check or ESC to quit: c
Current directory on that drive is C:\LIBREF
Type drive letter to check or ESC to quit:
chmod
────────────────────────────────────────────────────────────────────────────
Description
Changes the file-permission settings.
#include <sys\types.h>
#include <sys\stat.h>
#include <errno.h>
#include <io.h> Required only for function declarations
int chmod( char *filename, int pmode );
filename Path name of existing file
pmode Permission setting for file
Remarks
The chmod function changes the permission setting of the file specified by
filename. The permission setting controls read and write access to the file.
The constant expression pmode contains one or both of the manifest constants
S_IWRITE and S_IREAD, defined in SYS\STAT.H. Any other values for pmode are
ignored. When both constants are given, they are joined with the bitwise-OR
operator ( | ). The meaning of the pmode argument is as follows:
Value Meaning
────────────────────────────────────────────────────────────────────────────
S_IWRITE Writing permitted
S_IREAD Reading permitted
S_IREAD | S_IWRITE Reading and writing permitted
If write permission is not given, the file is read-only. Under DOS and OS/2,
all files are readable; it is not possible to give write-only permission.
Thus the modes S_IWRITE and S_IREAD | S_IWRITE are equivalent.
Return Value
The chmod function returns the value 0 if the permission setting is
successfully changed. A return value of -1 indicates an error; in this case,
errno is set to ENOENT, indicating that the specified file could not be
found.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
access, creat, fstat, open, stat
Example
/* CHMOD.C: This program uses chmod to change the mode of a file to
* read-only. It then attempts to modify the file.
*/
#include <sys\types.h>
#include <sys\stat.h>
#include <io.h>
#include <stdio.h>
#include <stdlib.h>
void main()
{
/* Make file read-only: */
if( chmod( "CHMOD.C", S_IREAD ) == -1 )
perror( "File not found\n" );
else
printf( "Mode changed to read-only\n" );
system( "echo /* End of file */ >> CHMOD.C" );
/* Change back to read/write: */
if( chmod( "CHMOD.C", S_IWRITE ) == -1 )
perror( "File not found\n" );
else
printf( "Mode changed to read/write\n" );
}
Output
Mode changed to read-only
Access denied
Mode changed to read/write
chsize
────────────────────────────────────────────────────────────────────────────
Description
Changes the file size.
#include <io.h> Required only for function declarations
#include <errno.h>
int chsize( int handle, long size );
handle Handle referring to open file
size New length of file in bytes
Remarks
The chsize function extends or truncates the file associated with handle to
the length specified by size. The file must be open in a mode that permits
writing. Null characters ('\0') are appended if the file is extended. If the
file is truncated, all data from the end of the shortened file to the
original length of the file is lost.
In DOS, the directory update is done when a file is closed. Consequently,
while a program is running, requests to determine the amount of free disk
space may receive inaccurate results.
Return Value
The chsize function returns the value 0 if the file size is successfully
changed. A return value of -1 indicates an error, and errno is set to one of
the following values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
EACCES Specified file is locked against access
(OS/2 and DOS versions 3.0 and later
only).
EBADF Specified file is read-only or an
invalid file handle.
ENOSPC No space is left on device.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
close, creat, open
Example
/* CHSIZE.C: This program uses filelength to report the size of a
* file before and after modifying it with chsize.
*/
#include <io.h>
#include <fcntl.h>
#include <sys\types.h>
#include <sys\stat.h>
#include <stdio.h>
void main()
{
int fh, result;
unsigned int nbytes = BUFSIZ;
/* Open a file */
if( (fh = open( "data", O_RDWR | O_CREAT, S_IREAD | S_IWRITE )) != -1 )
{
printf( "File length before: %ld\n", filelength( fh ) );
if( chsize( fh, 329678 ) == 0 )
printf( "Size successfully changed\n" );
else
printf( "Problem in changing the size\n" );
printf( "File length after: %ld\n", filelength( fh ) );
close( fh );
}
}
Output
File length before: 0
Size successfully changed
File length after: 329678
_clear87
────────────────────────────────────────────────────────────────────────────
Description
Gets and clears the floating-point status word.
#include <float.h>
unsigned int _clear87( void );
Remarks
The _clear87 function gets and clears the floating-point status word. The
floating-point status word is a combination of the 8087/80287 status word
and other conditions detected by the 8087/80287 exception handler, such as
floating-point stack overflow and underflow.
Return Value
The bits in the value returned indicate the floating-point status. See the
FLOAT.H include file for a complete definition of the bits returned by
_clear87.
Many of the math library functions modify the 8087/80287 status word, with
unpredictable results. Return values from _clear87 and _status87 become more
reliable as fewer floating-point operations are performed between known
states of the floating-point status word.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_control87, _status87
Example
/* CLEAR87.C: This program creates various floating-point problems,
* then uses _clear87 to report on these problems.
*/
#include <stdio.h>
#include <float.h>
void main()
{
double a = 1e-40, b;
float x, y;
printf( "Status: %.4x - clear\n", _clear87() );
/* Store into y is inexact and underflows: */
y = a;
printf( "Status: %.4x - inexact, underflow\n", _clear87() );
/* y is denormal: */
b = y;
printf( "Status: %.4x - denormal\n", _clear87() );
}
Output
Status: 0000 - clear
Status: 0030 - inexact, underflow
Status: 0002 - denormal
clearerr
────────────────────────────────────────────────────────────────────────────
Description
Resets the error indicator for a stream.
#include <stdio.h>
void clearerr( FILE *stream );
stream Pointer to FILE structure
Remarks
The clearerr function resets the error indicator and end-of-file indicator
for stream. Error indicators are not automatically cleared; once the error
indicator for a specified stream is set, operations on that stream continue
to return an error value until clearerr, fseek, fsetpos, or rewind is
called.
Return Value
None.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
eof, feof, ferror, perror
Example
/* CLEARERR.C: This program creates an error on the standard input
* stream, then clears it so that future reads won't fail.
*/
#include <stdio.h>
void main()
{
int c;
/* Create an error by writing to standard input. */
putc( 'c', stdin );
if( ferror( stdin ) )
{
perror( "Write error" );
clearerr( stdin );
}
/* See if read causes an error. */
printf( "Will input cause an error? " );
c = getc( stdin );
if( ferror( stdin ) )
{
perror( "Read error" );
clearerr( stdin );
}
}
Output
Write error: Error 0
Will input cause an error? n
_clearscreen
────────────────────────────────────────────────────────────────────────────
Description
Clears the specified area of the screen.
#include <graph.h>
void _far _clearscreen( short area );
area Target area
Remarks
The _clearscreen function erases the target area, filling it with the
current background color. The area parameter can be one of the following
manifest constants (defined in GRAPH.H):
Constant Action
────────────────────────────────────────────────────────────────────────────
_GCLEARSCREEN Clears and fills the entire screen
_GVIEWPORT Clears and fills only within the current
view port
_GWINDOW Clears and fills only within the current
text window
Return Value
None.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_getbkcolor, _setbkcolor
Example
/* CLRSCRN.C */
#include <conio.h>
#include <graph.h>
#include <stdlib.h>
void main()
{
short xhalf, yhalf, xquar, yquar;
struct videoconfig vc;
/* Find a valid graphics mode. */
if( !_setvideomode( _MAXRESMODE ) )
exit( 1 );
_getvideoconfig( &vc );
xhalf = vc.numxpixels / 2;
yhalf = vc.numypixels / 2;
xquar = xhalf / 2;
yquar = yhalf / 2;
_setviewport( 0, 0, xhalf - 1, yhalf - 1 );
_rectangle( _GBORDER, 0, 0, xhalf - 1, yhalf - 1 );
_ellipse( _GFILLINTERIOR, xquar / 4, yquar / 4,
xhalf - (xquar / 4), yhalf - (yquar / 4) );
getch();
_clearscreen( _GVIEWPORT );
getch();
_setvideomode( _DEFAULTMODE );
}
clock
────────────────────────────────────────────────────────────────────────────
Description
Calculates the time used by the calling process.
#include <time.h>
clock_t clock( void );
Remarks
The clock function tells how much processor time has been used by the
calling process. The time in seconds is approximated by dividing the clock
return value by the value of the CLOCKS_PER_SEC constant.
In other words, the clock function returns the number of processor timer
ticks that have elapsed. A timer tick is approximately equal to
1/CLOCKS_PER_SEC seconds.
Return Value
The clock function returns the product of the time in seconds and the value
of the CLOCKS_PER_SEC constant. If the processor time is not available, the
function returns the value -1, cast as clock_t.
Compatibility
ANSI DOS OS/2 ▼ UNIX ▼ XENIX
In both DOS and OS/2, clock returns the time elapsed since the process
started. This may not be equal to the actual processor time used by the
process.
In previous versions of Microsoft C, the CLOCKS_PER_SEC constant was called
CLK_TCK.
See Also
difftime, time
Example
/* CLOCK.C: This example prompts for how long the program is to run and
* then continuously displays the elapsed time for that period.
*/
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
void sleep( clock_t wait );
void main()
{
long i = 600000L;
clock_t start, finish;
double duration;
/* Delay for a specified time. */
printf( "Delay for three seconds\n" );
sleep( (clock_t)3 * CLOCKS_PER_SEC );
printf( "Done!\n" );
/* Measure the duration of an event. */
printf( "Time to do %ld empty loops is ", i );
start = clock();
while( i-- )
;
finish = clock();
duration = (double)(finish - start) / CLOCKS_PER_SEC;
printf( "%2.1f seconds\n", duration );
}
/* Pauses for a specified number of microseconds. */
void sleep( clock_t wait )
{
clock_t goal;
goal = wait + clock();
while( goal > clock() )
;
}
Output
Delay for five seconds
Done!
Time to do 900000 empty loops is 2.0 seconds
close
────────────────────────────────────────────────────────────────────────────
Description
Closes a file.
#include <io.h> Required only for function declarations
#include <errno.h>
int close( int handle );
handle Handle referring to open file
Remarks
The close function closes the file associated with handle.
Return Value
The close function returns 0 if the file was successfully closed. A return
value of -1 indicates an error, and errno is set to EBADF, indicating an
invalid file-handle argument.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
chsize, creat, dup, dup2, open, unlink
Example
/* OPEN.C: This program uses open to open a file named OPEN.C for input
* and a file named OPEN.OUT for output. The files are then closed.
*/
#include <fcntl.h>
#include <sys\types.h>
#include <sys\stat.h>
#include <io.h>
#include <stdio.h>
void main()
{
int fh1, fh2;
fh1 = open( "OPEN.C", O_RDONLY );
if( fh1 == -1 )
perror( "open failed on input file" );
else
{
printf( "open succeeded on input file\n" );
close( fh1 );
}
fh2 = open( "OPEN.OUT", O_WRONLY | O_CREAT, S_IREAD | S_IWRITE );
if( fh2 == -1 )
perror( "open failed on output file" );
else
{
printf( "open succeeded on output file\n" );
close( fh2 );
}
}
Output
open succeeded on input file
open succeeded on output file
_control87
────────────────────────────────────────────────────────────────────────────
Description
Gets and sets the floating-point control word.
#include <float.h>
unsigned int _control87( unsigned int new, unsigned int mask );
new New control-word bit values
mask Mask for new control-word bits to set
Remarks
The _control87 function gets and sets the floating-point control word. The
floating-point control word allows the program to change the precision,
rounding, and infinity modes in the floating-point-math package.
Floating-point exceptions can also be masked or unmasked using the
_control87 function.
If the value for mask is equal to 0, then _control87 gets the floating-point
control word. If mask is nonzero, then a new value for the control word is
set in the following manner: for any bit that is on (equal to 1) in mask,
the corresponding bit in new is used to update the control word. To put it
another way,
fpcntrl = ((fpcntrl & ~mask) | (new & mask))
where fpcntrl is the floating-point control word.
The possible values for the mask constant (mask) and new control values
(new) are shown in Table R.1.
Table R.1 Hex Values
╓┌────────────┌──────────┌────────────────┌──────────────────────────────────╖
Mask Hex Value Constant Hex Value
────────────────────────────────────────────────────────────────────────────
MCW_EM 0x003F
(Interrupt
exception)
EM_INVALID 0x0001
EM_DENORMAL 0x0002
EM_ZERODIVIDE 0x0004
EM_OVERFLOW 0x0008
EM_UNDERFLOW 0x0010
EM_INEXACT 0x0020
MCW_IC 0x1000
Mask Hex Value Constant Hex Value
────────────────────────────────────────────────────────────────────────────
MCW_IC 0x1000
(Infinity
control)
IC_AFFINE 0x1000
IC_PROJECTIVE 0x0000
MCW_RC 0x0C00
(Rounding
control)
RC_CHOP 0x0C00
RC_UP 0x0800
RC_DOWN 0x0400
Mask Hex Value Constant Hex Value
────────────────────────────────────────────────────────────────────────────
RC_DOWN 0x0400
RC_NEAR 0x0000
MCW_PC 0x0300
(Precision
control)
PC_24 (24 bits) 0x0000
PC_53 (53 bits) 0x0200
PC_64 (64 bits) 0x0300
────────────────────────────────────────────────────────────────────────────
Return Value
The bits in the value returned indicate the floating-point control state.
See the FLOAT.H include file for a complete definition of the bits returned
by _control87.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_clear87, _status87
Example
/* CNTRL87.C: This program uses _control87 to output the control word,
* set the precision to 24 bits, and reset the status to the default.
*/
#include <stdio.h>
#include <float.h>
void main()
{
double a = 0.1;
/* Show original control word and do calculation. */
printf( "Original: 0x%.4x\n", _control87( 0, 0 ) );
printf( "%1.1f * %1.1f = %.15e\n", a, a, a * a );
/* Set precision to 24 bits and recalculate. */
printf( "24-bit: 0x%.4x\n", _control87( PC_24, MCW_PC ) );
printf( "%1.1f * %1.1f = %.15e\n", a, a, a * a );
/* Restore to default and recalculate. */
printf( "Default: 0x%.4x\n", _control87( CW_DEFAULT, 0xffff ) );
printf( "%1.1f * %1.1f = %.15e\n", a, a, a * a );
}
Output
Original: 0x1332
0.1 * 0.1 = 1.000000000000000e-002
24-bit: 0x1332
0.1 * 0.1 = 9.999999776482582e-003
Default: 0x1032
0.1 * 0.1 = 1.000000000000000e-002
cos Functions
────────────────────────────────────────────────────────────────────────────
Description
Calculate the cosine (cos and cosl) or hyperbolic cosine (cosh and coshl).
#include <math.h>
double cos( double x );
double cosh( double x );
long double cosl( long double x );
long double coshl( long double x );
x Angle in radians
Remarks
The cos and cosh functions return the cosine and hyperbolic cosine,
respectively, of x.
The cosl and coshl functions are the 80-bit counterparts and use the 80-bit,
10-byte coprocessor form of arguments and return values. See the reference
page on the long double functions for more details on this data type.
Return Value
If x is large, a partial loss of significance in the result may occur in a
call to cos, in which case the function generates a PLOSS error. If x is so
large that significance is completely lost, cos prints a TLOSS message to
stderr and returns 0. In both cases, errno is set to ERANGE.
If the result is too large in a cosh call, the function returns HUGE_VAL and
sets errno to ERANGE.
Compatibility
cos, cosh
ANSI DOS OS/2 UNIX XENIX
cosl, coshl
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
acos functions, asin functions, atan functions, matherr, sin functions, tan
functions
Example
/* SINCOS.C: This program displays the sine, hyperbolic sine, cosine,
* and hyperbolic cosine of pi / 2.
*/
#include <math.h>
#include <stdio.h>
void main()
{
double pi = 3.1415926535;
double x, y;
x = pi / 2;
y = sin( x );
printf( "sin( %f ) = %f\n", x, y );
y = sinh( x );
printf( "sinh( %f ) = %f\n",x, y );
y = cos( x );
printf( "cos( %f ) = %f\n", x, y );
y = cosh( x );
printf( "cosh( %f ) = %f\n",x, y );
}
Output
sin( 1.570796 ) = 1.000000
sinh( 1.570796 ) = 2.301299
cos( 1.570796 ) = 0.000000
cosh( 1.570796 ) = 2.509178
cprintf
────────────────────────────────────────────────────────────────────────────
Description
Formats and prints to the console.
#include <conio.h> Required only for function declarations
int cprintf( char *format [[, argument]] ... );
format Format control string
argument Optional arguments
Remarks
The cprintf function formats and prints a series of characters and values
directly to the console, using the putch function to output characters. Each
argument (if any) is converted and output according to the corresponding
format specification in format. The format has the same form and function as
the format argument for the printf function; see printf for a description of
the format and arguments.
Note that unlike the fprintf, printf, and sprintf functions, cprintf does
not translate line-feed characters into carriage-return-line-feed
combinations on output.
Return Value
The cprintf function returns the number of characters printed.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
cscanf, fprintf, printf, sprintf, vprintf
Example
/* CPRINTF.C: This program displays some variables to the console. */
#include <conio.h>
void main()
{
int i = -16, h = 29;
unsigned u = 62511;
char c = 'A';
char s[] = "Test";
/* Note that console output does not translate \n as
* standard output does. Use \r\n instead.
*/
cprintf( "%d %.4x %u %c %s\r\n", i, h, u, c, s );
}
Output
-16 001d 62511 A Test
cputs
────────────────────────────────────────────────────────────────────────────
Description
Puts a string to the console.
#include <conio.h> Required only for function declarations
int cputs( char *string );
string Output string
Remarks
The cputs function writes the null-terminated string pointed to by string
directly to the console. Note that a carriage-return-line-feed (CR-LF)
combination is not automatically appended to the string.
Return Value
If successful, cputs returns a 0. If the function fails, it returns a
nonzero value.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
putch
Example
/* CPUTS.C: This program first displays a string to the console. */
#include <conio.h>
void main()
{
/* String to print at console. Note the \r (return) character. */
char *buffer = "Hello world (courtesy of cputs)!\r\n";
cputs( buffer );
}
Output
Hello world (courtesy of cputs)!
creat
────────────────────────────────────────────────────────────────────────────
Description
Creates a new file.
#include <sys\types.h>
#include <sys\stat.h>
#include <errno.h>
#include <io.h> Required only for function declarations
int creat( char *filename, int pmode );
filename Path name of new file
pmode Permission setting
Remarks
The creat function either creates a new file or opens and truncates an
existing file. If the file specified by filename does not exist, a new file
is created with the given permission setting and is opened for writing. If
the file already exists and its permission setting allows writing, creat
truncates the file to length 0, destroying the previous contents, and opens
it for writing.
The permission setting, pmode, applies to newly created files only. The new
file receives the specified permission setting after it is closed for the
first time. The integer expression pmode contains one or both of the
manifest constants S_IWRITE and S_IREAD, defined in SYS\STAT.H. When both of
the constants are given, they are joined with the bitwise-OR operator ( | ).
The pmode argument is set to one of the following values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
S_IWRITE Writing permitted
S_IREAD Reading permitted
S_IREAD | S_IWRITE Reading and writing permitted
If write permission is not given, the file is read-only. Under DOS and OS/2,
it is not possible to give write-only permission. Thus, the S_IWRITE and
S_IREAD | S_IWRITE modes are equivalent. Under DOS versions 3.0 and later,
files opened using creat are always opened in compatibility mode (see
sopen).
The creat function applies the current file-permission mask to pmode before
setting the permissions (see umask).
Note that the creat routine is provided primarily for compatibility with
previous libraries. A call to open with O_CREAT and O_TRUNC in the oflag
argument is equivalent to creat and is preferable for new code.
Return Value
If successful, creat returns a handle for the created file. Otherwise, it
returns -1 and sets errno to one of the following constants:
Value Meaning
────────────────────────────────────────────────────────────────────────────
EACCES Path name specifies an existing
read-only file or specifies a directory
instead of a file
EMFILE No more handles available (too many open
files)
ENOENT Path name not found
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
chmod, chsize, close, dup, dup2, open, sopen, umask
Example
/* CREAT.C: This program uses creat to create the file (or truncate the
* existing file) named data and open it for writing.
*/
#include <sys\types.h>
#include <sys\stat.h>
#include <io.h>
#include <stdio.h>
#include <stdlib.h>
void main()
{
int fh;
fh = creat( "data", S_IREAD | S_IWRITE );
if( fh == -1 )
perror( "Couldn't create data file" );
else
{
printf( "Created data file.\n" );
close( fh );
}
}
Output
Created data file.
cscanf
────────────────────────────────────────────────────────────────────────────
Description
Reads formatted data from the console.
#include <conio.h> Required only for function declarations
int cscanf( char *format [[, argument]] ... );
format Format-control string
argument Optional arguments
Remarks
The cscanf function reads data directly from the console into the locations
given by argument. The getche function is used to read characters. Each
optional argument must be a pointer to a variable with a type that
corresponds to a type specifier in format. The format controls the
interpretation of the input fields and has the same form and function as the
format argument for the scanf function; see scanf for a description of
format.
While cscanf normally echoes the input character, it will not do so if the
last call was to ungetch.
Return Value
The cscanf function returns the number of fields that were successfully
converted and assigned. The return value does not include fields that were
read but not assigned.
The return value is EOF for an attempt to read at end-of-file. This may
occur when keyboard input is redirected at the operating system command-line
level. A return value of 0 means that no fields were assigned.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
cprintf, fscanf, scanf, sscanf
Example
/* CSCANF.C: This program prompts for a string and uses cscanf to read
* in the response. Then cscanf returns the number of items matched,
* and the program displays that number.
*/
#include <stdio.h>
#include <conio.h>
void main()
{
int result, i[3];
cprintf( "Enter three integers: ");
result = cscanf( "%i %i %i", &i[0], &i[1], &i[2] );
cprintf( "\r\nYou entered " );
while( result-- )
cprintf( "%i ", i[result] );
cprintf( "\r\n" );
}
Output
Enter three integers: 34 43 987k
You entered 987 43 34
ctime
────────────────────────────────────────────────────────────────────────────
Description
Converts a time stored as a time_t value to a character string.
#include <time.h> Required only for function declarations
char *ctime( const time_t *timer );
timer Pointer to stored time
Remarks
The ctime function converts a time stored as a time_t value to a character
string. The timer value is usually obtained from a call to time, which
returns the number of seconds elapsed since 00:00:00 Greenwich mean time,
January 1, 1970.
The string result produced by ctime contains exactly 26 characters and has
the form of the following example:
Wed Jan 02 02:03:55 1980\n\0
A 24-hour clock is used. All fields have a constant width. The newline
character (\n) and the null character ('\0') occupy the last two positions
of the string.
Calls to the ctime function modify the single statically allocated buffer
used by the gmtime and the localtime functions. Each call to one of these
routines destroys the result of the previous call. The ctime function also
shares a static buffer with the asctime function. Thus, a call to ctime
destroys the results of any previous call to asctime, localtime, or gmtime.
Return Value
The ctime function returns a pointer to the character string result. If time
represents a date before 1980, ctime returns NULL.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
asctime, ftime, gmtime, localtime, time
Example
/* ASCTIME.C: This program places the system time in the long integer
aclock,
* translates it into the structure newtime and then converts it to
* string form for output, using the asctime function.
*/
#include <time.h>
#include <stdio.h>
struct tm *newtime;
time_t aclock;
void main()
{
time( &aclock ); /* Get time in seconds. */
newtime = localtime( &aclock ); /* Convert time to struct tm form.
*/
/* Print local time as a string. */
printf( "The current date and time are: %s\n", asctime( newtime ) );
}
Output
The current date and time are: Thu Jun 15 06:57:59 1989
cwait
────────────────────────────────────────────────────────────────────────────
Description
Waits until the child process terminates.
#include <process.h>
int cwait( int *termstat, int procid, int action );
termstat Address for termination status code
procid Process ID of child
action Action code
Remarks
The cwait function suspends the calling process until the specified child
process terminates.
If not NULL, termstat points to a buffer where cwait will place the
termination-status word and the return code of the terminated child process.
The termination-status word indicates whether or not the child process
terminated normally by calling the OS/2 DosExit function. (Programs that
terminate with exit or by "falling off the end of main" use DosExit
internally.) If the process did terminate normally, the low-order and
high-order bytes of the termination-status word are as follows:
Byte Contents
────────────────────────────────────────────────────────────────────────────
High order Contains the low-order byte of the
result code that the child code passed
to DosExit. The DosExit function is
called if the child process called exit
or _exit, returned from main, or reached
the end of main. The low-order byte of
the result code is either the low-order
byte of the argument to _exit or exit,
the low-order byte of the return value
from main, or a random value if the
child process reached the end of main.
Low order 0 (normal termination).
If the child process terminates without calling DosExit, the high-order and
low-order bytes of the termination-status word are as follows:
Byte Contents
────────────────────────────────────────────────────────────────────────────
High order 0
Low order Termination code from DosCWait:
Code Meaning
────────────────────────────────────────────────────────────────────────────
1 Hard-error abort
2 Trap operation
3 SIGTERM signal not
intercepted
The procid argument specifies which child-process termination to wait for.
This value is returned by the call to the spawn function that started the
child process. If the specified child process terminates before cwait is
called, the function returns immediately.
The action argument specifies when the parent process resumes execution, as
shown in the following list:
Value Meaning
────────────────────────────────────────────────────────────────────────────
WAIT_CHILD The parent process waits until the
specified child process has ended.
WAIT_GRANDCHILD The parent process waits until the
specified child process and all child
processes of that child process have
ended.
The WAIT_CHILD and WAIT_GRANDCHILD action codes are defined in PROCESS.H.
Return Value
If the cwait function returns after normal termination of the child process,
it returns the child's process ID.
If the cwait function returns after abnormal termination of the child
process, it returns -1 and sets errno to EINTR.
Otherwise, the cwait function returns -1 immediately and sets errno to one
of the following error codes:
Value Meaning
────────────────────────────────────────────────────────────────────────────
ECHILD No child process exists, or invalid
process ID
EINVAL Invalid action code
Compatibility
▼ ANSI ▼ DOS OS/2 ▼ UNIX ▼ XENIX
Note that the OS/2 DosExit function allows programs to return a 16-bit
result code. However, the wait and cwait functions return only the low-order
byte of that result code.
See Also
exit, _exit, spawn functions, wait
Example
/* CWAIT.C: This program launches several child processes and waits
* for a specified process to finish.
*/
#define INCL_NOPM
#define INCL_NOCOMMON
#define INCL_DOSPROCESS
#include <os2.h> /* DosSleep */
#include <process.h> /* cwait */
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
/* Macro to get a random integer within a specified range */
#define getrandom( min, max ) ((rand() % (int)(((max) + 1) - (min))) +
(min))
struct CHILD
{
int pid;
char name[10];
} child[4] = { { 0, "Ann" }, { 0, "Beth" }, { 0, "Carl" }, { 0, "Dave" }
};
void main( int argc, char *argv[] )
{
int termstat, pid, c, tmp;
srand( (unsigned)time( NULL ) ); /* Seed randomizer */
/* If no arguments, this is the parent. */
if( argc == 1 )
{
/* Spawn children in numeric order. */
for( c = 0; c < 4; c++ )
child[c].pid = spawnl( P_NOWAIT, argv[0], argv[0],
child[c].name, NULL );
/* Wait for randomly specified child, and respond when done. */
c = getrandom( 0, 3 );
printf( "Come here, %s\n", child[c].name );
cwait( &termstat, child[c].pid, WAIT_CHILD );
printf( "Thank you, %s\n", child[c].name );
}
/* If there are arguments, this must be a child. */
else
{
/* Delay for a period determined by process number. */
DosSleep( (argv[1][0] - 'A' + 1) * 1000L );
printf( "Hi, dad. It's %s.\n", argv[1] );
}
}
Output
Come here, Carl
Hi, dad. It's Ann.
Hi, dad. It's Beth.
Hi, dad. It's Carl.
Thank you, Carl
Hi, dad. It's Dave.
dieeetomsbin, dmsbintoieee
────────────────────────────────────────────────────────────────────────────
Description
Convert between IEEE double value and Microsoft (MS) binary double value.
#include <math.h>
int dieeetomsbin( double *src8, double *dst8 );
int dmsbintoieee( double *src8, double *dst8 );
src8 Buffer containing value to convert
dst8 Buffer to store converted value
Remarks
The dieeetomsbin routine converts a double-precision number in IEEE
(Institute of Electrical and Electronic Engineers) format to Microsoft (MS)
binary format. The routine dmsbintoieee converts a double-precision number
in MS binary format to IEEE format.
These routines allow C programs (which store floating-point numbers in the
IEEE format) to use numeric data in random-access data files created with
those versions of Microsoft BASIC that store floating-point numbers in MS
binary format, and vice versa.
The argument src8 is a pointer to the double value to be converted. The
result is stored at the location given by dst8.
These routines do not handle IEEE NANs ("not a number") and infinities. IEEE
denormals are treated as 0 in the conversions.
Return Value
These functions return 0 if the conversion is successful and 1 if the
conversion causes an overflow.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
fieeetomsbin, fmsbintoieee
difftime
────────────────────────────────────────────────────────────────────────────
Description
Finds the difference between two times.
#include <time.h> Required only for function declarations
double difftime( time_t timer1, time_t timer0 );
timer0 Beginning time
timer1 Ending time
Remarks
The difftime function computes the difference between the supplied time
values, timer0 and timer1.
Return Value
The difftime function returns, in seconds, the elapsed time from timer0 to
timer1. The value returned is a double-precision number.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
time
Example
/* DIFFTIME.C: This program calculates the amount of time needed to
* do a floating-point multiply 50000 times.
*/
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
void main()
{
time_t start, finish;
unsigned loop;
double result, elapsed_time;
printf( "This program will do a floating point multiply 50000 times\n"
);
printf( "Working...\n" );
time( &start );
for( loop = 0; loop < 50000L; loop++ )
result = 3.63 * 5.27;
time( &finish );
elapsed_time = difftime( finish, start );
printf( "\nProgram takes %6.2f seconds.\n", elapsed_time );
}
Output
This program will do a floating point multiply 50000 times
Working...
Program takes 4.00 seconds.
_displaycursor
────────────────────────────────────────────────────────────────────────────
Description
Sets the cursor toggle for graphics functions.
#include <graph.h>
short _far _displaycursor( short toggle );
toggle Cursor state
Remarks
Upon entry into each graphic routine, the screen cursor is turned off. The
_displaycursor function determines whether the cursor will be turned back on
when programs exit graphic routines. If toggle is set to _GCURSORON, the
cursor will be restored on exit. If toggle is set to _GCURSOROFF, the cursor
will be left off.
Return Value
The function returns the previous value of toggle. There is no error return.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_gettextcursor, _settextcursor
Example
/* DISCURS.C: This program changes the cursor shape using _gettextcursor
* and _settextcursor, and hides the cursor using _displaycursor.
*/
#include <conio.h>
#include <graph.h>
void main()
{
short oldcursor;
short newcursor = 0x007; /* Full block cursor */
/* Save old cursor shape and make sure cursor is on */
oldcursor = _gettextcursor();
_clearscreen( _GCLEARSCREEN );
_displaycursor( _GCURSORON );
_outtext( "\nOld cursor shape: " );
getch();
/* Change cursor shape */
_outtext( "\nNew cursor shape: " );
_settextcursor( newcursor );
getch();
/* Restore original cursor shape */
_outtext( "\n" );
_settextcursor( oldcursor );
}
div
────────────────────────────────────────────────────────────────────────────
Description
Computes the quotient and the remainder of two integer values.
#include <stdlib.h>
div_t div( int numer, int denom );
numer Numerator
denom Denominator
Remarks
The div function divides numer by denom, computing the quotient and the
remainder. The div_t structure contains the following elements:
Element Description
────────────────────────────────────────────────────────────────────────────
int quot Quotient
int rem Remainder
The sign of the quotient is the same as that of the mathematical quotient.
Its absolute value is the largest integer that is less than the absolute
value of the mathematical quotient. If the denominator is 0, the program
will terminate with an error message.
Return Value
The div function returns a structure of type div_t, comprising both the
quotient and the remainder. The structure is defined in STDLIB.H.
Compatibility
ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
ldiv
Example
/* DIV.C: This example takes two integers as command-line arguments and
* displays the results of the integer division. This program accepts
* two arguments on the command line following the program name, then
* calls div to divide the first argument by the second. Finally,
* it prints the structure members quot and rem.
*/
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
void main( int argc, char *argv[] )
{
int x,y;
div_t div_result;
x = atoi( argv[1] );
y = atoi( argv[2] );
printf( "x is %d, y is %d\n", x, y );
div_result = div( x, y );
printf( "The quotient is %d, and the remainder is %d\n",
div_result.quot, div_result.rem );
}
Output
[C:\LIBREF] div 876 13
x is 876, y is 13
The quotient is 67, and the remainder is 5
_dos_allocmem
────────────────────────────────────────────────────────────────────────────
Description
Allocates a block of memory, using DOS service 0x48.
#include <dos.h>
#include <errno.h>
unsigned _dos_allocmem( unsigned size, unsigned *seg );
size Block size to allocate
seg Return buffer for segment descriptor
Remarks
The _dos_allocmem function uses DOS service 0x48 to allocate a block of
memory size paragraphs long. (A paragraph is 16 bytes.) Allocated blocks are
always paragraph aligned. The segment descriptor for the initial segment of
the new block is returned in the word that seg points to. If the request
cannot be satisfied, the maximum possible size (in paragraphs) is returned
in this word instead.
Return Value
If successful, the _dos_allocmem returns 0. Otherwise, it returns the DOS
error code and sets errno to ENOMEM, indicating insufficient memory or
invalid arena (memory area) headers.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
alloca, calloc functions, _dos_freemem, _dos_setblock, halloc, malloc
functions
Example
/* DALOCMEM.C: This program allocates 20 paragraphs of memory, increases
* the allocation to 40 paragraphs, and then frees the memory space.
*/
#include <dos.h>
#include <stdio.h>
void main()
{
unsigned segment;
unsigned maxsize;
/* Allocate 20 paragraphs */
if( _dos_allocmem( 20, &segment ) != 0 )
printf( "allocation failed\n" );
else
printf( "allocation successful\n" );
/* Increase allocation to 40 paragraphs */
if( _dos_setblock( 40, segment, &maxsize ) != 0 )
printf( "allocation increase failed\n" );
else
printf( "allocation increase successful\n" );
/* free memory */
if( _dos_freemem( segment ) != 0 )
printf( "free memory failed\n" );
else
printf( "free memory successful\n" );
}
Output
allocation successful
allocation increase successful
free memory successful
_dos_close
────────────────────────────────────────────────────────────────────────────
Description
Closes a file using system call INT 0x3E.
#include <dos.h>
#include <errno.h>
unsigned _dos_close( int handle );
handle Target file handle
Remarks
The _dos_close function uses system call 0x3E to close the file indicated by
handle. The file's handle argument is returned by the call that created or
last opened the file.
Return Value
The function returns 0 if successful. Otherwise, it returns the DOS error
code and sets errno to EBADF, indicating an invalid file handle.
Do not use the DOS interface I/O routines with the console, low-level, or
stream I/O routines.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
close, creat, _dos_creat functions, _dos_open, _dos_read, _dos_write,
dup, open
Example
/* DOPEN.C: This program uses DOS I/O functions to open and close a file.
*/
#include <fcntl.h>
#include <stdio.h>
#include <dos.h>
void main()
{
int fh;
/* Open file with _dos_open function */
if( _dos_open( "data1", O_RDONLY, &fh ) != 0 )
perror( "Open failed on input file\n" );
else
printf( "Open succeeded on input file\n" );
/* Close file with _dos_close function */
if( _dos_close( fh ) != 0 )
perror( "Close failed\n" );
else
printf( "File successfully closed\n" );
}
Output
Open succeeded on input file
File successfully closed
_dos_creat Functions
────────────────────────────────────────────────────────────────────────────
Description
Create a new file.
#include <dos.h>
#include <errno.h>
unsigned _dos_creat( char *filename, unsigned attrib, int *handle );
unsigned _dos_creatnew( char *filename, unsigned attrib, int *handle );
filename File path name
attrib File attributes
handle Handle return buffer
Remarks
The _dos_creat and _dos_creatnew routines create and open a new file named
filename; this new file has the access attributes specified in the attrib
argument. The new file's handle is copied into the integer location pointed
to by handle. The file is opened for both read and write access. If file
sharing is installed, the file is opened in compatibility mode.
The _dos_creat routine uses system call INT 0x3C, and the _dos_creatnew
routine uses system call INT 0x5B. If the file already exists, _dos_creat
erases its contents and leaves its attributes unchanged; however, the
_dos_creatnew routine fails if the file already exists.
Return Value
If successful, both routines return 0. Otherwise, they return the DOS error
code and set errno to one of the following values:
Constant Meaning
────────────────────────────────────────────────────────────────────────────
EACCES Access denied because the directory is
full or, for _dos_creat only, the file
exists and cannot be overwritten
EEXIST File already exists (_dos_creatnew only)
EMFILE Too many open file handles
ENOENT Path or file not found
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
Example
/* DCREAT.C: This program creates a file using the _dos_creat function.
The
* program cannot create a new file using the _dos_creatnew function
* because it already exists.
*/
#include <stdio.h>
#include <stdlib.h>
#include <dos.h>
void main()
{
int fh1, fh2;
int result;
if( _dos_creat( "data", _A_NORMAL, &fh1 ) != 0 )
printf( "Couldn't create data file\n" );
else
{
printf( "Created data file.\n" );
/* If _dos_creat is successful, the _dos_creatnew call
* will fail since the file exists
*/
if( _dos_creatnew( "data", _A_RDONLY, &fh2 ) != 0 )
printf( "Couldn't create data file\n" );
else
{
printf( "Created data file.\n" );
_dos_close( fh2 );
}
_dos_close( fh1 );
}
}
Output
Created data file.
Couldn't create data file
_dos_find Functions
────────────────────────────────────────────────────────────────────────────
Description
Find the file with the specified attributes or find the next file with the
specified attributes.
#include <dos.h>
#include <errno.h>
unsigned _dos_findfirst( char *filename, unsigned attrib, struct find_t
*fileinfo );
unsigned _dos_findnext( struct find_t *fileinfo );
filename Target file name
attrib Target attributes
fileinfo File-information buffer
Remarks
The _dos_findfirst routine uses system call INT 0x4E to return information
about the first instance of a file whose name and attributes match filename
and attrib.
The filename argument may use wildcards (* and ?). The attrib argument can
be any of the following manifest constants:
Constant Meaning
────────────────────────────────────────────────────────────────────────────
_A_ARCH Archive. Set whenever the file is
changed, and cleared by the DOS BACKUP
command.
_A_HIDDEN Hidden file. Cannot be found with the
DOS DIR command. Returns information
about normal files as well as about
files with this attribute.
_A_NORMAL Normal. File can be read or written
without restriction.
_A_RDONLY Read-only. File cannot be opened for
writing, and a file with the same name
cannot be created. Returns information
about normal files as well as about
files with this attribute.
_A_SUBDIR Subdirectory. Returns information about
normal files as well as about files with
this attribute.
_A_SYSTEM System file. Cannot be found with the
DOS DIR command. Returns information
about normal files as well as about
files with this attribute.
_A_VOLID Volume ID. Only one file can have this
attribute, and it must be in the root
directory.
Multiple constants can be combined (with the OR operator), using the
vertical-bar ( | ) character.
If the attributes argument to either of these functions is _A_RDONLY,
_A_HIDDEN, _A_SYSTEM, or _A_SUBDIR, the function also returns any normal
attribute files that match the filename argument. That is, a normal file
does not have a read-only, hidden, system, or directory attribute.
Information is returned in a find_t structure, defined in DOS.H. The find_t
structure contains the following elements:
Element Description
────────────────────────────────────────────────────────────────────────────
char reserved[21] Reserved for use by DOS
char attrib Attribute byte for matched path
unsigned wr_time Time of last write to file
unsigned wr_date Date of last write to file
long size Length of file in bytes
char name[13] Null-terminated name of matched
file/directory, without
the path
The formats for the wr_time and wr_date elements are in DOS format and are
not usable by any other C run-time function. The time format is shown below:
Bits Contents
────────────────────────────────────────────────────────────────────────────
0 - 4 Number of 2-second increments (0 - 29)
5 -10 Minutes (0 - 59)
11-15 Hours (0 - 23)
The date format is shown below:
Bits Contents
────────────────────────────────────────────────────────────────────────────
0 - 4 Day of month (1-31)
5 - 8 Month (1-12)
9 -15 Year (relative to 1980)
Do not alter the contents of the buffer between a call to _dos_findfirst and
a subsequent call to the _dos_findnext function. Also, the buffer should not
be altered between calls to _dos_findnext.
The _dos_findnext routine uses system call 0x4F to find the next name, if
any, that matches the filename and attrib arguments specified in a prior
call to _dos_findfirst. The fileinfo argument must point to a structure
initialized by a previous call to _dos_findfirst. The contents of the
structure will be altered as described above if a match is found.
Return Value
If successful, both functions return 0. Otherwise, they return the DOS error
code and set errno to ENOENT, indicating that filename could not be
matched.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
Example
/* DFIND.C: This program finds and prints all files in the current
directory with
* the .c extension.
*/
#include <stdio.h>
#include <dos.h>
main()
{
struct find_t c_file;
/* find first .c file in current directory */
_dos_findfirst( "*.c", _A_NORMAL, &c_file );
printf( "Listing of .c files\n\n" );
printf( "File: %s is %ld bytes\n", c_file.name, c_file.size );
/* find the rest of the .c files */
while( _dos_findnext( &c_file ) == 0 )
printf( "File: %s is %ld bytes\n", c_file.name, c_file.size );
}
Output
Listing of .c files
File: CHDIR.C is 524 bytes
File: SIGFP.C is 2674 bytes
File: MAX.C is 258 bytes
File: CGETS.C is 577 bytes
File: FWRITE.C is 1123 bytes
_dos_freemem
────────────────────────────────────────────────────────────────────────────
Description
Releases a block of memory (INT 0x49).
#include <dos.h>
#include <errno.h>
unsigned _dos_freemem( unsigned seg );
seg Block to be released
Remarks
The _dos_freemem function uses system call 0x49 to release a block of memory
previously allocated by _dos_allocmem. The seg argument is a value returned
by a previous call to _dos_allocmem. The freed memory may no longer be used
by the application program.
Return Value
If successful, _dos_freemem returns 0. Otherwise, it returns the DOS error
code and sets errno to ENOMEM, indicating a bad segment value (one that does
not correspond to a segment returned by a previous _dos_allocmem call) or
invalid arena headers.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_dos_allocmem, _dos_setblock, free functions
Example
/* DALOCMEM.C: This program allocates 20 paragraphs of memory, increases
* the allocation to 40 paragraphs, and then frees the memory space.
*/
#include <dos.h>
#include <stdio.h>
void main()
{
unsigned segment;
unsigned maxsize;
/* Allocate 20 paragraphs */
if( _dos_allocmem( 20, &segment ) != 0 )
printf( "allocation failed\n" );
else
printf( "allocation successful\n" );
/* Increase allocation to 40 paragraphs */
if( _dos_setblock( 40, segment, &maxsize ) != 0 )
printf( "allocation increase failed\n" );
else
printf( "allocation increase successful\n" );
/* Free memory */
if( _dos_freemem( segment ) != 0 )
printf( "free memory failed\n" );
else
printf( "free memory successful\n" );
}
Output
allocation successful
allocation increase successful
free memory successful
_dos_getdate
────────────────────────────────────────────────────────────────────────────
Description
Gets current system date using system call INT 0x2A.
#include <dos.h>
void _dos_getdate( struct dosdate_t *date );
date Current system date
Remarks
The _dos_getdate routine uses system call 0x2A to obtain the current system
date. The date is returned in a dosdate_t structure, defined in DOS.H.
The dosdate_t structure contains the following elements:
Element Description
────────────────────────────────────────────────────────────────────────────
unsigned char day 1-31
unsigned char month 1-12
unsigned int year 1980 - 2099
unsigned char dayofweek 0 - 6 (0 = Sunday)
Return Value
None.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_dos_gettime, _dos_setdate, _dos_settime, gmtime, localtime, mktime,
_strdate, _strtime, time
Example
/* DGTIME.C: This program gets and displays current date and time values.
*/
#include <stdio.h>
#include <dos.h>
void main()
{
struct dosdate_t date;
struct dostime_t time;
/* Get current date and time values */
_dos_getdate( &date );
_dos_gettime( &time );
printf( "Today's date is %d-%d-%d\n", date.month, date.day, date.year
);
printf( "The time is %02d:%02d\n", time.hour, time.minute );
}
Output
Today's date is 6-15-1989
The time is 18:07
_dos_getdiskfree
────────────────────────────────────────────────────────────────────────────
Description
Gets disk information using system call INT 0x36.
#include <dos.h>
#include <errno.h>
unsigned _dos_getdiskfree( unsigned drive, struct diskfree_t *diskspace );
drive Drive number (default is 0)
diskspace Buffer to hold disk information
Remarks
The _dos_getdiskfree routine uses system call 0x36 to obtain information on
the disk drive specified by drive. The default drive is 0, drive A is 1,
drive B is 2, and so on. Information is returned in the diskfree_t structure
(defined in DOS.H) pointed to by diskspace.
The struct diskfree_t structure contains the following elements:
Element Description
────────────────────────────────────────────────────────────────────────────
unsigned total_clusters Total clusters on disk
unsigned avail_clusters Available clusters on disk
unsigned sectors_per_cluster Sectors per cluster
unsigned bytes_per_sector Bytes per sector
Return Value
If successful, the function returns 0. Otherwise, it returns a nonzero value
and sets errno to EINVAL, indicating that an invalid drive was specified.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_dos_getdrive, _dos_setdrive
Example
/* DGDISKFR.C: This program displays information about the default disk
drive. */
#include <stdio.h>
#include <dos.h>
main()
{
struct diskfree_t drive;
/* Get information on default disk drive 0 */
_dos_getdiskfree( 0, &drive );
printf( "total clusters: %d\n", drive.total_clusters );
printf( "available clusters: %d\n", drive.avail_clusters );
printf( "sectors per cluster: %d\n", drive.sectors_per_cluster );
printf( "bytes per sector: %d\n", drive.bytes_per_sector );
}
Output
total clusters: 9013
available clusters: 6030
sectors per cluster: 4
bytes per sector: 512
_dos_getdrive
────────────────────────────────────────────────────────────────────────────
Description
Gets the current disk drive using system call INT 0x19.
#include <dos.h>
void _dos_getdrive( unsigned *drive );
drive Current-drive return buffer
Remarks
The _dos_getdrive routine uses system call 0x19 to obtain the current disk
drive. The current drive is returned in the word that drive points to: 1 =
drive A, 2 = drive B, and so on.
Return Value
None.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_dos_getdiskfree, _dos_setdrive, _getdrive
Example
/* DGDRIVE.C: This program prints the letter of the current drive,
* changes the default drive to A, then returns the number of disk drives.
*/
#include <stdio.h>
#include <dos.h>
void main()
{
unsigned olddrive, newdrive;
unsigned number_of_drives;
/* Print current default drive information */
_dos_getdrive( &olddrive );
printf( "The current drive is: %c\n", 'A' + olddrive1 );
/* Set default drive to be drive A */
printf( "Changing default drive to A\n");
_dos_setdrive( 1, &number_of_drives );
/* Get new default drive information and total number of drives */
_dos_getdrive( &newdrive );
printf( "The current drive is: %c\n", 'A' + newdrive1 );
printf( "Number of logical drives: %d\n", number_of_drives );
/* Restore default drive */
_dos_setdrive( olddrive, &number_of_drives );
}
Output
The current drive is: C
Changing default drive to A
The current drive is: A
Number of logical drives: 26
_dos_getfileattr
────────────────────────────────────────────────────────────────────────────
Description
Gets the current attributes of a file or directory, using system call INT
0x43.
#include <dos.h>
#include <errno.h>
unsigned _dos_getfileattr( char *pathname, unsigned *attrib );
pathname Full path of target file/directory
attrib Word to store attributes in
Remarks
The _dos_getfileattr routine uses system call 0x43 to obtain the current
attributes of the file or directory pointed to by pathname . The attributes
are copied to the low-order byte of the attrib word. Attributes are
represented by manifest constants, as described below:
Constant Meaning
────────────────────────────────────────────────────────────────────────────
_A_ARCH Archive. Set whenever the file is
changed, or cleared by the DOS BACKUP
command.
_A_HIDDEN Hidden file. Cannot be found by a
directory search.
_A_NORMAL Normal. File can be read or written
without restriction.
_A_RDONLY Read-only. File cannot be opened for a
write, and a file with the same name
cannot be created.
_A_SUBDIR Subdirectory.
_A_SYSTEM System file. Cannot be found by a
directory search.
_A_VOLID Volume ID. Only one file can have this
attribute, and it must be in the root
directory.
Return Value
If successful, the function returns 0. Otherwise, it returns the DOS error
code and sets errno to ENOENT, indicating that the target file or directory
could be found.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
access, chmod, _dos_setfileattr, umask
Example
/* DGFILEAT.C: This program creates a file with the specified attributes,
* then prints this information before changing the file attributes back
* to normal.
*/
#include <stdio.h>
#include <dos.h>
void main()
{
unsigned oldattrib, newattrib;
int fh;
/* Get and display file attribute */
_dos_getfileattr( "DGFILEAT.C", &oldattrib );
printf( "Attribute: 0x%.4x\n", oldattrib );
if( ( oldattrib & _A_RDONLY ) != 0 )
printf( "Read only file\n" );
else
printf( "Not a read only file.\n" );
/* Reset file attribute to normal file */
_dos_setfileattr( "DGFILEAT.C", _A_RDONLY );
_dos_getfileattr( "DGFILEAT.C", &newattrib );
printf( "Attribute: 0x%.4x\n", newattrib );
/* Restore file attribute */
_dos_setfileattr( "DGFILEAT.C", oldattrib );
_dos_getfileattr( "DGFILEAT.C", &newattrib );
printf( "Attribute: 0x%.4x\n", newattrib );
}
Output
Attribute: 0x0020
Not a read only file.
Attribute: 0x0001
Attribute: 0x0020
_dos_getftime
────────────────────────────────────────────────────────────────────────────
Description
Gets the date and time a file was last written, using system call INT 0x57.
#include <dos.h>
#include <errno.h>
unsigned _dos_getftime( int handle, unsigned *date, unsigned *time );
handle Target file
date Date-return buffer
time Time-return buffer
Remarks
The _dos_getftime routine uses system call 0x57 to get the date and time
that the specified file was last written. The file must have been opened
with a call to _dos_open or _dos_creat prior to calling _dos_getftime. The
date and time are returned in the words pointed to by date and time. The
values appear in the DOS date and time format:
Time Bits Meaning
────────────────────────────────────────────────────────────────────────────
0 - 4 Number of 2-second increments (0 -29)
5 -10 Minutes (0 -59)
11-15 Hours (0 -23)
Date Bits Meaning
────────────────────────────────────────────────────────────────────────────
0 - 4 Day (1-31)
5 - 8 Month (1-12)
9 -15 Year (1980 -2099)
Return Value
If successful, the function returns 0. Otherwise, it returns the DOS error
code and sets errno to EBADF, indicating that an invalid file handle was
passed.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_dos_setftime, fstat, stat
Example
/* DGFTIME.C: This program displays and modifies the date and time
* fields of a file.
*/
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <dos.h>
void main()
{
/* FEDC BA98 7654 3210 */
unsigned new_date = 0x184f; /* 0001 1000 0100 1111 2/15/92 */
unsigned new_time = 0x48e0; /* 0100 1000 1110 0000 9:07 AM */
unsigned old_date, old_time;
int fh;
/* Open file with _dos_open function */
if( _dos_open( "dgftime.obj", O_RDONLY, &fh ) != 0 )
exit( 1 );
/* Get file date and time */
_dos_getftime( fh, &old_date, &old_time );
printf( "Old date field: 0x%.4x\n", old_date );
printf( "Old time field: 0x%.4x\n", old_time );
system( "dir dgftime.obj" );
/* Modify file date and time */
if( !_dos_setftime( fh, new_date, new_time ) )
{
_dos_getftime( fh, &new_date, &new_time );
printf( "New date field: 0x%.4x\n", new_date );
printf( "New time field: 0x%.4x\n", new_time );
system( "dir dgftime.obj" );
/* Restore date and time */
_dos_setftime( fh, old_date, old_time );
}
_dos_close( fh );
}
Output
Old date field: 0x12cf
Old time field: 0x94bb
Volume in drive C is OS2
Directory of C:\LIBREF
DGFTIME OBJ 3923 6-15-89 6:37p
1 File(s) 13676544 bytes free
New date field: 0x184f
New time field: 0x48e0
Volume in drive C is OS2
Directory of C:\LIBREF
DGFTIME OBJ 3923 2-15-92 9:07a
1 File(s) 13676544 bytes free
_dos_gettime
────────────────────────────────────────────────────────────────────────────
Description
Gets the current system time, using system call INT 0x2C.
#include <dos.h>
void _dos_gettime( struct dostime_t *time );
time Current system time
Remarks
The _dos_gettime routine uses system call 0x2C to obtain the current system
time. The time is returned in a dostime_t structure, defined in DOS.H.
The dostime_t structure contains the following elements:
Element Description
────────────────────────────────────────────────────────────────────────────
unsigned char hour 0 -23
unsigned char minute 0 -59
unsigned char second 0 -59
unsigned char hsecond 1/100 second; 0 -99
Return Value
None.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_dos_getdate, _dos_setdate, _dos_settime, gmtime, localtime, _strtime
Example
/* DGTIME.C: This program gets and displays current date and time values.
*/
#include <stdio.h>
#include <dos.h>
void main()
{
struct dosdate_t date;
struct dostime_t time;
/* Get current date and time values */
_dos_getdate( &date );
_dos_gettime( &time );
printf( "Today's date is %d-%d-%d\n", date.month, date.day, date.year
);
printf( "The time is %02d:%02d\n", time.hour, time.minute );
}
Output
Today's date is 6-15-1989
The time is 18:07
_dos_getvect
────────────────────────────────────────────────────────────────────────────
Description
Gets the current value of the interrupt vector, using system call INT 0x35.
#include <dos.h>
void ( _interrupt _far *_dos_getvect( unsigned intnum))();
intnum Target interrupt vector
Remarks
The _dos_getvect routine uses system call INT 0x35 to get the current value
of the interrupt vector specified by intnum.
This routine is typically used in conjunction with the _dos_setvect
function. To replace an interrupt vector, first save the current vector of
the interrupt using _dos_getvect. Then set the vector to your own interrupt
routine with _dos_setvect. The saved vector can later be restored, if
necessary, using _dos_setvect. The user-defined routine may also need the
original vector in order to call that vector or chain to it with
_chain_intr.
Return Value
The function returns a far pointer for the intnum interrupt to the current
handler, if there is one.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_chain_intr, _dos_keep, _dos_setvect
_dos_keep
────────────────────────────────────────────────────────────────────────────
Description
Installs TSR (terminate-and-stay-resident) programs in memory, using system
call INT 0x31.
#include <dos.h>
void _dos_keep( unsigned retcode, unsigned memsize );
retcode Exit status code
memsize Allocated resident memory (in 16-byte
paragraphs)
Remarks
The _dos_keep routine installs TSRs (terminate-and-stay-resident programs)
in memory, using system call INT 0x31.
The routine first exits the calling process, leaving it in memory. It then
returns the low-order byte of retcode to the parent of the calling process.
Before returning execution to the parent process, _dos_keep sets the
allocated memory for the now-resident process to memsize 16-byte paragraphs.
Any excess memory is returned to the system.
The _dos_keep function calls the same internal routines called by exit. It
therefore takes the following actions:
■ Calls atexit and onexit if defined.
■ Flushes all file buffers.
■ Restores interrupt vectors replaced by the C start-up code. The
primary one is interrupt 0 (divide by zero). If the emulator math
library is used and there is no coprocessor, interrupts 0x34 through
0x3D are restored. If there is a coprocessor, interrupt 2 is restored.
The _dos_keep function does not automatically close files; you should do
this specifically unless you want files opened by the TSR installation code
to remain open for the TSR.
Do not use the emulator math library in TSRs unless you are familiar with
the C start-up code and the coprocessor. Use the alternate math package (not
supplied with Microsoft QuickC) if the TSR must do floating-point math.
Do not run programs that use _dos_keep from inside the Microsoft
Programmer's WorkBench environment, since doing so causes subsequent memory
problems. The _dos_keep function terminates the program when executed in the
Programmer's WorkBench environment.
Return Value
None.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_cexit, _chain_intr, _dos_getvect, _dos_setvect, _exit
_dos_open
────────────────────────────────────────────────────────────────────────────
Description
Opens a file, using system call INT 0x3D.
#include <dos.h>
#include <errno.h>
#include <fcntl.h> Access mode constants
#include <share.h> Sharing mode constants
unsigned _dos_open( char *filename, unsigned mode, int *handle );
filename Path to an existing file
mode Permissions
handle Pointer to integer
Remarks
The _dos_open routine uses system call INT 0x3D to open the existing file
pointed to by filename. The handle for the opened file is copied into the
integer pointed to by handle. The mode argument specifies the file's access,
sharing, and inheritance modes by combining (with the OR operator) manifest
constants from the three groups shown below. At most, one access mode and
one sharing mode can be specified at a time.
╓┌─────────────┌────────────────────────────────┌────────────────────────────►
Constant Mode Meaning
─────────────────────────────────────────────────────────────────────────────
O_RDONLY Access Read-only
Constant Mode Meaning
─────────────────────────────────────────────────────────────────────────────
O_RDONLY Access Read-only
O_WRONLY Access Write-only
O_RDWR Access Both read and write
SH_COMPAT Sharing Compatibility
SH_DENYRW Sharing Deny reading and writing
SH_DENYWR Sharing Deny writing
SH_DENYRD Sharing Deny reading
SH_DENYNO Sharing Deny neither
O_NOINHERIT Inheritance by the child File is not inherited
process
Constant Mode Meaning
─────────────────────────────────────────────────────────────────────────────
Do not use the DOS interface I/O routines in conjunction with the console,
low-level, or stream I/O routines.
Return Value
If successful, the function returns 0. Otherwise, it returns the DOS error
code and sets errno to one of the following manifest constants:
Constant Meaning
────────────────────────────────────────────────────────────────────────────
EACCES Access denied (possible reasons include
specifying a directory or volume ID for
filename, or opening a read-only file
for write access)
EINVAL Sharing mode specified when file sharing
not installed, or
access-mode value is invalid
EMFILE Too many open file handles
ENOENT Path or file not found
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_dos_close, _dos_read, _dos_write
Example
/* DOPEN.C: This program uses DOS I/O functions to open and close a file.
*/
#include <fcntl.h>
#include <stdio.h>
#include <dos.h>
void main()
{
int fh;
/* Open file with _dos_open function */
if( _dos_open( "data1", O_RDONLY, &fh ) != 0 )
perror( "Open failed on input file\n" );
else
printf( "Open succeeded on input file\n" );
/* Close file with _dos_close function */
if( _dos_close( fh ) != 0 )
perror( "Close failed\n" );
else
printf( "File successfully closed\n" );
}
Output
Open succeeded on input file
File successfully closed
_dos_read
────────────────────────────────────────────────────────────────────────────
Description
Reads data from a file, using system call INT 0x3F.
#include <dos.h>
unsigned _dos_read( int handle, void _far *buffer, unsigned count,
unsigned *numread );
handle File to read
buffer Buffer to write to
count Number of bytes to read
numread Number of bytes actually read
Remarks
The _dos_read routine uses system call INT 0x3F to read count bytes of data
from the file specified by handle. The routine then copies the data to the
buffer pointed to by buffer. The integer pointed to by numread will show the
number of bytes actually read, which may be less than the number requested
in count. If the number of bytes actually read is 0, it means the routine
tried to read at end-of-file.
Do not use the DOS interface I/O routines in conjunction with the console,
low-level, or stream I/O routines.
Return Value
If successful, the function returns 0. Otherwise, it returns the DOS error
code and sets errno to one of the following constants:
Constant Meaning
────────────────────────────────────────────────────────────────────────────
EACCES Access denied (handle is not open for
read access)
EBADF File handle is invalid
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_dos_close, _dos_open, _dos_write, read
Example
/* DREAD.C: This program uses the DOS I/O operations to read the contents
* of a file.
*/
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <dos.h>
void main()
{
int fh;
char buffer[50];
unsigned number_read;
/* Open file with _dos_open function */
if( _dos_open( "dread.c", O_RDONLY, &fh ) != 0 )
perror( "Open failed on input file\n" );
else
printf( "Open succeeded on input file\n" );
/* Read data with _dos_read function */
_dos_read( fh, buffer, 50, &number_read );
printf( "First 40 characters are: %.40s\n\n", buffer );
/* Close file with _dos_close function */
_dos_close( fh );
}
Output
Open succeeded on input file
First 40 characters are: /* DREAD.C: This program uses the DOS I/
_dos_setblock
────────────────────────────────────────────────────────────────────────────
Description
Changes the size of a memory segment, using system call INT 0x4A.
#include <dos.h>
unsigned _dos_setblock( unsigned size, unsigned seg, unsigned *maxsize );
size New segment size
seg Target segment
maxsize Maximum-size buffer
Remarks
The _dos_setblock routine uses system call INT 0x4A to change the size of
seg, previously allocated by _dos_allocmem, to size paragraphs. If the
request cannot be satisfied, the maximum possible segment size is copied to
the buffer pointed to by maxsize.
Return Value
The function returns 0 if successful. If the call fails, it returns the DOS
error code and sets errno to ENOMEM, indicating a bad segment value was
passed. A bad segment value is one that does not correspond to a segment
returned from a previous _dos_allocmem call, or one that contains invalid
arena headers.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_dos_allocmem, _dos_freemem, realloc functions
Example
/* DALOCMEM.C: This program allocates 20 paragraphs of memory, increases
* the allocation to 40 paragraphs, and then frees the memory space.
*/
#include <dos.h>
#include <stdio.h>
void main()
{
unsigned segment;
unsigned maxsize;
/* Allocate 20 paragraphs */
if( _dos_allocmem( 20, &segment ) != 0 )
printf( "allocation failed\n" );
else
printf( "allocation successful\n" );
/* Increase allocation to 40 paragraphs */
if( _dos_setblock( 40, segment, &maxsize ) != 0 )
printf( "allocation increase failed\n" );
else
printf( "allocation increase successful\n" );
/* Free memory */
if( _dos_freemem( segment ) != 0 )
printf( "free memory failed\n" );
else
printf( "free memory successful\n" );
}
Output
allocation successful
allocation increase successful
free memory successful
_dos_setdate
────────────────────────────────────────────────────────────────────────────
Description
Sets the current system date, using system call INT 0x2B.
#include <dos.h>
unsigned _dos_setdate( struct dosdate_t *date );
date New system date
Remarks
The _dos_setdate routine uses system call INT 0x2B to set the current system
date. The date is stored in the dosdate_t structure pointed to by date,
defined in DOS.H. The dosdate_t structure contains the following elements:
Element Description
────────────────────────────────────────────────────────────────────────────
unsigned char day 1 -31
unsigned char month 1 -12
unsigned int year 1980 - 2099
unsigned char dayofweek 0 - 6 (0 = Sunday)
Return Value
If successful, the function returns 0. Otherwise, it returns a nonzero value
and sets errno to EINVAL, indicating an invalid date was specified.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_dos_gettime, _dos_setdate, _dos_settime, gmtime, localtime, mktime,
_strdate, _strtime, time
Example
/* DSTIME.C: This program changes the time and date values and displays
the
* new date and time values.
*/
#include <dos.h>
#include <conio.h>
#include <stdio.h>
#include <time.h>
void main()
{
struct dosdate_t olddate, newdate = { { 4 }, { 7 }, { 1984 } };
struct dostime_t oldtime, newtime = { { 3 }, { 45 }, { 30 }, { 0 } };
char datebuf[40], timebuf[40];
/* Get current date and time values */
_dos_getdate( &olddate );
_dos_gettime( &oldtime );
printf( "%s %s\n" , _strdate( datebuf ), _strtime( timebuf ) );
/* Modify date and time structures */
_dos_setdate( &newdate );
_dos_settime( &newtime );
printf( "%s %s\n" , _strdate( datebuf ), _strtime( timebuf ) );
/* Restore old date and time */
_dos_setdate( &olddate );
_dos_settime( &oldtime );
}
Output
06/15/89 18:26:09
07/04/84 03:45:30
_dos_setdrive
────────────────────────────────────────────────────────────────────────────
Description
Sets the default drive, using system call INT 0x0E.
#include <dos.h>
void _dos_setdrive( unsigned drive, unsigned *numdrives );
drive New default drive
numdrives Total drives available
Remarks
The _dos_setdrive routine uses system call INT 0x0E to set the current
default drive to the drive argument: 1 = drive A, 2 = drive B, and so on.
The numdrives argument indicates the total number of drives in the system.
If this value is 4, for example, it does not mean the drives are designated
A, B, C, and D; it means only that four drives are in the system.
Return Value
There is no return value. If an invalid drive number is passed, the function
fails without indication. Use the _dos_getdrive routine to verify whether
the desired drive has been set.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_dos_getdiskfree, _dos_getdrive
Example
/* DGDRIVE.C: This program prints the letter of the current drive,
* changes the default drive to A, then returns the number of disk drives.
*/
#include <stdio.h>
#include <dos.h>
void main()
{
unsigned olddrive, newdrive;
unsigned number_of_drives;
/* Print current default drive information */
_dos_getdrive( &olddrive );
printf( "The current drive is: %c\n", 'A' + olddrive1 );
/* Set default drive to be drive A */
printf( "Changing default drive to A\n");
_dos_setdrive( 1, &number_of_drives );
/* Get new default drive information and total number of drives */
_dos_getdrive( &newdrive );
printf( "The current drive is: %c\n", 'A' + newdrive1 );
printf( "Number of logical drives: %d\n", number_of_drives );
/* Restore default drive */
_dos_setdrive( olddrive, &number_of_drives );
}
Output
The current drive is: C
Changing default drive to A
The current drive is: A
Number of logical drives: 26
_dos_setfileattr
────────────────────────────────────────────────────────────────────────────
Description
Sets the attributes of the file or directory, using system call INT 0x43.
#include <dos.h>
unsigned _dos_setfileattr( char *pathname, unsigned attrib );
pathname Full path of target file/directory
attrib New attributes
Remarks
The _dos_setfileattr routine uses system call INT 0x43 to set the attributes
of the file or directory pointed to by pathname. The actual attributes are
contained in the low-order byte of the attrib word. Attributes are
represented by manifest constants, as described below:
Constant Meaning
────────────────────────────────────────────────────────────────────────────
_A_ARCH Archive. Set whenever the file is
changed, or cleared by the DOS BACKUP
command.
_A_HIDDEN Hidden file. Cannot be found by a
directory search.
_A_NORMAL Normal. File can be read or written to
without restriction.
_A_RDONLY Read-only. File cannot be opened for
writing, and a file with the same name
cannot be created.
_A_SUBDIR Subdirectory.
_A_SYSTEM System file. Cannot be found by a
directory search.
_A_VOLID Volume ID. Only one file can have this
attribute, and it must be in the root
directory.
Return Value
The function returns 0 if successful. Otherwise, it returns the DOS error
code and sets errno to one of the following:
Constant Meaning
────────────────────────────────────────────────────────────────────────────
EACCES Access denied; cannot change the volume
ID or the
subdirectory.
ENOENT No file or directory matching the target
was found.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_dos_getfileattr
Example
/* DGFILEAT.C: This program creates a file with the specified attributes,
* then prints this information before changing the file attributes back
* to normal.
*/
#include <stdio.h>
#include <dos.h>
void main()
{
unsigned oldattrib, newattrib;
int fh;
/* Get and display file attribute */
_dos_getfileattr( "DGFILEAT.C", &oldattrib );
printf( "Attribute: 0x%.4x\n", oldattrib );
if( ( oldattrib & _A_RDONLY ) != 0 )
printf( "Read only file\n" );
else
printf( "Not a read only file.\n" );
/* Reset file attribute to normal file */
_dos_setfileattr( "DGFILEAT.C", _A_RDONLY );
_dos_getfileattr( "DGFILEAT.C", &newattrib );
printf( "Attribute: 0x%.4x\n", newattrib );
/* Restore file attribute */
_dos_setfileattr( "DGFILEAT.C", oldattrib );
_dos_getfileattr( "DGFILEAT.C", &newattrib );
printf( "Attribute: 0x%.4x\n", newattrib );
}
Output
Attribute: 0x0020
Not a read only file.
Attribute: 0x0001
Attribute: 0x0020
_dos_setftime
────────────────────────────────────────────────────────────────────────────
Description
Sets the date and time for a file, using system call INT 0x57.
#include <dos.h>
unsigned _dos_setftime( int handle, unsigned date, unsigned time );
handle Target file
date Date of last write
time Time of last write
Remarks
The _dos_setftime routine uses system call INT 0x57 to set the date and time
at which the file identified by handle was last written to. These values
appear in the DOS date and time format, described in the following lists:
Time Bits Meaning
────────────────────────────────────────────────────────────────────────────
0 - 4 Number of two-second increments (0 -29)
5 - 10 Minutes (0 -59)
11-15 Hours (0 -23)
Date Bits Meaning
────────────────────────────────────────────────────────────────────────────
0 - 4 Day (1-31)
5 -8 Month (1-12)
9 -15 Year since 1980 (for example, 1989 is
stored as 9)
Return Value
If successful, the function returns 0. Otherwise, it returns the DOS error
code and sets errno to EBADF, indicating that an invalid file handle was
passed.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_dos_getftime, fstat, stat
Example
/* DGFTIME.C: This program displays and modifies the date and time
* fields of a file.
*/
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <dos.h>
void main()
{
/* FEDC BA98 7654 3210 */
unsigned new_date = 0x184f; /* 0001 1000 0100 1111 2/15/92 */
unsigned new_time = 0x48e0; /* 0100 1000 1110 0000 9:07 AM */
unsigned old_date, old_time;
int fh;
/* Open file with _dos_open function */
if( _dos_open( "dgftime.obj", O_RDONLY, &fh ) != 0 )
exit( 1 );
/* Get file date and time */
_dos_getftime( fh, &old_date, &old_time );
printf( "Old date field: 0x%.4x\n", old_date );
printf( "Old time field: 0x%.4x\n", old_time );
system( "dir dgftime.obj" );
/* Modify file date and time */
if( !_dos_setftime( fh, new_date, new_time ) )
{
_dos_getftime( fh, &new_date, &new_time );
printf( "New date field: 0x%.4x\n", new_date );
printf( "New time field: 0x%.4x\n", new_time );
system( "dir dgftime.obj" );
/* Restore date and time */
_dos_setftime( fh, old_date, old_time );
}
_dos_close( fh );
}
Output
Old date field: 0x12cf
Old time field: 0x94bb
Volume in drive C is OS2
Directory of C:\LIBREF
DGFTIME OBJ 3923 6-15-89 6:37p
1 File(s) 13676544 bytes free
New date field: 0x184f
New time field: 0x48e0
Volume in drive C is OS2
Directory of C:\LIBREF
DGFTIME OBJ 3923 2-15-92 9:07a
1 File(s) 13676544 bytes free
_dos_settime
────────────────────────────────────────────────────────────────────────────
Description
Sets the current system time, using system call INT 0x2D.
#include <dos.h>
unsigned _dos_settime( struct dostime_t *time );
time New system time
Remarks
The _dos_settime routine uses system call INT 0x2D to set the current system
time to the value stored in the dostime_t structure that time points to, as
defined in DOS.H. The dostime_t structure contains the following elements:
Element Description
────────────────────────────────────────────────────────────────────────────
unsigned char hour 0 -23
unsigned char minute 0 -59
unsigned char second 0 -59
unsigned char hsecond Hundredths of a second; 0 -99
Return Value
If successful, the function returns 0. Otherwise, it returns a nonzero value
and sets errno to EINVAL, indicating an invalid time was specified.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_dos_getdate, _dos_gettime, _dos_setdate, gmtime, localtime, mktime,
_strdate, _strtime
Example
/* DSTIME.C: This program changes the time and date values and displays
the
* new date and time values.
*/
#include <dos.h>
#include <conio.h>
#include <stdio.h>
#include <time.h>
void main()
{
struct dosdate_t olddate, newdate = { { 4 }, { 7 }, { 1984 } };
struct dostime_t oldtime, newtime = { { 3 }, { 45 }, { 30 }, { 0 } };
char datebuf[40], timebuf[40];
/* Get current date and time values */
_dos_getdate( &olddate );
_dos_gettime( &oldtime );
printf( "%s %s\n" , _strdate( datebuf ), _strtime( timebuf ) );
/* Modify date and time structures */
_dos_setdate( &newdate );
_dos_settime( &newtime );
printf( "%s %s\n" , _strdate( datebuf ), _strtime( timebuf ) );
/* Restore old date and time */
_dos_setdate( &olddate );
_dos_settime( &oldtime );
}
Output
06/15/89 18:26:09
07/04/84 03:45:30
_dos_setvect
────────────────────────────────────────────────────────────────────────────
Description
Sets the current value of the interrupt vector, using system call INT 0x25.
#include <dos.h>
void _dos_setvect( unsigned intnum, void( _interrupt _far *handler)( ));
intnum Target-interrupt vector
handler Interrupt handler for which to assign
intnum
Remarks
The _dos_setvect routine uses system call INT 0x25 to set the current value
of the interrupt vector intnum to the function pointed to by handler.
Subsequently, whenever the intnum interrupt is generated, the handler
routine will be called. If handler is a C function, it must have been
previously declared with the interrupt attribute. Otherwise, you must make
sure that the function satisfies the requirements for an interrupt-handling
routine. For example, if handler is an assembler function, it must be a far
routine that returns with an IRET instead of a RET.
The interrupt attribute indicates that the function is an interrupt handler.
The compiler generates appropriate entry and exit sequences for the
interrupt-handling function, including saving and restoring all registers
and executing an IRET instruction to return.
The _dos_setvect routine is generally used with the _dos_getvect function.
To replace an interrupt vector, first save the current vector of the
interrupt using _dos_getvect. Then set the vector to your own interrupt
routine with _dos_setvect. The saved vector can later be restored, if
necessary, using _dos_setvect. The user-defined routine may also need the
original vector in order to call it or to chain to it with _chain_intr.
Registers and Interrupt Functions
When you call an interrupt function, the DS register is initialized to the C
data segment. This allows you to access global variables from within an
interrupt function.
In addition, all registers except SS are saved on the stack. You can access
these registers within the function if you declare a function parameter list
containing a formal parameter for each saved register. The following example
illustrates such a declaration:
void _interrupt _far int_handler( unsigned _es, unsigned _ds,
unsigned _di, unsigned _si,
unsigned _bp, unsigned _sp,
unsigned _bx, unsigned _dx,
unsigned _cx, unsigned _ax,
unsigned _ip, unsigned _cs,
unsigned _flags )
{
.
.
.
}
The formal parameters must appear in the opposite order from which they are
pushed onto the stack. You can omit parameters from the end of the list in a
declaration, but not from the beginning. For example, if your handler needs
to use only DI and SI, you must still provide ES and DS, but not necessarily
BX or DX.
You can pass additional arguments if your interrupt handler will be called
directly from C rather than by an INT instruction. To do this, you must
declare all register parameters and then declare your parameter at the end
of the list.
The compiler always saves and restores registers in the same, fixed order.
Thus, no matter what names you use in the formal parameter list, the first
parameter in the list refers to ES, the second refers to DS, and so on. If
your interrupt routines will use in-line assembler, you should distinguish
the parameter names so that they will not be the same as the real register
names.
If you change any of the register parameters of an interrupt function while
the function is executing, the corresponding register contains the changed
value when the function returns. For example:
void _interrupt _far int_handler( unsigned _es, unsigned _ds,
unsigned _di, unsigned _si )
{
_di = -1;
}
This code causes the DI register to contain -1 when the handler function
returns. It is not a good idea to modify the values of the parameters
representing the IP and CS registers in interrupt functions. If you must
modify a particular flag (such as the carry flag for certain DOS and BIOS
interrupt routines), use the OR operator ( | ) so that other bits in the
flag register are not changed.
When an interrupt function is called by an INT instruction, the
interrupt-enable flag is cleared. If your interrupt function needs to do
significant processing, you should use the _enable function to set the
interrupt flag so that interrupts can be handled.
Precautions for Interrupt Functions
Since DOS is not reentrant (a DOS interrupt cannot be called from inside a
DOS interrupt), it is usually not safe to call from inside an interrupt
function any standard library function that calls DOS INT 21H. Similar
precautions apply to many BIOS functions. Functions that rely on INT 21H
calls include I/O functions and the _dos family of functions. Functions that
rely on the machine's BIOS include graphics functions and the _bios family
of functions. It is usually safe to use functions that do not rely on INT
21H or BIOS, such as string-handling functions. Before using a standard
library function in an interrupt function, be sure that you are familiar
with the action of the library function.
Return Value
None.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_chain_intr, _dos_getvect, _dos_keep
_dos_write
────────────────────────────────────────────────────────────────────────────
Description
Writes a buffer to a file, using system call INT 0x40.
#include <dos.h>
unsigned _dos_write( int handle, void _far *buffer, unsigned count,
unsigned *numwrt );
handle File to write to
buffer Buffer to write from
count Number of bytes to write
numwrt Number of bytes actually written
Remarks
The _dos_write routine uses system call INT 0x40 to write data to the file
that handle references; count bytes of data from the buffer to which buffer
points are written to the file. The integer pointed to by numwrt will be the
number of bytes actually written, which may be less than the number
requested.
Do not use the DOS interface routines with the console, low-level, or stream
I/O routines.
Return Value
If successful, the function returns 0. Otherwise, it returns the DOS error
code and sets errno to one of the following manifest constants:
Constant Meaning
────────────────────────────────────────────────────────────────────────────
EACCES Access denied (handle references a file
not open for write
access)
EBADF Invalid file handle
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_dos_close, _dos_open, _dos_read, write
Example
/* DWRITE.C: This program uses DOS I/O functions to write to a file. */
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <dos.h>
void main()
{
char out_buffer[] = "Hello";
int fh;
unsigned n_written;
/* Open file with _dos_creat function */
if( _dos_creat( "data", _A_NORMAL, &fh ) == 0 )
{
/* Write data with _dos_write function */
_dos_write( fh, out_buffer, 5, &n_written );
printf( "Number of characters written: %d\n", n_written );
_dos_close( fh );
printf( "Contents of file are:\n" );
system( "type data" );
}
}
Output
Number of characters written: 5
Contents of file are:
Hello
dosexterr
────────────────────────────────────────────────────────────────────────────
Description
Gets register values returned by INT 0x59.
#include <dos.h>
int dosexterr( struct DOSERROR *errorinfo );
errorinfo Extended DOS error information
Remarks
The dosexterr function obtains the extended error information returned by
the DOS system call INT 0x59 and stores the values in the structure pointed
to by errorinfo. This function is useful when making system calls under DOS
versions 3.0 or later, which offer extended error handling.
The structure type DOSERROR is defined in DOS.H. The DOSERROR structure
contains the following elements:
Element Description
────────────────────────────────────────────────────────────────────────────
int exterror AX register contents
char class BH register contents
char action BL register contents
char locus CH register contents
Giving a NULL pointer argument causes dosexterr to return the value in AX
without filling in the structure fields. See MS-DOS Encyclopedia (Duncan,
ed.; Redmond, WA: Microsoft Press, 1988) or Programmer's PC Sourcebook
(Hogan; Redmond, WA: Microsoft Press, 1988) for more information on the
register contents.
Return Value
The dosexterr function returns the value in the AX register (identical to
the value in the exterror structure field).
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
The dosexterr function should be used only under DOS versions 3.0 or later.
See Also
perror
Example
/* DOSEXERR.C: This program tries to open the file test.dat. If the
* attempted open operation fails, the program uses dosexterr to display
* extended error information.
*/
#include <dos.h>
#include <io.h>
#include <fcntl.h>
#include <stdio.h>
void main()
{
struct DOSERROR doserror;
int fd;
/* Attempt to open a non-existent file */
if( (fd = open( "NOSUCHF.ILE", O_RDONLY )) == -1 )
{
dosexterr( &doserror );
printf( "Error: %d Class: %d Action: %d Locus: %d\n",
doserror.exterror, doserror.class,
doserror.action, doserror.locus );
}
else
{
printf( "Open succeeded so no extended information printed\n" );
close( fd );
}
}
Output
Error: 2 Class: 8 Action: 3 Locus: 2
dup, dup2
────────────────────────────────────────────────────────────────────────────
Description
Create a second handle for an open file (dup), or reassign a file handle
(dup2).
#include <io.h Required only for function declarations
int dup( int handle );
int dup2( int handle1, int handle2 );
handle, handle1 Handle referring to open file
handle2 Any handle value
Remarks
The dup and dup2 functions cause a second file handle to be associated with
a currently open file. Operations on the file can be carried out using
either file handle. The type of access allowed for the file is unaffected by
the creation of a new handle.
The dup function returns the next available file handle for the given file.
The dup2 function forces handle2 to refer to the same file as handle1. If
handle2 is associated with an open file at the time of the call, that file
is closed.
Return Value
The dup function returns a new file handle. The dup2 function returns 0 to
indicate success. Both functions return -1 if an error occurs and set errno
to one of the following values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
EBADF Invalid file handle
EMFILE No more file handles available (too many
open files)
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
close, creat, open
Example
/* DUP.C: This program uses the variable old to save the original stdout.
* It then opens a new file named new and forces stdout to refer
* to it. Finally, it restores stdout to its original state.
*/
#include <io.h>
#include <stdlib.h>
#include <stdio.h>
void main()
{
int old;
FILE *new;
old = dup( 1 ); /* "old" now refers to "stdout" */
/* Note: file handle 1 == "stdout" */
if( old == -1 )
{
perror( "dup( 1 ) failure" );
exit( 1 );
}
write( old, "This goes to stdout first\r\n", 27 );
if( ( new = fopen( "data", "w" ) ) == NULL )
{
puts( "Can't open file 'data'\n" );
exit( 1 );
}
/* stdout now refers to file "data" */
if( -1 == dup2( fileno( new ), 1 ) )
{
perror( "Can't dup2 stdout" );
exit( 1 );
}
puts( "This goes to file 'data'\r\n" );
/* Flush stdout stream buffer so it goes to correct file */
fflush( stdout );
fclose( new );
/* Restore original stdout */
dup2( old, 1 );
puts( "This goes to stdout\n" );
puts( "The file 'data' contains:" );
system( "type data" );
}
Output
This goes to stdout first
This goes to stdout
The file 'data' contains:
This goes to file 'data'
ecvt
────────────────────────────────────────────────────────────────────────────
Description
Converts a double number to a string.
#include <stdlib.h> Required only for function declarations
char *ecvt( double value, int count, int *dec, int *sign );
value Number to be converted
count Number of digits stored
dec Stored decimal-point position
sign Sign of converted number
Remarks
The ecvt function converts a floating-point number to a character string.
The value argument is the floating-point number to be converted. The ecvt
function stores up to count digits of value as a string and appends a null
character ('\0'). If the number of digits in value exceeds count, the
low-order digit is rounded. If there are fewer than count digits, the string
is padded with zeros.
Only digits are stored in the string. The position of the decimal point and
the sign of value can be obtained from dec and sign after the call. The dec
argument points to an integer value giving the position of the decimal point
with respect to the beginning of the string. A 0 or negative integer value
indicates that the decimal point lies to the left of the first digit. The
sign argument points to an integer indicating the sign of the converted
number. If the integer value is 0, the number is positive. Otherwise, the
number is negative.
The ecvt and fcvt functions use a single statically allocated buffer for the
conversion. Each call to one of these routines destroys the result of the
previous call.
Return Value
The ecvt function returns a pointer to the string of digits. There is no
error return.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
atof, atoi, atol, fcvt, gcvt
Example
/* ECVT.C: This program uses ecvt to convert a floating-point
* number to a character string.
*/
#include <stdlib.h>
#include <stdio.h>
void main()
{
int decimal, sign;
char *buffer;
int precision = 10;
double source = 3.1415926535;
buffer = ecvt( source, precision, &decimal, &sign );
printf( "source: %2.10f buffer: '%s' decimal: %d sign: %d\n",
source, buffer, decimal, sign );
}
Output
source: 3.1415926535 buffer: '3141592654' decimal: 1 sign: 0
_ellipse Functions
────────────────────────────────────────────────────────────────────────────
Description
Draw ellipses.
#include <graph.h>
short _far _ellipse( short control, short x1, short y1, short x2, short y2
);
short _far _ellipse_w( short control, double wx1, double wy1, double wx2,
double wy2 );
short _far _ellipse_wxy( short control, struct _wxycoord _far *pwxy1,
struct _wxycoord _far *pwxy2 );
control Fill flag
x1, y1 Upper-left corner of bounding rectangle
x2, y2 Lower-right corner of bounding rectangle
wx1, wy1 Upper-left corner of bounding rectangle
wx2, wy2 Lower-right corner of bounding rectangle
pwxy1 Upper-left corner of bounding rectangle
pwxy2 Lower-right corner of bounding rectangle
Remarks
The _ellipse functions draw ellipses or circles. The borders are drawn in
the current color. In the _ellipse function, the center of the ellipse is
the center of the bounding rectangle defined by the view-coordinate points
(x1, y1) and (x2, y2).
In the _ellipse_w function, the center of the ellipse is the center of the
bounding rectangle defined by the window-coordinate points (wx1, wy1) and
(wx2, wy2).
In the _ellipse_wxy function, the center of the ellipse is the center of the
bounding rectangle defined by the window-coordinate pairs (pwxy1) and
(pwxy2).
If the bounding-rectangle arguments define a point or a vertical or
horizontal line, no figure is drawn.
The control argument can be one of the following manifest constants:
Constant Action
────────────────────────────────────────────────────────────────────────────
_GFILLINTERIOR Fills the ellipse using the current fill
mask
_GBORDER Does not fill the ellipse
The control option given by _GFILLINTERIOR is equivalent to a subsequent
call to the _floodfill function, using the center of the ellipse as the
starting point and the current color (set by _setcolor) as the boundary
color.
Return Value
The _ellipse functions return a nonzero value if the ellipse is drawn
successfully; otherwise, they return 0.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_arc functions, _floodfill, _grstatus, _lineto functions, _pie
functions, _polygon functions, _rectangle functions, _setcolor,
_setfillmask
Example
/* ELLIPSE.C: This program draws a simple ellipse. */
#include <conio.h>
#include <stdlib.h>
#include <graph.h>
void main()
{
/* Find a valid graphics mode. */
if( !_setvideomode( _MAXRESMODE ) )
exit( 1 );
_ellipse( _GFILLINTERIOR, 80, 50, 240, 150 );
/* Strike any key to clear screen. */
getch();
_setvideomode( _DEFAULTMODE );
}
_enable
────────────────────────────────────────────────────────────────────────────
Description
Enables interrupts.
#include <dos.h>
void _enable( void );
Remarks
The _enable routine enables interrupts by executing an 8086 STI machine
instruction.
Return Value
None.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_disable
_endthread
────────────────────────────────────────────────────────────────────────────
Description
Terminates an OS/2 thread.
#include <process.h> Multithread version of PROCESS.H
void _far _endthread( void );
Description
The _endthread function terminates a thread created by _beginthread.
Because threads terminate automatically, the _endthread function is normally
not required. It is used to terminate a thread conditionally.
The OS/2 function DosExit should not be used to terminate threads created by
the _beginthread function. If DosExit is used, the results are
unpredictable.
Return Value
None.
Compatibility
▼ ANSI ▼ DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_beginthread
Example
See the example for _beginthread.
eof
────────────────────────────────────────────────────────────────────────────
Description
Tests for end-of-file.
#include <io.h> Required only for function declarations
int eof( int handle );
handle Handle referring to open file
Remarks
The eof function determines whether the end of the file associated with
handle has been reached.
Return Value
The eof function returns the value 1 if the current position is end-of-file,
or 0 if it is not. A return value of -1 indicates an error; in this case,
errno is set to EBADF, indicating an invalid file handle.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
clearerr, feof, ferror, perror
Example
/* EOF.C: This program reads data from a file ten bytes at a time
* until the end of the file is reached or an error is encountered.
*/
#include <io.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
void main()
{
int fh, count, total = 0;
char buf[10];
if( (fh = open( "eof.c", O_RDONLY )) == - 1 )
exit( 1 );
/* Cycle until end of file reached: */
while( !eof( fh ) )
{
/* Attempt to read in 10 bytes: */
if( (count = read( fh, buf, 10 )) == -1 )
{
perror( "Read error" );
break;
}
/* Total up actual bytes read */
total += count;
}
printf( "Number of bytes read = %d\n", total );
close( fh );
}
Output
Number of bytes read = 715
exec Functions
────────────────────────────────────────────────────────────────────────────
Description
Load and execute new child processes.
#include <process.h> Required only for function declarations
int execl( char *cmdname, char *arg0, ... char *argn, NULL );
int execle( char *cmdname, char *arg0, ... char *argn, NULL,
char **envp );
int execlp( char *cmdname, char *arg0, ... char *argn, NULL );
int execlpe( char *cmdname, char *arg0, ... char *argn, NULL,
char **envp );
int execv( char *cmdname, char **argv );
int execve( char *cmdname, char **argv, char **envp );
int execvp( char *cmdname, char **argv );
int execvpe( char *cmdname, char **argv, char **envp );
cmdname Path name of file to be executed
arg0, ... argn List of pointers to arguments
argv Array of pointers to arguments
envp Array of pointers to environment
settings
Remarks
The exec functions load and execute new child processes. When the call is
successful in DOS, the child process is placed in the memory previously
occupied by the calling process. Under OS/2, calling an exec function is
equivalent to calling the corresponding function with the P_NOWAITO argument
specified, followed by a call to the exit function. Sufficient memory must
be available for loading and executing the child process.
All of the exec functions use the same operating system function. The
letter(s) at the end of the function name determine the specific variation,
as shown in the following list:
Letter Variation
────────────────────────────────────────────────────────────────────────────
e An array of pointers to environment
arguments is explicitly passed to the
child process.
l Command-line arguments are passed
individually to the exec function.
p Uses the PATH environment variable to
find the file to be
executed.
v Command-line arguments are passed to the
exec function as an array of pointers.
The cmdname argument specifies the file to be executed as the child process.
It can specify a full path (from the root), a partial path (from the current
working directory), or just a file name. If cmdname does not have a
file-name extension or does not end with a period (.), the exec function
searches for the named file; if the search is unsuccessful, it tries the
same base name, first with the extension .COM, then with the extension .EXE.
If cmdname has an extension, only that extension is used in the search. If
cmdname ends with a period, the exec calls search for cmdname with no
extension. The execlp, execlpe, execvp, and execvpe routines search for
cmdname (using the same procedures) in the directories specified by the PATH
environment variable.
If cmdname contains a drive specifier or any slashes (i.e., if it is a
relative path name), the exec call searches only for the specified file and
no path searching is done.
Arguments are passed to the new process by giving one or more pointers to
character strings as arguments in the exec call. These character strings
form the argument list for the child process. The combined length of the
strings forming the argument list for the new process must not exceed 128
bytes (in real mode only). The terminating null character ('\0') for each
string is not included in the count, but space characters (inserted
automatically to separate the arguments) are counted.
The argument pointers can be passed as separate arguments (execl, execle,
execlp, and execlpe) or as an array of pointers (execv, execve, execvp, and
execvpe). At least one argument, arg0, must be passed to the child process;
this argument is argv[0] of the child process. Usually, this argument is a
copy of the cmdname argument. (A different value will not produce an error.)
Under versions of DOS earlier than 3.0, the passed value of arg0 is not
available for use in the child process. However, under OS/2 and under DOS
versions 3.0 and later, cmdname is available as arg0.
The execl, execle, execlp, and execlpe calls are typically used when the
number of arguments is known in advance. The argument arg0 is usually a
pointer to cmdname. The arguments arg1 through argn point to the character
strings forming the new argument list. A null pointer must follow argn to
mark the end of the argument list.
The execv, execve, execvp, and execvpe calls are useful when the number of
arguments to the new process is variable. Pointers to the arguments are
passed as an array, argv. The argument argv[0] is usually a pointer to
cmdname. The arguments argv[1] through argv[n] point to the character
strings forming the new argument list. The argument argv[n+1] must be a NULL
pointer to mark the end of the argument list.
Files that are open when an exec call is made remain open in the new
process. In the execl, execlp, execv, and execvp calls, the child process
inherits the environment of the parent. The execle, execlpe, execve, and
execvpe calls allow the user to alter the environment for the child process
by passing a list of environment settings through the envp argument. The
argument envp is an array of character pointers, each element of which
(except for the final element) points to a null-terminated string defining
an environment variable. Such a string usually has the form
NAME=value
where NAME is the name of an environment variable and value is the string
value to which that variable is set. (Note that value is not enclosed in
double quotation marks.) The final element of the envp array should be NULL.
When envp itself is NULL, the child process inherits the environment
settings of the parent process.
A program executed with one of the exec family of functions is always loaded
into memory as if the "maximum allocation" field in the program's .EXE file
header is set to the default value of 0FFFFH. You can use the EXEMOD utility
to change the maximum allocation field of a program; however, such a program
invoked with one of the exec functions may behave differently from a program
invoked directly from the operating-system command line or with one of the
spawn functions.
The exec calls do not preserve the translation modes of open files. If the
child process must use files inherited from the parent, the setmode routine
should be used to set the translation mode of these files to the desired
mode.
You must explicitly flush (using fflush or flushall) or close any stream
prior to the exec function call.
Signal settings are not preserved in child processes that are created by
calls to exec routines. The signal settings are reset to the default in the
child process.
Return Value
The exec functions do not normally return to the calling process. If an exec
function returns, an error has occurred and the return value is -1. The
errno variable is set to one of the following values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
E2BIG The argument list exceeds 128 bytes, or
the space required for the environment
information exceeds 32K.
EACCES The specified file has a locking or
sharing violation
(OS/2, and DOS versions 3.0 or later).
EMFILE Too many files open (the specified file
must be opened to determine whether it
is executable).
ENOENT File or path name not found.
ENOEXEC The specified file is not executable or
has an invalid
executable-file format.
ENOMEM Not enough memory is available to
execute the child process; or the
available memory has been corrupted; or
an invalid block exists, indicating that
the parent process was not allocated
properly.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
Because of differences in DOS versions 2.0 and 2.1, child processes
generated by the exec family of functions (or by the equivalent spawn
functions with the P_OVERLAY argument) may cause fatal system errors when
they exit. If you are running DOS 2.0 or 2.1, you must upgrade to DOS
version 3.0 or later to use these functions.
Bound programs cannot use the exec family of functions in real mode.
See Also
abort, atexit, exit, _exit, onexit, spawn functions, system
Example
/* EXEC.C: This program accepts a number in the range 1 through 8 from the
* command line. Based on the number it receives, it executes one of the
* eight different procedures that spawn the process named child. For
* some of these procedures, the child.exe file must be in the same
* directory; for others, it need only be in the same path.
*/
#include <stdio.h>
#include <process.h>
char *my_env[] = {
"THIS=environment will be",
"PASSED=to child.exe by the",
"EXECLE=and",
"EXECLPE=and",
"EXECVE=and",
"EXECVPE=functions",
NULL
};
void main( int argc, char *argv[] )
{
char *args[4];
int result;
args[0] = "child"; /* Set up parameters to send */
args[1] = "execv??";
args[2] = "two";
args[3] = NULL;
switch( argv[1][0] ) /* Based on first letter of argument */
{
case '1':
execl( argv[2], argv[2], "execl", "two", NULL );
break;
case '2':
execle( argv[2], argv[2], "execle", "two", NULL, my_env );
break;
case '3':
execlp( argv[2], argv[2], "execlp", "two", NULL );
break;
case '4':
execlpe( argv[2], argv[2], "execlpe", "two", NULL, my_env );
break;
case '5':
execv( argv[2], args );
break;
case '6':
execve( argv[2], args, my_env );
break;
case '7':
execvp( argv[2], args );
break;
case '8':
execvpe( argv[2], args, my_env );
break;
default:
printf( "SYNTAX: EXEC <1-8> <childprogram>\n" );
exit( 1 );
}
printf( "Process was not spawned.\n" );
printf( "Program 'child' was not found." );
}
exit, _exit
────────────────────────────────────────────────────────────────────────────
Description
Terminate the calling process after cleanup (exit) or immediately ( _exit).
#include <process.h> Required only for function declarations
#include <stdlib.h> Use either PROCESS.H or STDLIB.H
void exit( int status );
void _exit( int status );
status Exit status
Remarks
The exit and _exit functions terminate the calling process. The exit
function first calls, in LIFO (last-in-first-out) order, the functions
registered by atexit and onexit, then flushes all file buffers before
terminating the process. The _exit function terminates the process without
processing atexit or onexit functions or flushing stream buffers. The status
value is typically set to 0 to indicate a normal exit and set to some other
value to indicate an error.
Although the exit and _exit calls do not return a value, the low-order byte
of status is made available to the waiting parent process, if one exists,
after the calling process exits. The status value is available to the
operating-system batch command ERRORLEVEL.
The behavior of the exit, _exit, _cexit, and _c_exit functions is as
follows:
Function Action
────────────────────────────────────────────────────────────────────────────
exit Performs complete C library termination
procedures, terminates the process, and
exits with the supplied status code.
_exit Performs "quick" C library termination
procedures, terminates the process, and
exits with the supplied status code.
_cexit Performs complete C library termination
procedures and returns to caller, but
does not terminate the process.
_c_exit Performs "quick" C library termination
procedures and returns to caller, but
does not terminate the process.
Return Value
None.
Compatibility
exit
ANSI DOS OS/2 UNIX XENIX
_exit
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
abort, atexit, _cexit, exec functions, onexit, spawn functions, system
Example
/* EXITER.C: This program prompts the user for a yes or no and returns
* a DOS error code of 1 if the user answers Y or y; otherwise it
* returns 0. The error code could be tested in a batch file.
*/
#include <conio.h>
#include <stdlib.h>
void main()
{
char ch;
cputs( "Yes or no? " );
ch = getch();
cputs( "\r\n" );
if( toupper( ch ) == 'Y' )
exit( 1 );
else
exit( 0 );
}
exp, expl
────────────────────────────────────────────────────────────────────────────
Description
Calculate the exponential.
#include <math.h>
double exp( double x );
long double expl( long double x );
x Floating-point value
Remarks
The exp and expl functions return the exponential function of their
floating-point arguments (x).
The expl function is the 80-bit counterpart; it uses an 80-bit, 10-byte
coprocessor form of arguments and return values. See the reference page on
the long double functions for more details on this data type.
Return Value
These functions return ex. The functions return HUGE_VAL on overflow and set
errno to ERANGE; on underflow, they return 0 but do not set errno.
Compatibility
exp
ANSI DOS OS/2 UNIX XENIX
expl
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
log functions
Example
/* EXP.C */
#include <math.h>
#include <stdio.h>
void main()
{
double x = 2.302585093, y;
y = exp( x );
printf( "exp( %f ) = %f\n", x, y );
}
Output
exp( 2.302585 ) = 10.000000
_expand Functions
────────────────────────────────────────────────────────────────────────────
Description
Changes the size of a memory block.
#include <malloc.h> Required only for function declarations
void *_expand( void *memblock, size_t size );
void _based( void ) *_bexpand( _segment seg, void _based( void )
*memblock,
size_t size );
void _far *_fexpand( void _far *memblock, size_t size );
void _near *_nexpand( void _near *memblock, size_t size );
memblock Pointer to previously allocated memory
block
size New size in bytes
seg Value of base segment
Remarks
The _expand family of functions changes the size of a previously allocated
memory block by attempting to expand or contract the block without moving
its location in the heap. The memblock argument points to the beginning of
the block. The size argument gives the new size of the block, in bytes. The
contents of the block are unchanged up to the shorter of the new and old
sizes.
The memblock argument can also point to a block that has been freed, as long
as there has been no intervening call to calloc, _expand, malloc, or
realloc. If memblock points to a freed block, the block remains free after a
call to one of the _expand functions.
The seg argument is the segment address of the _based heap.
In large data models (compact-, large-, and huge-model programs), _expand
maps to _fexpand. In small data models ( tiny-, small-, and medium-model
programs), expand maps to _nexpand.
The various _expand functions change the size of the storage block in the
data segments shown in the list below:
Function Data Segment
────────────────────────────────────────────────────────────────────────────
_expand Depends on data model of program
_bexpand Based heap specified by seg, or in all
based heaps if seg
is zero
_fexpand Far heap (outside default data segment)
_nexpand Near heap (inside default data segment)
Return Value
The _expand family of functions returns a void pointer to the reallocated
memory block. Unlike realloc, _expand cannot move a block to change its
size. This means the memblock argument to _expand is the same as the return
value if there is sufficient memory available to expand the block without
moving it.
With the exception of the _bexpand function, these functions return NULL if
there is insufficient memory available to expand the block to the given size
without moving it. The _bexpand function returns _NULLOFF if insufficient
memory is available. The item pointed to by memblock will have been expanded
as much as possible in its current location.
The storage space pointed to by the return value is guaranteed to be
suitably aligned for storage of any type of object. The new size of the item
can be checked with the _msize function. To get a pointer to a type other
than void, use a type cast on the return value.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
calloc functions, free functions, malloc functions, _msize functions,
realloc functions
Example
/* EXPAND.C */
#include <stdio.h>
#include <malloc.h>
#include <stdlib.h>
void main()
{
char *bufchar;
printf( "Allocate a 512 element buffer\n" );
if( (bufchar = (char *)calloc( 512, sizeof( char ) )) == NULL )
exit( 1 );
printf( "Allocated %d bytes at %Fp\n",
_msize( bufchar ), (void _far *)bufchar );
if( (bufchar = (char *)_expand( bufchar, 1024 )) == NULL )
printf( "Can't expand" );
else
printf( "Expanded block to %d bytes at %Fp\n",
_msize( bufchar ), (void _far *)bufchar );
/* Free memory */
free( bufchar );
exit( 0 );
}
Output
Allocate a 512 element buffer
Allocated 512 bytes at 0067:142A
Expanded block to 1024 bytes at 0067:142A
fabs, fabsl
────────────────────────────────────────────────────────────────────────────
Description
Calculate the absolute value of their floating-point arguments.
#include <math.h>
double fabs( double x );
long double fabsl( long double x );
x Floating-point value
Remarks
The fabs and fabsl functions calculate the absolute value of their
floating-point arguments.
The fabsl function is the 80-bit counterpart; it uses an 80-bit, 10-byte
coprocessor form of arguments and return values. See the reference page on
the long double functions for more details on this data type.
Return Value
These functions return the absolute value of their arguments. There is no
error return.
Compatibility
fabs
ANSI DOS OS/2 UNIX XENIX
fabsl
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
abs, cabs, labs
Example
/* ABS.C: This program computes and displays the absolute values of
* several numbers.
*/
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
void main()
{
int ix = -4, iy;
long lx = -41567L, ly;
double dx = -3.141593, dy;
iy = abs( ix );
printf( "The absolute value of %d is %d\n", ix, iy);
ly = labs( lx );
printf( "The absolute value of %ld is %ld\n", lx, ly);
dy = fabs( dx );
printf( "The absolute value of %f is %f\n", dx, dy );
}
Output
The absolute value of -4 is 4
The absolute value of -41567 is 41567
The absolute value of -3.141593 is 3.141593
fclose, fcloseall
────────────────────────────────────────────────────────────────────────────
Description
Closes a stream (fclose) or closes all open streams (fcloseall).
#include <stdio.h>
int fclose( FILE *stream );
int fcloseall( void );
stream Pointer to FILE structure
Remarks
The fclose function closes stream. The fcloseall function closes all open
streams except stdin, stdout, stderr (and in DOS, stdaux and stdprn). It
also closes and deletes any temporary files created by tmpfile.
In both functions, all buffers associated with the stream are flushed prior
to closing. System-allocated buffers are released when the stream is closed.
Buffers assigned by the user with setbuf and setvbuf are not automatically
released.
Return Value
The fclose function returns 0 if the stream is successfully closed. The
fcloseall function returns the total number of streams closed. Both
functions return EOF to indicate an error.
Compatibility
fclose
ANSI DOS OS/2 UNIX XENIX
fcloseall
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
close, fdopen, fflush, fopen, freopen
Example
/* FOPEN.C: This program opens files named "data" and "data2". It uses
* fclose to close "data" and fcloseall to close all remaining files.
*/
#include <stdio.h>
FILE *stream, *stream2;
void main()
{
int numclosed;
/* Open for read (will fail if 'data does not exist) */
if( (stream = fopen( "data", "r" )) == NULL )
printf( "The file 'data' was not opened\n" );
else
printf( "The file 'data' was opened\n" );
/* Open for write */
if( (stream2 = fopen( "data2", "w+" )) == NULL )
printf( "The file 'data2' was not opened\n" );
else
printf( "The file 'data2' was opened\n" );
/* Close stream */
if( fclose( stream ) )
printf( "The file 'data' was not closed\n" );
/* All other files are closed: */
numclosed = fcloseall( );
printf( "Number of files closed by fcloseall: %u\n", numclosed );
}
Output
The file 'data' was opened
The file 'data2' was opened
Number of files closed by fcloseall: 1
fcvt
────────────────────────────────────────────────────────────────────────────
Description
Converts a floating-point number to a string.
#include <stdlib.h> Required only for function declarations
char *fcvt( double value, int count, int *dec, int *sign );
value Number to be converted
count Number of digits after decimal point
dec Pointer to stored decimal-point position
sign Pointer to stored sign indicator
Remarks
The fcvt function converts a floating-point number to a null-terminated
character string. The value argument is the floating-point number to be
converted. The fcvt function stores the digits of value as a string and
appends a null character ('\0'). The count argument specifies the number of
digits to be stored after the decimal point. Excess digits are rounded off
to count places. If there are fewer than count digits of precision, the
string is padded with zeros.
Only digits are stored in the string. The position of the decimal point and
the sign of value can be obtained from dec and sign after the call. The dec
argument points to an integer value; this integer value gives the position
of the decimal point with respect to the beginning of the string. A zero or
negative integer value indicates that the decimal point lies to the left of
the first digit. The argument sign points to an integer indicating the sign
of value. The integer is set to 0 if value is positive and is set to a
nonzero number if value is negative.
The ecvt and fcvt functions use a single statically allocated buffer for the
conversion. Each call to one of these routines destroys the results of the
previous call.
Return Value
The fcvt function returns a pointer to the string of digits. There is no
error return.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
atof, atoi, atol, ecvt, gcvt
Example
/* FCVT.C: This program converts the constant 3.1415926535 to a string and
* sets the pointer *buffer to point to that string.
*/
#include <stdlib.h>
#include <stdio.h>
void main()
{
int decimal, sign;
char *buffer;
double source = 3.1415926535;
buffer = fcvt( source, 7, &decimal, &sign );
printf( "source: %2.10f buffer: '%s' decimal: %d sign: %d\n",
source, buffer, decimal, sign );
}
Output
source: 3.1415926535 buffer: '31415927' decimal: 1 sign: 0
fdopen
────────────────────────────────────────────────────────────────────────────
Description
Opens a stream using a handle.
#include <stdio.h>
FILE *fdopen( int handle, char *mode );
handle Handle referring to open file
mode Type of access permitted
Remarks
The fdopen function associates an input/output stream with the file
identified by handle, thus allowing a file opened for "low-level" I/O to be
buffered and formatted. (See Section 2.7, "Input and Output," for an
explanation of stream I/O and low-level I/O.) The mode character string
specifies the type of access requested for the file, as shown below. The
following list gives the mode string used in the fopen and fdopen functions
and the corresponding oflag arguments used in the open and sopen functions.
A complete description of the mode string argument is given in the remarks
section of the fopen function.
Type String Equivalent Value for open/sopen
────────────────────────────────────────────────────────────────────────────
"r" O_RDONLY
"w" O_WRONLY (usually O_WRONLY | O_CREAT |
O_TRUNC)
"a" O_WRONLY | O_APPEND (usually O_WRONLY |
O_CREAT | O_APPEND)
"r+" O_RDWR
"w+" O_RDWR (usually O_RDWR | O_CREAT |
O_TRUNC)
"a+" O_RDWR | O_APPEND (usually O_RDWR |
O_APPEND | O_CREAT )
In addition to the values listed above, one of the following characters can
be included in the mode string to specify the translation mode for newlines.
These characters correspond to the constants used in the open and sopen
functions, as shown below:
Mode Equivalent Value for open/sopen
────────────────────────────────────────────────────────────────────────────
t O_TEXT
b O_BINARY
If t or b is not given in the mode string, the translation mode is defined
by the default-mode variable _fmode.
The t option is not part of the ANSI standard for fopen and fpopen, but is
instead a Microsoft extension and should not be used where ANSI portability
is desired.
Return Value
The fdopen function returns a pointer to the open stream. A null pointer
value indicates an error.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
dup, dup2, fclose, fcloseall, fopen, freopen, open
Example
/* FDOPEN.C: This program opens a file using low-level I/O, then uses
* fdopen to switch to stream access. It counts the lines in the file.
*/
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <io.h>
void main()
{
FILE *stream;
int fh, count = 0;
char inbuf[128];
/* Open a file handle. */
if( (fh = open( "fdopen.c", O_RDONLY )) == -1 )
exit( 1 );
/* Change handle access to stream access. */
if( (stream = fdopen( fh, "r" )) == NULL )
exit( 1 );
while( fgets( inbuf, 128, stream ) != NULL )
count++;
/* After fdopen, close with fclose, not close. */
fclose( stream );
printf( "Lines in file: %d\n", count );
}
Output
Lines in file: 31
feof
────────────────────────────────────────────────────────────────────────────
Description
Tests for end-of-file on a stream.
#include <stdio.h>
int feof( FILE *stream );
stream Pointer to FILE structure
Remarks
The feof routine (implemented as a macro) determines whether the end of
stream has been reached. Once the end of the file is reached, read
operations return an end-of-file indicator until the stream is closed or
until rewind, fsetpos, fseek, or clearerr is called against it.
Return Value
The feof function returns a nonzero value after the first read operation
that attempts to read past the end of the file. It returns 0 if the current
position is not end-of-file. There is no error return.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
clearerr, eof, ferror, perror
Example
/* FEOF.C: This program uses feof to indicate when it reaches the end
* of the file FEOF.C. It also checks for errors with ferror.
*/
#include <stdio.h>
#include <stdlib.h>
void main()
{
int count, total = 0;
char buffer[100];
FILE *stream;
if( (stream = fopen( "feof.c", "r" )) == NULL )
exit( 1 );
/* Cycle until end of file reached: */
while( !feof( stream ) )
{
/* Attempt to read in 10 bytes: */
count = fread( buffer, sizeof( char ), 100, stream );
if( ferror( stream ) )
{
perror( "Read error" );
break;
}
/* Total up actual bytes read */
total += count;
}
printf( "Number of bytes read = %d\n", total );
fclose( stream );
}
Output
Number of bytes read = 697
ferror
────────────────────────────────────────────────────────────────────────────
Description
Tests for an error on a stream.
#include <stdio.h>
int ferror( FILE *stream );
stream Pointer to FILE structure
Remarks
The ferror routine (implemented as a macro) tests for a reading or writing
error on the file associated with stream. If an error has occurred, the
error indicator for the stream remains set until the stream is closed or
rewound, or until clearerr is called against it.
Return Value
If no error has occurred on stream, ferror returns 0. Otherwise, it returns
a nonzero value.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
clearerr, eof, feof, fopen, perror
Example
/* FEOF.C: This program uses feof to indicate when it reaches the end
* of the file FEOF.C. It also checks for errors with ferror.
*/
#include <stdio.h>
#include <stdlib.h>
void main()
{
int count, total = 0;
char buffer[100];
FILE *stream;
if( (stream = fopen( "feof.c", "r" )) == NULL )
exit( 1 );
/* Cycle until end of file reached: */
while( !feof( stream ) )
{
/* Attempt to read in 10 bytes: */
count = fread( buffer, sizeof( char ), 100, stream );
if( ferror( stream ) )
{
perror( "Read error" );
break;
}
/* Total up actual bytes read */
total += count;
}
printf( "Number of bytes read = %d\n", total );
fclose( stream );
}
Output
Number of bytes read = 697
fflush
────────────────────────────────────────────────────────────────────────────
Description
Flushes a stream.
#include <stdio.h>
int fflush( FILE *stream );
stream Pointer to FILE structure
Remarks
If the file associated with stream is open for output, fflush writes to that
file the contents of the buffer associated with the stream. If the stream is
open for input, fflush clears the contents of the buffer. The fflush
function negates the effect of any prior call to ungetc against stream.
Buffers are automatically flushed when they are full, when the stream is
closed, or when a program terminates normally without closing the stream.
The stream remains open after the call. The fflush function has no effect on
an unbuffered stream.
Return Value
The fflush function returns the value 0 if the buffer was successfully
flushed. The value 0 is also returned in cases in which the specified stream
has no buffer or is open for reading only. A return value of EOF indicates
an error.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
fclose, flushall, setbuf
Example
/* FFLUSH.C */
#include <stdio.h>
#include <conio.h>
void main()
{
int integer;
char string[81];
/* Read each word as a string. */
printf( "Enter a sentence of four words with scanf: " );
for( integer = 0; integer < 4; integer++ )
{
scanf( "%s", string );
printf( "%s\n", string );
}
/* You must flush the input buffer before using gets. */
fflush( stdin );
printf( "Enter the same sentence with gets: " );
gets( string );
printf( "%s\n", string );
}
Output
Enter a sentence of four words with scanf: This is a test
This
is
a
test
Enter the same sentence with gets: This is a test
This is a test
fgetc, fgetchar
────────────────────────────────────────────────────────────────────────────
Description
Read a character from a stream (fgetc) or stdin (fgetchar).
#include <stdio.h>
int fgetc( FILE *stream );
int fgetchar( void );
stream Pointer to FILE structure
Remarks
The fgetc function reads a single character from the current position of the
file associated with stream. The character is converted and returned as an
int. The function then increments the associated file pointer (if any) to
point to the next character. The fgetchar function is equivalent to
fgetc(stdin).
The fgetc and fgetchar routines are identical to getc and getchar, but they
are functions rather than macros.
Return Value
The fgetc and fgetchar functions return the character read. They return EOF
to indicate an error or end-of-file. Use feof or ferror to distinguish
between an error and an end-of-file condition.
Compatibility
fgetc
ANSI DOS OS/2 UNIX XENIX
fgetchar
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
fputc, fputchar, getc, getchar
Example
/* FGETC.C: This program uses getc to read the first 80 input characters
* (or until the end of input) and place them into a string named buffer.
*/
#include <stdio.h>
#include <stdlib.h>
void main()
{
FILE *stream;
char buffer[81];
int i, ch;
/* Open file to read line from: */
if( (stream = fopen( "fgetc.c", "r" )) == NULL )
exit( 0 );
/* Read in first 80 characters and place them in "buffer": */
ch = fgetc( stream );
for( i=0; (i < 80 ) && ( feof( stream ) == 0 ); i++ )
{
buffer[i] = ch;
ch = fgetc( stream );
}
/* Add null to end string */
buffer[i] = '\0';
printf( "%s\n", buffer );
fclose( stream );
}
Output
/* FGETC.C: This program uses getc to read the first 80 input characters
/* (or
fgetpos
────────────────────────────────────────────────────────────────────────────
Description
Gets a stream's file-position indicator.
#include <stdio.h>
int fgetpos( FILE *stream, fpos_t *pos );
stream Target stream
pos Position-indicator storage
Remarks
The fgetpos function gets the current value of the stream argument's
file-position indicator and stores it in the object pointed to by pos. The
fsetpos function can later use information stored in pos to reset the stream
argument's pointer to its position at the time fgetpos was called.
The pos value is stored in an internal format and is intended for use only
by the fgetpos and fsetpos functions.
Return Value
If successful, the fgetpos function returns 0. On failure, it returns a
nonzero value and sets errno to one of the following manifest constants
(defined in STDIO.H):
Constant Meaning
────────────────────────────────────────────────────────────────────────────
EBADF The specified stream is not a valid file
handle or is not
accessible.
EINVAL The stream value is invalid.
Compatibility
ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
fsetpos
Example
/* FGETPOS.C: This program opens a file and reads bytes at several
* different locations.
*/
#include <stdio.h>
void main()
{
FILE *stream;
fpos_t pos;
int val;
char buffer[20];
if( (stream = fopen( "fgetpos.c", "rb" )) == NULL )
printf( "Trouble opening file\n" );
else
{
/* Read some data and then check the position. */
fread( buffer, sizeof( char ), 10, stream );
if( fgetpos( stream, &pos ) != 0 )
perror( "fgetpos error" );
else
{
fread( buffer, sizeof( char ), 10, stream );
printf( "10 bytes at byte %ld: %.10s\n", pos, buffer );
}
/* Set a new position and read more data */
pos = 140;
if( fsetpos( stream, &pos ) != 0 )
perror( "fsetpos error" );
fread( buffer, sizeof( char ), 10, stream );
printf( "10 bytes at byte %ld: %.10s\n", pos, buffer );
fclose( stream );
}
}
Output
10 bytes at byte 10: .C: This p
10 bytes at byte 140: FILE *
fgets
────────────────────────────────────────────────────────────────────────────
Description
Gets a string from a stream.
#include <stdio.h>
char *fgets( char *string, int n, FILE *stream );
string Storage location for data
n Number of characters stored
stream Pointer to FILE structure
Remarks
The fgets function reads a string from the input stream argument and stores
it in string. Characters are read from the current stream position up to and
including the first newline character ('\n'), up to the end of the stream,
or until the number of characters read is equal to n - 1, whichever comes
first. The result is stored in string, and a null character ('\0') is
appended. The newline character, if read, is included in the string. If n is
equal to 1, string is empty (""). The fgets function is similar to the gets
function; however, gets replaces the newline character with NULL.
Return Value
If successful, the fgets function returns string. It returns NULL to
indicate either an error or end-of-file condition. Use feof or ferror to
determine whether an error occurred.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
fputs, gets, puts
Example
/* FGETS.C: This program uses fgets to display a line from a file on the
* screen.
*/
#include <stdio.h>
FILE *stream;
void main()
{
char line[100], *result;
if( (stream = fopen( "fgets.c", "r" )) != NULL )
{
if( fgets( line, 100, stream ) == NULL)
printf( "fgets error\n" );
else
printf( "%s", line);
fclose( stream );
}
}
Output
/* FGETS.C: This program uses fgets to display a line from a file on the
fieeetomsbin, fmsbintoieee
────────────────────────────────────────────────────────────────────────────
Description
Convert floating-point numbers between IEEE and Microsoft binary formats.
#include <math.h>
int fieeetomsbin( float *src4, float *dst4 );
int fmsbintoieee( float *src4, float *dst4 );
scr4 Value to be converted
dst4 Converted value
Remarks
The fieeetomsbin routine converts a single-precision floating-point number
in IEEE (Institute of Electrical and Electronic Engineers) format to
Microsoft (MS) binary format.
The fmsbintoieee routine converts a floating-point number in Microsoft
binary format to IEEE format.
These routines allow C programs (which store floating-point numbers in the
IEEE format) to use numeric data in random-access data files created with
Microsoft BASIC (which stores floating-point numbers in the Microsoft binary
format), and vice versa.
The argument src4 points to the float value to be converted. The result is
stored at the location given by dst4.
These routines do not handle IEEE NANs ("not a number") and infinities. IEEE
denormals are treated as 0 in the conversions.
Return Value
These functions return 0 if the conversion is successful and 1 if the
conversion causes an overflow.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
dieeetomsbin, dmsbintoieee
filelength
────────────────────────────────────────────────────────────────────────────
Description
Gets the length of a file.
#include <io.h> Required only for function declarations
long filelength( int handle );
handle Target file handle
Remarks
The filelength function returns the length, in bytes, of the target file
associated with handle.
Return Value
The filelength function returns the file length in bytes. A return value of
-1L indicates an error, and an invalid handle sets errno to EBADF.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
chsize, fileno, fstat, stat
Example
/* CHSIZE.C: This program uses filelength to report the size of a
* file before and after modifying it with chsize.
*/
#include <io.h>
#include <fcntl.h>
#include <sys\types.h>
#include <sys\stat.h>
#include <stdio.h>
void main()
{
int fh, result;
unsigned int nbytes = BUFSIZ;
/* Open a file */
if( (fh = open( "data", O_RDWR | O_CREAT, S_IREAD | S_IWRITE )) != -1 )
{
printf( "File length before: %ld\n", filelength( fh ) );
if( chsize( fh, 329678 ) == 0 )
printf( "Size successfully changed\n" );
else
printf( "Problem in changing the size\n" );
printf( "File length after: %ld\n", filelength( fh ) );
close( fh );
}
}
Output
File length before: 0
Size successfully changed
File length after: 329678
fileno
────────────────────────────────────────────────────────────────────────────
Description
Gets the file handle associated with a stream.
#include <stdio.h>
int fileno( FILE *stream );
stream Pointer to FILE structure
Remarks
The fileno routine returns the file handle currently associated with stream.
This routine is implemented as a macro.
Return Value
The fileno routine returns the file handle. There is no error return. The
result is undefined if stream does not specify an open file.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
fdopen, filelength, fopen, freopen
Example
/* FILENO.C: This program uses fileno to obtain the file handle for
* some standard C streams.
*/
#include <stdio.h>
void main()
{
printf( "The file handle for stdin is %d\n", fileno( stdin ) );
printf( "The file handle for stdout is %d\n", fileno( stdout ) );
printf( "The file handle for stderr is %d\n", fileno( stderr ) );
}
Output
The file handle for stdin is 0
The file handle for stdout is 1
The file handle for stderr is 2
_floodfill, _floodfill_w
────────────────────────────────────────────────────────────────────────────
Description
Fill an area of a display using the current color and fill mask
#include <graph.h>
short _far _floodfill( short x, short y, short boundary );
short _far _floodfill_w( double wx, double wy, short boundary );
x, y Start point
wx, wy Start point
boundary Boundary color of area to be filled
Remarks
The functions in the _floodfill family fill an area of the display, using
the current color and fill mask. The _floodfill routine begins filling at
the view-coordinate point (x, y). The _floodfill_w routine begins filling at
the window-coordinate point (wx, wy).
If this point lies inside the figure, the interior is filled; if it lies
outside the figure, the background is filled. The point must be inside or
outside the figure to be filled, not on the figure boundary itself. Filling
occurs in all directions, stopping at the color of boundary.
Return Value
The _floodfill functions return a nonzero value if the fill is successful.
It returns 0 if the fill could not be completed, the starting point lies on
the boundary color, or the start point lies outside the clipping region.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_ellipse functions, _getcolor, _getfillmask, _grstatus, _pie functions,
_setfillmask, _setcliprgn, _setcolor
Example
/* FLOODFIL.C: This program draws a series of nested rectangles in
* different colors, constantly changing the background color.
*/
#include <conio.h>
#include <stdlib.h>
#include <graph.h>
void main()
{
int loop;
int xvar, yvar;
/* find a valid graphics mode */
if( !_setvideomode( _MAXCOLORMODE ) )
exit( 1 );
for( xvar = 163, loop = 0; xvar < 320; loop++, xvar += 3 )
{
_setcolor( loop % 16 );
yvar = xvar * 5 / 8;
_rectangle( _GBORDER, 320-xvar, 200-yvar, xvar, yvar );
_setcolor( rand() % 16 );
_floodfill( 0, 0, loop % 16 );
}
getch();
_setvideomode( _DEFAULTMODE );
}
floor, floorl
────────────────────────────────────────────────────────────────────────────
Description
Calculate the floor of a value.
#include <math.h>
double floor( double x );
long double floorl( long double x );
x Floating-point value
Remarks
The floor and floorl functions return a floating-point value representing
the largest integer that is less than or equal to x.
The floorl function is the 80-bit counterpart, and it uses the 80-bit,
10-byte coprocessor form of arguments and return values. See the reference
page on the long double functions for more details on this data type.
Return Value
These functions return the floating-point result. There is no error return.
Compatibility
floor
ANSI DOS OS/2 UNIX XENIX
floorl
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
ceil, fmod
Example
/* FLOOR.C: This example displays the largest integers less than or equal
* to the floating-point values 2.8 and -2.8. It then shows the smallest
* integers greater than or equal to 2.8 and -2.8.
*/
#include <math.h>
#include <stdio.h>
void main()
{
double y;
y = floor( 2.8 );
printf( "The floor of 2.8 is %f\n", y );
y = floor( -2.8 );
printf( "The floor of -2.8 is %f\n", y );
y = ceil( 2.8 );
printf( "The ceil of 2.8 is %f\n", y );
y = ceil( -2.8 );
printf( "The ceil of -2.8 is %f\n", y );
}
Output
The floor of 2.8 is 2.000000
The floor of -2.8 is -3.000000
The ceil of 2.8 is 3.000000
The ceil of -2.8 is -2.000000
flushall
────────────────────────────────────────────────────────────────────────────
Description
Flushes all streams; clears all buffers.
#include <stdio.h>
int flushall( void );
Remarks
The flushall function writes to its associated files the contents of all
buffers associated with open output streams. All buffers associated with
open input streams are cleared of their current contents. The next read
operation (if there is one) then reads new data from the input files into
the buffers.
Buffers are automatically flushed when they are full, when streams are
closed, or when a program terminates normally without closing streams.
All streams remain open after the call to flushall.
Return Value
The flushall function returns the number of open streams (input and output).
There is no error return.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
fflush
Example
/* FLUSHALL.C: This program uses flushall to flush all open buffers. */
#include <stdio.h>
void main()
{
int numflushed;
numflushed = flushall();
printf( "There were %d streams flushed\n", numflushed );
}
Output
There were 3 streams flushed
fmod, fmodl
────────────────────────────────────────────────────────────────────────────
Description
Calculates the floating-point remainder.
#include <math.h>
double fmod( double x, double y );
long double fmodl( long double x, long double y );
x, y Floating-point values
Remarks
The fmod and fmodl functions calculate the floating-point remainder f of x /
y such that x = i * y + f, where i is an integer, f has the same sign as
x, and the absolute value of f is less than the absolute value of y.
The fmodl function is the 80-bit counterpart; it uses the 80-bit, 10-byte
coprocessor form of arguments and return values. See the discussion of the
long double functions for more details on this data type.
Return Value
These functions return the floating-point remainder. If y is 0, the function
returns 0.
Compatibility
fmod
ANSI DOS OS/2 UNIX XENIX
fmodl
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
ceil, fabs, floor
Example
/* FMOD.C: This program displays a floating-point remainder. */
#include <math.h>
#include <stdio.h>
void main()
{
double x = -10.0, y = 3.0, z;
z = fmod( x, y );
printf( "The remainder of %.2f / %.2f is %f\n", x, y, z );
}
Output
The remainder of -10.00 / 3.00 is -1.000000
fopen
────────────────────────────────────────────────────────────────────────────
Description
Opens a file.
#include <stdio.h>
FILE *fopen( const char *filename, const char *mode );
filename Path name of file
mode Type of access permitted
Remarks
The fopen function opens the file specified by filename. The character
string mode specifies the type of access requested for the file, as follows:
Type Description
────────────────────────────────────────────────────────────────────────────
"r" Opens for reading. If the file does not
exist or cannot be found, the fopen call
will fail.
"w" Opens an empty file for writing. If the
given file exists, its contents are
destroyed.
"a" Opens for writing at the end of the file
(appending); creates the file first if
it doesn't exist.
"r+" Opens for both reading and writing. (The
file must exist.)
"w+" Opens an empty file for both reading and
writing. If the given file exists, its
contents are destroyed.
"a+" Opens for reading and appending; creates
the file first if it doesn't exist.
When a file is opened with the "a" or "a+" access type, all write operations
occur at the end of the file. Although the file pointer can be repositioned
using fseek or rewind, the file pointer is always moved back to the end of
the file before any write operation is carried out. Thus, existing data
cannot be overwritten.
When the "r+", "w+", or "a+" access type is specified, both reading and
writing are allowed (the file is said to be open for "update"). However,
when you switch between reading and writing, there must be an intervening
fsetpos, fseek, or rewind operation. The current position can be specified
for the fsetpos or fseek operation, if desired.
In addition to the values listed above, one of the following characters can
be included in mode to specify the translation mode for newline characters:
Mode Meaning
────────────────────────────────────────────────────────────────────────────
t Open in text (translated) mode. In this
mode, carriage-return-line-feed (CR-LF)
combinations are translated into single
line feeds (LF) on input and LF
characters are translated to CR-LF
combinations on output. Also, CTRL+Z is
interpreted as an end-of-file character
on input. In files opened for reading or
for reading/writing, fopen checks for a
CTRL+Z at the end of the file and
removes it, if possible. This is done
because using the fseek and ftell
functions to move within a file that
ends with a CTRL+Z may cause fseek to
behave improperly near the end of the
file.
b Open in binary (untranslated) mode; the
above translations are suppressed.
If t or b is not given in mode, the translation mode is defined by the
default-mode variable _fmode. If t or b is prefixed to the argument, the
function will fail and return NULL.
See Section 2.7, "Input and Output," for a discussion of text and binary
modes.
Return Value
The fopen function returns a pointer to the open file. A null pointer value
indicates an error.
Compatibility
ANSI DOS OS/2 UNIX XENIX
Note that the t option is not part of the ANSI standard for fopen; it is a
Microsoft extension and should not be used where ANSI portability is
desired.
See Also
fclose, fcloseall, fdopen, ferror, fileno, freopen, open, setmode
Example
/* FOPEN.C: This program opens files named "data" and "data2". It uses
* fclose to close "data" and fcloseall to close all remaining files.
*/
#include <stdio.h>
FILE *stream, *stream2;
void main()
{
int numclosed;
/* Open for read (will fail if 'data' does not exist) */
if( (stream = fopen( "data", "r" )) == NULL )
printf( "The file 'data' was not opened\n" );
else
printf( "The file 'data' was opened\n" );
/* Open for write */
if( (stream2 = fopen( "data2", "w+" )) == NULL )
printf( "The file 'data2' was not opened\n" );
else
printf( "The file 'data2' was opened\n" );
/* Close stream */
if( fclose( stream ) )
printf( "The file 'data' was not closed\n" );
/* All other files are closed: */
numclosed = fcloseall( );
printf( "Number of files closed by fcloseall: %u\n", numclosed );
}
Output
The file 'data' was opened
The file 'data2' was opened
Number of files closed by fcloseall: 1
FP_OFF, FP_SEG
────────────────────────────────────────────────────────────────────────────
Description
Get or set a far-pointer offset (FP_OFF) or a far-pointer segment (FP_SEG).
#include <dos.h>
unsigned FP_OFF( void _far *address );
unsigned FP_SEG( void _far *address );
address Far pointer to memory address
Remarks
The FP_OFF and FP_SEG macros can be used to set or get the offset and
segment, respectively, of the far pointer at address.
Return Value
The FP_OFF macro returns an offset. The FP_SEG macro returns a segment
address.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
Example
/* FP_SEG.C: This program uses FP_SEG and FP_OFF to obtain
* the segment and offset of the long pointer p.
*/
#include <dos.h>
#include <malloc.h>
#include <stdio.h>
void main()
{
void _far *p;
unsigned int seg_val;
unsigned int off_val;
p = _fmalloc( 100 ); /* Points pointer at something */
seg_val = FP_SEG( p ); /* Gets address pointed to */
off_val = FP_OFF( p );
printf( "Segment is %.4X; Offset is %.4X\n", seg_val, off_val );
}
Output
Segment is 00C7; Offset is 0016
_fpreset
────────────────────────────────────────────────────────────────────────────
Description
Resets the floating-point package.
#include <float.h>
void _fpreset( void );
Remarks
The _fpreset function reinitializes the floating-point-math package. This
function is usually used in conjunction with signal, system, or the exec or
spawn functions.
If a program traps floating-point error signals (SIGFPE) with signal, it can
safely recover from floating-point errors by invoking _fpreset and using
longjmp.
In DOS versions prior to 3.0, a child process executed by exec, spawn, or
system may affect the floating-point state of the parent process if an 8087
or 80287 coprocessor is used. If you are using either coprocessor, the
following precautions are recommended:
■ The exec, spawn, and system functions should not be called during the
evaluation of a floating-point expression.
■ The _fpreset function should be called after these routines if there
is a possibility of the child process performing any floating-point
operations.
Return Value
None.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
exec functions, signal, spawn functions
Example
/* FPRESET.C: This program uses signal to set up a routine for handling
* floating-point errors.
*/
#include <stdio.h>
#include <signal.h>
#include <setjmp.h>
#include <stdlib.h>
#include <float.h>
#include <math.h>
#include <string.h>
jmp_buf mark; /* Address for long jump to jump to */
int fperr; /* Global error number */
void fphandler( int sig, int num ); /* Prototypes */
void fpcheck( void );
void main()
{
double n1, n2, r;
int jmpret;
/* Set up floating point error handler. */
if( signal( SIGFPE, fphandler ) == SIG_ERR )
{
fprintf( stderr, "Couldn't set SIGFPE\n" );
abort();
}
/* Save stack environment for return in case of error. First time
* through, jmpret is 0, so true conditional is executed. If an
* error occurs, jmpret will be set to -1 and false conditional
* will be executed.
*/
jmpret = setjmp( mark );
if( jmpret == 0 )
{
printf( "Test for invalid operation - " );
printf( "enter two numbers: " );
scanf( "%lf %lf", &n1, &n2 );
r = n1 / n2;
/* This won't be reached if error occurs. */
printf( "\n\n%4.3g / %4.3g = %4.3g\n", n1, n2, r );
r = n1 * n2;
/* This won't be reached if error occurs. */
printf( "\n\n%4.3g * %4.3g = %4.3g\n", n1, n2, r );
}
else
fpcheck();
}
/* Handles SIGFPE (floating point error) interrupt. */
void fphandler( int sig, int num )
{
/* Set global for outside check since we don't want to do I/O in the
* handler.
*/
fperr = num;
/* Initialize floating-point package. */
_fpreset();
/* Restore calling environment and jump back to setjmp. Return -1
* so that setjmp will return false for conditional test.
*/
longjmp( mark, -1 );
}
void fpcheck()
{
char fpstr[30];
switch( fperr )
{
case FPE_INVALID:
strcpy( fpstr, "Invalid number" );
break;
case FPE_OVERFLOW:
strcpy( fpstr, "Overflow" );
break;
case FPE_UNDERFLOW:
strcpy( fpstr, "Underflow" );
break;
case FPE_ZERODIVIDE:
strcpy( fpstr, "Divide by zero" );
break;
default:
strcpy( fpstr, "Other floating point error" );
break;
}
printf( "Error %d: %s\n", fperr, fpstr );
}
Output
Test for invalid operation - enter two numbers: 5 0
Error 131: Divide by zero
fprintf
────────────────────────────────────────────────────────────────────────────
Description
Prints formatted data to a stream.
#include <stdio.h>
int fprintf( FILE *stream, const char *format [[, argument]]... );
stream Pointer to FILE structure
format Format-control string
argument Optional arguments
Remarks
The fprintf function formats and prints a series of characters and values to
the output stream. Each argument (if any) is converted and output according
to the corresponding format specification in format.
The format argument has the same form and function that it does for the
printf function; see the Remarks section for the printf function for more
information on format and argument.
Return Value
The fprintf function returns the number of characters printed, or a negative
value in the case of an output error.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
cprintf, fscanf, printf, sprintf
Example
/* FPRINTF.C: This program uses fprintf to format various data and
* print them to the file named FPRINTF.OUT. It then displays
* FPRINTF.OUT on the screen using the system function to invoke
* the DOS TYPE command.
*/
#include <stdio.h>
#include <process.h>
FILE *stream;
void main()
{
int i = 10;
double fp = 1.5;
char s[] = "this is a string";
char c = '\n';
stream = fopen( "fprintf.out", "w" );
fprintf( stream, "%s%c", s, c );
fprintf( stream, "%d\n", i );
fprintf( stream, "%f\n", fp );
fclose( stream );
system( "type fprintf.out" );
}
Output
this is a string
10
1.500000
fputc, fputchar
────────────────────────────────────────────────────────────────────────────
Description
Write a character to a stream (fputc) or to stdout (fputchar).
#include <stdio.h>
int fputc( int c, FILE *stream );
int fputchar( int c );
c Character to be written
stream Pointer to FILE structure
Remarks
The fputc function writes the single character c to the output stream at the
current position. The fputchar function is equivalent to fputc(c, stdout).
The fputc and fputchar routines are similar to putc and putchar, but are
functions rather than macros.
Return Value
The fputc and fputchar functions return the character written. A return
value of EOF indicates an error.
Compatibility
fputc
ANSI DOS OS/2 UNIX XENIX
fputchar
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
fgetc, fgetchar, putc, putchar
Example
/* FPUTC.C: This program uses fputc and fputchar to send a character
* array to stdout.
*/
#include <stdio.h>
void main()
{
char strptr1[] = "This is a test of fputc!!\n";
char strptr2[] = "This is a test of fputchar!!\n";
char *p;
/* Print line to stream using fputc. */
p = strptr1;
while( (*p != '\0') && fputc( *(p++), stdout ) != EOF )
;
/* Print line to stream using fputchar. */
p = strptr2;
while( (*p != '\0') && fputchar( *(p++) ) != EOF )
;
}
Output
This is a test of fputc!!
This is a test of fputchar!!
fputs
────────────────────────────────────────────────────────────────────────────
Description
Writes a string to a stream.
#include <stdio.h>
int fputs( const char *string, FILE *stream );
string String to be output
stream Pointer to FILE structure
Remarks
The fputs function copies string to the output stream at the current
position. The terminating null character ('\0') is not copied.
Return Value
The fputs function returns a nonnegative value if it is successful. If an
error occurs, it returns EOF.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
fgets, gets, puts
Example
/* FPUTS.C: This program uses fputs to write a single line to the
* stdout stream.
*/
#include <stdio.h>
void main()
{
fputs( "Hello world from fputs.\n", stdout );
}
Output
Hello world from fputs.
fread
────────────────────────────────────────────────────────────────────────────
Description
Reads data from a stream.
#include <stdio.h>
size_t fread( void *buffer, size_t size, size_t count, FILE *stream );
buffer Storage location for data
size Item size in bytes
count Maximum number of items to be read
stream Pointer to FILE structure
Remarks
The fread function reads up to count items of size bytes from the input
stream and stores them in buffer. The file pointer associated with stream
(if there is one) is increased by the number of bytes actually read.
If the given stream is opened in text mode, carriage-return-line-feed pairs
are replaced with single line-feed characters. The replacement has no effect
on the file pointer or the return value.
The file-pointer position is indeterminate if an error occurs. The value of
a partially read item cannot be determined.
Return Value
The fread function returns the number of full items actually read, which may
be less than count if an error occurs or if the file end is encountered
before reaching count.
The feof or ferror function should be used to distinguish a read error from
an end-of-file condition. If size or count is 0, fread returns 0 and the
buffer contents are unchanged.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
fwrite, read
Example
/* FREAD.C: This program opens a file named FREAD.OUT and writes 25
* characters to the file. It then tries to open FREAD.OUT and
* read in 25 characters. If the attempt succeeds, the program
* displays the number of actual items read.
*/
#include <stdio.h>
void main()
{
FILE *stream;
char list[30];
int i, numread, numwritten;
/* Open file in text mode: */
if( (stream = fopen( "fread.out", "w+t" )) != NULL )
{
for ( i = 0; i < 25; i++ )
list[i] = 'z' - i;
/* Write 25 characters to stream */
numwritten = fwrite( list, sizeof( char ), 25, stream );
printf( "Wrote %d items\n", numwritten );
fclose( stream );
}
else
printf( "Problem opening the file\n" );
if( (stream = fopen( "fread.out", "r+t" )) != NULL )
{
/* Attempt to read in 25 characters */
numread = fread( list, sizeof( char ), 25, stream );
printf( "Number of items read = %d\n", numread );
printf( "Contents of buffer = %.25s\n", list );
fclose( stream );
}
else
printf( "Was not able to open the file\n" );
}
Output
Wrote 25 items
Number of items read = 25
Contents of buffer = zyxwvutsrqponmlkjihgfedcb
free Functions
────────────────────────────────────────────────────────────────────────────
Description
Deallocate a memory block.
#include <stdlib.h> For ANSI compatibility (free only)
#include <malloc.h> Required only for function declarations
void free( void *memblock );
void _bfree( _segment seg, void _based( void ) *memblock );
void _ffree( void _far *memblock );
void _nfree( void _near *memblock );
memblock Allocated memory block
seg Based-heap segment selector
Remarks
The free family of functions deallocates a memory block. The argument
memblock points to a memory block previously allocated through a call to
calloc, malloc, or realloc. The number of bytes freed is the number of bytes
specified when the block was allocated (or reallocated, in the case of
realloc). After the call, the freed block is available for allocation.
The seg argument specifies the based heap containing the memory block to be
freed by the _bfree function.
Attempting to free an invalid pointer may affect subsequent allocation and
cause errors. An invalid pointer is one not allocated with the appropriate
call.
The following restrictions apply to use of the free, _bfree, _ffree, and
_nfree functions:
Blocks allocated with: Should be freed with:
────────────────────────────────────────────────────────────────────────────
calloc, malloc, realloc free
_bcalloc, _bmalloc, _brealloc _bfree
_fcalloc, _fmalloc, _frealloc _ffree
_ncalloc, _nmalloc, _nrealloc _nfree
A NULL pointer argument is ignored.
In large data models (compact-, large-, and huge-model programs), free maps
to _ffree. In small data models (tiny-, small-, and medium-model programs),
free maps to _nfree.
The various free functions deallocate a memory block in the segments shown
in the list below:
Function Data Segment
────────────────────────────────────────────────────────────────────────────
free Depends on data model of program
_bfree Based heap specified by seg value
_ffree Far heap (outside default data segment)
_nfree Near heap (inside default data segment)
Return Value
None.
Compatibility
free
ANSI DOS OS/2 UNIX XENIX
_bfree, _ffree, _nfree
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
calloc functions, malloc functions, realloc functions
Example
/* MALLOC.C: This program allocates memory with malloc, then frees
* the memory with free.
*/
#include <stdlib.h> /* Definition of _MAX_PATH */
#include <stdio.h>
#include <malloc.h>
void main()
{
char *string;
/* Allocate space for a path name */
string = malloc( _MAX_PATH );
if( string == NULL )
printf( "Insufficient memory available\n" );
else
printf( "Memory space allocated for path name\n" );
free( string );
printf( "Memory freed\n" );
}
Output
Memory space allocated for path name
Memory freed
_freect
────────────────────────────────────────────────────────────────────────────
Description
Returns the amount of memory available for memory allocation.
#include <malloc.h> Required only for function declarations
unsigned int _freect( size_t size );
size Item size in bytes
Remarks
The _freect function tells you how much memory is available for dynamic
memory allocation in the near heap. It does so by returning the approximate
number of times your program can call _nmalloc (or malloc in small data
models) to allocate an item size bytes long in the near heap (default data
segment).
Return Value
The _freect function returns the number of calls as an unsigned integer.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
calloc functions, _expand functions, malloc functions, _memavl, _msize
functions, realloc functions
Example
/* FREECT.C: This program determines how much free space is available for
* integers in the default data segment. Then it allocates space for
* 1,000 integers and checks the space again, using _freect.
*/
#include <malloc.h>
#include <stdio.h>
void main()
{
int i;
/* First report on the free space: */
printf( "Integers (approximate) available on heap: %u\n\n",
_freect( sizeof( int ) ) );
/* Allocate space for 1000 integers: */
for( i = 0; i < 1000; ++i )
malloc( sizeof( int ) );
/* Report again on the free space: */
printf( "After allocating space for 1000 integers:\n" );
printf( "Integers (approximate) available on heap: %u\n\n",
_freect( sizeof( int ) ) );
}
Output
Integers (approximate) available on heap: 15212
After allocating space for 1000 integers:
Integers (approximate) available on heap: 14084
freopen
────────────────────────────────────────────────────────────────────────────
Description
Reassigns a file pointer.
#include <stdio.h>
FILE *freopen( const char *filename, const char *mode, FILE *stream );
filename Path name of new file
mode Type of access permitted
stream Pointer to FILE structure
Remarks
The freopen function closes the file currently associated with stream and
reassigns stream to the file specified by filename. The freopen function is
typically used to redirect the pre-opened files stdin, stdout, and stderr to
files specified by the user. The new file associated with stream is opened
with mode, which is a character string specifying the type of access
requested for the file, as follows:
Type Description
────────────────────────────────────────────────────────────────────────────
"r" Opens for reading. If the file does not
exist or cannot be found, the freopen
call fails.
"w" Opens an empty file for writing. If the
given file exists, its contents are
destroyed.
"a" Opens for writing at the end of the file
(appending); creates the file first if
it does not exist.
"r+" Opens for both reading and writing. (The
file must exist.)
"w+" Opens an empty file for both reading and
writing. If the given file exists, its
contents are destroyed.
"a+" Opens for reading and appending; creates
the file first if it does not exist.
Use the "w" and "w+" types with care, as they can destroy existing files.
When a file is opened with the "a" or "a+" access type, all write operations
take place at the end of the file. Although the file pointer can be
repositioned using fseek or rewind, the file pointer is always moved back to
the end of the file before any write operation is carried out. Thus,
existing data cannot be overwritten.
When the "r+", "w+", or "a+" access type is specified, both reading and
writing are allowed (the file is said to be open for "update"). However,
when you switch between reading and writing, there must be an intervening
fsetpos, fseek, or rewind operation. The current position can be specified
for the fsetpos or fseek operation, if desired.
In addition to the values listed above, one of the following characters may
be included in the mode string to specify the translation mode for newlines.
Mode Meaning
────────────────────────────────────────────────────────────────────────────
t Open in text (translated) mode;
carriage-return-line-feed
(CR-LF) combinations are translated into
single line-feed (LF) characters on
input; LF characters are translated to
CR-LF combinations on output. Also,
CTRL+Z is interpreted as an end-of-file
character on input. In files opened for
reading, or writing and reading, the
run-time library checks for a CTRL+Z at
the end of the file and removes it, if
possible. This is done because using the
fseek and ftell functions to move within
a file may cause fseek to behave
improperly near the end of the file.
b Open in binary (untranslated) mode; the
above translations are suppressed.
If t or b is not given in the mode string, the translation mode is defined
by the default mode variable _fmode.
See Section 2.7, "Input and Output," for a discussion of text and binary
modes.
Return Value
The freopen function returns a pointer to the newly opened file. If an error
occurs, the original file is closed and the function returns a NULL pointer
value.
Compatibility
ANSI DOS OS/2 UNIX XENIX
The t option is not part of the ANSI standard for freopen; it is a Microsoft
extension that should not be used where ANSI portability is desired.
See Also
fclose, fcloseall, fdopen, fileno, fopen, open, setmode
Example
/* FREOPEN.C: This program reassigns stdaux to the file
* named FREOPEN.OUT and writes a line to that file.
*/
#include <stdio.h>
#include <stdlib.h>
FILE *stream;
void main()
{
/* Reassign "stdaux" to "freopen.out": */
stream = freopen( "freopen.out", "w", stdaux );
if( stream == NULL )
fprintf( stdout, "error on freopen\n" );
else
{
fprintf( stream, "This will go to the file 'freopen.out'\n" );
fprintf( stdout, "successfully reassigned\n" );
fclose( stream );
}
system( "type freopen.out" );
}
Output
successfully reassigned
This will go to the file 'freopen.out'
frexp, frexpl
────────────────────────────────────────────────────────────────────────────
Description
Get the mantissa and exponent of a floating-point number.
#include <math.h>
double frexp( double x, int *expptr );
long double frexpl( long double x, int *expptr );
x Floating-point value
expptr Pointer to stored integer exponent
Remarks
The frexp and frexpl functions break down the floating-point value (x) into
a mantissa (m) and an exponent (n), such that the absolute value of m is
greater than or equal to 0.5 and less than 1.0, and x = m*2n. The integer
exponent n is stored at the location pointed to by expptr.
The frexpl function is the 80-bit counterpart and uses an 80-bit, 10-byte
coprocessor form of arguments and return values. See the reference page on
the long double functions for more details on this data type.
Return Value
These functions return the mantissa. If x is 0, the function returns 0 for
both the mantissa and the exponent. There is no error return.
Compatibility
frexp
ANSI DOS OS/2 UNIX XENIX
frexpl
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
ldexp functions, modf
Example
/* FREXP.C: This program calculates frexp( 16.4, &n ), then displays y
* and n.
*/
#include <math.h>
#include <stdio.h>
void main()
{
double x, y;
int n;
x = 16.4;
y = frexp( x, &n );
printf( "frexp( %f, &n ) = %f, n = %d\n", x, y, n );
}
Output
frexp( 16.400000, &n ) = 0.512500, n = 5
fscanf
────────────────────────────────────────────────────────────────────────────
Description
Reads formatted data from a stream.
#include <stdio.h>
int fscanf( FILE *stream, const char *format [[, argument]]... )
stream Pointer to FILE structure
format Format-control string
argument Optional arguments
Remarks
The fscanf function reads data from the current position of stream into the
locations given by argument (if any). Each argument must be a pointer to a
variable with a type that corresponds to a type specifier in format. The
format controls the interpretation of the input fields and has the same form
and function as the format argument for the scanf function; see scanf for a
description of format.
Return Value
The fscanf function returns the number of fields that were successfully
converted and assigned. The return value does not include fields that were
read but not assigned.
The return value is EOF for an error or end-of-file on stream before the
first conversion. A return value of 0 means that no fields were assigned.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
cscanf, fprintf, scanf, sscanf
Example
/* FSCANF.C: This program writes formatted data to a file. It
* then uses fscanf to read the various data back from the file.
*/
#include <stdio.h>
FILE *stream;
void main()
{
long l;
float fp;
char s[81];
char c;
int result;
stream = fopen( "fscanf.out", "w+" );
if( stream == NULL )
printf( "The file fscanf.out was not opened\n" );
else
{
fprintf( stream, "%s %ld %f%c", "a-string", 65000, 3.14159, 'x' );
/* Set pointer to beginning of file: */
fseek( stream, 0L, SEEK_SET );
/* Read data back from file: */
fscanf( stream, "%s", s );
fscanf( stream, "%ld", &l );
fscanf( stream, "%f", &fp );
fscanf( stream, "%c", &c );
/* Output data read: */
printf( "%s\n", s );
printf( "%ld\n", l );
printf( "%f\n", fp );
printf( "%c\n", c );
fclose( stream );
}
}
Output
a-string
65000
3.141590
x
fseek
────────────────────────────────────────────────────────────────────────────
Description
Moves the file pointer to a specified location.
#include <stdio.h>
int fseek( FILE *stream, long offset, int origin );
stream Pointer to FILE structure
offset Number of bytes from origin
origin Initial position
Remarks
The fseek function moves the file pointer (if any) associated with stream to
a new location that is offset bytes from origin. The next operation on the
stream takes place at the new location. On a stream open for update, the
next operation can be either a read or a write.
The argument origin must be one of the following constants defined in
STDIO.H:
Origin Definition
────────────────────────────────────────────────────────────────────────────
SEEK_CUR Current position of file pointer
SEEK_END End of file
SEEK_SET Beginning of file
The fseek function can be used to reposition the pointer anywhere in a file.
The pointer can also be positioned beyond the end of the file. However, an
attempt to position the pointer in front of the beginning of the file causes
an error.
The fseek function clears the end-of-file indicator and negates the effect
of any prior ungetc calls against stream.
When a file is opened for appending data, the current file position is
determined by the last I/O operation, not by where the next write would
occur. If no I/O operation has yet occurred on a file opened for appending,
the file position is the start of the file.
For streams opened in text mode, fseek has limited use because
carriage-return-line-feed translations can cause fseek to produce unexpected
results. The only fseek operations guaranteed to work on streams opened in
text mode are the following:
■ Seeking with an offset of 0 relative to any of the origin values
■ Seeking from the beginning of the file with an offset value returned
from a call to ftell
Return Value
If successful, fseek returns 0. Otherwise, it returns a nonzero value. On
devices incapable of seeking, the return value is undefined.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
ftell, lseek, rewind
Example
/* FSEEK.C: This program opens the file FSEEK.OUT and
* moves the pointer to the file's beginning.
*/
#include <stdio.h>
void main()
{
FILE *stream;
char line[81];
int result;
stream = fopen( "fseek.out", "w+" );
if( stream == NULL )
printf( "The file fseek.out was not opened\n" );
else
{
fprintf( stream, "The fseek begins here: "
"This is the file 'fseek.out'.\n" );
result = fseek( stream, 23L, SEEK_SET);
if( result )
perror( "Fseek failed" );
else
{
printf( "File pointer is set to middle of first line.\n" );
fgets( line, 80, stream );
printf( "%s", line );
}
fclose( stream );
}
}
Output
File pointer is set to middle of first line.
This is the file 'fseek.out'.
fsetpos
────────────────────────────────────────────────────────────────────────────
Description
Sets the stream-position indicator.
#include <stdio.h>
int fsetpos( FILE *stream, const fpos_t *pos ) ;
stream Target stream
pos Position-indicator storage
Remarks
The fsetpos function sets the file-position indicator for stream to the
value of pos, which is obtained in a prior call to fgetpos against stream.
The function clears the end-of-file indicator and undoes any effects of the
ungetc function on stream. After calling fsetpos, the next operation on
stream may be either input or output.
Return Value
If successful, the fsetpos function returns 0. On failure, the function
returns a nonzero value and sets errno to one of the following manifest
constants (defined in ERRNO.H):
Constant Meaning
────────────────────────────────────────────────────────────────────────────
EBADF The object that stream points to is not
a valid file handle, or the file is not
accessible.
EINVAL An invalid stream value was passed.
Compatibility
ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
fgetpos
Example
/* FGETPOS.C: This program opens a file and reads bytes at several
* different locations.
*/
#include <stdio.h>
void main()
{
FILE *stream;
fpos_t pos;
int val;
char buffer[20];
if( (stream = fopen( "fgetpos.c", "rb" )) == NULL )
printf( "Trouble opening file\n" );
else
{
/* Read some data and then check the position. */
fread( buffer, sizeof( char ), 10, stream );
if( fgetpos( stream, &pos ) != 0 )
perror( "fgetpos error" );
else
{
fread( buffer, sizeof( char ), 10, stream );
printf( "10 bytes at byte %ld: %.10s\n", pos, buffer );
}
/* Set a new position and read more data. */
pos = 140;
if( fsetpos( stream, &pos ) != 0 )
perror( "fsetpos error" );
fread( buffer, sizeof( char ), 10, stream );
printf( "10 bytes at byte %ld: %.10s\n", pos, buffer );
fclose( stream );
}
}
Output
10 bytes at byte 10: .C: This p
10 bytes at byte 140: FILE *
_fsopen
────────────────────────────────────────────────────────────────────────────
Description
Opens a stream with file sharing.
#include <stdio.h>
#include <share.h> shflag constants
FILE *_fsopen( const char *filename, const char *mode, int shflag );
filename File name to open
mode Type of access permitted
shflag Type of sharing allowed
Remarks
The _fsopen function opens the file specified by filename as a stream and
prepares the file for subsequent shared reading or writing, as defined by
the mode and shflag arguments.
The character string mode specifies the type of access requested for the
file, as follows:
Type Description
────────────────────────────────────────────────────────────────────────────
"r" Opens for reading. If the file does not
exist or cannot be found, the _fsopen
call will fail.
"w" Opens an empty file for writing. If the
given file exists, its contents are
destroyed.
"a" Opens for writing at the end of the file
(appending); creates the file first if
it does not exist.
"r+" Opens for both reading and writing. (The
file must exist.)
"w+" Opens an empty file for both reading and
writing. If the given file exists, its
contents are destroyed.
"a+" Opens for reading and appending; creates
the file first if it does not exist.
Use the "w" and "w+" types with care, as they can destroy existing files.
When a file is opened with the "a" or "a+" access type, all write operations
occur at the end of the file. Although the file pointer can be repositioned
using fseek or rewind, the file pointer is always moved back to the end of
the file before any write operation is carried out. Thus, existing data
cannot be overwritten.
When the "r+", "w+", or "a+" access type is specified, both reading and
writing are allowed (the file is said to be open for "update"). However,
when switching between reading and writing, there must be an intervening
fsetpos, fseek, or rewind operation. The current position can be specified
for the fsetpos or fseek operation, if desired.
In addition to the values listed above, one of the following characters can
be included in mode to specify the translation mode for newlines:
Mode Meaning
────────────────────────────────────────────────────────────────────────────
t Open in text (translated) mode. In this
mode, carriage-return-line-feed (CR-LF)
combinations are translated into single
line feeds (LF) on input and LF
characters are translated to CR-LF
combinations on output. Also, CTRL+Z is
interpreted as an end-of-file character
on input. In files opened for reading or
reading/writing, _fsopen checks for a
CTRL+Z at the end of the file and
removes it, if possible. This is done
because using the fseek and ftell
functions to move within a file that
ends with a CTRL+Z may cause fseek to
behave improperly near the end of the
file.
b Open in binary (untranslated) mode; the
above translations are suppressed.
If t or b is not given in mode, the translation mode is defined by the
default-mode variable _fmode. If t or b is prefixed to the argument, the
function will fail and will return NULL.
See Section 2.7, "Input and Output," for a discussion of text and binary
modes.
The argument shflag is a constant expression consisting of one of the
following manifest constants, defined in SHARE.H. If SHARE.COM ─or
SHARE.EXE for some versions of DOS─ is not installed, DOS ignores the
sharing mode. (See your system documentation for detailed information about
sharing modes.)
Constant Meaning
────────────────────────────────────────────────────────────────────────────
SH_COMPAT Sets compatibility mode (not available
in OS/2)
SH_DENYNO Permits read and write access
SH_DENYRD Denies read access to file
SH_DENYRW Denies read and write access to file
SH_DENYWR Denies write access to file
The _fsopen function should be used only under OS/2 and DOS versions 3.0 and
later. Under earlier versions of DOS, the shflag argument is ignored.
Return Value
The _fsopen function returns a pointer to the stream. A NULL pointer value
indicates an error.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
fclose, fcloseall, fdopen, ferror, fileno, fopen, freopen, open, setmode,
sopen
Example
/* FSOPEN.C: This program opens files named "data" and "data2". It uses
* fclose to close "data" and fcloseall to close all remaining files.
*/
#include <stdio.h>
#include <share.h>
FILE *stream;
void main()
{
FILE *stream;
/* Open output file for writing. Using _fsopen allows us to ensure
* that no one else writes to the file while we are writing to it.
*/
if( (stream = _fsopen( "outfile", "wt", SH_DENYWR )) != NULL )
{
fprintf( stream, "No one else in the network can write "
"to this file until we are done.\n" );
fclose( stream );
}
/* Now others can write to the file while we read it. */
system( "type outfile" );
}
Output
No one else in the network can write to this file until we are done.
fstat
────────────────────────────────────────────────────────────────────────────
Description
Gets information about an open file.
#include <sys\types.h>
#include <sys\stat.h>
int fstat( int handle, struct stat *buffer );
handle Handle of open file
buffer Pointer to structure to store results
Remarks
The fstat function obtains information about the open file associated with
handle and stores it in the structure pointed to by buffer. The structure,
whose type stat is defined in SYS\STAT.H, contains the following fields:
Field Value
────────────────────────────────────────────────────────────────────────────
st_atime Time of last modification of file (same
as st_mtime and st_ctime).
st_ctime Time of last modification of file (same
as st_atime and st_mtime).
st_dev Either the drive number of the disk
containing the file, or handle in the
case of a device (same as st_rdev).
st_mode Bit mask for file-mode information. The
S_IFCHR bit is set if
handle refers to a device. The S_IFREG
bit is set if handle refers to an
ordinary file. The read/write bits are
set according to the file's permission
mode. (S_IFCHR and other constants are
defined in SYS\ STAT.H.)
st_mtime Time of last modification of file (same
as st_atime and st_ctime).
st_nlink Always 1.
st_rdev Either the drive number of the disk
containing the file, or handle in the
case of a device (same as st_dev).
st_size Size of the file in bytes.
If handle refers to a device, the size and time fields in the stat structure
are not meaningful.
Return Value
The fstat function returns the value 0 if the file-status information is
obtained. A return value of -1 indicates an error; in this case, errno is
set to EBADF, indicating an invalid file handle.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
In OS/2, the st_dev field does not contain meaningful information. In fact,
it is set to zero. OS/2 provides no way to recover the host drive from just
the open file handle.
See Also
access, chmod, filelength, stat
Example
/* FSTAT.C: This program uses fstat to report the size of a file
* named FSTAT.OUT.
*/
#include <io.h>
#include <fcntl.h>
#include <time.h>
#include <sys\types.h>
#include <sys\stat.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
void main()
{
struct stat buf;
int fh, result;
char buffer[] = "A line to output";
if( (fh = open( "fstat.out", O_CREAT | O_WRONLY | O_TRUNC )) == -1 )
exit( 1 );
write( fh, buffer, strlen( buffer ) );
/* Get data associated with "fh": */
result = fstat( fh, &buf );
/* Check if statistics are valid: */
if( result != 0 )
printf( "Bad file handle\n" );
else
{
printf( "File size : %ld\n", buf.st_size );
printf( "Drive number : %d\n", buf.st_dev );
printf( "Time modified : %s", ctime( &buf.st_atime ) );
}
close( fh );
}
Output
File size : 16
Drive number : 0
Time modified : Thu Jun 15 21:38:46 1989
ftell
────────────────────────────────────────────────────────────────────────────
Description
Gets the current position of a file pointer.
#include <stdio.h>
long ftell( FILE *stream );
stream Target FILE structure
Remarks
The ftell function gets the current position of the file pointer (if any)
associated with stream. The position is expressed as an offset relative to
the beginning of the stream.
Note that when a file is opened for appending data, the current file
position is determined by the last I/O operation, not by where the next
write would occur. For example, if a file is opened for an append and the
last operation was a read, the file position is the point where the next
read operation would start, not where the next write would start. (When a
file is opened for appending, the file position is moved to end-of-file
before any write operation.) If no I/O operation has yet occurred on a file
opened for appending, the file position is the beginning of the file.
Return Value
The ftell function returns the current file position. The value returned by
ftell may not reflect the physical byte offset for streams opened in text
mode, since text mode causes carriage-return-line-feed translation. Use
ftell in conjunction with the fseek function to return to file locations
correctly. On error, the function returns -1L and errno is set to one of the
following constants, defined in ERRNO.H:
Constant Description
────────────────────────────────────────────────────────────────────────────
EBADF Bad file number. The stream argument is
not a valid file-handle value or does
not refer to an open file.
EINVAL Invalid argument. An invalid stream
argument was passed to the function.
On devices incapable of seeking (such as terminals and printers), or when
stream does not refer to an open file, the return value is undefined.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
fgetpos, fseek, lseek, tell
Example
/* FTELL.C: This program opens a file named FTELL.C for reading and
* tries to read 100 characters. It then uses ftell to determine the
* position of the file pointer and displays this position.
*/
#include <stdio.h>
FILE *stream;
void main()
{
long position;
char list[100];
if( (stream = fopen( "ftell.c", "rb" )) != NULL )
{
/* Move the pointer by reading data: */
fread( list, sizeof( char ), 100, stream );
/* Get position after read: */
position = ftell( stream );
printf( "Position after trying to read 100 bytes: %ld\n", position
);
fclose( stream );
}
}
Output
Position after trying to read 100 bytes: 100
ftime
────────────────────────────────────────────────────────────────────────────
Description
Gets the current time.
#include <sys\types.h>
#include <sys\timeb.h>
void ftime( struct timeb *timeptr );
timeptr Pointer to structure defined in
SYS\TIMEB.H
Remarks
The ftime function gets the current time and stores it in the structure
pointed to by timeptr. The timeb structure is defined in SYS\TIMEB.H. It
contains four fields (dstflag, millitm, time, and timezone), which have the
following values:
Field Value
────────────────────────────────────────────────────────────────────────────
dstflag Nonzero if daylight saving time is
currently in effect for the local time
zone. (See tzset for an explanation of
how daylight saving time is determined.)
millitm Fraction of a second in milliseconds.
The last digit is always 0 since millitm
is incremented to the nearest
one-hundredth of a second.
time Time in seconds since 00:00:00 Greenwich
mean time, January 1, 1970.
timezone Difference in minutes, moving westward,
between Greenwich mean time and local
time. The value of timezone is set from
the value of the global variable
timezone (see tzset).
Return Value
The ftime function gives values to the fields in the structure pointed to by
timeptr. It does not return a value.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
asctime, ctime, gmtime, localtime, time, tzset
Example
/* FTIME.C: This program uses ftime to obtain the current time
* and then stores this time in timebuffer.
*/
#include <stdio.h>
#include <sys\timeb.h>
#include <time.h>
void main()
{
struct timeb timebuffer;
char *timeline;
ftime( &timebuffer );
timeline = ctime( & ( timebuffer.time ) );
printf( "The time is %.19s.%hu %s",
timeline, timebuffer.millitm, &timeline[20] );
}
Output
The time is Thu Jun 15 21:40:34.870 1989
_fullpath
────────────────────────────────────────────────────────────────────────────
Description
Makes an absolute path name from a relative path name.
#include <stdlib.h>
char *_fullpath( char *buffer, const char *pathname, size_t maxlen );
buffer Full path-name buffer
pathname Relative path name
maxlen Length of the buffer pointed to by
buffer
Remarks
The _fullpath routine converts the partial path stored in pathname to a
fully qualified path that is stored in buffer. Unlike _makepath, the
_fullpath routine can be used with .\ and ..\ in the path.
If the length of the fully qualified path is greater than the value of
maxlen, then NULL is returned; otherwise, the address of buffer is returned.
If the buffer is NULL, _fullpath will allocate a buffer of MAX_PATH size and
the maxlen argument is ignored.
If the pathname argument specifies a disk drive, the current directory of
this drive is combined with the path. If the drive is not valid, _fullpath
returns NULL.
Return Value
The _fullpath function returns a pointer to the buffer containing the
absolute path (buffer). If there is an error, _fullpath returns NULL.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
getcwd, _getdcwd, _makepath, _splitpath
Example
/* FULLPATH.C: This program demonstrates how _fullpath creates a full
* path from a partial path.
*/
#include <stdio.h>
#include <conio.h>
#include <stdlib.h>
#include <direct.h>
char full[_MAX_PATH], part[_MAX_PATH];
void main()
{
while( 1 )
{
printf( "Enter partial path or ENTER to quit: " );
gets( part );
if( part[0] == 0 )
break;
if( _fullpath( full, part, _MAX_PATH ) != NULL )
printf( "Full path is: %s\n", full );
else
printf( "Invalid path\n" );
}
}
Output
Enter partial path or ENTER to quit: ..
Full path is: C:\
Enter partial path or ENTER to quit: ..\include
Full path is: C:\include
Enter partial path or ENTER to quit: p:
Full path is: P:\
Enter partial path or ENTER to quit: fullpath.c
Full path is: C:\LIBREF\fullpath.c
Enter partial path or ENTER to quit:
fwrite
────────────────────────────────────────────────────────────────────────────
Description
Writes data to a stream.
#include <stdio.h>
size_t fwrite( const void *buffer, size_t size, size_t count, FILE *stream
);
buffer Pointer to data to be written
size Item size in bytes
count Maximum number of items to be written
stream Pointer to FILE structure
Remarks
The fwrite function writes up to count items, of length size each, from
buffer to the output stream. The file pointer associated with stream (if
there is one) is incremented by the number of bytes actually written.
If stream is opened in text mode, each carriage return is replaced with a
carriage-return-line-feed pair. The replacement has no effect on the return
value.
Return Value
The fwrite function returns the number of full items actually written, which
may be less than count if an error occurs. Also, if an error occurs, the
file-position indicator cannot be determined.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
fread, write
Example
/* FREAD.C: This program opens a file named FREAD.OUT and writes 25
* characters to the file. It then tries to open FREAD.OUT and
* read in 25 characters. If the attempt succeeds, the program
* displays the number of actual items read.
*/
#include <stdio.h>
void main()
{
FILE *stream;
char list[30];
int i, numread, numwritten;
/* Open file in text mode: */
if( (stream = fopen( "fread.out", "w+t" )) != NULL )
{
for ( i = 0; i < 25; i++ )
list[i] = 'z' - i;
/* Write 25 characters to stream */
numwritten = fwrite( list, sizeof( char ), 25, stream );
printf( "Wrote %d items\n", numwritten );
fclose( stream );
}
else
printf( "Problem opening the file\n" );
if( (stream = fopen( "fread.out", "r+t" )) != NULL )
{
/* Attempt to read in 25 characters */
numread = fread( list, sizeof( char ), 25, stream );
printf( "Number of items read = %d\n", numread );
printf( "Contents of buffer = %.25s\n", list );
fclose( stream );
}
else
printf( "Was not able to open the file\n" );
}
Output
Wrote 25 items
Number of items read = 25
Contents of buffer = zyxwvutsrqponmlkjihgfedcb
gcvt
────────────────────────────────────────────────────────────────────────────
Description
Converts a floating-point value to a string, which it stores in a buffer.
#include <stdlib.h> Required only for function declarations
char *gcvt( double value, int digits, char *buffer );
value Value to be converted
digits Number of significant digits stored
buffer Storage location for result
Remarks
The gcvt function converts a floating-point value to a character string and
stores the string in buffer. The buffer should be large enough to
accommodate the converted value plus a terminating null character ('\0'),
which is appended automatically. There is no provision for overflow.
The gcvt function attempts to produce digits significant digits in decimal
format. If this is not possible, it produces digits significant digits in
exponential format. Trailing zeros may be suppressed in the conversion.
Return Value
The gcvt function returns a pointer to the string of digits. There is no
error return.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
atof, atoi, atol, ecvt, fcvt
Example
/* GCVT.C: This program converts -3.1415e5 to its string representation.
*/
#include <stdlib.h>
#include <stdio.h>
void main()
{
char buffer[50];
double source = -3.1415e5;
gcvt( source, 7, buffer );
printf( "source: %f buffer: '%s'\n", source, buffer );
}
Output
source: -314150.000000 buffer: '-314150.'
_getactivepage
────────────────────────────────────────────────────────────────────────────
Description
Gets the current active page number.
#include <graph.h>
short _far _getactivepage( void );
Remarks
The _getactivepage function returns the number of the current active page.
Return Value
The function returns the number of the current active page. All hardware
combinations support at least one page (page number 0). In OS/2, only page 0
is valid.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_getactivepage, _getvideoconfig, _getvisualpage, _grstatus,
_setactivepage, _setvideomode, _setvisualpage
Example
/* PAGE.C illustrates video page functions including:
* _getactivepage _getvisualpage _setactivepage _setvisualpage
*/
#include <conio.h>
#include <graph.h>
#include <stdlib.h>
void main()
{
short oldvpage, oldapage, page, row, col, line;
struct videoconfig vc;
char buf[80];
_getvideoconfig( &vc );
if( vc.numvideopages < 4 )
exit( 1 ); /* Fail for OS/2 or monochrome. */
oldapage = _getactivepage();
oldvpage = _getvisualpage();
_displaycursor( _GCURSOROFF );
/* Draw arrows in different place on each page. */
for( page = 1; page < 4; page++ )
{
_setactivepage( page );
_settextposition( 12, 16 * page );
_outtext( ">>>>>>>>" );
}
while( !kbhit() )
/* Cycle through pages 1 to 3 to show moving image. */
for( page = 1; page < 4; page++ )
_setvisualpage( page );
getch();
/* Restore original page (normally 0) to restore screen. */
_setactivepage( oldapage );
_setvisualpage( oldvpage );
_displaycursor( _GCURSORON );
}
_getarcinfo
────────────────────────────────────────────────────────────────────────────
Description
Determines the endpoints in viewport coordinates of the most recently drawn
arc or pie.
#include <graph.h>
short _far _getarcinfo( struct xycoord _far *start, struct xycoord _far
*end,
struct xycoord _far *fillpoint );
start Starting point of arc
end Ending point of arc
fillpoint Point at which pie fill will begin
Remarks
The _getarcinfo function determines the endpoints in viewport coordinates of
the most recently drawn arc or pie.
If successful, the _getarcinfo function updates the start and end xycoord
structures to contain the endpoints (in viewport coordinates) of the arc
drawn by the most recent call to one of the _arc or _pie functions.
In addition, fillpoint specifies a point from which a pie can be filled.
This is useful for filling a pie in a color different from the border color.
After a call to _getarcinfo, change colors using the _setcolor function. Use
the color, along with the coordinates in fillpoint, as arguments for the
floodfill function.
Return Value
The _getarcinfo function returns a nonzero value if successful. If neither
the _arc nor the _pie function has been successfully called since the last
time the screen was cleared or a new graphics mode or viewport was selected,
the _getarcinfo function returns 0.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_arc functions, _floodfill, _getvideoconfig, _grstatus, _pie functions
Example
See the example for _arc.
_getbkcolor
────────────────────────────────────────────────────────────────────────────
Description
Gets the current background color.
#include <graph.h>
long _far _getbkcolor( void );
Remarks
The _getbkcolor function returns the current background color. The default
is 0.
In a color text mode such as _TEXTC80, _setbkcolor accepts, and _getbkcolor
returns, a color index. For example, _setbkcolor(2L) sets the background
color to color index 2. The actual color displayed depends on the palette
mapping for color index 2. The default for color index 2 is green in a color
text mode.
In a color graphics mode such as _ERESCOLOR, _setbkcolor accepts and
_getbkcolor returns a color value (as used in _remappalette). The value for
the simplest background colors is given by the manifest constants defined in
the GRAPH.H include file. For example, _setbkcolor( _GREEN) sets the
background color in a graphics mode to green. These manifest constants are
provided as a convenience in defining and manipulating the most common
colors. In general, the actual range of colors is much greater.
In most cases, whenever an argument is long, it refers to a color value, and
whenever it is short, it refers to a color index. The two exceptions are
_setbkcolor and _getbkcolor, described above. For a more complete discussion
of colors, see _remappalette.
Return Value
The function returns the current background color value. There is no error
return.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_remappalette, _setbkcolor
Example
See the example for _getcolor.
getc, getchar
────────────────────────────────────────────────────────────────────────────
Description
Reads a character from a stream (getc), or gets a character from stdin
(getchar).
#include <stdio.h>
int getc( FILE *stream );
int getchar( void );
stream Current stream
Remarks
The getc macro reads a single character from the stream position and
increments the associated file pointer (if there is one) to point to the
next character. The getchar macro is identical to getc(stdin).
The getc and getchar routines are similar to fgetc and fgetchar,
respectively, but are macros rather than functions.
Return Value
The getc and getchar macros return the character read. A return value of EOF
indicates an error or end-of-file condition. Use ferror or feof to determine
whether an error or end-of-file occurred.
Compatibility
getc
ANSI DOS OS/2 UNIX XENIX
getchar
ANSI DOS OS/2 UNIX XENIX
See Also
fgetc, fgetchar, getch, getche, putc, putchar, ungetc
Example
/* GETC.C: This program uses getchar to read a single line of input
* from stdin, places this input in buffer, then terminates the
* string before printing it to the screen.
*/
#include <stdio.h>
void main()
{
char buffer[81];
int i, ch;
printf( "Enter a line: " );
/* Read in single line from "stdin": */
for( i = 0; (i < 80) && ((ch = getchar()) != EOF) && (ch != '\n'); i++
)
buffer[i] = ch;
/* Terminate string with null character: */
buffer[i] = '\0';
printf( "%s\n", buffer );
}
Output
Enter a line: This is a line of text.
This is a line of text.
getch, getche
────────────────────────────────────────────────────────────────────────────
Description
Get a character from the console without echo (getch) or with echo (getche).
#include <conio.h> Required only for function declarations
int getch( void );
int getche( void );
Remarks
The getch function reads a single character from the console without
echoing. The getche function reads a single character from the console and
echoes the character read. Neither function can be used to read CTRL+C.
When reading a function key or cursor-moving key, the getch and getche
functions must be called twice; the first call returns 0 or 0xE0, and the
second call returns the actual key code.
Return Value
The getch function returns the character read. There is no error return.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
cgets, getchar, ungetch
Example
/* GETCH.C: This program reads characters from the keyboard until it
* receives a 'Y' or 'y'.
*/
#include <conio.h>
#include <ctype.h>
void main()
{
int ch;
cputs( "Type 'Y' when finished typing keys: " );
do
{
ch = getch();
ch = toupper( ch );
} while( ch != 'Y' );
putch( ch );
putch( '\r' ); /* Carriage return */
putch( '\n' ); /* Line feed */
}
Output
Type 'Y' when finished typing keys: Y
_getcolor
────────────────────────────────────────────────────────────────────────────
Description
Gets the current color.
#include <graph.h>
short _far _getcolor( void );
Remarks
The _getcolor function returns the current graphics color index. The default
is the highest legal value of the current palette.
Return Value
The _getcolor function returns the current color index.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_setcolor
Example
/* OUTTXT.C: This example illustrates text output functions:
* _gettextcolor _getbkcolor _gettextposition _outtext
* _settextcolor _setbkcolor _settextposition
*/
#include <conio.h>
#include <stdio.h>
#include <graph.h>
char buffer [80];
void main()
{
/* Save original foreground, background, and text position. */
short blink, fgd, oldfgd;
long bgd, oldbgd;
struct rccoord oldpos;
/* Save original foreground, background, and text position. */
oldfgd = _gettextcolor();
oldbgd = _getbkcolor();
oldpos = _gettextposition();
_clearscreen( _GCLEARSCREEN );
/* First time no blink, second time blinking. */
for( blink = 0; blink <= 16; blink += 16 )
{
/* Loop through 8 background colors. */
for( bgd = 0; bgd < 8; bgd++ )
{
_setbkcolor( bgd );
_settextposition( (short)bgd + ((blink / 16) * 9) + 3, 1 );
_settextcolor( 7 );
sprintf(buffer, "Back: %d Fore:", bgd );
_outtext( buffer );
/* Loop through 16 foreground colors. */
for( fgd = 0; fgd < 16; fgd++ )
{
_settextcolor( fgd + blink );
sprintf( buffer, " %2d ", fgd + blink );
_outtext( buffer );
}
}
}
getch();
/* Restore original foreground, background, and text position. */
_settextcolor( oldfgd );
_setbkcolor( oldbgd );
_clearscreen( _GCLEARSCREEN );
_settextposition( oldpos.row, oldpos.col );
}
_getcurrentposition Functions
────────────────────────────────────────────────────────────────────────────
Description
Get the current position and return it as a structure.
#include <graph.h>
struct xycoord _far _getcurrentposition( void );
struct _wxycoord _far _getcurrentposition_w( void );
Remarks
The _getcurrentposition functions return the coordinates of the current
graphics output position. The _getcurrentposition function returns the
position as an xycoord structure, defined in GRAPH.H.
The xycoord structure contains the following elements:
Element Description
────────────────────────────────────────────────────────────────────────────
short xcoord x coordinate
short ycoord y coordinate
The _getcurrentposition_w function returns the position as an _wxycoord
structure, defined in GRAPH.H.
The _wxycoord structure contains the following elements:
Element Description
────────────────────────────────────────────────────────────────────────────
double wx window x coordinate
double wy window y coordinate
The current position can be changed by the _lineto, _moveto, and _outgtext
functions.
The default position, set by _setvideomode, _setvideomoderows, or
_setviewport, is the center of the viewport.
Only graphics output starts at the current position; these functions do not
affect text output, which begins at the current text position. (See
_settextposition for more information.)
Return Value
The _getcurrentposition function returns the coordinates of the current
graphics output position. There is no error return.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_grstatus, _lineto functions, _moveto functions, _outgtext
Example
/* GCURPOS.C: This program sets a random current location, then gets that
* location with _getcurrentposition.
*/
#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#include <graph.h>
char buffer[255];
void main()
{
struct videoconfig vc;
struct xycoord position;
/* Find a valid graphics mode. */
if( !_setvideomode( _MAXRESMODE ) )
exit( 1 );
_getvideoconfig( &vc );
/* Move to random location and report that location. */
_moveto( rand() % vc.numxpixels, rand() % vc.numypixels );
position = _getcurrentposition();
sprintf( buffer, "x = %d, y = %d", position.xcoord, position.ycoord );
_settextposition( 1, 1 );
_outtext( buffer );
getch();
_setvideomode( _DEFAULTMODE );
}
getcwd
────────────────────────────────────────────────────────────────────────────
Description
Gets the current working directory.
#include <direct.h> Required only for function declarations
char *getcwd( char *buffer, int maxlen );
buffer Storage location for path name
maxlen Maximum length of path name
Remarks
The getcwd function gets the full path name of the current working directory
and stores it at buffer. The integer argument maxlen specifies the maximum
length for the path name. An error occurs if the length of the path name
(including the terminating null character) exceeds maxlen.
The buffer argument can be NULL; a buffer of at least size maxlen (more only
if necessary) will automatically be allocated, using malloc, to store the
path name. This buffer can later be freed by calling free and passing it the
getcwd return value (a pointer to the allocated buffer).
Return Value
The getcwd function returns a pointer to buffer. A NULL return value
indicates an error, and errno is set to one of the following values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
ENOMEM Insufficient memory to allocate maxlen
bytes (when a NULL argument is given as
buffer)
ERANGE Path name longer than maxlen characters
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
chdir, mkdir, rmdir
Example
/* This program places the name of the current directory in the buffer
* array, then displays the name of the current directory on the screen.
* Specifying a length of _MAX_DIR leaves room for the longest legal
* directory name.
*/
#include <direct.h>
#include <stdlib.h>
#include <stdio.h>
void main()
{
char buffer[_MAX_DIR];
/* Get the current working directory: */
if( getcwd( buffer, _MAX_DIR ) == NULL )
perror( "getcwd error" );
else
printf( "%s\n", buffer );
}
Output
C:\LIBREF
_getdcwd
────────────────────────────────────────────────────────────────────────────
Description
Gets full path name of current working directory, including disk drive.
#include <direct.h> Required only for function declarations
char *_getdcwd( int drive, char *buffer, int maxlen );
drive Disk drive
buffer Storage location for path name
maxlen Maximum length of path name
Remarks
The _getdcwd function gets the full path name of the current working
directory, including disk drive specification, and stores it at buffer. The
argument maxlen specifies the maximum length for the path name. An error
occurs if the length of the path name (including the terminating null
character) exceeds maxlen.
The drive argument specifies the drive (0 = default drive, 1=A, 2=B, etc.).
The buffer argument can be NULL; a buffer of at least size maxlen (more only
if necessary) will automatically be allocated, using malloc, to store the
path name. This buffer can later be freed by calling free and passing it the
_getdcwd return value (a pointer to the allocated buffer).
Return Value
The _getdcwd function returns buffer. A NULL return value indicates an
error, and errno is set to one of the following values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
ENOMEM Insufficient memory to allocate maxlen
bytes (when a NULL argument is given as
buffer)
ERANGE Path name longer than maxlen characters
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
chdir, getcwd, _getdrive, mkdir, rmdir
Example
/* GETDRIVE.C illustrates drive functions including:
* _getdrive _chdrive _getdcwd
*/
#include <stdio.h>
#include <conio.h>
#include <direct.h>
#include <stdlib.h>
void main()
{
int ch, drive, curdrive;
static char path[_MAX_PATH];
/* Save current drive. */
curdrive = _getdrive();
printf( "Available drives are: \n" );
/* If we can switch to the drive, it exists. */
for( drive = 1; drive <= 26; drive++ )
if( !_chdrive( drive ) )
printf( "%c: ", drive + 'A' - 1 );
while( 1 )
{
printf( "\nType drive letter to check or ESC to quit: " );
ch = getch();
if( ch == 27 )
break;
if( isalpha( ch ) )
putch( ch );
if( _getdcwd( toupper( ch ) - 'A' + 1, path, _MAX_PATH ) != NULL )
printf( "\nCurrent directory on that drive is %s\n", path );
}
/* Restore original drive. This is only necessary for DOS. Under OS/2
* the current drive of the calling process is always restored.
*/
_chdrive( curdrive );
printf( "\n" );
}
Output
Available drives are:
A: B: C:
Type drive letter to check or ESC to quit: q
Type drive letter to check or ESC to quit: a
Current directory on that drive is A:\
Type drive letter to check or ESC to quit: c
Current directory on that drive is C:\LIBREF
Type drive letter to check or ESC to quit:
_getdrive
────────────────────────────────────────────────────────────────────────────
Description
Gets the current disk drive.
#include <direct.h>
int _getdrive( void );
Remarks
The _getdrive function returns the current working drive (1=A, 2=B, etc.).
Return Value
The return value is stated above. There is no error return.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_chdrive, _dos_getdrive, _dos_setdrive, _getcwd, _getdcwd
Example
See the example for _getdcwd.
getenv
────────────────────────────────────────────────────────────────────────────
Description
Gets a value from the environment table.
#include <stdlib.h> Required only for function declarations
char *getenv( const char *varname );
varname Name of environment variable
Remarks
The getenv function searches the list of environment variables for an entry
corresponding to varname. Environment variables define the environment in
which a process executes. (For example, the LIB environment variable defines
the default search path for libraries to be linked with a program.) Because
the getenv function is case sensitive, the varname variable should match the
case of the environment variable.
The getenv function returns a pointer to an entry in the environment table.
It is, however, only safe to retrieve the value of the environment variable
using the returned pointer. To modify the value of an environmental
variable, use the putenv function.
The getenv and putenv functions use the copy of the environment contained in
the global variable environ to access the environment. Programs that use the
envp argument to main and the putenv function may retrieve invalid
information. The safest programming practice is to use getenv and putenv.
Return Value
The getenv function returns a pointer to the environment table entry
containing the current string value of varname. The return value is NULL if
the given variable is not currently defined.
Compatibility
ANSI DOS OS/2 UNIX XENIX
The getenv function operates only on the data structures accessible to the
run-time library and not on the environment "segment" created for a process
by DOS or OS/2.
See Also
putenv
Example
/* GETENV.C: This program uses getenv to retrieve the LIB environment
* variable and then uses putenv to change it to a new value.
*/
#include <stdlib.h>
#include <stdio.h>
main()
{
char *libvar;
/* Get the value of the LIB environment variable. */
libvar = getenv( "LIB" );
if( libvar != NULL )
printf( "Original LIB variable is: %s\n", libvar );
/* Attempt to change path. Note that this only affects the environment
* variable of the current process. The command processor's environment
* is not changed.
*/
putenv( "LIB=c:\\mylib;c:\\yourlib" );
/* Get new value. */
libvar = getenv( "LIB" );
if( libvar != NULL )
printf( "New LIB variable is: %s\n", libvar );
}
Output
Original LIB variable is: C:\LIB
New LIB variable is: c:\mylib;c:\yourlib
_getfillmask
────────────────────────────────────────────────────────────────────────────
Description
Gets the current fill mask for some graphics routines.
#include <graph.h>
unsigned char _far * _far _getfillmask( unsigned char _far *mask );
mask Mask array
Remarks
Some graphics routines (_ellipse, _floodfill, _pie, _polygon, and
_rectangle) can fill part or all of the screen with the current color or
background color. The fill mask controls the pattern used for filling.
The _getfillmask function returns the current fill mask. The mask is an
8-by-8-bit array, in which each bit represents a pixel. If the bit is 1, the
corresponding pixel is set to the current color; if the bit is 0, the pixel
is left unchanged. The mask is repeated over the entire fill area. If no
fill mask is set, or if mask is NULL, a solid (unpatterned) fill is
performed using the current color.
Return Value
If no mask is set, the function returns NULL.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_ellipse functions, _floodfill, _pie functions, _polygon functions,
_rectangle functions, _setfillmask
Example
/* GFILLMSK.C: This program illustrates _getfillmask and _setfillmask. */
#include <conio.h>
#include <stdlib.h>
#include <graph.h>
void ellipsemask( short x1, short y1, short x2, short y2, char _far
*newmask );
unsigned char mask1[8] = { 0x43, 0x23, 0x7c, 0xf7, 0x8a, 0x4d, 0x78, 0x39
};
unsigned char mask2[8] = { 0x18, 0xad, 0xc0, 0x79, 0xf6, 0xc4, 0xa8, 0x23
};
char oldmask[8];
void main()
{
int loop;
/* Find a valid graphics mode. */
if( !_setvideomode( _MAXRESMODE ) )
exit( 1 );
/* Set first fill mask and draw rectangle. */
_setfillmask( mask1 );
_rectangle( _GFILLINTERIOR, 20, 20, 100, 100 );
getch();
/* Call routine that saves and restores mask. */
ellipsemask( 60, 60, 150, 150, mask2 );
getch();
/* Back to original mask. */
_rectangle( _GFILLINTERIOR, 120, 120, 190, 190 );
getch();
_setvideomode( _DEFAULTMODE );
}
/* Draw an ellipse with a specified fill mask. */
void ellipsemask( short x1, short y1, short x2, short y2, char _far
*newmask )
{
unsigned char savemask[8];
_getfillmask( savemask ); /* Save mask */
_setfillmask( newmask ); /* Set new mask */
_ellipse( _GFILLINTERIOR, x1, y1, x2, y2 ); /* Use new mask */
_setfillmask( savemask ); /* Restore original */
}
_getfontinfo
────────────────────────────────────────────────────────────────────────────
Description
Gets the current font characteristics.
#include <graph.h>
short _far _getfontinfo( struct _fontinfo _far *fontbuffer );
fontbuffer Buffer to hold font information
Remarks
The _getfontinfo function gets the current font characteristics and stores
them in a _fontinfo structure, defined in GRAPH.H.
The _fontinfo structure contains the following elements:
Element Contents
────────────────────────────────────────────────────────────────────────────
int type Specifies vector (1) or bit-mapped (0)
font
int ascent Specifies pixel distance from top to
baseline
int pixwidth Specifies the character width in pixels;
0 indicates a proportional font
int pixheight Specifies the character height in pixels
int avgwidth Specifies the average character width in
pixels
char filename [81] Specifies the file name, including the
path
char facename [32] Specifies the font name
Return Value
The _getfontinfo function returns a negative number if a font has not been
registered or loaded.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_getgtextextent, _outgtext, _registerfonts, _setfont, _setgtextvector,
_unregisterfonts
Example
See the example for _outgtext.
_getgtextextent
────────────────────────────────────────────────────────────────────────────
Description
Gets the width in pixels of font-based text.
#include <graph.h>
short _far _getgtextextent( unsigned char _far *text );
text Text to be analyzed
Remarks
The _getgtextextent function returns the width in pixels that would be
required to print the text string using _outgtext with the current font.
This function is particularly useful for determining the size of text that
uses proportionally spaced fonts.
Return Value
The _getgtextextent function returns the width in pixels. It returns -1 if a
font has not been registered.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_getfontinfo, _outgtext, _registerfonts, _setfont, _unregisterfonts
Example
See the example for _outgtext.
_getimage Functions
────────────────────────────────────────────────────────────────────────────
Description
Store images in buffers.
#include <graph.h>
void _far _getimage( short x1, short y1, short x2, short y2, char _huge
*image );
void _far _getimage_w( double wx1, double wy1, double wx2, double wy2,
char _huge *image );
void _far _getimage_wxy( struct_wxycoord _far *pwxy1,
struct_wxycoord _far *pwxy2, char _huge *image );
x1, y1 Upper-left corner of bounding rectangle
x2, y2 Lower-right corner of bounding rectangle
wx1, wy1 Upper-left corner of bounding rectangle
wx2, wy2 Lower-right corner of bounding rectangle
pwxy1 Upper-left corner of bounding rectangle
pwxy2 Lower-right corner of bounding rectangle
image Storage buffer for screen image
Remarks
The _getimage functions store the screen image defined by a specified
bounding rectangle into the buffer pointed to by image.
The _getimage function defines the bounding rectangle with the view
coordinates (x1, y1) and (x2, y2).
The _getimage_w function defines the bounding rectangle with the window
coordinates (wx1, wy1) and (wx2, wy2).
The _getimage_wxy function defines the bounding rectangle with the
window-coordinate pairs pwxy1 and pwxy2.
The buffer must be large enough to hold the image. You can determine the
size by calling the appropriate _imagesize function at run time, or by using
the formula described on the _imagesize reference page.
Return Value
None. Use _grstatus to check success.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_grstatus, _imagesize functions, _putimage functions
Example
/* GIMAGE.C: This example illustrates animation routines including:
* _imagesize _getimage _putimage
*/
#include <conio.h>
#include <stddef.h>
#include <stdlib.h>
#include <malloc.h>
#include <graph.h>
short action[5] = { _GPSET, _GPRESET, _GXOR, _GOR, _GAND };
char *descrip[5] = { "PSET ", "PRESET", "XOR ", "OR ", "AND " };
void exitfree( char _huge *buffer );
void main()
{
char _huge *buffer; /* Far pointer (with _fmalloc) could be used.
*/
long imsize;
short i, x, y = 30;
if( !_setvideomode( _MAXRESMODE ) )
exit( 1 );
/* Measure the image to be drawn and allocate memory for it. */
imsize = (size_t)_imagesize( -16, -16, +16, +16 );
buffer = halloc( imsize, sizeof( char ) );
if ( buffer == (char _far *)NULL )
exit( 1 );
_setcolor( 3 );
for ( i = 0; i < 5; i++ )
{
/* Draw ellipse at new position and get a copy of it. */
x = 50; y += 40;
_ellipse( _GFILLINTERIOR, x - 15, y - 15, x + 15, y + 15 );
_getimage( x - 16, y - 16, x + 16, y + 16, buffer );
if( _grstatus() )
exitfree( buffer ); /* Quit on error
*/
/* Display action type and copy a row of ellipses with that type. */
_settextposition( 1, 1 );
_outtext( descrip[i] );
while( x < 260 )
{
x += 5;
_putimage( x - 16, y - 16, buffer, action[i] );
if( _grstatus() < 0 ) /* Ignore warnings, quit on errors.
*/
exitfree( buffer );
}
getch();
}
exitfree( buffer );
}
void exitfree( char _huge *buffer )
{
hfree( buffer );
exit( !_setvideomode( _DEFAULTMODE ) );
}
_getlinestyle
────────────────────────────────────────────────────────────────────────────
Description
Gets the current line style.
#include <graph.h>
unsigned short _far _getlinestyle( void );
Remarks
Some graphics routines ( _lineto, _polygon, and _rectangle) output straight
lines to the screen. The type of line can be controlled with the current
line-style mask.
The _getlinestyle function returns the current line-style mask. The mask is
a 16-bit array in which each bit represents a pixel in the line being drawn.
If the bit is 1, the corresponding pixel is set to the color of the line
(the current color). If the bit is 0, the corresponding pixel is left
unchanged. The mask is repeated over the length of the line. The default
mask is 0xFFFF (a solid line).
Return Value
If no mask has been set, _getlinestyle returns the default mask.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_lineto functions, _polygon functions, _rectangle functions,
_setlinestyle, _setwritemode
Example
/* GLINESTY.C: This program illustrates _setlinestyle and _getlinestyle.
*/
#include <conio.h>
#include <stdlib.h>
#include <graph.h>
void zigzag( short x1, short y1, short size );
void main()
{
/* Find a valid graphics mode. */
if( !_setvideomode( _MAXCOLORMODE ) )
exit( 1 );
/* Set line style and draw rectangle. */
_setlinestyle( 0x4d );
_rectangle( _GBORDER, 10, 10, 60, 60 );
getch();
/* Draw figure with function that changes and restores line style. */
zigzag( 100, 100, 90 );
getch();
/* Original style reused. */
_rectangle( _GBORDER, 190, 190, 130, 130 );
getch();
_setvideomode( _DEFAULTMODE );
}
/* Draw box with changing line styles. Restore original style. */
void zigzag( short x1, short y1, short size )
{
short x, y, oldcolor;
unsigned short oldstyle;
unsigned short style[16] = { 0x0001, 0x0003, 0x0007, 0x000f,
0x001f, 0x003f, 0x007f, 0x00ff,
0x01ff, 0x03ff, 0x07ff, 0x0fff,
0x1fff, 0x3fff, 0x7fff, 0xffff };
oldcolor = _getcolor();
oldstyle = _getlinestyle(); /* Save old line style.
*/
for( x = 3, y = 3; x < size; x += 3, y += 3 )
{
_setcolor( x % 16 );
_setlinestyle( style[x % 16] ); /* Set and use new line styles
*/
_rectangle( _GBORDER, x1 - x, y1 - y, x1 + x, y1 + y );
}
_setlinestyle( oldstyle ); /* Restore old line style.
*/
_setcolor( oldcolor );
}
_getphyscoord
────────────────────────────────────────────────────────────────────────────
Description
Gets physical coordinates.
#include <graph.h>
struct xycoord _far _getphyscoord( short x, short y );
x, y View coordinates to translate
Remarks
The _getphyscoord function translates the view coordinates (x, y) to
physical coordinates and returns them in an xycoord structure, defined in
GRAPH.H.
The xycoord structure contains the following elements:
Element Description
────────────────────────────────────────────────────────────────────────────
short xcoord x coordinate
short ycoord y coordinate
Return Value
None.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_getviewcoord functions, _grstatus, _setvieworg, _setviewport
Example
See the example for _setwindow.
getpid
────────────────────────────────────────────────────────────────────────────
Description
Gets the process identification.
#include <process.h> Required only for function declarations
int getpid( void );
Remarks
The getpid function returns the process ID, an integer that uniquely
identifies the calling process.
Return Value
The getpid function returns the process ID. There is no error return.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
mktemp
Example
/* GETPID.C: This program uses getpid to obtain the process ID and
* then prints the ID.
*/
#include <stdio.h>
#include <process.h>
void main( )
{
/* If run from DOS, shows different ID for DOS than for DOS shell.
* If execed or spawned, shows ID of parent.
*/
printf( "\nProcess id of parent: %d\n", getpid() );
}
Output
Process id of parent: 828
_getpixel Functions
────────────────────────────────────────────────────────────────────────────
Description
Get pixel values.
#include <graph.h>
short _far _getpixel( short x, short y );
short _far _getpixel_w( double wx, double wy );
x, y Pixel position
wx, wy Pixel position
Remarks
The functions in the _getpixel family return the pixel value (a color index)
at a specified location. The _getpixel function uses the view coordinate (x,
y). The _getpixel_w function uses the window coordinate (wx, wy). The range
of possible pixel values is determined by the current video mode. The color
translation of pixel values is determined by the current palette.
Return Value
If successful, the function returns the color index. If the function fails
(for example, the point lies outside the clipping region, or the program is
in a text mode), it returns -1.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_getvideoconfig, _grstatus, _remapallpalette, _remappalette,
_selectpalette, _setpixel functions, _setvideomode
Example
/* GPIXEL.C: This program assigns different colors to randomly
* selected pixels.
*/
#include <conio.h>
#include <stdlib.h>
#include <graph.h>
void main()
{
short xvar, yvar;
struct videoconfig vc;
/* Find a valid graphics mode. */
if( !_setvideomode( _MAXCOLORMODE ) )
exit( 1 );
_getvideoconfig( &vc );
/* Draw filled ellipse to turn on certain pixels. */
_ellipse( _GFILLINTERIOR, vc.numxpixels / 6, vc.numypixels / 6,
vc.numxpixels / 6 * 5, vc.numypixels / 6 * 5
);
/* Draw random pixels in random colors... */
while( !kbhit() )
{
/* ...but only if they are already on (inside the ellipse). */
xvar = rand() % vc.numxpixels;
yvar = rand() % vc.numypixels;
if( _getpixel( xvar, yvar ) != 0 )
{
_setcolor( rand() % 16 );
_setpixel( xvar, yvar );
}
}
getch(); /* Throw away the keystroke. */
_setvideomode( _DEFAULTMODE );
}
gets
────────────────────────────────────────────────────────────────────────────
Description
Gets a line from the stdin stream.
#include <stdio.h>
char *gets( char *buffer );
buffer Storage location for input string
Remarks
The gets function reads a line from the standard input stream stdin and
stores it in buffer. The line consists of all characters up to and including
the first newline character (\n). The gets function then replaces the
newline character with a null character ('\0') before returning the line. In
contrast, the fgets function retains the newline character.
Return Value
If successful, the gets function returns its argument. A NULL pointer
indicates an error or end-of-file condition. Use ferror or feof to determine
which one has occurred.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
fgets, fputs, puts
Example
/* GETS.C */
#include <stdio.h>
void main()
{
char line[81];
printf( "Input a string: " );
gets( line );
printf( "The line entered was: %s\n", line );
}
Output
Input a string: This is a string
The line entered was: This is a string
_gettextcolor
────────────────────────────────────────────────────────────────────────────
Description
Gets the current text color.
#include <graph.h>
short _far _gettextcolor( void );
Remarks
The _gettextcolor function returns the color index of the current text
color. The text color is set by the _settextcolor function and affects text
output with the _outtext and _outmem functions only. The _setcolor function
sets the color for font text output using the _outgtext function.
The default is 7 in test modes; it is the highest legal color index of the
current palette in graphics modes.
Return Value
The _gettextcolor function returns the color index of the current text
color.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_getvideoconfig, _remappalette, _selectpalette, _setcolor, _settextcolor
Example
See the example for _gettextposition.
_gettextcursor
────────────────────────────────────────────────────────────────────────────
Description
Gets the current cursor attribute.
#include <graph.h>
short _far _gettextcursor( void );
Remarks
The _gettextcursor function returns the current cursor attribute (i.e., the
shape). This function works only in text video modes.
Return Value
The function returns the current cursor attribute, or -1 if an error occurs
(such as a call to the function in a graphics mode).
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_displaycursor, _grstatus, _settextcursor
Example
See the example for _settextcursor.
_gettextposition
────────────────────────────────────────────────────────────────────────────
Description
Gets the current text position.
#include <graph.h>
struct rccoord _far _gettextposition( void );
Remarks
The _gettextposition function returns the current text position as an
rccoord structure, defined in GRAPH.H.
The rccoord structure contains the following elements:
Element Description
────────────────────────────────────────────────────────────────────────────
short row Row coordinate
short col Column coordinate
Remarks
The text position given by the coordinates (1,1) is defined as the
upper-left corner of the text window.
Text output from the _outtext and _outmem functions begins at the current
text position. Font text is not affected by the current text position. Font
text output begins at the current graphics output position, which is a
separate position.
Return Value
None.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_getcurrentposition functions, _moveto functions, _outmem, _outtext,
_settextposition, _settextwindow, _wrapon
Example
/* OUTTXT.C: This example illustrates text output functions:
* _gettextcolor _getbkcolor _gettextposition _outtext
* _settextcolor _setbkcolor _settextposition
*/
#include <conio.h>
#include <stdio.h>
#include <graph.h>
char buffer [80];
void main()
{
/* Save original foreground, background, and text position. */
short blink, fgd, oldfgd;
long bgd, oldbgd;
struct rccoord oldpos;
/* Save original foreground, background, and text position. */
oldfgd = _gettextcolor();
oldbgd = _getbkcolor();
oldpos = _gettextposition();
_clearscreen( _GCLEARSCREEN );
/* First time no blink, second time blinking. */
for( blink = 0; blink <= 16; blink += 16 )
{
/* Loop through 8 background colors. */
for( bgd = 0; bgd < 8; bgd++ )
{
_setbkcolor( bgd );
_settextposition( (short)bgd + ((blink / 16) * 9) + 3, 1 );
_settextcolor( 7 );
sprintf(buffer, "Back: %d Fore:", bgd );
_outtext( buffer );
/* Loop through 16 foreground colors. */
for( fgd = 0; fgd < 16; fgd++ )
{
_settextcolor( fgd + blink );
sprintf( buffer, " %2d ", fgd + blink );
_outtext( buffer );
}
}
}
getch();
/* Restore original foreground, background, and text position. */
_settextcolor( oldfgd );
_setbkcolor( oldbgd );
_clearscreen( _GCLEARSCREEN );
_settextposition( oldpos.row, oldpos.col );
}
_gettextwindow
────────────────────────────────────────────────────────────────────────────
Description
Gets the boundaries of the current text window.
#include <graph.h>
void _far _gettextwindow( short _far *r1, short _far *c1, short _far *r2,
short _far *c2 );
r1 Top row of current text window
c1 Leftmost column of current text window
r2 Bottom row of current text window
c2 Rightmost column of current text window
Remarks
The _gettextwindow function finds the boundaries of the current text window.
The text window is the region of the screen to which output from the
_outtext and _outmem functions is limited. By default, this is the entire
screen, unless it has been redefined by the _settextwindow function.
The window defined by _settextwindow has no effect on output from the
_outgtext function. Text displayed with _outgtext is limited to the current
viewport.
Return Value
None.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_gettextposition, _outmem, _outtext, _scrolltextwindow,
_settextposition, _settextwindow, _wrapon
Example
See the example for _scrolltextwindow.
_getvideoconfig
────────────────────────────────────────────────────────────────────────────
Description
Gets graphics video configuration information.
#include <graph.h>
struct videoconfig _far * _far _getvideoconfig( struct videoconfig _far
*config );
config Configuration information
Remarks
The _getvideoconfig function returns the current graphics environment
configuration in a videoconfig structure, defined in GRAPH.H.
The values returned reflect the currently active video adapter and monitor,
as well as the current video mode.
The videoconfig structure contains the following members, each of which is
of type short:
Member Contents
────────────────────────────────────────────────────────────────────────────
adapter Active display adapter
bitsperpixel Number of bits per pixel
memory Adapter video memory in kilobytes
mode Current video mode
monitor Active display monitor
numcolors Number of color indices
numtextcols Number of text columns available
numtextrows Number of text rows available
numvideopages Number of available video pages
numxpixels Number of pixels on the x axis
numypixels Number of pixels on the y axis
The values for the adapter member of the videoconfig structure are given by
the manifest constants shown in the list below. For any applicable adapter (
_CGA, _EGA, or _VGA), the corresponding Olivetti(R) adapter ( _OCGA, _OEGA,
or _OVGA) represents a superset of graphics capabilities.
Adapter Constant Meaning
────────────────────────────────────────────────────────────────────────────
_CGA Color Graphics Adapter
_EGA Enhanced Graphics Adapter
_HGC Hercules(R) Graphics Card
_MCGA Multicolor Graphics Array
_MDPA Monochrome Display Printer Adapter
_OCGA Olivetti (AT&T(R)) Color Graphics
Adapter
_OEGA Olivetti (AT&T) Enhanced Graphics
Adapter
_OVGA Olivetti (AT&T) Video Graphics Array
_VGA Video Graphics Array
The values for the monitor member of the videoconfig structure are given by
the manifest constants listed below:
Monitor Constant Meaning
────────────────────────────────────────────────────────────────────────────
_ANALOG Analog monochrome and color
_ANALOGCOLOR Analog color only
_ANALOGMONO Analog monochrome only
_COLOR Color (or enhanced monitor emulating a
color monitor)
_ENHCOLOR Enhanced color
_MONO Monochrome monitor
In every text mode, including monochrome, the _getvideoconfig function
returns the value 32 for the number of available colors. The value 32
indicates the range of values (0 -31) accepted by the _settextcolor
function. This includes 16 normal colors (0 -15) and 16 blinking colors (16
-31). Blinking is selected by adding 16 to the normal color index. Because
monochrome text mode has fewer unique display attributes, some color indices
are redundant. However, because blinking is selected in the same manner,
monochrome text mode has the same range (0 -31) as other text modes.
Return Value
The _getvideoconfig function returns the video configuration information in
a structure, as noted above. There is no error return.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_setvideomode, _setvideomoderows
Example
/* GVIDCFG.C: This program displays information about the current
* video configuration.
*/
#include <stdio.h>
#include <graph.h>
void main()
{
struct videoconfig vc;
short c;
char b[500]; /* Buffer for string */
_getvideoconfig( &vc );
/* Write all information to a string, then output string. */
c = sprintf( b, "X pixels: %d\n", vc.numxpixels );
c += sprintf( b + c, "Y pixels: %d\n", vc.numypixels );
c += sprintf( b + c, "Text columns: %d\n", vc.numtextcols );
c += sprintf( b + c, "Text rows: %d\n", vc.numtextrows );
c += sprintf( b + c, "Colors: %d\n", vc.numcolors );
c += sprintf( b + c, "Bits/pixel: %d\n", vc.bitsperpixel );
c += sprintf( b + c, "Video pages: %d\n", vc.numvideopages );
c += sprintf( b + c, "Mode: %d\n", vc.mode );
c += sprintf( b + c, "Adapter: %d\n", vc.adapter );
c += sprintf( b + c, "Monitor: %d\n", vc.monitor );
c += sprintf( b + c, "Memory: %d\n", vc.memory );
_outtext( b );
}
Output
X pixels: 0
Y pixels: 0
Text columns: 80
Text rows: 25
Colors: 32
Bits/pixel: 0
Video pages: 1
Mode: 3
Adapter: 8
Monitor: 24
Memory: 256
_getviewcoord Functions
────────────────────────────────────────────────────────────────────────────
Description
Translate coordinates to view coordinates.
#include <graph.h>
struct xycoord _far _getviewcoord( short x, short y );
struct xycoord _far _getviewcoord_w( double wx, double wy );
struct xycoord _far _getviewcoord_wxy( struct _wxycoord _far *pwxy1 );
x, y Physical point to translate
wx, wy Window point to translate
pwxy1 Window point to translate
Remarks
The _getviewcoord routines translate the specified coordinates (x, y) from
one coordinate system to view coordinates and then return them in an xycoord
structure, defined in GRAPH.H. The xycoord structure contains the following
elements:
Element Description
────────────────────────────────────────────────────────────────────────────
short xcoord x coordinate
short ycoord y coordinate
The various _getviewcoord routines translate in the following manner:
Routine Translation
────────────────────────────────────────────────────────────────────────────
_getviewcoord Physical coordinates (x, y) to view
coordinates
_getviewcoord_w Window coordinates (wx, wy) to view
coordinates
_getviewcoord_wxy Window coordinates structure (pwxy1) to
view coordinates
────────────────────────────────────────────────────────────────────────────
C 5.1 Version Difference
In Microsoft C version 5.1, the function _getviewcoord was called
_getlogcoord.
────────────────────────────────────────────────────────────────────────────
Return Value
The _getviewcoord function returns the coordinates as noted above. There is
no error return.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_getphyscoord, _getwindowcoord, _grstatus
Example
See the example for _setwindow.
_getvisualpage
────────────────────────────────────────────────────────────────────────────
Description
Gets the current visual page number.
#include <graph.h>
short _far _getvisualpage( void );
Remarks
The _getvisualpage function returns the current visual page number.
Return Value
The function returns the number of the current visual page. All hardware
combinations support at least one page (page number 0). In OS/2, only page 0
is available.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_getactivepage, _gettextcolor, _gettextposition, _outtext,
_setactivepage, _settextcolor, _settextposition, _settextwindow,
_setvideomode, _setvisualpage, _wrapon
Example
See the example for _getactivepage.
getw
────────────────────────────────────────────────────────────────────────────
Description
Gets an integer from a stream.
#include <stdio.h>
int getw( FILE *stream );
stream Pointer to FILE structure
Remarks
The getw function reads the next binary value of type int from the file
associated with stream and increments the associated file pointer (if there
is one) to point to the next unread character. The getw function does not
assume any special alignment of items in the stream.
Return Value
The getw function returns the integer value read. A return value of EOF may
indicate an error or end-of-file. However, since the EOF value is also a
legitimate integer value, feof or ferror should be used to verify an
end-of-file or error condition.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
The getw function is provided primarily for compatibility with previous
libraries. Note that portability problems may occur with getw, since the
size of the int type and the ordering of bytes within the int type differ
across systems.
See Also
putw
Example
/* GETW.C: This program uses getw to read a word from a stream,
* then performs an error check.
*/
#include <stdio.h>
#include <stdlib.h>
void main()
{
FILE *stream;
int i;
if( (stream = fopen( "getw.c", "rb" )) == NULL )
printf( "Couldn't open file\n" );
else
{
/* Read a word from the stream: */
i = getw( stream );
/* If there is an error... */
if( ferror( stream ) )
{
printf( "getw failed\n" );
clearerr( stream );
}
else
printf( "First data word in file: 0x%.4x\n", i );
fclose( stream );
}
}
Output
First data word in file: 0x2a2f
_getwindowcoord
────────────────────────────────────────────────────────────────────────────
Description
Translates view coordinates to window coordinates.
#include <graph.h>
struct _wxycoord _far _getwindowcoord( short x, short y );
x, y Physical point to translate
Remarks
The _getwindowcoord function translates the view coordinates (x, y) to
window coordinates and returns them in the _wxycoord structure, defined in
GRAPH.H.
The _wxycoord structure contains the following elements:
Element Description
────────────────────────────────────────────────────────────────────────────
double wx x coordinate
double wy y coordinate
Return Value
The function returns the coordinates in the _wxycoord structure. There is no
error return.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_getphyscoord, _getviewcoord functions, _moveto functions, _setwindow
Example
See the example for _setwindow.
_getwritemode
────────────────────────────────────────────────────────────────────────────
Description
Gets the current logical mode for line drawing.
#include <graph.h>
short _far _getwritemode( void );
Remarks
The _getwritemode function returns the current logical write mode, which is
used when drawing lines with the _lineto, _polygon, and _rectangle
functions.
The default value is _GPSET, which causes lines to be drawn in the current
graphics color. The other possible return values are _GXOR, _GAND, _GOR, and
_GPRESET. See _putimage for more details on these manifest constants.
Return Value
The _getwritemode function returns the current logical write mode, or -1 if
not in graphics mode.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_grstatus, _lineto functions, _putimage functions, _rectangle functions,
_setcolor, _setlinestyle, _setwritemode
Example
/* GWRMODE.C: This program illustrates _getwritemode and _setwritemode. */
#include <conio.h>
#include <stdlib.h>
#include <graph.h>
short wmodes[5] = { _GPSET, _GPRESET, _GXOR, _GOR, _GAND };
char *wmstr[5] = { "PSET ", "PRESET", "XOR ", "OR ", "AND " };
void box( short x, short y, short size, short writemode, short fillmode );
void main()
{
short i, x, y;
/* Find a valid graphics mode. */
if( !_setvideomode( _MAXCOLORMODE ) )
exit( 1 );
x = y = 70;
box( x, y, 50, _GPSET, _GFILLINTERIOR );
_setcolor( 2 );
box( x, y, 40, _GPSET, _GFILLINTERIOR );
for( i = 0; i < 5; i++ )
{
_settextposition( 1, 1 );
_outtext( wmstr[i] );
box( x += 12, y += 12, 50, wmodes[i], _GBORDER );
getch();
}
_setvideomode( _DEFAULTMODE );
}
void box( short x, short y, short size, short writemode, short fillmode )
{
short wm, side;
wm = _getwritemode(); /* Save write mode and set new. */
_setwritemode( writemode );
_rectangle( fillmode, x - size, y - size, x + size, y + size );
_setwritemode( wm ); /* Restore original write mode. */
}
gmtime
────────────────────────────────────────────────────────────────────────────
Description
Converts a time value to a structure.
#include <time.h>
struct tm *gmtime( const time_t *timer );
timer Pointer to stored time
Remarks
The gmtime function converts the timer value to a structure. The timer
argument represents the seconds elapsed since 00:00:00, January 1, 1970,
Greenwich mean time. This value is usually obtained from a call to the timer
function.
The gmtime function breaks down the timer value and stores it in a structure
of type tm, defined in TIME.H. (See asctime for a description of the
structure members.) The structure result reflects Greenwich mean time, not
local time.
The fields of the structure type tm store the following values, each of
which is an int:
Field Value Stored
────────────────────────────────────────────────────────────────────────────
tm_sec Seconds
tm_min Minutes
tm_hour Hours (0-24)
tm_mday Day of month (1-31)
tm_mon Month (0-11; January = 0)
tm_year Year (current year minus 1900)
tm_wday Day of week (0-6; Sunday = 0)
tm_yday Day of year (0-365; January 1 = 0)
tm_isdst Always 0 for gmtime
The gmtime, mktime, and localtime functions use a single statically
allocated structure to hold the result. Each call to one of these routines
destroys the result of any previous call.
DOS and OS/2 do not accommodate dates prior to 1980. If timer represents a
date prior to 1980, gmtime returns NULL.
Return Value
The gmtime function returns a pointer to the structure result. There is no
error return.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
asctime, ctime, ftime, localtime, time
Example
/* GMTIME.C: This program uses gmtime to convert a long-integer
* representation of Greenwich mean time to a structure named newtime,
* then uses asctime to convert this structure to an output string.
*/
#include <time.h>
#include <stdio.h>
void main()
{
struct tm *newtime;
long ltime;
time( <ime );
/* Obtain Greenwich mean time: */
newtime = gmtime( <ime );
printf( "Greenwich mean time is %s\n", asctime( newtime ) );
}
Output
Greenwich mean time is Fri Jun 16 16:37:53 1989
_grstatus
────────────────────────────────────────────────────────────────────────────
Description
Returns the status of the most recent graphics function call.
#include <graph.h>
short _far _grstatus( void );
Remarks
The _grstatus function returns the status of the most recently used graphics
function. The _grstatus function can be used immediately following a call to
a graphics routine to determine if errors or warnings were generated. Return
values less than 0 are errors, and values greater than 0 are warnings.
The following manifest constants are defined in the GRAPH.H header file for
use with the _grstatus function:
╓┌──────┌──────────────────────┌─────────────────────────────────────────────►
Value Constant Meaning
─────────────────────────────────────────────────────────────────────────────
0 _GROK Success
Value Constant Meaning
─────────────────────────────────────────────────────────────────────────────
-1 _GRERROR Graphics error
-2 _GRMODENOTSUPPORTED Requested video mode not supported
-3 _GRNOTINPROPERMODE Requested routine only works in certain video
modes
-4 _GRINVALIDPARAMETER One or more parameters invalid
-5 _GRFONTFILENOTFOUND No matching font file found
-6 _GRINVALIDFONTFILE One or more font files invalid
-7 _GRCORRUPTEDFONTFILE One or more font files inconsistent
-8 _GRINSUFFICIENTMEMORY Not enough memory to allocate buffer or to
complete a _floodfill operation
Value Constant Meaning
─────────────────────────────────────────────────────────────────────────────
-9 _GRINVALIDIMAGEBUFFER Image buffer data inconsistent
1 _GRMOOUTPUT No action taken
2 _GRCLIPPED Output was clipped to viewport
3 _GRPARAMETERALTERED One or more input parameters was altered to be
within range, or pairs of parameters were
interchanged to be in the proper order
─────────────────────────────────────────────────────────────────────────────
After a graphics call, use an if statement to compare the return value of
_grstatus to _GROK. For example:
if( _grstatus < _GROK )
/*handle graphics error*/ ;
The functions listed below cannot cause errors, and they all set _grstatus
to GROK:
╓┌────────────────┌─────────────────┌────────────────────────────────────────╖
────────────────────────────────────────────────────────────────────────────
_displaycursor _gettextposition _outmem
_getactivepage _gettextwindow _outtext
_getgtextvector _getvideoconfig _unregisterfonts
_gettextcolor _getvisualpage _wrapon
See the list below for the graphics functions that affect _grstatus. The
list shows error or warning messages that can be set by the graphics
function. In addition to the error codes listed, all of these functions can
produce the _GRERROR error code.
╓┌───────────────────────────────────┌───────────────────────────────────────►
Function Possible _grstatus
G Error Codes
─────────────────────────────────────────────────────────────────────────────
_arc functions _GRNOTINPROPERMODE,
_GRINVALIDPARAMETER
_clearscreen _GRNOTINPROPERMODE,
_GRINVALIDPARAMETER
_ellipse functions _GRNOTINPROPERMODE,
_GRINVALIDPARAMETER,
_GRINSUFFICIENTMEMORY
_getarcinfo _GRNOTINPROPERMODE
_getcurrentposition _GRNOTINPROPERMODE
functions
_getfontinfo ( _GRERROR only)
Function Possible _grstatus
G Error Codes
─────────────────────────────────────────────────────────────────────────────
_getfontinfo ( _GRERROR only)
_getgtextextent ( _GRERROR only)
_getgtextvector _GRPARAMETERALTERED
_getimage _GRNOTINPROPERMODE
_getphyscoord _GRNOTINPROPERMODE
_getpixel _GRNOTINPROPERMODE
_gettextcursor _GRNOTINPROPERMODE
_getviewcoord functions _GRNOTINPROPERMODE
Continued on next page
Function Possible _grstatus
G Error Codes
─────────────────────────────────────────────────────────────────────────────
_getwindowcoord _GRNOTINPROPERMODE
_getwritemode _GRNOTINPROPERMODE
_imagesize functions _GRNOTINPROPERMODE
_lineto functions _GRNOTINPROPERMODE
_moveto functions _GRNOTINPROPERMODE
_outgtext _GRNOTINPROPERMODE
_pie functions _GRNOTINPROPERMODE,
_GRINVALIDPARAMETER,
_GRINSUFFICIENTMEMORY
Function Possible _grstatus
G Error Codes
─────────────────────────────────────────────────────────────────────────────
_GRINSUFFICIENTMEMORY
_polygon functions _GRNOTINPROPERMODE,
_GRINVALIDPARAMETER,
_GRINSUFFICIENTMEMORY
_putimage functions _GRERROR,
_GRNOTINPROPERMODE,
_GRINVALIDPARAMETER,
_GRINVALIDIMAGEBUFFER
_rectangle functions _GRNOTINPROPERMODE,
_GRINVALIDPARAMETER,
_GRINSUFFICIENTMEMORY
_registerfonts _GRCORRUPTEDFONTFILE,
_GRFONTFILENOTFOUND,
_GRINSUFFICIENTMEMORY,
Function Possible _grstatus
G Error Codes
─────────────────────────────────────────────────────────────────────────────
_GRINSUFFICIENTMEMORY,
_GRINVALIDFONTFILE
_scrolltextwindow
_selectpalette _GRNOTINPROPERMODE,
_GRINVALIDPARAMETER
_setactivepage _GRINVALIDPARAMETER
_setbkcolor _GRINVALIDPARAMETER
_setcliprgn _GRNOTINPROPERMODE
_setcolor _GRNOTINPROPERMODE
_setfont _GRERROR,
_GRFONTFILENOTFOUND,
Function Possible _grstatus
G Error Codes
─────────────────────────────────────────────────────────────────────────────
_GRFONTFILENOTFOUND,
_GRINSUFFICIENTMEMORY,
_GRPARAMETERALTERED
Continued on next page
_setgtextvector _GRPARAMETERALTERED
_settextcolor
_settextcursor _GRNOTINPROPERMODE
_settextposition
_settextrows _GRINVALIDPARAMETER
_settextwindow
Function Possible _grstatus
G Error Codes
─────────────────────────────────────────────────────────────────────────────
_setvideomode _GRERROR,
_GRMODENOTSUPPORTED,
_GRINVALIDPARAMETER
_setvideomoderows _GRERROR,
_GRMODENOTSUPPORTED,
_GRINVALIDPARAMETER
_setvieworg _GRNOTINPROPERMODE
_setviewport _GRNOTINPROPERMODE
_setvisualpage _GRINVALIDPARAMETER
_setwindow _GRNOTINPROPERMODE,
_GRINVALIDPARAMETER
Function Possible _grstatus
G Error Codes
─────────────────────────────────────────────────────────────────────────────
_setwritemode _GRNOTINPROPERMODE,
_GRINVALIDPARAMETER
─────────────────────────────────────────────────────────────────────────────
Return Value
The _grstatus function returns the status of the most recently used graphics
function.
See Also
_arc functions, _ellipse functions, _floodfill, _lineto functions, _pie
functions, _remapallpalette, _setactivepage, _setbkcolor, _setcolor,
_setpixel functions, _settextcolor, _settextcursor, _setvisualpage,
_setwindow, _setwritemode
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
halloc
────────────────────────────────────────────────────────────────────────────
Description
Allocates a huge memory block.
#include <malloc.h> Required only for function declarations
void _huge *halloc( long num, size_t size );
num Number of elements
size Length in bytes of each element
Remarks
The halloc function allocates a huge array from the operating system
consisting of num elements, each of which is size bytes long. Each element
is initialized to 0. If the size of the array is greater than 128K (131,072
bytes), the size of an array element must then be a power of 2.
Return Value
The halloc function returns a void huge pointer to the allocated space,
which is guaranteed to be suitably aligned for storage of any type of
object. To get a pointer to a type other than void huge, use a type cast on
the return value. If the request cannot be satisfied, the return value is
NULL.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
calloc functions, free functions, hfree, malloc functions
Example
/* HALLOC.C: This program uses halloc to allocate space for 30,000 long
* integers, then uses hfree to deallocate the memory.
*/
#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
void main()
{
long _huge *hbuf;
/* Allocate huge buffer */
hbuf = (long _huge *)halloc( 30000L, sizeof( long ) );
if ( hbuf == NULL )
printf( "Insufficient memory available\n" );
else
printf( "Memory successfully allocated\n" );
/* Free huge buffer */
hfree( hbuf );
}
Output
Memory successfully allocated
_hard Functions
────────────────────────────────────────────────────────────────────────────
Description
Handle critical error conditions.
#include <dos.h>
void _harderr( void( _far *handler )());
void _hardresume( int result );
void _hardretn( int error );
handler ( ) New INT 0x24 handler
result Handler return parameter
error Error to return from
Remarks
These three functions are used to handle critical error conditions that use
DOS interrupt 0x24. The _harderr function installs a new critical-error
handler for interrupt 0x24.
The _hardresume and _hardreturn functions control how the program will
return from the new critical-error handler installed by _harderr. The
_hardresume function returns to DOS from a user-installed critical-error
handler, and the _hardreturn function returns directly to the application
program from a user-installed critical-error handler.
The _harderr function does not directly install the handler pointed to by
handler; instead, _harderr installs a handler that calls the function
referenced by handler. The handler calls the function with the following
parameters:
handler(unsigned deverror, unsigned errcode, unsigned far *devhdr);
The deverror argument is the device error code. It contains the AX register
value passed by DOS to the INT 0x24 handler. The errcode argument is the DI
register value that DOS passes to the handler. The low-order byte of errcode
can be one of the following values:
Code Meaning
────────────────────────────────────────────────────────────────────────────
0 Attempt to write to a write-protected
disk
1 Unknown unit
2 Drive not ready
3 Unknown command
4 Cyclic-redundancy-check error in data
5 Bad drive-request structure length
6 Seek error
7 Unknown media type
8 Sector not found
9 Printer out of paper
10 Write fault
11 Read fault
12 General failure
The devhdr argument is a far pointer to a device header that contains
descriptive information about the device on which the error occurred. The
user-defined handler must not change the information in the device-header
control block.
Errors on Disk Devices
If the error occurred on a disk device, the high-order bit (bit 15) of the
deverror argument will be set to 0, and the deverror argument will indicate
the following:
Bit Meaning
────────────────────────────────────────────────────────────────────────────
15 Disk error if false (0).
14 Not used.
13 "Ignore" response not allowed if false
(0).
12 "Retry" response not allowed if false
(0).
11 "Fail" response not allowed if false
(0). Note that DOS changes "fail" to
"abort".
10, 9
Code Location
────────────────────────────────────────────────────────────────────────────
00 DOS
01 File allocation table
10 Directory
11 Data area
8 Read error if false; write error if
true.
The low-order byte of deverror indicates the drive in which the error
occurred (0 = drive A, 1 = drive B, etc.).
Errors on Other Devices
If the error occurs on a device other than a disk drive, the high-order bit
(bit 15) of the deverror argument is 1. The attribute word located at offset
4 in the device-header block indicates the type of device that had the
error. If bit 15 of the attribute word is 0, the error is a bad memory image
of the file allocation table. If the bit is 1, the error occurred on a
character device and bits 0-3 of the attribute word indicate the type of
device, as shown in the following list:
Bit Meaning
────────────────────────────────────────────────────────────────────────────
0 Current standard input
1 Current standard output
2 Current null device
3 Current clock device
Restrictions on Handler Functions
The user-defined handler function can issue only system calls 0x01 through
0x0C, or 0x59. Thus, many of the standard C run-time functions (such as
stream I/O and low-level I/O) cannot be used in a hardware error handler.
Function 0x59 can be used to obtain further information about the error that
occurred.
Using _hardresume and _harderr
If the handler returns, it can do so -
1. From the return statement
2. From the _hardresume function
3. From the _hardretn function
If the handler returns from _hardresume or from a return statement, the
handler returns to DOS.
The _hardresume function should be called only from within the user-defined
hardware error-handler function. The result supplied to _hardresume must be
one of the following constants:
Constant Action
────────────────────────────────────────────────────────────────────────────
_HARDERR_ABORT Abort the program by issuing INT 0x23
_HARDERR_FAIL Fail the system call that is in progress
(this is not supported on DOS 2. x)
_HARDERR_IGNORE Ignore the error
_HARDERR_RETRY Retry the operation
The _hardretn function allows the user-defined hardware error handler to
return directly to the application program rather than returning to DOS. The
application resumes at the point just after the failing I/O function
request. The _hardretn function should be called only from within a
user-defined hardware error-handler function.
The error parameter of _hardretn should be a DOS error code, as opposed to
the XENIX-style error code that is available in errno. Refer to MS-DOS
Encyclopedia (Duncan, ed.; Redmond, Wa.: Microsoft Press, 1988) or
Programmer's PC Sourcebook (Hogan; Redmond, Wa.: Microsoft Press, 1988) for
information about the DOS error codes that may be returned by a given DOS
function call.
If the failing I/O function request is an INT 0x21 function greater than or
equal to function 0x38, _hardretn will then return to the application with
the carry flag set and the AX register set to the _hardretn error parameter.
If the failing INT 0x21 function request is less than function 0x38 and the
function can return an error, the AL register will be set to 0xFF on return
to the application. If the failing INT 0x21 does not have a way of returning
an error condition (which is true of certain INT 0x21 functions below 0x38),
the error parameter of _hardretn is not used, and no error code is returned
to the application.
Return Value
None.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_chain_intr, _dos_getvect, _dos_setvect
_heapadd Functions
────────────────────────────────────────────────────────────────────────────
Description
Add memory to the heap (_heapadd) or to the based heap (_bheapadd).
#include <malloc.h> Required only for function declarations
int _heapadd( void _far *memblock, size_t size );
int _bheapadd( _segment seg, void _based (void) *memblock, size_t size );
seg Based-heap segment selector
buffer Pointer to heap memory
size Size in bytes of memory to add
Remarks
The _heapadd and _bheapadd functions add an unused piece of memory to the
heap. The _bheapadd function adds the memory to the based heap specified by
seg. The _heapadd function looks at the segment value and, if it is DGROUP,
adds the memory to the near heap. Otherwise, _heapadd adds the memory to the
far heap.
Return Value
These functions return 0 if successful, or -1 if an error occurred.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
free functions, halloc, hfree, malloc functions, realloc functions
Example
/* HEAPMIN.C: This program illustrates heap management using
* _heapadd and _heapmin.
*/
#include <stdio.h>
#include <conio.h>
#include <process.h>
#include <malloc.h>
void heapdump( char *msg ); /* Prototype */
char s1[] = { "Here are some strings that we use at first, then don't\n"
};
char s2[] = { "need any more. We'll give their space to the heap.\n" };
void main()
{
int *p[3], i;
printf( "%s%s", s1, s2 );
heapdump( "Initial heap" );
/* Give space of used strings to heap. */
_heapadd( s1, sizeof( s1 ) );
_heapadd( s2, sizeof( s2 ) );
heapdump( "After adding used strings" );
/* Allocate some blocks. Some may use string blocks from _heapadd. */
for( i = 0; i < 2; i++ )
if( (p[i] = (int *)calloc( 10 * (i + 1), sizeof( int ) )) == NULL
)
{
--i;
break;
}
heapdump( "After allocating memory" );
/* Free some of the blocks. */
free( p[1] );
free( p[2] );
heapdump( "After freeing memory" );
/* Minimize heap. */
_heapmin();
heapdump( "After compacting heap" );
}
/* Walk through heap entries, displaying information about each block. */
void heapdump( char *msg )
{
struct _heapinfo hi;
printf( "%s\n", msg );
hi._pentry = NULL;
while( _heapwalk( &hi ) == _HEAPOK )
printf( "\t%s block at %Fp of size %u\t\n",
hi._useflag == _USEDENTRY ? "USED" : "FREE",
hi._pentry,
hi._size );
getch();
}
Output
Here are some strings that we use at first, then don't
need any more. We'll give their space to the heap.
Initial heap
USED block at 2D39:0E9C of size 364
USED block at 2D39:100A of size 36
USED block at 2D39:1030 of size 512
FREE block at 2D39:1232 of size 460
After adding used strings
FREE block at 2D39:0044 of size 52
FREE block at 2D39:007A of size 50
USED block at 2D39:00AE of size 3564
USED block at 2D39:0E9C of size 364
USED block at 2D39:100A of size 36
USED block at 2D39:1030 of size 512
FREE block at 2D39:1232 of size 460
After allocating memory
USED block at 2D39:0044 of size 20
USED block at 2D39:005A of size 40
FREE block at 2D39:0084 of size 40
USED block at 2D39:00AE of size 3564
USED block at 2D39:0E9C of size 364
USED block at 2D39:100A of size 36
USED block at 2D39:1030 of size 512
FREE block at 2D39:1232 of size 460
After freeing memory
USED block at 2D39:0044 of size 20
FREE block at 2D39:005A of size 40
FREE block at 2D39:0084 of size 40
USED block at 2D39:00AE of size 3564
USED block at 2D39:0E9C of size 364
USED block at 2D39:100A of size 36
USED block at 2D39:1030 of size 512
FREE block at 2D39:1232 of size 460
After compacting heap
USED block at 2D39:0044 of size 20
FREE block at 2D39:005A of size 82
USED block at 2D39:00AE of size 3564
USED block at 2D39:0E9C of size 364
USED block at 2D39:100A of size 36
USED block at 2D39:1030 of size 512
FREE block at 2D39:1232 of size 12
_heapchk Functions
────────────────────────────────────────────────────────────────────────────
Description
Run consistency checks on the heap.
#include <malloc.h>
int _heapchk( void );
int _bheapchk( _segment seg );
int _fheapchk( void );
int _nheapchk( void );
seg Specified base heap
Remarks
The _heapchk routines help to debug heap-related problems by checking for
minimal consistency of the heap.
Each function checks a particular heap, as listed below:
Function Heap Checked
────────────────────────────────────────────────────────────────────────────
_heapchk Depends on data model of program
_bheapchk Based heap specified by seg value
_fheapchk Far heap (outside the default data
segment)
_nheapchk Near heap (inside the default data
segment)
In large data models (that is, compact-, large-, and huge-model programs),
_heapchk maps to _fheapchk. In small data models (tiny-, small-, and
medium-model programs), _heapchk maps to _nheapchk.
Return Value
All four routines return an integer value that is one of the following
manifest constants (defined in MALLOC.H):
Constant Meaning
────────────────────────────────────────────────────────────────────────────
_HEAPBADBEGIN Initial header information cannot be
found, or it is bad
_HEAPBADNODE Bad node has been found, or the heap is
damaged
_HEAPEMPTY Heap has not been initialized
_HEAPOK Heap appears to be consistent
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_heapset functions, _heapwalk functions
Example
/* HEAPCHK.C: This program checks the heap for consistency
* and prints an appropriate message.
*/
#include <malloc.h>
#include <stdio.h>
void main()
{
int heapstatus;
char *buffer;
/* Allocate and deallocate some memory */
if( (buffer = (char *)malloc( 100 )) != NULL )
free( buffer );
/* Check heap status */
heapstatus = _heapchk();
switch( heapstatus )
{
case _HEAPOK:
printf(" OK - heap is fine\n" );
break;
case _HEAPEMPTY:
printf(" OK - heap is empty\n" );
break;
case _HEAPBADBEGIN:
printf( "ERROR - bad start of heap\n" );
break;
case _HEAPBADNODE:
printf( "ERROR - bad node in heap\n" );
break;
}
}
Output
OK - heap is fine
_heapmin Functions
────────────────────────────────────────────────────────────────────────────
Description
Release unused heap memory to the operating system.
#include <malloc.h>
int _heapmin( void );
int _bheapmin( _segment seg )
int _fheapmin( void );
int _nheapmin( void );
seg Specified based-heap selector
Remarks
The _heapmin functions minimize the heap by releasing unused heap memory to
the operating system.
The various _heapmin functions release unused memory in these heaps:
Function Heap Minimized
────────────────────────────────────────────────────────────────────────────
_heapmin Depends on data model of program
_bheapmin Based heap specified by seg value;
_NULLSEG specifies all based heaps
_fheapmin Far heap (outside default data segment)
_nheapmin Near heap (inside default data segment)
In large data models (that is, compact-, large-, and huge-model programs),
_heapmin maps to _fheapmin. In small data models (tiny-, small-, and
medium-model programs), _heapmin maps to _nheapmin.
Based-heap segments are never freed (i.e., unlinked from the based heap list
and released back to the operating system) by the _bheapmin function. The
_bfreeseg function is used for that purpose.
Return Value
The _heapmin functions return 0 if the function completed successfully, or
-1 in the case of an error.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_bfreeseg, free functions, malloc functions
_heapset Functions
────────────────────────────────────────────────────────────────────────────
Description
Check heaps for minimal consistency and set the free entries to a specified
value.
#include <malloc.h>
int _heapset( unsigned int fill );
int _bheapset( _segment seg, unsigned int fill );
int _fheapset( unsigned int fill );
int _nheapset( unsigned int fill );
fill Fill character
seg Specified based-heap segment selector
Remarks
The _heapset family of routines helps debug heap-related problems in
programs by showing free memory locations or nodes unintentionally
overwritten.
The _heapset routines first check for minimal consistency on the heap in a
manner identical to that of the _heapchk functions. After the consistency
check, the _heapset functions set each byte of the heap's free entries to
the fill value. This known value shows which memory locations of the heap
contain free nodes and which locations contain data that were
unintentionally written to freed memory.
The various _heapset functions check and fill these heaps:
Function Heap Filled
────────────────────────────────────────────────────────────────────────────
_heapset Depends on data model of program
_bheapset Based heap specified by seg value;
_NULLSEG specifies all based heaps
_fheapset Far heap (outside default data segment)
_nheapset Near heap (inside default data segment)
In large data models (that is, compact-, large-, and huge-model programs),
_heapset maps to _fheapset. In small data models (tiny-, small-, and
medium-model programs), _heapset maps to _nheapset.
Return Value
All four routines return an int whose value is one of the following manifest
constants (defined in MALLOC.H):
Constant Meaning
────────────────────────────────────────────────────────────────────────────
_HEAPBADBEGIN Initial header information cannot be
found, or it is invalid
_HEAPBADNODE Bad node has been found, or the heap is
damaged
_HEAPEMPTY Heap has not been initialized
_HEAPOK Heap appears to be consistent
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_heapchk functions, _heapwalk functions
Example
/* HEAPSET.C: This program checks the heap and fills in free entries
* with the character 'Z'.
*/
#include <malloc.h>
#include <stdio.h>
#include <stdlib.h>
void main()
{
int heapstatus;
char *buffer;
if( (buffer = malloc( 1 )) == NULL ) /* Make sure heap is initialized */
exit( 0 );
heapstatus = _heapset( 'Z' ); /* Fill in free entries */
switch( heapstatus )
{
case _HEAPOK:
printf( "OK - heap is fine\n" );
break;
case _HEAPEMPTY:
printf( "OK - heap is empty\n" );
break;
case _HEAPBADBEGIN:
printf( "ERROR - bad start of heap\n" );
break;
case _HEAPBADNODE:
printf( "ERROR - bad node in heap\n" );
break;
}
free( buffer );
}
Output
OK - heap is fine
_heapwalk Functions
────────────────────────────────────────────────────────────────────────────
Description
Traverse the heap and return information about the next entry.
include <malloc.h>
int _heapwalk( _HEAPINFO *entryinfo );
int _bheapwalk( _segment seg, _HEAPINFO *entryinfo );
int _fheapwalk( _HEAPINFO *entryinfo );
int _nheapwalk(_HEAPINFO *entryinfo);
entryinfo Buffer to contain heap information
seg Based-heap segment selector
Remarks
The _heapwalk family of routines helps debug heap-related problems in
programs.
The _heapwalk routines walk through the heap, traversing one entry per call,
and return a pointer to a _heapinfo structure that contains information
about the next heap entry. The _heapinfo structure, defined in MALLOC.H,
contains the following elements:
Element Description
────────────────────────────────────────────────────────────────────────────
int far *_pentry Heap entry pointer
size_t _size Size of heap entry
int _useflag Entry "in use" flag
A call to _heapwalk that returns _HEAPOK stores the size of the entry in the
_size field and sets the _useflag field to either _FREEENTRY or _USEDENTRY
(both are constants defined in MALLOC.H). To obtain this information about
the first entry in the heap, pass the _heapwalk routine a pointer to a
_heapinfo structure whose _pentry field is NULL.
The various _heapwalk functions walk through and gather information on these
heaps:
Function Heap Walked
────────────────────────────────────────────────────────────────────────────
_heapwalk Depends on data model of program
_bheapwalk Based heap specified by seg value;
_NULLSEG specifies all based heaps
_fheapwalk Far heap (outside default data segment)
_nheapwalk Near heap (inside default data segment)
In large data models (that is, compact-, large-, and huge-model programs),
_heapwalk maps to _fheapwalk. In small data models (tiny-, small-, and
medium-model programs), _heapwalk maps to _nheapwalk.
Return Value
All three routines return one of the following manifest constants (defined
in MALLOC.H):
Constant Meaning
────────────────────────────────────────────────────────────────────────────
_HEAPBADBEGIN The initial header information cannot be
found, or it is invalid.
_HEAPBADNODE A bad node has been found, or the heap
is damaged.
_HEAPBADPTR The _pentry field of the _heapinfo
structure does not contain a valid
pointer into the heap.
_HEAPEND The end of the heap has been reached
successfully.
_HEAPEMPTY The heap has not been initialized.
_HEAPOK No errors so far; the _heapinfo
structure contains information about the
next entry.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_heapchk functions, _heapset functions
Example
/* HEAPWALK.C: This program "walks" the heap, starting at the beginning
* (_pentry = NULL). It prints out each heap entry's use, location,
* and size. It also prints out information about the overall state
* of the heap as soon as _heapwalk returns a value other than _HEAPOK.
*/
#include <stdio.h>
#include <malloc.h>
void heapdump( void );
void main()
{
char *buffer;
heapdump();
if( (buffer = malloc( 59 )) != NULL )
{
heapdump();
free( buffer );
}
heapdump();
}
void heapdump( void )
{
struct _heapinfo hinfo;
int heapstatus;
hinfo._pentry = NULL;
while( ( heapstatus = _heapwalk( &hinfo ) ) == _HEAPOK )
{
printf( "%6s block at %Fp of size %4.4X\n",
( hinfo._useflag == _USEDENTRY ? "USED" : "FREE" ),
hinfo._pentry, hinfo._size );
}
switch( heapstatus )
{
case _HEAPEMPTY:
printf( "OK - empty heap\n" );
break;
case _HEAPEND:
printf( "OK - end of heap\n" );
break;
case _HEAPBADPTR:
printf( "ERROR - bad pointer to heap\n" );
break;
case _HEAPBADBEGIN:
printf( "ERROR - bad start of heap\n" );
break;
case _HEAPBADNODE:
printf( "ERROR - bad node in heap\n" );
break;
}
}
Output
USED block at 0067:103E of size 000E
USED block at 0067:104E of size 01F4
USED block at 0067:1244 of size 0026
USED block at 0067:126C of size 0200
FREE block at 0067:146E of size 0B90
OK - end of heap
USED block at 0067:103E of size 000E
USED block at 0067:104E of size 01F4
USED block at 0067:1244 of size 0026
USED block at 0067:126C of size 0200
USED block at 0067:146E of size 003C
FREE block at 0067:14AC of size 0B52
OK - end of heap
USED block at 0067:103E of size 000E
USED block at 0067:104E of size 01F4
USED block at 0067:1244 of size 0026
USED block at 0067:126C of size 0200
FREE block at 0067:146E of size 003C
FREE block at 0067:14AC of size 0B52
OK - end of heap
hfree
────────────────────────────────────────────────────────────────────────────
Description
Frees a huge memory block.
#include <malloc.h> Required only for function declarations
void hfree( void _huge *memblock );
memblock Pointer to allocated memory block
Remarks
The hfree function deallocates a memory block; the freed memory is returned
to the operating system. The memblock argument points to a memory block
previously allocated through a call to halloc. The number of bytes freed is
the number of bytes specified when the block was allocated.
Note that attempting to free an invalid memblock argument (one not allocated
with halloc) may affect subsequent allocation and cause errors.
Return Value
None.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
halloc
Example
/* HALLOC.C: This program uses halloc to allocate space for 30,000 long
* integers, then uses hfree to deallocate the memory.
*/
#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
void main()
{
long _huge *hbuf;
/* Allocate huge buffer */
hbuf = (long _huge *)halloc( 30000L, sizeof( long ) );
if ( hbuf == NULL )
printf( "Insufficient memory available\n" );
else
printf( "Memory successfully allocated\n" );
/* Free huge buffer */
hfree( hbuf );
}
Output
Memory successfully allocated
hypot, hypotl
────────────────────────────────────────────────────────────────────────────
Description
Calculate the hypotenuse.
#include <math.h>
double hypot( double x, double y );
long double hypotl( long double x, long double y );
x, y Floating-point values
Remarks
The hypot and hypotl functions calculate the length of the hypotenuse of a
right triangle, given the length of the two sides x and y (or xl and yl). A
call to hypot is equivalent to the following:
sqrt(x*x + y*y);
The hypotl function uses the 80-bit, 10-byte coprocessor form of arguments
and return values. See the reference page on the long double functions for
more details on this data type.
Return Value
The functions return the length of the hypotenuse. If an overflow results,
the functions return HUGE_VAL and set errno to ERANGE.
Compatibility
hypot
▼ ANSI DOS OS/2 UNIX XENIX
hypotl
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
cabs
Example
/* HYPOT.C: This program prints the hypotenuse of a right triangle. */
#include <math.h>
#include <stdio.h>
void main()
{
double x = 3.0, y = 4.0;
printf( "If a right triangle has sides %2.1f and %2.1f, "
"its hypotenuse is %2.1f\n", x, y, hypot( x, y ) );
}
Output
If a right triangle has sides 3.0 and 4.0, its hypotenuse is 5.0
_imagesize Functions
────────────────────────────────────────────────────────────────────────────
Description
Get amount of memory required to store graphics images.
#include <graph.h>
long _far _imagesize( short x1, short y1, short x2, short y2 );
long _far _imagesize_w( double wx1, double wy1, double wx2, double wy2 );
long _far _imagesize_wxy( struct _wxycoord _far *pwxy1,
struct _wxycoord _far *pwxy2 );
x1, y1 Upper-left corner of bounding rectangle
x2, y2 Lower-right corner of bounding rectangle
wx1, wy1 Upper-left corner of bounding rectangle
wx2, wy2 Lower-right corner of bounding rectangle
pwxy1 Upper-left corner of bounding rectangle
pwxy2 Lower-right corner of bounding rectangle
Remarks
The functions in the _imagesize family return the number of bytes needed to
store the image defined by the bounding rectangle and specified by the
coordinates given in the function call.
The _imagesize function defines the bounding rectangle in terms of
view-coordinate points (x1, y1) and (x2, y2).
The _imagesize_w function defines the bounding rectangle in terms of
window-coordinate points (x1, y1) and (x2, y2).
The _imagesize_wxy function defines the bounding rectangle in terms of the
window-coordinate pairs pwxy1 and pwxy2.
The number of bytes needed to store the image is determined by the following
formula:
xwid = abs(x1-x2)+1;
ywid = abs(y1-y2)+1;
size = 4+((long)((xwid*bits_per_pixel+7)/8)*(long)ywid);
A call to _getvideoconfig stores the bits_per_pixel information in the
bitsperpixel field of a videoconfig structure.
Return Value
The function returns the storage size of the image in bytes. There is no
error return.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_getimage functions, _getvideoconfig, _putimage functions
Example
See the example for _getimage.
inp, inpw
────────────────────────────────────────────────────────────────────────────
Description
Input a byte (inp) or a word (inpw) from a port.
#include <conio.h> Required only for function declarations
int inp( unsigned port );
unsigned inpw( unsigned port );
port Port number
Remarks
The inp and inpw functions read a byte and a word, respectively, from the
specified input port. The input value can be any unsigned integer in the
range 0 - 65,535.
To use inp and inpw in OS/2 protected mode, you must use a .DEF file to
declare the IOSEG segment that the run-time library uses to perform
input/output on the port. In addition, the intrinsic (/Oi) versions of these
functions do not work unless you put the code in a segment that is marked
with the IOPL keyword in the .DEF file.
Because you cannot do IOPL from a regular code segment, the run-time library
declares a separate code segment called _IOSEG. In order to use inp, inpw,
outp, or outpw in any of the protected-mode run-time libraries (?LIBCP,
LLIBCDLL, LLIBCMT, or CDLLOBJS-based DLL), you must have a .DEF file
containing this line:
SEGMENTS _IOSEG CLASS 'IOSEG_CODE' IOPL
Return Value
The functions return the byte or word read from port. There is no error
return.
Compatibility
▼ ANSI DOS OS2 ▼ UNIX ▼ XENIX
See Also
outp, outpw
Example
See the example for outp.
int86
────────────────────────────────────────────────────────────────────────────
Description
Executes the 8086 interrupt.
#include <dos.h>
int int86( int intnum, union REGS *inregs, union REGS *outregs );
intnum Interrupt number
inregs Register values on call
outregs Register values on return
Remarks
The int86 function executes the 8086-processor-family interrupt specified by
the interrupt number intnum. Before executing the interrupt, int86 copies
the contents of inregs to the corresponding registers. After the interrupt
returns, the function copies the current register values to outregs. It also
copies the status of the system carry flag to the cflag field in the outregs
argument. The inregs and outregs arguments are unions of type REGS. The
union type is defined in the include file DOS.H.
Do not use the int86 function to call interrupts that modify the DS
register. Instead, use the int86x function. The int86x function loads the DS
and ES registers from the segregs parameter and also stores the DS and ES
registers into segregs after the function call.
The REGS type is defined in the include file DOS.H.
Return Value
The return value is the value in the AX register after the interrupt
returns. If the cflag field in outregs is nonzero, an error has occurred; in
such cases, the _doserrno variable is also set to the corresponding error
code.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
bdos, int86x, intdos, intdosx
Example
/* INT86.C: This program uses int86 to call the BIOS video service
* (INT 10H) to get information about the cursor.
*/
#include <dos.h>
#include <stdio.h>
void main()
{
union REGS inregs, outregs;
/* Set up to get cursor information. */
inregs.h.ah = 3; /* Get Cursor Position function */
inregs.h.bh = 0; /* Page 0 */
/* Execute video interrupt: */
int86( 0x10, &inregs, &outregs );
/* Display results. */
printf( "Cursor position\n\tRow: %d\n\tColumn: %d\n",
outregs.h.dh, outregs.h.dl );
printf( "Cursor shape\n\tStart: %d\n\tEnd: %d\n",
outregs.h.ch, outregs.h.cl );
}
Output
Cursor position
Row: 2
Column: 0
Cursor shape
Start: 6
End: 7
int86x
────────────────────────────────────────────────────────────────────────────
Description
Executes the 8086 interrupt; accepts segment-register values.
#include <dos.h>
int int86x( int intnum, union REGS *inregs, union REGS *outregs,
struct SREGS *segregs );
intnum Interrupt number
inregs Register values on call
outregs Register values on return
segregs Segment-register values on call
Remarks
The int86x function executes the 8086-processor-family interrupt specified
by the interrupt number intnum. Unlike the int86 function, int86x accepts
segment-register values in segregs, enabling programs that use large-model
data segments or far pointers to specify which segment or pointer should be
used during the system call.
Before executing the specified interrupt, int86x copies the contents of
inregs and segregs to the corresponding registers. Only the DS and ES
register values in segregs are used. After the interrupt returns, the
function copies the current register values to outregs, cop-ies the current
ES and DS values to segregs, and restores DS. It also copies the status of
the system carry flag to the cflag field in outregs.
The REGS and SREGS types are defined in the include file DOS.H.
Segment values for the segregs argument can be obtained by using either the
segread function or the FP_SEG macro.
Return Value
The return value is the value in the AX register after the interrupt
returns. If the cflag field in outregs is nonzero, an error has occurred; in
such cases, the _doserrno variable is also set to the corresponding error
code.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
bdos, FP_SEG, int86, intdos, intdosx, segread
Example
/* INT86X.C: In this program, int86x executes an INT 21H instruction
* to invoke DOS system call 43H (change file attributes). The program
* uses int86x because the file, which is referenced with a far pointer,
* may be in a segment other than the default data segment. Thus, the
* program must explicitly set the DS register with the SREGS structure.
*/
#include <signal.h>
#include <dos.h>
#include <stdio.h>
#include <process.h>
char _far *filename = "int86x.c";
void main()
{
union REGS inregs, outregs;
struct SREGS segregs;
int result;
inregs.h.ah = 0x43; /* DOS function to change attributes */
inregs.h.al = 0; /* Subfunction 0 to get attributes) */
inregs.x.dx = FP_OFF( filename ); /* DS:DX points to file name */
segregs.ds = FP_SEG( filename );
result = int86x( 0x21, &inregs, &outregs, &segregs );
if( outregs.x.cflag )
printf( "Can't get file attributes; error no. %d\n", result);
else
printf( "Attribs = 0x%.4x\n", outregs.x.cx );
}
Output
Attribs = 0x0020
intdos
────────────────────────────────────────────────────────────────────────────
Description
Executes the DOS system call.
#include <dos.h>
int intdos( union REGS *inregs, union REGS *outregs );
inregs Register values on call
outregs Register values on return
Remarks
The intdos function invokes the DOS system call specified by register values
defined in inregs and returns the effect of the system call in outregs. The
inregs and outregs arguments are unions of type REGS. The REGS type is
defined in the include file DOS.H.
To invoke a system call, intdos executes an INT 21H instruction. Before
executing the instruction, the function copies the contents of inregs to the
corresponding registers. After the INT instruction returns, intdos copies
the current register values to outregs. It also copies the status of the
system carry flag to the cflag field in outregs. A nonzero cflag field
indicates the flag was set by the system call and also indicates an error
condition.
The intdos function is used to invoke DOS system calls that take arguments
for input or output in registers other than DX (DH/DL) and AL. The intdos
function is also used to invoke system calls that indicate errors by setting
the carry flag. Under any other conditions, the bdos function can be used.
Do not use the intdos function to call interrupts that modify the DS
register. Instead, use the intdosx or int86x function.
Return Value
The intdos function returns the value of the AX register after the system
call is completed. If the cflag field in outregs is nonzero, an error has
occurred and _doserrno is also set to the corresponding error code.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
bdos, intdosx
Example
/* INTDOS.C: This program uses intdos to invoke DOS system call 2AH
* (gets the current date).
*/
#include <dos.h>
#include <stdio.h>
void main()
{
union REGS inregs, outregs;
inregs.h.ah = 0x2a; /* DOS Get Date function: */
intdos( &inregs, &outregs );
printf( "Date: %d/%d/%d\n", outregs.h.dh, outregs.h.dl, outregs.x.cx );
}
Output
Date: 6/16/1989
intdosx
────────────────────────────────────────────────────────────────────────────
Description
Executes the DOS system call; accepts segment-register values.
#include <dos.h>
int intdosx( union REGS *inregs, union REGS *outregs, struct SREGS
*segregs );
inregs Register values on call
outregs Register values on return
segregs Segment-register values on call
Remarks
The intdosx function invokes the DOS system call specified by register
values defined in inregs and returns the results of the system call in
outregs. Unlike the intdos function, intdosx accepts segment-register values
in segregs, enabling programs that use large-model data segments or far
pointers to specify which segment or pointer should be used during the
system call. The REGS and SREGS types are defined in the include file DOS.H.
To invoke a system call, intdosx executes an INT 21H instruction. Before
executing the instruction, the function copies the contents of inregs and
segregs to the corresponding registers. Only the DS and ES register values
in segregs are used. After the INT instruction returns, intdosx copies the
current register values to outregs and restores DS. It also copies the
status of the system carry flag to the cflag field in outregs. A nonzero
cflag field indicates the flag was set by the system call and also indicates
an error condition.
The intdosx function is used to invoke DOS system calls that take an
argument in the ES register or that take a DS register value different from
the default data segment.
Segment values for the segregs argument can be obtained by using either the
segread function or the FP_SEG macro.
Return Value
The intdosx function returns the value of the AX register after the system
call is completed. If the cflag field in outregs is nonzero, an error has
occurred; in such cases, _doserrno is also set to the corresponding error
code.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
bdos, FP_SEG, intdos, segread
Example
/* INTDOSX.C */
#include <dos.h>
#include <stdio.h>
char _far *buffer = "Dollar-sign terminated string\n\r\n\r$";
void main()
{
union REGS inregs, outregs;
struct SREGS segregs;
/* Print a $-terminated string on the screen using DOS function 0x09.
*/
inregs.h.ah = 0x9;
inregs.x.dx = FP_OFF( buffer );
segregs.ds = FP_SEG( buffer );
intdosx( &inregs, &outregs, &segregs );
}
Output
Dollar-sign terminated string
is Functions
────────────────────────────────────────────────────────────────────────────
Description
Test characters for specified conditions.
#include <ctype.h>
int isalnum( int c );
int isalpha( int c );
int isascii( int c );
int iscntrl( int c );
int isdigit( int c );
int isgraph( int c );
int islower( int c );
int isprint( int c );
int ispunct( int c );
int isspace( int c );
int isupper( int c );
int isxdigit( int c );
c Integer to be tested
Remarks
Each function in the is family tests a given integer value, returning a
nonzero value if the integer satisfies the test condition and 0 if it does
not. The ASCII character set is assumed.
The is functions and their test conditions are listed below:
Function Test Condition
────────────────────────────────────────────────────────────────────────────
isalnum Alphanumeric ('A'-'Z', 'a'-'z', or
'0'-'9')
isalpha Letter ('A'-'Z' or 'a'-'z')
isascii ASCII character (0x00 - 0x7F)
iscntrl Control character (0x00 - 0x1F or 0x7F)
isdigit Digit ('0'-'9')
isgraph Printable character except space (' ')
islower Lowercase letter ('a'-'z')
isprint Printable character (0x20 - 0x7E)
ispunct Punctuation character
isspace White-space character (0x09 - 0x0D or
0x20)
isupper Uppercase letter ('A'-'Z')
isxdigit Hexadecimal digit ('A'-'F','a'-'f', or
'0'-'9')
The isascii routine produces meaningful results for all integer values.
However, the remaining routines produce a defined result only for integer
values corresponding to the ASCII character set (that is, only where isascii
holds true) or for the non-ASCII value EOF (defined in STDIO.H).
These routines are implemented both as functions and as macros. For details
on choosing a function or a macro implementation, see Section 1.4, "Choosing
Between Functions and Macros."
Return Value
These routines return a nonzero value if the integer satisfies the test
condition and 0 if it does not.
Compatibility
isalnum, isalpha, iscntrl, isdigit, isgraph, islower, isprint, ispunct,
isspace, isupper, isxdigit
ANSI DOS OS/2 UNIX XENIX
isascii
▼ ANSI DOS OS/2 UNIX XENIX
See Also
toascii, tolower, toupper functions
Example
/* ISFAM.C: This program tests all characters between 0x0 and 0x7F,
* then displays each character with abbreviations for the character-type
* codes that apply.
*/
#include <stdio.h>
#include <ctype.h>
void main()
{
int ch;
for( ch = 0; ch <= 0x7F; ch++ )
{
printf( "%.2x ", ch );
printf( " %c", isprint( ch ) ? ch : '\0' );
printf( "%4s", isalnum( ch ) ? "AN" : "" );
printf( "%3s", isalpha( ch ) ? "A" : "" );
printf( "%3s", isascii( ch ) ? "AS" : "" );
printf( "%3s", iscntrl( ch ) ? "C" : "" );
printf( "%3s", isdigit( ch ) ? "D" : "" );
printf( "%3s", isgraph( ch ) ? "G" : "" );
printf( "%3s", islower( ch ) ? "L" : "" );
printf( "%3s", ispunct( ch ) ? "PU" : "" );
printf( "%3s", isspace( ch ) ? "S" : "" );
printf( "%3s", isprint( ch ) ? "PR" : "" );
printf( "%3s", isupper( ch ) ? "U" : "" );
printf( "%3s", isxdigit( ch ) ? "X" : "" );
printf( "\n" );
}
}
Output
00 AS C
01 AS C
02 AS C
.
.
.
38 8 AN AS D G PR X
39 9 AN AS D G PR X
3a : AS G PU PR
3b ; AS G PU PR
3c < AS G PU PR
3d = AS G PU PR
3e > AS G PU PR
3f ? AS G PU PR
40 @ AS G PU PR
41 A AN A AS G PR U X
42 B AN A AS G PR U X
.
.
.
isatty
────────────────────────────────────────────────────────────────────────────
Description
Checks for a character device.
#include <io.h> Required only for function declarations
int isatty( int handle );
handle Handle referring to device to be tested
Remarks
The isatty function determines whether handle is associated with a character
device (a terminal, console, printer, or serial port).
Return Value
The isatty function returns a nonzero value if the device is a character
device. Otherwise, the return value is 0.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
Example
/* ISATTY.C: This program checks to see whether stdout has been
* redirected to a file.
*/
#include <stdio.h>
#include <io.h>
void main()
{
if( isatty( fileno( stdout ) ) )
printf( "stdout has not been redirected to a file\n" );
else
printf( "stdout has been redirected to a file\n");
}
Output
stdout has not been redirected to a file
itoa
────────────────────────────────────────────────────────────────────────────
Description
Converts an integer to a string.
#include <stdlib.h> Required only for function declarations
char *itoa( int value, char *string, int radix );
value Number to be converted
string String result
radix Base of value
Remarks
The itoa function converts the digits of the given value argument to a
null-terminated character string and stores the result (up to 17 bytes) in
string. The radix argument specifies the base of value; it must be in the
range 2-36. If radix equals 10 and value is negative, the first character of
the stored string is the minus sign (-).
Return Value
The itoa function returns a pointer to string. There is no error return.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
ltoa, ultoa
Example
/* ITOA.C: This program converts integers of various sizes to strings
* in various radixes.
*/
#include <stdlib.h>
#include <stdio.h>
void main()
{
char buffer[20];
int i = 3445;
long l = -344115L;
unsigned long ul = 1234567890UL;
itoa( i, buffer, 10 );
printf( "String of integer %d (radix 10): %s\n", i, buffer );
itoa( i, buffer, 16 );
printf( "String of integer %d (radix 16): 0x%s\n", i, buffer );
itoa( i, buffer, 2 );
printf( "String of integer %d (radix 2): %s\n", i, buffer );
ltoa( l, buffer, 16 );
printf( "String of long int %ld (radix 16): 0x%s\n", l, buffer );
ultoa( ul, buffer, 16 );
printf( "String of unsigned long %lu (radix 16): 0x%s\n", ul, buffer );
}
Output
String of integer 3445 (radix 10): 3445
String of integer 3445 (radix 16): 0xd75
String of integer 3445 (radix 2): 110101110101
String of long int -344115 (radix 16): 0xfffabfcd
String of unsigned long 1234567890 (radix 16): 0x499602d2
kbhit
────────────────────────────────────────────────────────────────────────────
Description
Checks the console for keyboard input.
#include <conio.h> Required only for function declarations
int kbhit( void );
Remarks
The kbhit function checks the console for a recent keystroke. If the
function returns a nonzero value, a keystroke is waiting in the buffer. The
program can then call getch or getche to get the keystroke.
Return Value
The kbhit function returns a nonzero value if a key has been pressed.
Otherwise, it re-turns 0.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
Example
/* KBHIT.C: This program loops until the user presses a key.
* If kbhit returns nonzero, a keystroke is waiting in the buffer.
* The program can call getch or getche to get the keystroke.
*/
#include <conio.h>
#include <stdio.h>
void main()
{
/* Display message until key is pressed. */
while( !kbhit() )
cputs( "Hit me!! " );
/* Use getch to throw key away. */
printf( "\nKey struck was '%c'\n", getch() );
getch();
}
Output
Hit me!! Hit me!! Hit me!! Hit me!! Hit me!! Hit me!! Hit me!!
Key struck was 'k'
labs
────────────────────────────────────────────────────────────────────────────
Description
Calculates the absolute value of a long integer.
#include <stdlib.h> Required only for function declarations
#include <math.h>
long labs( long n );
n Long-integer value
Remarks
The labs function produces the absolute value of its long-integer argument
n.
Return Value
The labs function returns the absolute value of its argument. There is no
error return.
Compatibility
ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
abs, cabs, fabs
Example
/* ABS.C: This program computes and displays the absolute values of
* several numbers.
*/
#include <stdio.h>
#include <math.h>
#include <stdlib.h>
void main()
{
int ix = -4, iy;
long lx = -41567L, ly;
double dx = -3.141593, dy;
iy = abs( ix );
printf( "The absolute value of %d is %d\n", ix, iy);
ly = labs( lx );
printf( "The absolute value of %ld is %ld\n", lx, ly);
dy = fabs( dx );
printf( "The absolute value of %f is %f\n", dx, dy );
}
Output
The absolute value of -4 is 4
The absolute value of -41567 is 41567
The absolute value of -3.141593 is 3.141593
ldexp, ldexpl
────────────────────────────────────────────────────────────────────────────
Description
Compute a real number from the mantissa and exponent.
#include <math.h>
double ldexp( double x, int exp );
long double ldexpl( long double x, int exp );
x Floating-point value
exp Integer exponent
Remarks
The ldexp and ldexpl functions calculate the value of x * 2exp.
Return Value
The ldexp and ldexpl functions return x * 2exp. If an overflow results, the
functions return ± HUGE_VAL (depending on the sign of x) and set errno to
ERANGE.
The ldexpl function uses the 80-bit, 10-byte coprocessor form of arguments
and return values. See the reference page on the long double functions for
more details on this data type.
Compatibility
ldexp
ANSI DOS OS/2 UNIX XENIX
ldexpl
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
frexp, modf
Example
/* LDEXP.C */
#include <math.h>
#include <stdio.h>
void main()
{
double x = 4.0, y;
int p = 3;
y = ldexp( x, p );
printf( "%2.1f times two to the power of %d is %2.1f\n", x, p, y );
}
Output
4.0 times two to the power of 3 is 32.0
ldiv
────────────────────────────────────────────────────────────────────────────
Description
Computes the quotient and remainder of a long integer.
#include <stdlib.h>
ldiv_t ldiv ( long int numer, long int denom );
numer Numerator
denom Denominator
Remarks
The ldiv function divides numer by denom, computing the quotient and the
remainder. The sign of the quotient is the same as that of the mathematical
quotient. Its absolute value is the largest integer that is less than the
absolute value of the mathematical quotient. If the denominator is 0, the
program will terminate with an error message.
The ldiv function is similar to the div function, with the difference being
that the arguments and the members of the returned structure are all of type
long int.
The ldiv_t structure, defined in STDLIB.H, contains the following elements:
Element Description
────────────────────────────────────────────────────────────────────────────
long int quot Quotient
long int rem Remainder
Return Value
The ldiv function returns a structure of type ldiv_t, comprising both the
quotient and the remainder.
Compatibility
ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
div
Example
/* LDIV.C: This program takes two long integers as command-line
* arguments and displays the results of the integer division.
*/
#include <stdlib.h>
#include <math.h>
#include <stdio.h>
void main()
{
long x = 5149627, y = 234879;
ldiv_t div_result;
div_result = ldiv( x, y );
printf( "For %ld / %ld, the quotient is %ld, and the remainder is
%ld\n",
x, y, div_result.quot, div_result.rem );
}
Output
For 5149627 / 234879, the quotient is 21, and the remainder is 217168
lfind
────────────────────────────────────────────────────────────────────────────
Description
Performs a linear search for the specified key.
#include <search.h> Required only for function declarations
char *lfind( const void *key, const void *base, unsigned int *num,
unsigned int width,
int ( *compare )( const void *elem1, const void *elem2 ) );
key Object to search for
base Pointer to base of search data
num Number of array elements
width Width of array elements
compare( ) Pointer to comparison routine
elem1 Pointer to the key for the search
elem2 Pointer to the array element to be
compared with the key
Remarks
The lfind function performs a linear search for the value key in an array of
num elements; each element is width bytes in size. (Unlike bsearch, lfind
does not require the array to be sorted.) The base argument is a pointer to
the base of the array to be searched.
The compare argument is a pointer to a user-supplied routine that compares
two array elements and then returns a value specifying their relationship.
The lfind function calls the compare routine one or more times during the
search, passing pointers to two array elements on each call. This routine
must compare the elements, then return one of the following values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
Nonzero Elements are different
0 Elements are identical
Return Value
If the key is found, lfind returns a pointer to the element of the array at
base that matches key. If the key is not found, lfind returns NULL.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
bsearch, lsearch, qsort
Example
/* LFIND.C: This program uses lfind to search for the word "hello"
* in the command-line arguments.
*/
#include <search.h>
#include <string.h>
#include <stdio.h>
int compare( char **arg1, char **arg2 );
void main( int argc, char **argv )
{
char **result;
char *key = "hello";
result = (char **)lfind( (char *)&key, (char *)argv,
&argc, sizeof( char * ), compare );
if( result )
printf( "%s found\n", *result );
else
printf( "hello not found!\n" );
}
int compare(char ** arg1, char **arg2 )
{
return( strcmpi( *arg1, *arg2 ) );
}
Output
[C:\LIBREF] lfind What if I said Hello world
Hello found
_lineto Functions
────────────────────────────────────────────────────────────────────────────
Description
Draw lines to specified points.
#include <graph.h>
short _far _lineto( short x, short y );
short _far _lineto_w( double wx, double wy );
x, y End point
wx, wy End point
Remarks
The functions in the _lineto family draw a line from the current graphics
position up to and including the destination point. The destination point
for the _lineto function is given by the view-coordinate point (x, y). The
destination point for the _lineto_w function is given by the
window-coordinate point (wx, wy).
The line is drawn using the current color, logical write mode, and line
style. If no error occurs, _lineto sets the current graphics position to the
view-coordinate point (x, y); _lineto_w sets the current position to the
window-coordinate point (wx, wy).
If you use _floodfill to fill in a closed figure drawn with _lineto calls,
the figure must be drawn with a solid line-style pattern.
Return Value
The _lineto and _lineto_w routines return a nonzero value if anything is
drawn; otherwise, they return 0.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_getcurrentposition functions, _moveto functions, _setlinestyle
Example
/* MOVETO.C: This program draws line segments of different colors. */
#include <graph.h>
#include <stdlib.h>
#include <conio.h>
void main()
{
short x, y, xinc, yinc, color = 1;
struct videoconfig v;
/* Find a valid graphics mode. */
if( !_setvideomode( _MAXCOLORMODE ) )
exit( 1 );
_getvideoconfig( &v );
xinc = v.numxpixels / 50;
yinc = v.numypixels / 50;
for( x = 0, y = v.numypixels - 1; x < v.numxpixels; x += xinc, y -=
yinc )
{
_setcolor( color++ % 16 );
_moveto( x, 0 );
_lineto( 0, y );
}
getch();
_setvideomode( _DEFAULTMODE );
}
localeconv
────────────────────────────────────────────────────────────────────────────
Description
Gets detailed information on locale settings.
#include <locale.h>
struct lconv *localeconv( void );
Remarks
The localeconv function gets detailed information on the locale-specific
settings for numeric formatting of the program's current locale. This
information is stored in a structure of type lconv.
The lconv structure, defined in LOCALE.H, contains the following elements:
Element Description
────────────────────────────────────────────────────────────────────────────
char *decimal_point Decimal-point character for nonmonetary
quantities.
char *thousands_sep Character used to separate groups of
digits to the left of the decimal point
for non-monetary quantities.
char *grouping Size of each group of digits in
non-monetary quantities.
char *int_curr_symbol International currency symbol for the
current locale. The first three
characters specify the alphabetic
international currency symbol as defined
in the ISO 4217 Codes for the
Representation of Currency and Funds
standard. The fourth character
(immediately preceding the null
character) is used to separate the
international currency symbol from the
monetary quantity.
char *currency_symbol Local currency symbol for the current
locale.
char *mon_decimal_point Decimal-point character for monetary
quantities.
char *mon_thousands_sep Separator for groups of digits to the
left of the decimal place in monetary
quantities.
char *mon_grouping Size of each group of digits in monetary
quantities.
char *positive_sign String denoting sign for nonnegative
monetary quantities.
char *negative_sign String denoting sign for negative
monetary
quantities.
char int_frac_digits Number of digits to the right of the
decimal point in internationally
formatted
monetary quantities.
char frac_digits Number of digits to the right of the
decimal point in formatted monetary
quantities.
char p_cs_precedes Set to 1 if the currency symbol precedes
the value for a nonnegative formatted
monetary quantity. Set to 0 if the
symbol follows the value.
char p_sep_by_space Set to 1 if the currency symbol is
separated by a space from the value for
a non-negative formatted monetary
quantity. Set to 0 if there is no space
separation.
char n_cs_precedes Set to 1 if the currency symbol precedes
the value for a negative formatted
monetary quantity. Set to 0 if the
symbol succeeds the value.
char n_sep_by_space Set to 1 if the currency symbol is
separated by a space from the value for
a negative formatted monetary quantity.
Set to 0 if there is no space
separation.
char p_sign_posn Position of positive sign in nonnegative
formatted monetary quantities.
char n_sign_posn Position of positive sign in negative
formatted monetary quantities.
The elements of grouping and mon_grouping are interpreted according to the
following rules:
Value Interpretation
────────────────────────────────────────────────────────────────────────────
CHAR_MAX No further grouping is to be performed.
0 The previous element is to be repeatedly
used for the remainder of the digits.
n The integer value n is the number of
digits that make up the current group.
The next element is examined to
determine the size of the next group of
digits before the current group.
The values for p_sign_posn and n_sign_posn are interpreted according to the
following rules:
Value Interpretation
────────────────────────────────────────────────────────────────────────────
0 Parentheses surround the quantity and
currency symbol
1 Sign string precedes the quantity and
currency symbol
2 Sign string follows the quantity and
currency symbol
3 Sign string immediately precedes the
currency symbol
4 Sign string immediately follows the
currency symbol
Return Value
The localeconv function returns a pointer to a structure of lconv type.
Calls to the setlocale function with category values of LC_ALL, LC_MONETARY,
or LC_NUMERIC will overwrite the contents of the structure.
Compatibility
ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
setlocale, strcoll, strftime, strxfrm
localtime
────────────────────────────────────────────────────────────────────────────
Description
Converts a time value and corrects for the local time zone.
#include <time.h>
struct tm *localtime( const time_t *timer );
timer Pointer to stored time
Remarks
The localtime function converts a time stored as a time_t value and stores
the result in a structure of type tm. The long value timer represents the
seconds elapsed since 00:00:00, January 1, 1970, Greenwich mean time; this
value is usually obtained from the time function.
The fields of the structure type tm store the following values:
Element Value Stored
────────────────────────────────────────────────────────────────────────────
int tm_sec Seconds
int tm_min Minutes
int tm_hour Hours (0 -24)
int tm_mday Day of month (1-31)
int tm_mon Month (0 -11; January = 0)
int tm_year Year (current year minus 1900)
int tm_wday Day of week (0 - 6; Sunday = 0)
int tm_yday Day of year (0 -365; January 1 = 0)
int tm_isdst Nonzero if daylight saving time is in
effect, otherwise 0
Note that the gmtime, mktime, and localtime functions use a single
statically allocated tm structure for the conversion. Each call to one of
these routines destroys the result of the previous call.
The localtime function makes corrections for the local time zone if the user
first sets the environment variable TZ. When TZ is set, three other
environment variables (timezone, daylight, and tzname) are automatically set
as well. See tzset for a description of these variables.
The TZ variable is not part of the ANSI standard definition of localtime but
is a Microsoft extension.
Return Value
The localtime function returns a pointer to the structure result. DOS and
OS/2 do not accommodate dates prior to 1980. If the value in timer
represents a date prior to January 1, 1980, the function returns NULL.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
asctime, ctime, ftime, gmtime, time, tzset
Example
/* LOCALTIM.C: This program uses time to get the current time and
* then uses localtime to convert this time to a structure representing
* the local time. The program converts the result from a 24-hour clock
* to a 12-hour clock and determines the proper extension (AM or PM).
*/
#include <stdio.h>
#include <string.h>
#include <time.h>
void main()
{
struct tm *newtime;
char am_pm[] = "AM";
time_t long_time;
time( &long_time ); /* Get time as long integer. */
newtime = localtime( &long_time ); /* Convert to local time. */
if( newtime->tm_hour < 12 ) /* Set up extension. */
strcpy( am_pm, "AM" );
if( newtime->tm_hour > 12 ) /* Convert from 24-hour */
newtime->tm_hour -=12; /* to 12-hour clock. */
printf( "%.19s %s\n", asctime( newtime ), am_pm );
}
Output
Fri Jun 16 06:27:02 AM
locking
────────────────────────────────────────────────────────────────────────────
Description
Locks or unlocks bytes of a file.
#include <sys\locking.h>
#include <io.h> Required only for function declarations
int locking( int handle, int mode, long nbytes );
handle File handle
mode File-locking mode
nbytes Number of bytes to lock
Remarks
The locking function locks or unlocks nbytes bytes of the file specified by
handle. Locking bytes in a file prevents access to those bytes by other
processes. All locking or unlocking begins at the current position of the
file pointer and proceeds for the next nbytes bytes. It is possible to lock
bytes past the end of the file.
The mode argument specifies the locking action to be performed. It must be
one of the following manifest constants:
Constant Action
────────────────────────────────────────────────────────────────────────────
LK_LOCK Locks the specified bytes. If the bytes
cannot be locked, immediately tries
again after 1 second. If, after 10
attempts, the bytes cannot be locked,
returns an error.
LK_NBLCK Locks the specified bytes. If bytes
cannot be locked, returns an error.
LK_NBRLCK Same as LK_NBLCK.
LK_RLCK Same as LK_LOCK.
LK_UNLCK Unlocks the specified bytes. (The bytes
must have been previously locked.)
More than one region of a file can be locked, but no overlapping regions are
allowed.
When a region of a file is being unlocked, it must correspond to a region
that was previously locked. The locking function does not merge adjacent
regions; if two locked regions are adjacent, each region must be unlocked
separately.
Regions should be locked only briefly and should be unlocked before closing
a file or exiting the program.
The locking function should be used only under OS/2 or under DOS versions
3.0 and later; it has no effect under earlier versions of DOS. Also, file
sharing must be loaded to use the locking function. Note that under DOS
versions 3.0 and 3.1, the files locked by parent processes may become
unlocked when child processes exit.
Return Value
The locking function returns 0 if successful. A return value of -1 indicates
failure, and errno is set to one of the following values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
EACCES Locking violation (file already locked
or unlocked).
EBADF Invalid file handle.
EDEADLOCK Locking violation. This is returned when
the LK_LOCK or LK_RLCK flag is specified
and the file cannot be locked after 10
attempts.
EINVAL An invalid argument was given to the
function.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
creat, open
Example
/* LOCKING.C: This program opens a file with sharing. It locks some
* bytes before reading them, then unlocks them. Note that the program
* works correctly only if the following conditions are met:
* - The file exists
* - The program is run under OS/2, under DOS 3.0 or later
* with file sharing installed (SHARE.COM or SHARE.EXE), or
* if a Microsoft Networks compatible network is running
*/
#include <io.h>
#include <sys\types.h>
#include <sys\stat.h>
#include <sys\locking.h>
#include <share.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
void main()
{
int fh, numread;
long pos, result;
char buffer[40];
/* Quit if can't open file or DOS version doesn't support sharing. */
fh = sopen( "locking.c", O_RDWR, SH_DENYNO, S_IREAD | S_IWRITE );
if( (fh == -1) || (_osmajor < 3) )
exit( 1 );
/* Lock some bytes and read them. Then unlock. */
if( locking( fh, LK_NBLCK, 30L ) != -1 )
{
printf( "No one can change these bytes while I'm reading them\n" );
numread = read( fh, buffer, 30 );
printf( "%d bytes read: %.30s\n", numread, buffer );
locking( fh, LK_UNLCK, 30L );
printf( "Now I'm done. Do what you will with them\n" );
}
else
perror( "Locking failed\n" );
close( fh );
}
Output
No one can change these bytes while I'm reading them
30 bytes read: /* LOCKING.C: This program ope
Now I'm done. Do what you will with them
log Functions
────────────────────────────────────────────────────────────────────────────
Description
Calculate logarithms.
#include <math.h>
double log( double x );
double log10( double x );
long double logl( long double x );
long double log10l( long double x );
x Value whose logarithm is to be found
Remarks
The log and log10 functions calculate the natural logarithm and the base-10
logarithm, respectively, of x. The logl and log10l functions are the 80-bit
counterparts and use the 80-bit, 10-byte coprocessor form of arguments and
return values. See the reference page on the long double functions for more
details on this data type.
Return Value
The log functions return the logarithm of the argument x. If x is negative,
the functions print a DOMAIN error message to stderr, return the value
-HUGE_VAL, and set errno to EDOM. If x is 0, the functions print a SING
error message to stderr, return the value -HUGE_VAL, and set errno to
ERANGE.
Error handling can be modified by using the matherr or _matherrl routine.
Compatibility
log, log10
ANSI DOS OS/2 UNIX XENIX
logl, log10l
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
exp, matherr, pow functions
Example
/* LOG.C: This program uses log and log10 to calculate the natural
* logarithm and the base-10 logarithm of 9,000.
*/
#include <math.h>
#include <stdio.h>
void main()
{
double x = 9000.0;
double y;
y = log( x );
printf( "log( %.2f ) = %f\n", x, y );
y = log10( x );
printf( "log10( %.2f ) = %f\n", x, y );
}
Output
log( 9000.00 ) = 9.104980
log10( 9000.00 ) = 3.954243
long double Functions
────────────────────────────────────────────────────────────────────────────
The 8087 family of numeric coprocessor chips supports the 80-bit precision
floating-point data type. In Microsoft C, version 6.0, the long double
functions, whose names end with l, map the C long double type into this
80-bit, 10-byte form. Unlike the regular floating-point functions (such as
acos), which return values of type double, these long double functions (such
as acosl) return values of type long double. The long double functions also
return their values on the coprocessor stack for all calling conventions.
The long double type is also supported by the addition of the "L" prefix for
a floating-point format specification in the printf and scanf family of
functions.
The long double versions are described on the reference pages for their
regular counterparts. These are the regular C run-time math functions with
corresponding long double equivalents:
Regular Function Long Double Form
────────────────────────────────────────────────────────────────────────────
acos acosl
asin asinl
atan atanl
atan2 atan2l
atof _atold
cabs cabsl
ceil ceill
cos cosl
cosh coshl
exp expl
fabs fabsl
floor floorl
fmod fmodl
frexp frexpl
hypot hypotl
ldexp ldexpl
log logl
log10 log10l
matherr _matherrl
modf modfl
pow powl
sin sinl
sinh sinhl
sqrt sqrtl
tan tanl
tanh tanhl
longjmp
────────────────────────────────────────────────────────────────────────────
Description
Restores stack environment and execution locale.
#include <setjmp.h>
void longjmp( jmp_buf env, int value );
env Variable in which environment is stored
value Value to be returned to setjmp call
Remarks
The longjmp function restores a stack environment and execution locale
previously saved in env by setjmp. The setjmp and longjmp functions provide
a way to execute a nonlocal goto; they are typically used to pass execution
control to error handling or recovery code in a previously called routine
without using the normal call and return conventions.
A call to setjmp causes the current stack environment to be saved in env. A
subsequent call to longjmp restores the saved environment and returns
control to the point immediately following the corresponding setjmp call.
Execution resumes as if value had just been returned by the setjmp call. The
values of all variables (except register variables) that are accessible to
the routine receiving control contain the values they had when longjmp was
called. The values of register variables are unpredictable.
The longjmp function must be called before the function that called setjmp
returns. If longjmp is called after the function calling setjmp returns,
unpredictable program behavior results.
The value returned by setjmp must be nonzero. If value is passed as 0, the
value 1 is substituted in the actual return.
Observe the following three restrictions when using longjmp:
1. Do not assume that the values of the register variables will remain
the same. The values of register variables in the routine calling
setjmp may not be restored to the proper values after longjmp is
executed.
2. Do not use longjmp to transfer control from within one overlay to
within another. The overlay manager keeps the overlay in memory after
a call to longjmp.
3. Do not use longjmp to transfer control out of an interrupt-handling
routine unless the interrupt is caused by a floating-point exception.
In this case, a program may return from an interrupt handler via
longjmp if it first reinitializes the floating-point math package by
calling _fpreset.
Return Value
None.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
setjmp
Example
See the example for _fpreset.
_lrotl, _lrotr
────────────────────────────────────────────────────────────────────────────
Description
Rotate bits to the left (_lrotl) or right (_lrotr).
#include <stdlib.h>
unsigned long _lrotl( unsigned long value, int shift );
unsigned long _lrotr( unsigned long value, int shift );
value Value to be rotated
shift Number of bits to shift
Remarks
The _lrotl and _lrotr functions rotate value by shift bits. The _lrotl
function rotates the value left. The _lrotr function rotates the value
right. Both functions "wrap" bits rotated off one end of value to the other
end.
Return Value
Both functions return the rotated value. There is no error return.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_rotl, _rotr
Example
/* LROT.C */
#include <stdlib.h>
#include <stdio.h>
void main()
{
unsigned long val = 0x0fac35791;
printf( "0x%8.8lx rotated left eight times is 0x%8.8lx\n",
val, _lrotl( val, 8 ) );
printf( "0x%8.8lx rotated right four times is 0x%8.8lx\n",
val, _lrotr( val, 4 ) );
}
Output
0xfac35791 rotated left eight times is 0xc35791fa
0xfac35791 rotated right four times is 0x1fac3579
lsearch
────────────────────────────────────────────────────────────────────────────
Description
Performs a linear search for a value; adds to end of list if not found.
#include <search.h> Required only for function declarations
char *lsearch( const void *key, const void *base, unsigned int *num,
unsigned int width, int ( *compare )( const void *elem1, const void *elem2
) );
key Object to search for
base Pointer to base of search data
num Number of elements
width Width of elements
compare Pointer to comparison routine
elem1 Pointer to the key for the search
elem2 Pointer to the array element to be
compared with the key
Remarks
The lsearch function performs a linear search for the value key in an array
of num elements, each of width bytes in size. (Unlike bsearch, lsearch does
not require the array to be sorted.) The base argument is a pointer to the
base of the array to be searched.
If key is not found, lsearch adds it to the end of the array.
The compare argument is a pointer to a user-supplied routine that compares
two array elements and returns a value specifying their relationship. The
lsearch function calls the compare routine one or more times during the
search, passing pointers to two array elements on each call. This routine
must compare the elements, then return one of the following values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
Nonzero Elements are different
0 Elements are identical
Return Value
If the key is found, lsearch returns a pointer to the element of the array
at base that matches key. If the key is not found, lsearch returns a pointer
to the newly added item at the end of the array.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
bsearch, lfind
Example
See the example for lfind.
lseek
────────────────────────────────────────────────────────────────────────────
Description
Moves a file pointer to the specified location.
#include <io.h> Required only for function declarations
#include <stdio.h>
long lseek( int handle, long offset, int origin );
handle Handle referring to open file
offset Number of bytes from origin
origin Initial position
Remarks
The lseek function moves the file pointer associated with handle to a new
location that is offset bytes from origin. The next operation on the file
occurs at the new location. The origin argument must be one of the following
constants, which are defined in STDIO.H:
Origin Definition
────────────────────────────────────────────────────────────────────────────
SEEK_SET Beginning of file
SEEK_CUR Current position of file pointer
SEEK_END End of file
The lseek function can be used to reposition the pointer anywhere in a file.
The pointer can also be positioned beyond the end of the file. However, an
attempt to position the pointer before the beginning of the file causes an
error.
Return Value
The lseek function returns the offset, in bytes, of the new position from
the beginning of the file. The function returns -1L to indicate an error and
sets errno to one of the following values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
EBADF Invalid file handle
EINVAL Invalid value for origin, or position
specified by offset is before the
beginning of the file
On devices incapable of seeking (such as terminals and printers), the return
value is undefined.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
fseek, tell
Example
/* LSEEK.C: This program first opens a file named LSEEK.C.
* It then uses lseek to find the beginning of the file,
* to find the current position in the file, and to find
* the end of the file.
*/
#include <io.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
void main()
{
int fh;
long pos; /* Position of file pointer */
char buffer[10];
fh = open( "lseek.c", O_RDONLY );
/* Seek the beginning of the file: */
pos = lseek( fh, 0L, SEEK_SET );
if( pos == -1L )
perror( "lseek to beginning failed" );
else
printf( "Position for beginning of file seek = %ld\n", pos );
/* Move file pointer a little */
read( fh, buffer, 10 );
/* Find current position: */
pos = lseek( fh, 0L, SEEK_CUR );
if( pos == -1L )
perror( "lseek to current position failed" );
else
printf( "Position for current position seek = %ld\n", pos );
/* Set the end of the file: */
pos = lseek( fh, 0L, SEEK_END );
if( pos == -1L )
perror( "lseek to end failed" );
else
printf( "Position for end of file seek = %ld\n", pos );
close( fh );
}
Output
Position for beginning of file seek = 0
Position for current position seek = 10
Position for end of file seek = 1183
ltoa
────────────────────────────────────────────────────────────────────────────
Description
Converts a long integer to a string.
#include <stdlib.h> Required only for function declarations
char *ltoa( long value, char *string, int radix );
value Number to be converted
string String result
radix Base of value
Remarks
The ltoa function converts the digits of value to a null-terminated
character string and stores the result (up to 33 bytes) in string. The radix
argument specifies the base of value, which must be in the range 2-36. If
radix equals 10 and value is negative, the first character of the stored
string is the minus sign (-).
Return Value
The ltoa function returns a pointer to string. There is no error return.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
itoa, ultoa
Example
/* ITOA.C: This program converts integers of various sizes to strings
* in various radixes.
*/
#include <stdlib.h>
#include <stdio.h>
void main()
{
char buffer[20];
int i = 3445;
long l = -344115L;
unsigned long ul = 1234567890UL;
itoa( i, buffer, 10 );
printf( "String of integer %d (radix 10): %s\n", i, buffer );
itoa( i, buffer, 16 );
printf( "String of integer %d (radix 16): 0x%s\n", i, buffer );
itoa( i, buffer, 2 );
printf( "String of integer %d (radix 2): %s\n", i, buffer );
ltoa( l, buffer, 16 );
printf( "String of long int %ld (radix 16): 0x%s\n", l, buffer );
ultoa( ul, buffer, 16 );
printf( "String of unsigned long %lu (radix 16): 0x%s\n", ul, buffer );
}
Output
String of integer 3445 (radix 10): 3445
String of integer 3445 (radix 16): 0xd75
String of integer 3445 (radix 2): 110101110101
String of long int -344115 (radix 16): 0xfffabfcd
String of unsigned long 1234567890 (radix 16): 0x499602d2
_makepath
────────────────────────────────────────────────────────────────────────────
Description
Creates a single path name.
#include <stdlib.h>
void _makepath( char *path, char *drive, char *dir, char *fname, char *ext
);
path Full path-name buffer
drive Drive letter
dir Directory path
fname File name
ext File extension
Remarks
The _makepath routine creates a single path name, composed of a drive
letter, directory path, file name, and file-name extension. The path
argument should point to an empty buffer large enough to hold the complete
path name. The constant _MAX_PATH, defined in STDLIB.H, specifies the
maximum size path that the _makepath function can handle. The other
arguments point to buffers containing the path-name elements:
Buffer Description
────────────────────────────────────────────────────────────────────────────
drive The drive argument contains a letter (A,
B, etc.) corresponding to the desired
drive and an optional trailing colon.
The _makepath routine will insert the
colon automatically in the composite
path name if it is missing. If drive is
a null character or an empty string, no
drive letter and colon will appear in
the composite path string.
dir The dir argument contains the path of
directories, not including the drive
designator or the actual file name. The
trailing slash is optional, and either
forward slashes ( / ) or backslashes ( \
) or both may be used in a single dir
argument. If a trailing slash ( / or \ )
is not specified, it will be inserted
automatically. If dir is a null
character or an empty string, no slash
is inserted in the composite path
string.
fname The fname argument contains the base
file name without any extensions. If
fname is NULL or points to an empty
string, no file name is inserted in the
composite path string.
ext The ext argument contains the actual
file-name extension, with or without a
leading period (.). The _makepath
routine will insert the period
automatically if it does not appear in
ext. If ext is a null character or an
empty string, no period is inserted in
the composite path string.
There are no size limits on any of the above four fields. However, the
composite path must be no larger than the _MAX_PATH constant. The _MAX_PATH
limit permits a path name much larger than any of the current versions of
DOS or OS/2 will handle.
Return Value
None.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_fullpath, _splitpath
Example
/* MAKEPATH.C */
#include <stdlib.h>
#include <stdio.h>
void main()
{
char path_buffer[_MAX_PATH];
char drive[_MAX_DRIVE];
char dir[_MAX_DIR];
char fname[_MAX_FNAME];
char ext[_MAX_EXT];
_makepath( path_buffer, "c", "\\c60\\clibref\\", "makepath", "c" );
printf( "Path created with _makepath: %s\n\n", path_buffer );
_splitpath( path_buffer, drive, dir, fname, ext );
printf( "Path extracted with _splitpath:\n" );
printf( " Drive: %s\n", drive );
printf( " Dir: %s\n", dir );
printf( " Filename: %s\n", fname );
printf( " Ext: %s\n", ext );
}
Output
Path created with _makepath: c:\c60\clibref\makepath.c
Path extracted with _splitpath:
Drive: c:
Dir: \c60\clibref\
Filename: makepath
Ext: .c
♀
malloc Functions
────────────────────────────────────────────────────────────────────────────
Description
Allocate memory blocks.
#include <stdlib.h> For ANSI compatibility (malloc only)
#include <malloc.h> Required only for function declarations
void *malloc( size_t size );
void _based(void) *_bmalloc( _segment seg, size_t size );
void _far *_fmalloc( size_t size );
void _near *_nmalloc( size_t size );
size Bytes to allocate
seg Based heap segment selector
Remarks
Functions in the malloc family allocate a memory block of at least size
bytes. The block may be larger than size bytes because of space required for
alignment and maintenance information. If size is 0, each of these functions
allocates a zero-length item in the heap and returns a valid pointer to that
item.
The storage space pointed to by the return value is guaranteed to be
suitably aligned for storage of any type of object. To get a pointer to a
type other than void, use a type cast on the return value.
In large data models (compact-, large-, and huge-model programs), malloc
maps to _fmalloc. In small data models (tiny-, small-, and medium-model
programs), malloc maps to _nmalloc.
The _fmalloc function allocates a memory block of at least size bytes in the
far heap, which is outside the default data segment. The return value is a
far pointer to void.
The _bmalloc function allocates a memory block of at least size bytes in the
based heap segment specified by the segment selector seg.
The malloc functions allocate memory in the heap segment specified below.
Function Heap Segment
────────────────────────────────────────────────────────────────────────────
malloc Depends on data model of program
_bmalloc Based heap segment specified by seg
value
_fmalloc Far heap (outside default data segment)
_nmalloc Near heap (within default data segment)
If you are creating programs to run in both real mode and protected mode,
you should probably bind with APILMR.OBJ as well as API.LIB and OS2.LIB.
This is necessary if a program will use the _nmalloc function.
The functions listed below call the malloc family of routines. In addition,
the C start-up code uses malloc to allocate storage for the environ/envp and
argv strings and arrays.
The following routines call malloc:
╓┌─────────┌─────────┌───────────────────────────────────────────────────────╖
────────────────────────────────────────────────────────────────────────────
calloc fseek _searchenv
────────────────────────────────────────────────────────────────────────────
execv fsetpos spawnv
execve fullpath spawnve
execvp fwrite spawnvp
execvpe getc spawnvpe
execl getchar spawnl
execle getcwd spawnle
execlp _getcwd spawnlp
execlpe gets spawnlpe
fgetc getw strdup
fgetchar _popen system
────────────────────────────────────────────────────────────────────────────
fgetchar _popen system
fgets printf scanf
fprint putc setvbuf
fputc putchar tempnam
fputchar putenv ungetc
fputs puts vfprintf
fread putw vprintf
fscanf
The following routines call malloc only in the multithread run-time
libraries (LLIBCMT, LLIBCDLL, CDLLOBJS), not in the regular run-time
libraries:
╓┌─────────────┌──────────┌──────────────────────────────────────────────────╖
────────────────────────────────────────────────────────────────────────────
asctime localtime _strerrpr
_beginthread mktime tmpfile
ctime sterror tmpnam
gmtime
The following routines call _nmalloc:
────────────────────────────────────────────────────────────────────────────
_nrealloc
_ncalloc
_nstrdup
realloc (in small data models)
The following routines call _fmalloc:
────────────────────────────────────────────────────────────────────────────
_frealloc
_fcalloc
_fstrdup
realloc (in large data models)
────────────────────────────────────────────────────────────────────────────
C5.1 Differences
In Microsoft C version 5.1, the _fmalloc function would retry allocating
within the default data segment (i.e., in the near heap) if sufficient
memory was not available outside the default data segment. Version 6.0
returns NULL under these conditions.
In version 5.1, the start-up code used malloc only if wild-card expansion
was used.
The _freect, _memavl, and _memmax functions called malloc in version 5.1 but
do not do so in version 6.0.
────────────────────────────────────────────────────────────────────────────
Return Value
The malloc function returns a void pointer to the allocated space. The
_nmalloc function returns a ( void _near * ) and _fmalloc returns a ( void
_far * ). The _bmalloc function returns a ( void _based( void ) * ).
The _malloc, _fmalloc and _nmalloc functions return NULL if there is
insufficient memory available. The _bmalloc function returns _NULLOFF if
there is insufficient memory available.
Always check the return from the malloc function, even if the amount of
memory requested is small.
Compatibility
malloc
ANSI DOS OS/2 UNIX XENIX
_bmalloc, _fmalloc, _nmalloc
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
calloc functions, free functions, realloc functions
Example
/* MALLOC.C: This program allocates memory with malloc, then frees
* the memory with free.
*/
#include <stdlib.h> /* Definition of _MAX_PATH */
#include <stdio.h>
#include <malloc.h>
void main()
{
char *string;
/* Allocate space for a path name */
string = malloc( _MAX_PATH );
if( string == NULL )
printf( "Insufficient memory available\n" );
else
printf( "Memory space allocated for pathname\n" );
free( string );
printf( "Memory freed\n" );
}
Output
Memory space allocated for pathname
Memory freed
matherr, _matherrl
────────────────────────────────────────────────────────────────────────────
Description
Handle math errors.
#include <math.h>
int matherr( struct exception *except );
int _matherrl( struct _exceptionl *except );
except Pointer to structure containing error
information
Remarks
The matherr functions process errors generated by the functions of the math
library. The math functions call the appropriate matherr routine whenever an
error is detected. The _matherrl function uses the 80-bit, 10-byte
coprocessor form of arguments and return values. See the reference page on
the long double functions for more details on this data type.
The user can provide a different definition of the matherr or _matherrl
function to carry out special error handling.
When an error occurs in a math routine, matherr is called with a pointer to
an exception type structure (defined in MATH.H) as an argument.
The exception structure contains the following elements:
Element Description
────────────────────────────────────────────────────────────────────────────
int type Exception type
char *name Name of function where error occurred
double arg1, arg2 First and second (if any) argument to
function
double retval Value to be returned by function
The type specifies the type of math error. It is one of the following
values, defined in MATH.H:
Value Meaning
────────────────────────────────────────────────────────────────────────────
DOMAIN Argument domain error
SING Argument singularity
OVERFLOW Overflow range error
PLOSS Partial loss of significance
TLOSS Total loss of significance
UNDERFLOW Underflow range error
The structure member name is a pointer to a null-terminated string
containing the name of the function that caused the error. The structure
members arg1 and arg2 specify the values that caused the error. (If only one
argument is given, it is stored in arg1.)
The default return value for the given error is retval. If you change the
return value, remember that the return value must specify whether an error
actually occurred. If the matherr function returns 0, an error message is
displayed and errno is set to an appropriate error value. If matherr returns
a nonzero value, no error message is displayed, and errno remains unchanged.
Return Value
The matherr functions should return 0 to indicate an error, and a nonzero
value to indicate successful corrective action.
Compatibility
matherr
▼ ANSI DOS OS/2 UNIX XENIX
_matherrl
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
acos functions, asin functions, atan functions, bessel functions, cabs, cos
functions, exp, hypot, log functions, pow, sin functions, sqrt, tan
functions
Example
/* MATHERR.C: To use matherr, you must turn off the Extended Dictionary
* flag within the Microsoft Programmer's WorkBench environment, or use
the
* /NOE linker option outside the environment. For example:
* CL matherr.c /link /NOE
*/
#include <math.h>
#include <string.h>
#include <stdio.h>
void main()
{
/* Do several math operations that cause errors. The matherr
* routine handles DOMAIN errors, but lets the system handle
* other errors normally.
*/
printf( "log( -2.0 ) = %e\n", log( -2.0 ) );
printf( "log10( -5.0 ) = %e\n", log10( -5.0 ) );
printf( "log( 0.0 ) = %e\n", log( 0.0 ) );
}
/* Handle several math errors caused by passing a negative argument
* to log or log10 (DOMAIN errors). When this happens, matherr returns
* the natural or base-10 logarithm of the absolute value of the
* argument and suppresses the usual error message.
*/
int matherr( struct exception *except )
{
/* Handle DOMAIN errors for log or log10. */
if( except->type == DOMAIN )
{
if( strcmp( except->name, "log" ) == 0 )
{
except->retval = log( -(except->arg1) );
printf( "Special: using absolute value: %s: DOMAIN error\n",
except->name );
return 1;
}
else if( strcmp( except->name, "log10" ) == 0 )
{
except->retval = log10( -(except->arg1) );
printf( "Special: using absolute value: %s: DOMAIN error\n",
except->name );
return 1;
}
}
else
{
printf( "Normal: " );
return 0; /* Else use the default actions */
}
}
Output
Special: using absolute value: log: DOMAIN error
log( -2.0 ) = 6.931472e-001
Special: using absolute value: log10: DOMAIN error
log10( -5.0 ) = 6.989700e-001
Normal: log: SING error
log( 0.0 ) = -1.797693e+308
max
────────────────────────────────────────────────────────────────────────────
Description
Returns the larger of two values.
#include <stdlib.h>
type max( type a, type b );
type Any numeric data type
a, b Values of any numeric type to be
compared
Remarks
The max macro compares two values and returns the value of the larger one.
The arguments can be of any numeric data type, signed or unsigned. Both
arguments and the return value must be of the same data type.
Return Value
The macro returns the larger of the two arguments.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
min
Example
/* MINMAX.C */
#include <stdlib.h>
#include <stdio.h>
void main()
{
int a = 10;
int b = 21;
printf( "The larger of %d and %d is %d\n", a, b, max( a, b ) );
printf( "The smaller of %d and %d is %d\n", a, b, min( a, b ) );
}
Output
The larger of 10 and 21 is 21
The smaller of 10 and 21 is 10
_memavl
────────────────────────────────────────────────────────────────────────────
Description
Returns the size of memory available.
#include <malloc.h> Required only for function declarations
size_t _memavl( void );
Remarks
The _memavl function returns the approximate size, in bytes, of the memory
available for dynamic memory allocation in the near heap (default data
segment). The _memavl function can be used with calloc, malloc, or realloc
in tiny, small, and medium memory models and with _ncalloc, _nmalloc or
_nrealloc in any memory model.
The number returned by the _memavl function may not be the number of
contiguous bytes. Consequently, a call to malloc requesting allocation of
the size returned by _memavl may not succeed. Use the _memmax function to
find the size of the largest available contiguous block of memory.
Return Value
The _memavl function returns the size in bytes as an unsigned integer.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
calloc functions, _freect, malloc functions, _memmax, realloc functions
Example
/* MEMAVL.C: This program uses _memavl to determine the amount of
* memory available for dynamic allocation. It then uses malloc to
* allocate space for 5,000 long integers and uses _memavl again to
* determine the new amount of available memory.
*/
#include <malloc.h>
#include <stdio.h>
void main()
{
long *longptr;
printf( "Memory available before _nmalloc = %u\n", _memavl() );
if( (longptr = _nmalloc( 5000 * sizeof( long ) )) != NULL )
{
printf( "Memory available after _nmalloc = %u\n", _memavl() );
_nfree( longptr );
}
}
Output
Memory available before _nmalloc = 60906
Memory available after _nmalloc = 40390
memccpy, _fmemccpy
────────────────────────────────────────────────────────────────────────────
Description
Copy characters from a buffer.
#include <memory.h> Required only for function declarations
#include <string.h> Use either STRING.H or MEMORY.H
void *memccpy( void *dest, void *src, int c, unsigned int count );
void _far * _far _fmemccpy( void _far *dest, void _far *src, int c,
unsigned int count );
dest Pointer to destination
src Pointer to source
c Last character to copy
count Number of characters
Remarks
The memccpy and _fmemccpy functions copy 0 or more bytes of src to dest,
halting when the character c has been copied or when count bytes have been
copied, whichever comes first.
The _fmemccpy function is a model-independent (large-model) form of the
memccpy function. It can be called from any point in any program.
Return Value
If the character c is copied, memccpy or _fmemccpy returns a pointer (or far
pointer) to the byte in dest that immediately follows the character. If c is
not copied, memccpy returns NULL.
Compatibility
memccpy
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
_fmemccpy
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
memchr, memcmp, memcpy, memset
Example
/* MEMCCPY.C */
#include <memory.h>
#include <stdio.h>
#include <string.h>
char string1[60] = "The quick brown dog jumps over the lazy fox";
void main()
{
char buffer[61];
char *pdest;
printf( "Function:\tmemccpy 60 characters or to character 's'\n" );
printf( "Source:\t\t%s\n", string1 );
pdest = memccpy( buffer, string1, 's', 60 );
*pdest = '\0';
printf( "Result:\t\t%s\n", buffer );
printf( "Length:\t\t%d characters\n\n", strlen( buffer ) );
}
Output
Function: memccpy 60 characters or to character 's'
Source: The quick brown dog jumps over the lazy fox
Result: The quick brown dog jumps
Length: 25 characters
memchr, _fmemchr
────────────────────────────────────────────────────────────────────────────
Description
Find characters in a buffer.
#include <memory.h> Required only for function declarations
#include <string.h> Use either STRING.H (for ANSI
compatibility) or MEMORY.H
void *memchr( const void *buf, int c, size_t count );
void _far * _far _fmemchr( const void _far *buf, int c, size_t count );
buf Pointer to buffer
c Character to look for
count Number of characters
Remarks
The memchr and _fmemchr functions look for the first occurrence of c in the
first count bytes of buf. They stop when they find c or when they have
checked the first count bytes.
The _fmemchr function is a model-independent (large-model) form of the
memchr function. It can be called from any point in any program.
Return Value
If successful, memchr or _fmemchr returns a pointer (or a far pointer) to
the first location of c in buf. Otherwise, they return NULL.
Compatibility
memchr
ANSI DOS OS/2 UNIX XENIX
_fmemchr
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
memccpy, memcmp, memcpy, memset, strchr
Example
/* MEMCHR.C */
#include <memory.h>
#include <stdio.h>
int ch = 'r';
char str[] = "lazy";
char string[] = "The quick brown dog jumps over the lazy fox";
char fmt1[] = " 1 2 3 4 5";
char fmt2[] = "12345678901234567890123456789012345678901234567890";
void main()
{
char *pdest;
int result;
printf( "String to be searched:\n\t\t%s\n", string );
printf( "\t\t%s\n\t\t%s\n\n", fmt1, fmt2 );
printf( "Search char:\t%c\n", ch );
pdest = memchr( string, ch, sizeof( string ) );
result = pdest - string + 1;
if( pdest != NULL )
printf( "Result:\t\t%c found at position %d\n\n", ch, result );
else
printf( "Result:\t\t%c not found\n" );
}
Output
String to be searched:
The quick brown dog jumps over the lazy fox
1 2 3 4 5
12345678901234567890123456789012345678901234567890
Search char: r
Result: r found at position 12
memcmp, _fmemcmp
────────────────────────────────────────────────────────────────────────────
Description
Compare characters in two buffers.
#include <memory.h> Required only for function declarations
#include <string.h> Use either STRING.H (for ANSI
compatibility) or MEMORY.H
int memcmp( const void *buf1, const void *buf2, size_t count );
int _far _fmemcmp( const void _far *buf1, const void _far *buf2, size_t
count );
buf1 First buffer
buf2 Second buffer
count Number of characters
Remarks
The memcmp and _fmemcmp functions compare the first count bytes of buf1 and
buf2 and return a value indicating their relationship, as follows:
Value Meaning
────────────────────────────────────────────────────────────────────────────
< 0 buf1 less than buf2
= 0 buf1 identical to buf2
> 0 buf1 greater than buf2
The _fmemcmp function is a model-independent (large-model) form of the
memcmp function. It can be called from any point in program.
There is a semantic difference between the function version of memcmp and
its intrinsic version. The function version supports huge pointers in
compact-, large-, and huge-model programs, but the intrinsic version does
not.
Return Value
The memcmp function returns an integer value, as described above.
Compatibility
memcmp
ANSI DOS OS/2 UNIX XENIX
_fmemcmp
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
memccpy, memchr, memcpy, memset, strcmp, strncmp
Example
/* MEMCMP.C: This program uses memcmp to compare the strings named
* first and second. If the first 19 bytes of the strings are
* equal, the program considers the strings to be equal.
*/
#include <string.h>
#include <stdio.h>
void main()
{
char first[] = "12345678901234567890";
char second[] = "12345678901234567891";
int result;
printf( "Compare '%.19s' to '%.19s':\n", first, second );
result = memcmp( first, second, 19 );
if( result < 0 )
printf( "First is less than second.\n" );
else if( result == 0 )
printf( "First is equal to second.\n" );
else if( result > 0 )
printf( "First is greater than second.\n" );
printf( "Compare '%.20s' to '%.20s':\n", first, second );
result = memcmp( first, second, 20 );
if( result < 0 )
printf( "First is less than second.\n" );
else if( result == 0 )
printf( "First is equal to second.\n" );
else if( result > 0 )
printf( "First is greater than second.\n" );
}
Output
Compare '1234567890123456789' to '1234567890123456789':
First is equal to second.
Compare '12345678901234567890' to '12345678901234567891':
First is less than second.
memcpy, _fmemcpy
────────────────────────────────────────────────────────────────────────────
Description
Copy characters between buffers.
#include <memory.h> Required only for function declarations
#include <string.h> Use either STRING.H (for ANSI
compatibility) or MEMORY.H
void *memcpy( void *dest, const void *src, size_t count );
void _far * _far _fmemcpy( void _far *dest, const void _far *src, size_t
count );
dest New buffer
src Buffer to copy from
count Number of characters to copy
Remarks
The memcpy and _fmemcpy functions copy count bytes of src to dest. If the
source and destination overlap, these functions do not ensure that the
original source bytes in the overlapping region are copied before being
overwritten. Use memmove to handle overlapping regions.
The _fmemcpy function is a model-independent (large-model) form of the
memcpy function. It can be called from any point in any program.
There is a semantic difference between the function version of memcpy and
its intrinsic version. The function version supports huge pointers in
compact-, large-, and huge-model programs, but the intrinsic version does
not.
Return Value
The memcpy and _fmemcpy functions return a pointer to dest.
Compatibility
memcpy
ANSI DOS OS/2 UNIX XENIX
_fmemcpy
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
memccpy, memchr, memcmp, memmove, memset, strcpy, strncpy
Example
/* MEMCPY.C. Illustrate overlapping copy: memmove handles it
* correctly; memcpy does not.
*/
#include <memory.h>
#include <string.h>
#include <stdio.h>
char string1[60] = "The quick brown dog jumps over the lazy fox";
char string2[60] = "The quick brown fox jumps over the lazy dog";
/* 1 2 3 4 5
* 12345678901234567890123456789012345678901234567890
*/
void main()
{
printf( "Function:\tmemcpy without overlap\n" );
printf( "Source:\t\t%s\n", string1 + 40 );
printf( "Destination:\t%s\n", string1 + 16 );
memcpy( string1 + 16, string1 + 40, 3 );
printf( "Result:\t\t%s\n", string1 );
printf( "Length:\t\t%d characters\n\n", strlen( string1 ) );
/* Restore string1 to original contents */
memcpy( string1 + 16, string2 + 40, 3 );
printf( "Function:\tmemmove with overlap\n" );
printf( "Source:\t\t%s\n", string2 + 4 );
printf( "Destination:\t%s\n", string2 + 10 );
memmove( string2 + 10, string2 + 4, 40 );
printf( "Result:\t\t%s\n", string2 );
printf( "Length:\t\t%d characters\n\n", strlen( string2 ) );
printf( "Function:\tmemcpy with overlap\n" );
printf( "Source:\t\t%s\n", string1 + 4 );
printf( "Destination:\t%s\n", string1 + 10 );
memcpy( string1 + 10, string1 + 4, 40 );
printf( "Result:\t\t%s\n", string1 );
printf( "Length:\t\t%d characters\n\n", strlen( string1 ) );
}
Output
Function: memcpy without overlap
Source: fox
Destination: dog jumps over the lazy fox
Result: The quick brown fox jumps over the lazy fox
Length: 43 characters
Function: memmove with overlap
Source: quick brown fox jumps over the lazy dog
Destination: brown fox jumps over the lazy dog
Result: The quick quick brown fox jumps over the lazy dog
Length: 49 characters
Function: memcpy with overlap
Source: quick brown dog jumps over the lazy fox
Destination: brown dog jumps over the lazy fox
Result: The quick quick quick quick quick quick quick quic
Length: 50 characters
memicmp, _fmemicmp
────────────────────────────────────────────────────────────────────────────
Description
Compare characters in two buffers (case-insensitive).
#include <memory.h> Required only for function declarations
#include <string.h> Use either STRING.H or MEMORY.H
int memicmp( void *buf1, void *buf2, unsigned int count );
int _far _fmemicmp( void _far *buf1, void _far *buf2, unsigned int count
);
buf1 First buffer
buf2 Second buffer
count Number of characters
Remarks
The memicmp and _fmemicmp functions compare the first count characters of
the two buffers buf1 and buf2 byte-by-byte. The comparison is made without
regard to the case of letters in the two buffers; that is, uppercase and
lowercase letters are considered equivalent. The memicmp and _fmemicmp
functions return a value indicating the relationship of the two buffers, as
follows:
Value Meaning
────────────────────────────────────────────────────────────────────────────
< 0 buf1 less than buf2
= 0 buf1 identical to buf2
> 0 buf1 greater than buf2
The _fmemicmp function is a model-independent (large-model) form of the
memicmp function. It can be called from any point in any program.
Return Value
The memicmp and _fmemicmp functions return an integer value, as described
above.
Compatibility
memicmp
▼ ANSI DOS OS/2 UNIX XENIX
_fmemicmp
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
memccpy, memchr, memcmp, memcpy, memset, stricmp, strnicmp
Example
/* MEMICMP.C: This program uses memicmp to compare the first
* 29 letters of the strings named first and second without
* regard to the case of the letters.
*/
#include <memory.h>
#include <stdio.h>
#include <string.h>
void main()
{
int result;
char first[] = "Those Who Will Not Learn from History";
char second[] = "THOSE WHO WILL NOT LEARN FROM their mistakes";
/* Note that the 29th character is right here ^ */
printf( "Compare '%.29s' to '%.29s'\n", first, second );
result = memicmp( first, second, 29 );
if( result < 0 )
printf( "First is less than second.\n" );
else if( result == 0 )
printf( "First is equal to second.\n" );
else if( result > 0 )
printf( "First is greater than second.\n" );
}
Output
Compare 'Those Who Will Not Learn from' to 'THOSE WHO WILL NOT LEARN FROM'
First is equal to second.
_memmax
────────────────────────────────────────────────────────────────────────────
Description
Finds the size of the largest contiguous memory block.
#include <malloc.h>
size_t _memmax( void );
Remarks
The _memmax function returns the size (in bytes) of the largest contiguous
block of memory that can be allocated from the near heap (i.e., the default
data segment). Calling _nmalloc with the value returned by the _memmax
function will succeed as long as _memmax returns a nonzero value.
Return Value
The function returns the block size, if successful. Otherwise, it returns 0,
indicating that nothing more can be allocated from the near heap.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
malloc functions, msize functions
Example
/* MEMMAX.C: This program uses _memmax and _nmalloc to allocate
* the largest block of memory available in the near heap.
*/
#include <stddef.h>
#include <malloc.h>
#include <stdio.h>
void main()
{
size_t contig;
char *p;
/* Determine contiguous memory size */
contig = _memmax();
printf( "Largest block of available memory is %u bytes long\n", contig
);
if( contig )
{
p = _nmalloc( contig * sizeof( int ) );
if( p == NULL )
printf( "Error with malloc (should never occur)\n" );
else
{
printf( "Maximum allocation succeeded\n" );
free( p );
}
}
else
printf( "Near heap is already full\n" );
}
Output
Largest block of available memory is 60844 bytes long
Maximum allocation succeeded
memmove, _fmemmove
────────────────────────────────────────────────────────────────────────────
Description
Move one buffer to another.
#include <string.h>
void *memmove( void *dest, const void *src, size_t count );
void _far * _far _fmemmove( void _far *dest, const void _far *src, size_t
count );
dest Destination object
src Source object
count Number of characters to copy
Remarks
The memmove and _fmemmove functions copy count characters from the source
(src) to the destination (dest). If some regions of the source area and the
destination overlap, the memmove and _fmemmove functions ensure that the
original source bytes in the overlapping region are copied before being
overwritten.
The _fmemmove function is a model-independent (large-model) form of the
memmove function. It can be called from any point in any program.
Return Value
The memmove and _fmemmove functions return the value of dest.
Compatibility
memmove
ANSI DOS OS/2 ▼ UNIX ▼ XENIX
_fmemmove
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
memccpy, memcpy, strccpy, strncpy
Example
/* MEMCPY.C. Illustrate overlapping copy: memmove handles it
* correctly; memcpy does not.
*/
#include <memory.h>
#include <string.h>
#include <stdio.h>
char string1[60] = "The quick brown dog jumps over the lazy fox";
char string2[60] = "The quick brown fox jumps over the lazy dog";
/* 1 2 3 4 5
* 12345678901234567890123456789012345678901234567890
*/
void main()
{
printf( "Function:\tmemcpy without overlap\n" );
printf( "Source:\t\t%s\n", string1 + 40 );
printf( "Destination:\t%s\n", string1 + 16 );
memcpy( string1 + 16, string1 + 40, 3 );
printf( "Result:\t\t%s\n", string1 );
printf( "Length:\t\t%d characters\n\n", strlen( string1 ) );
/* Restore string1 to original contents */
memcpy( string1 + 16, string2 + 40, 3 );
printf( "Function:\tmemmove with overlap\n" );
printf( "Source:\t\t%s\n", string2 + 4 );
printf( "Destination:\t%s\n", string2 + 10 );
memmove( string2 + 10, string2 + 4, 40 );
printf( "Result:\t\t%s\n", string2 );
printf( "Length:\t\t%d characters\n\n", strlen( string2 ) );
printf( "Function:\tmemcpy with overlap\n" );
printf( "Source:\t\t%s\n", string1 + 4 );
printf( "Destination:\t%s\n", string1 + 10 );
memcpy( string1 + 10, string1 + 4, 40 );
printf( "Result:\t\t%s\n", string1 );
printf( "Length:\t\t%d characters\n\n", strlen( string1 ) );
}
Output
Function: memcpy without overlap
Source: fox
Destination: dog jumps over the lazy fox
Result: The quick brown fox jumps over the lazy fox
Length: 43 characters
Function: memmove with overlap
Source: quick brown fox jumps over the lazy dog
Destination: brown fox jumps over the lazy dog
Result: The quick quick brown fox jumps over the lazy dog
Length: 49 characters
Function: memcpy with overlap
Source: quick brown dog jumps over the lazy fox
Destination: brown dog jumps over the lazy fox
Result: The quick quick quick quick quick quick quick quic
Length: 50 characters
memset, _fmemset
────────────────────────────────────────────────────────────────────────────
Description
Set buffers to a specified character.
#include <memory.h> Required only for function declarations
#include <string.h> Use either STRING.H (for ANSI
compatibility) or MEMORY.H
void *memset( void *dest, int c, size_t count );
void _far * _far _fmemset( void _far *dest, int c, size_t count );
dest Pointer to destination
c Character to set
count Number of characters
Remarks
The memset and _fmemset functions set the first count bytes of dest to the
character c.
The _fmemset function is a model-independent (large-model) form of the
memset function. It can be called from any point in any program.
There is a semantic difference between the function version of memset and
its intrinsic version. The function version supports huge pointers in
compact-, large-, and huge-model programs, but the intrinsic version does
not.
Return Value
The memset and _fmemset functions return a pointer to dest.
Compatibility
memset
ANSI DOS OS/2 UNIX XENIX
_fmemset
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
memccpy, memchr, memcmp, memcpy, strnset
Example
/* MEMSET.C: This program uses memset to set the first four bytes
* of buffer to "*".
*/
#include <memory.h>
#include <stdio.h>
void main()
{
char buffer[] = "This is a test of the memset function";
printf( "Before: %s\n", buffer );
memset( buffer, '*', 4 );
printf( "After: %s\n", buffer );
}
Output
Before: This is a test of the memset function
After: **** is a test of the memset function
min
────────────────────────────────────────────────────────────────────────────
Description
Returns the smaller of two values.
#include <stdlib.h>
type min( type a, type b );
type Any numeric data type
a, b Values of any numeric type to be
compared
Remarks
The min macro compares two values and returns the value of the smaller one.
The arguments can be of any numeric data type, signed or unsigned. Both
arguments and the return value must be of the same data type.
Return Value
The macro returns the smaller of the two arguments.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
max
Example
/* MINMAX.C */
#include <stdlib.h>
#include <stdio.h>
void main()
{
int a = 10;
int b = 21;
printf( "The larger of %d and %d is %d\n", a, b, max( a, b ) );
printf( "The smaller of %d and %d is %d\n", a, b, min( a, b ) );
}
Output
The larger of 10 and 21 is 21
The smaller of 10 and 21 is 10
mkdir
────────────────────────────────────────────────────────────────────────────
Description
Creates a new directory.
#include <direct.h> Required only for function declarations
int mkdir( char *dirname );
dirname Path name for new directory
Remarks
The mkdir function creates a new directory with the specified dirname. Only
one directory can be created at a time, so only the last component of
dirname can name a new directory.
The mkdir function does not do any translation of path-name delimiters. Both
DOS and OS/ 2 accept either " \" or "/ " internally as valid delimiters
within path names.
Return Value
The mkdir function returns the value 0 if the new directory was created. A
return value of -1 indicates an error, and errno is set to one of the
following values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
EACCES Directory not created. The given name is
the name of an
existing file, directory, or device.
ENOENT Path name not found.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
chdir, rmdir
Example
/* MAKEDIR.C */
#include <direct.h>
#include <stdlib.h>
#include <stdio.h>
void main()
{
int result;
if( mkdir( "\\testtmp" ) == 0 )
{
printf( "Directory '\\testtmp' was successfully created\n" );
system( "dir \\testtmp" );
if( rmdir( "\\testtmp" ) == 0 )
printf( "Directory '\\testtmp' was successfully removed\n" );
else
printf( "Problem removing directory '\\testtmp'\n" );
}
else
printf( "Problem creating directory '\\testtmp'\n" );
}
Output
Directory '\testtmp' was successfully created
The volume label in drive C is OS2.
Directory of C:\TESTTMP
. <DIR> 6-19-89 11:20a
.. <DIR> 6-19-89 11:20a
2 File(s) 12730368 bytes free
Directory '\testtmp' was successfully removed
mktemp
────────────────────────────────────────────────────────────────────────────
Description
Creates a unique file name.
#include <io.h> Required only for function declarations
char *mktemp( char *template );
template File-name pattern
Remarks
The mktemp function creates a unique file name by modifying the given
template argument. The template argument has the form:
baseXXXXXX
where base is the part of the new file name that you supply, and the X's are
placeholders for the part supplied by mktemp; mktemp preserves base and
replaces the six trailing X's with an alphanumeric character followed by a
five-digit value. The five-digit value is a unique number identifying the
calling process. The alphanumeric character is 0 ('0') the first time mktemp
is called with a given template.
In subsequent calls from the same process with copies of the same template,
mktemp checks to see if previously returned names have been used to create
files. If no file exists for a given name, mktemp returns that name. If
files exist for all previously returned names, mktemp creates a new name by
replacing the alphanumeric character in the name with the next available
lowercase letter. For example, if the first name returned is t012345 and
this name is used to create a file, the next name returned will be ta12345.
When creating new names, mktemp uses, in order, '0' and then the lowercase
letters 'a' through 'z'.
Note that the original template is modified by the first call to mktemp. If
you then call the mktemp function again with the same template (i.e., the
original one), you will get an error.
The mktemp function generates unique file names but does not create or open
files.
Return Value
The mktemp function returns a pointer to the modified template. The return
value is NULL if the template argument is badly formed or no more unique
names can be created from the given template.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
fopen, getpid, open, tempnam, tmpfile
Example
/* MKTEMP.C: The program uses mktemp to create five unique file names.
* It opens each file name to ensure that the next name is unique.
*/
#include <io.h>
#include <string.h>
#include <stdio.h>
char *template = "fnXXXXXX";
char *result;
char names[5][9];
void main()
{
int i;
FILE *fp;
for( i = 0; i < 5; i++ )
{
strcpy( names[i], template );
/* Attempt to find a unique file name: */
result = mktemp( names[i] );
if( result == NULL )
printf( "Problem creating the template" );
else
{
if( (fp = fopen( result, "w" )) != NULL )
printf( "Unique file name is %s\n", result );
else
printf( "Cannot open %s\n", result );
fclose( fp );
}
}
}
Output
Unique file name is fn000686
Unique file name is fna00686
Unique file name is fnb00686
Unique file name is fnc00686
Unique file name is fnd00686
mktime
────────────────────────────────────────────────────────────────────────────
Description
Converts the local time to a calendar value.
#include <time.h>
time_t mktime( struct tm *timeptr );
timeptr Pointer to time structure
Remarks
The mktime function converts the supplied time structure (possibly
incomplete) pointed to by timeptr into a fully defined structure with
"normalized" values and then converts it to a time_t calendar time value.
The structure for the tm is described in the reference page for asctime.
The converted time has the same encoding as the values returned by the time
function. The original values of the tm_wday and tm_yday components of the
timeptr structure are ignored, and the original values of the other
components are not restricted to their normal ranges.
If successful, mktime sets the values of tm_wday and tm_yday appropriately,
and sets the other components to represent the specified calendar time, but
with their values forced to the normal ranges; the final value of tm_mday is
not set until tm_mon and tm_year are determined.
DOS and OS/2 do not accommodate dates prior to 1980. If timeptr references a
date before January 1, 1980, mktime returns -1.
Note that the gmtime and localtime functions use a single statically
allocated buffer for the conversion. If you supply this buffer to mktime,
the previous contents will be destroyed.
Return Value
The mktime function returns the specified calendar time encoded as a value
of type time_t. If the calendar time cannot be represented, the function
returns the value -1 cast as type time_t.
Compatibility
ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
asctime, gmtime, localtime, time
Example
/* MKTIME.C: The example takes a number of days as input and returns
* the time, the current date, and the specified number of days.
*/
#include <time.h>
#include <stdio.h>
void main()
{
struct tm when;
time_t now, result;
int days;
time( &now );
when = *localtime( &now );
printf( "Current time is %s\n", asctime( &when ) );
printf( "How many days to look ahead: " );
scanf( "%d", &days );
when.tm_mday = when.tm_mday + days;
if( (result = mktime( &when )) != (time_t)-1 )
printf( "In %d days the time will be %s\n",
days, asctime( &when ) );
else
perror( "mktime failed" );
}
Output
Current time is Mon Jun 19 11:45:20 1989
How many days to look ahead: 23
In 23 days the time will be Wed Jul 12 11:45:20 1989
modf, modfl
────────────────────────────────────────────────────────────────────────────
Description
Split a floating-point value into a mantissa and an exponent.
#include <math.h>
double modf( double x, double *intptr );
long double modfl( long double x, long double *intptr );
x Floating-point value
intptr Pointer to stored integer portion
Remarks
The modf functions break down the floating-point value x into fractional and
integer parts, each of which has the same sign as x. The signed fractional
portion of x is returned. The integer portion is stored as a floating-point
value at intptr.
The modfl function uses the 80-bit, 10-byte coprocessor form of arguments
and return values. See the reference page on the long double functions for
more details on this data type.
Return Value
The modf and modfl functions return the signed fractional portion of x.
There is no error return.
Compatibility
modf
ANSI DOS OS/2 UNIX XENIX
modfl
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
frexp, ldexp
Example
/* MODF.C */
#include <math.h>
#include <stdio.h>
void main()
{
double x, y, n;
x = -14.87654321; /* Divide x into its fractional */
y = modf( x, &n ); /* and integer parts */
printf( "For %f, the fraction is %f and the integer is %.f\n", x, y, n
);
}
Output
For -14.876543, the fraction is -0.876543 and the integer is -14
movedata
────────────────────────────────────────────────────────────────────────────
Description
Moves characters to another segment.
#include <memory.h> Required only for function declarations
#include <string.h> Use either STRING.H (for ANSI
compatibility) or MEMORY.H
void movedata( unsigned int srcseg, unsigned int srcoff, unsigned int
destseg,
unsigned int destoff, unsigned int count );
srcseg Segment address of source
srcoff Segment offset of source
destseg Segment address of destination
destoff Segment offset of destination
count Number of bytes
Remarks
The movedata function copies count bytes from the source address specified
by srcseg:srcoff to the destination address specified by destseg:destoff.
The movedata function was intended to move far data in small-data-model
programs. The newer model-independent _fmemcpy and _fmemmove functions
should be used instead of the movedata function. In large-data-model
programs, the memcpy and memmove functions can also be used.
Segment values for the srcseg and destseg arguments can be obtained by using
either the segread function or the FP_SEG macro.
The movedata function does not handle all cases of overlapping moves
correctly. These occur when part of the destination is the same memory area
as part of the source. The memmove function correctly handles overlapping
moves.
Return Value
None.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
FP_OFF, FP_SEG, memcpy, memmove, segread
Example
/* MOVEDATA.C */
#include <memory.h>
#include <stdio.h>
#include <string.h>
#include <dos.h>
#include <malloc.h>
char _far *src = "This is a test.";
void main()
{
char _far *dest;
if( (dest = _fmalloc( 80 )) != NULL )
{
movedata( FP_SEG( src ), FP_OFF( src ),
FP_SEG( dest ), FP_OFF( dest ), _fstrlen( src ) + 1 );
printf( "The source data at %Fp is '%Fs'\n", src, src );
printf( "The destination data at %Fp is '%Fs'\n", dest, dest );
_ffree( dest );
}
}
Output
The source data at 2D0A:02B8 is 'This is a test.'
The destination data at 3D0B:0016 is 'This is a test.'
_moveto Functions
────────────────────────────────────────────────────────────────────────────
Description
Move current graphics positions.
#include <graph.h>
struct xycoord _far _moveto( short x, short y );
struct _wxycoord _far _moveto_w( double wx, double wy );
x, y View-coordinate point
wx, wy Window-coordinate point
Remarks
The _moveto functions move the current position to the specified point. The
_moveto function uses the view-coordinate point (x, y) as the current
position. The _moveto_w function uses the window-coordinate point (wx, wy)
as the current position. No drawing takes place.
Return Value
The function returns the coordinates of the previous position. The _moveto
function returns the coordinates in an xycoord structure. The xycoord
structure, defined in GRAPH.H, contains the following elements:
Element Description
────────────────────────────────────────────────────────────────────────────
short xcoord x coordinate
short ycoord y coordinate
The _moveto_w function returns the coordinates in an _wxycoord structure,
defined in GRAPH.H. The _wxycoord structure contains the following elements:
Element Description
────────────────────────────────────────────────────────────────────────────
double wx x window coordinate
double wy y window coordinate
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_lineto functions
Example
/* MOVETO.C: This program draws line segments of different colors. */
#include <graph.h>
#include <stdlib.h>
#include <conio.h>
void main()
{
short x, y, xinc, yinc, color = 1;
struct videoconfig v;
/* Find a valid graphics mode. */
if( !_setvideomode( _MAXCOLORMODE ) )
exit( 1 );
_getvideoconfig( &v );
xinc = v.numxpixels / 50;
yinc = v.numypixels / 50;
for( x = 0, y = v.numypixels - 1; x < v.numxpixels; x += xinc, y -=
yinc )
{
_setcolor( color++ % 16 );
_moveto( x, 0 );
_lineto( 0, y );
}
getch();
_setvideomode( _DEFAULTMODE );
}
_msize Functions
────────────────────────────────────────────────────────────────────────────
Description
Return the size of a memory block allocated in the heap.
#include <malloc.h> Required only for function declarations
size_t _msize( void *memblock );
size_t _bmsize( _segment seg, void _based( void ) *memblock );
size_t _fmsize( void _far *memblock );
size_t _nmsize( void _near *memblock );
memblock Pointer to memory block
seg Based-heap segment selector
Remarks
The _msize family of functions returns the size, in bytes, of the memory
block allocated by a call to the appropriate version of the calloc, malloc,
or realloc functions.
In large data models (compact-, large-, and huge-model programs), _msize
maps to _fmsize. In small data models (tiny-, small-, and medium-model
programs), _msize maps to _nmsize.
The _nmsize function returns the size (in bytes) of the memory block
allocated by a call to _nmalloc, and the _fmsize function returns the size
(in bytes) of the memory block allocated by a call to _fmalloc or _frealloc.
The _bmsize function returns the size of a block allocated in segment seg by
a call to _bmalloc, _bcalloc, or _brealloc.
The location of the memory block is indicated below:
Function Data Segment
────────────────────────────────────────────────────────────────────────────
_msize Depends on data model of program
_bmsize Based heap segment specified by seg
value
_fmsize Far heap segment (outside default data
segment)
_nmsize Default data segment (inside near heap)
Return Value
All four functions return the size (in bytes) as an unsigned integer.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
calloc functions, _expand functions, malloc functions, realloc functions
Example
/* REALLOC.C: This program allocates a block of memory for buffer
* and then uses _msize to display the size of that block. Next, it
* uses realloc to expand the amount of memory used by buffer
* and then calls _msize again to display the new amount of
* memory allocated to buffer.
*/
#include <stdio.h>
#include <malloc.h>
#include <stdlib.h>
void main()
{
long *buffer;
size_t size;
if( (buffer = (long *)malloc( 1000 * sizeof( long ) )) == NULL )
exit( 1 );
size = _msize( buffer );
printf( "Size of block after malloc of 1000 longs: %u\n", size );
/* Reallocate and show new size: */
if( (buffer = realloc( buffer, size + (1000 * sizeof( long )) )) ==
NULL )
exit( 1 );
size = _msize( buffer );
printf( "Size of block after realloc of 1000 more longs: %u\n", size );
free( buffer );
}
Output
Size of block after malloc of 1000 longs: 4000
Size of block after realloc of 1000 more longs: 8000
onexit
────────────────────────────────────────────────────────────────────────────
Description
Registers a routine to be called at exit time.
#include <stdlib.h>
onexit_t onexit( onexit_t func );
func Pointer to function to be called at exit
Remarks
The onexit function is passed the address of a function (func) to be called
when the program terminates normally. Successive calls to onexit create a
register of functions that is executed in LIFO (last-in-first-out) order. No
more than 32 functions can be registered with onexit; onexit returns the
value NULL if the number of functions exceeds 32. The functions passed to
onexit cannot take parameters.
The onexit function is not part of the ANSI definition, but is instead a
Microsoft extension. The ANSI-standard atexit function does the same thing
as onexit, and should be used instead of onexit when ANSI portability is
desired.
All routines passed to onexit should have the _loadds attribute if used in
multithread dynamic-link libraries.
Return Value
The onexit function returns a pointer to the function if successful and
returns NULL if there is no space left to store the function pointer.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
exit
Example
/* ONEXIT.C */
#include <stdlib.h>
#include <stdio.h>
/* Prototypes */
void fn1( void ), fn2( void ), fn3( void ), fn4( void );
void main()
{
onexit( fn1 );
onexit( fn2 );
onexit( fn3 );
onexit( fn4 );
printf( "This is executed first.\n" );
}
void fn1()
{
printf( "next.\n" );
}
void fn2()
{
printf( "executed " );
}
void fn3()
{
printf( "is " );
}
void fn4()
{
printf( "This " );
}
Output
This is executed first.
This is executed next.
open
────────────────────────────────────────────────────────────────────────────
Description
Opens a file.
#include <fcntl.h>
#include <sys\types.h>
#include <sys\stat.h>
#include <io.h> Required only for function declarations
int open( char *filename, int oflag [[, int pmode]] );
filename File name
oflag Type of operations allowed
pmode Permission mode
Remarks
The open function opens the file specified by filename and prepares the file
for subsequent reading or writing, as defined by oflag. The oflag argument
is an integer expression formed from one or more of the manifest constants
defined in FCNTL.H (listed below). When two or more manifest constants are
used to form the oflag argument, the constants are combined with the
bitwise-OR operator ( | ). See Section 2.5, "File Handling," for a
discussion of binary and text modes.
The FCNTL.H file defines the following manifest constants:
Constant Meaning
────────────────────────────────────────────────────────────────────────────
O_APPEND Repositions the file pointer to the end
of the file before every write
operation.
O_BINARY Opens file in binary (untranslated)
mode.
O_CREAT Creates and opens a new file for
writing; this has no effect if the file
specified by filename exists.
O_EXCL Returns an error value if the file
specified by filename exists. Only
applies when used with O_CREAT.
O_RDONLY Opens file for reading only; if this
flag is given, neither O_RDWR nor
O_WRONLY can be given.
O_RDWR Opens file for both reading and writing;
if this flag is given, neither O_RDONLY
nor O_WRONLY can be given.
O_TEXT Opens file in text (translated) mode.
O_TRUNC Opens and truncates an existing file to
zero length; the file must have write
permission. The contents of the file are
destroyed. If this flag is given, you
cannot specify O_RDONLY.
O_WRONLY Opens file for writing only; if this
flag is given, neither O_RDONLY nor
O_RDWR can be given.
────────────────────────────────────────────────────────────────────────────
WARNING
Use the O_TRUNC flag with care, as it destroys the complete contents of an
existing file.
────────────────────────────────────────────────────────────────────────────
Either O_RDONLY, O_RDWR, or O_WRONLY must be given to specify the access
mode. There is no default value for the access mode.
The pmode argument is required only when O_CREAT is specified. If the file
exists, pmode is ignored. Otherwise, pmode specifies the file's permission
settings, which are set when the new file is closed for the first time. The
pmode is an integer expression containing one or both of the manifest
constants S_IWRITE and S_IREAD, defined in SYS\STAT.H. When both constants
are given, they are joined with the bitwise-OR operator ( | ). The meaning
of the pmode argument is as follows:
Value Meaning
────────────────────────────────────────────────────────────────────────────
S_IWRITE Writing permitted
S_IREAD Reading permitted
S_IREAD | S_IWRITE Reading and writing permitted
If write permission is not given, the file is read-only. Under DOS and OS/2,
all files are readable; it is not possible to give write-only permission.
Thus the modes S_IWRITE and S_IREAD | S_IWRITE are equivalent.
The open function applies the current file-permission mask to pmode before
setting the permissions (see umask).
The filename argument used in the open function is affected by the DOS
APPEND command.
Note that under DOS versions 3.0 and later, a problem occurs when SHARE is
installed and a new file is opened with oflag set to O_CREAT | O_RDONLY or
O_CREAT | O _WRONLY and pmode set to S_IREAD. Under these conditions, the
operating system prematurely closes the file during system calls made within
open. This problem does not occur under OS/2.
To work around the problem, open the file with the pmode argument set to
S_IWRITE. Then close the file and use chmod to change the access mode back
to S_IREAD. Another work-around is to open the file with pmode set to
S_IREAD and oflag set to O_CREAT | O_RDWR.
Return Value
The open function returns a file handle for the opened file. A return value
of -1 indicates an error, and errno is set to one of the following values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
EACCES Given path name is a directory; or an
attempt was made to open a read-only
file for writing; or a sharing violation
occurred (the file's sharing mode does
not allow the specified operations).
EEXIST The O_CREAT and O_EXCL flags are
specified, but the named file already
exists.
EINVAL An invalid oflag or pmode argument was
given.
EMFILE No more file handles available (too many
open files).
ENOENT File or path name not found.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
access, chmod, close, creat, dup, dup2, fopen, sopen, umask
Example
/* OPEN.C: This program uses open to open a file named OPEN.C for input
* and a file named OPEN.OUT for output. The files are then closed.
*/
#include <fcntl.h>
#include <sys\types.h>
#include <sys\stat.h>
#include <io.h>
#include <stdio.h>
void main()
{
int fh1, fh2;
fh1 = open( "OPEN.C", O_RDONLY );
if( fh1 == -1 )
perror( "open failed on input file" );
else
{
printf( "open succeeded on input file\n" );
close( fh1 );
}
fh2 = open( "OPEN.OUT", O_WRONLY | O_CREAT, S_IREAD | S_IWRITE );
if( fh2 == -1 )
perror( "open failed on output file" );
else
{
printf( "open succeeded on output file\n" );
close( fh2 );
}
}
Output
open succeeded on input file
open succeeded on output file
_outgtext
────────────────────────────────────────────────────────────────────────────
Description
Prints font-based text in graphics mode.
#include <graph.h>
void _far_outgtext( unsigned char_far *text );
text Text string to output
Remarks
The _outgtext function outputs on the screen the null-terminated string that
text points to. The text is output using the current font at the current
graphics position and in the current color.
No formatting is provided, in contrast to the standard console I/O library
routines such as printf.
After it outputs the text, _outgtext updates the current graphics position.
The _outgtext function operates only in graphics video modes (e.g.,
_MRES4COLOR). Because it is a graphics function, the color of text is set by
the _setcolor function, not by the _settextcolor function.
Return Value
None.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_moveto functions, _setcolor, _setfont
Example
/* OUTGTXT.C illustrates font output using functions:
* _registerfonts _setfont _outgtext
* _unregisterfonts _getfontinfo _getgtextextent
* _setgtextvector
*/
#include <conio.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <graph.h>
#define NFONTS 6
unsigned char *face[NFONTS] =
{
"Courier", "Helvetica", "Times Roman", "Modern", "Script", "Roman"
};
unsigned char *options[NFONTS] =
{
"courier", "helv", "tms rmn", "modern", "script", "roman"
};
void main()
{
unsigned char list[20];
char fondir[_MAX_PATH];
struct videoconfig vc;
struct _fontinfo fi;
short fontnum, x, y;
/* Read header info from all .FON files in current or given directory.
*/
if( _registerfonts( "*.FON" ) <= 0 )
{
_outtext( "Enter full path where .FON files are located: " );
gets( fondir );
strcat( fondir, "\\*.FON" );
if( _registerfonts( fondir ) <= 0 )
{
_outtext( "Error: can't register fonts" );
exit( 1 );
}
}
/* Set highest available graphics mode and get configuration. */
if( !_setvideomode( _MAXRESMODE ) )
exit( 1 );
_getvideoconfig( &vc );
/* Display each font name centered on screen. */
for( fontnum = 0; fontnum < NFONTS; fontnum++ )
{
/* Build options string. */
strcat( strcat( strcpy( list, "t'" ), options[fontnum] ), "'");
strcat( list, "h30w24b" );
_clearscreen( _GCLEARSCREEN );
if( _setfont( list ) >= 0 )
{
/* Use length of text and height of font to center text. */
x = (vc.numxpixels / 2) - (_getgtextextent( face[fontnum] ) /
2);
y = (vc.numypixels / 2) + (_getgtextextent( face[fontnum] ) /
2);
if( _getfontinfo( &fi ) )
{
_outtext( "Error: Can't get font information" );
break;
}
_moveto( x, y );
if( vc.numcolors > 2 )
_setcolor( fontnum + 2 );
/* Rotate and display text. */
_setgtextvector( 1, 0 );
_outgtext( face[fontnum] );
_setgtextvector( 0, 1 );
_outgtext( face[fontnum] );
_setgtextvector( -1, 0 );
_outgtext( face[fontnum] );
_setgtextvector( 0, -1 );
_outgtext( face[fontnum] );
}
else
{
_outtext( "Error: Can't set font: " );
_outtext( list );
}
getch();
}
_unregisterfonts();
_setvideomode( _DEFAULTMODE );
}
_outmem
────────────────────────────────────────────────────────────────────────────
Description
Prints text of a specified length in graphics mode.
#include <graph.h>
void _far_outmem( unsigned char_far *text, short length );
text Text string to output
length Length of string to output
Remarks
The _outmem function outputs the string that text points to. The length
argument specifies the number of characters to output.
Unlike _outtext, the _outmem function prints all characters literally,
including ASCII 10, 13, and 0 as the equivalent graphics characters. No
formatting is provided. Text is printed using the current text color,
starting at the current text position.
To output text using special fonts, you must use the _outgtext function.
Return Value
None.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_outtext, _settextcolor, _settextposition, _settextwindow
Example
/* OUTMEM.C illustrates:
* _outmem
*/
#include <stdio.h>
#include <graph.h>
void main()
{
int i, len;
char tmp[10];
_clearscreen( _GCLEARSCREEN );
for( i = 0; i < 256; i++ )
{
_settextposition( (i % 24) + 1, (i / 24) * 7 );
len = sprintf( tmp, "%3d %c", i, i );
_outmem( tmp, len );
}
_settextposition( 24, 1 );
}
outp, outpw
────────────────────────────────────────────────────────────────────────────
Description
Outputs a byte (outp) or a word (outpw) at a port.
#include <conio.h> Required only for function declarations
int outp( unsigned port, int databyte );
unsigned outpw( unsigned port, unsigned dataword );
port Port number
databyte Output value
dataword Output value
Remarks
The outp and outpw functions write a byte and a word, respectively, to the
specified output port. The port argument can be any unsigned integer in the
range 0 - 65,535; byte can be any integer in the range 0 - 255; and
dataword can be any value in the range 0 - 65,535.
Both outp and outpw are supported in OS/2. You must use a .DEF file to
declare the IOSEG segment the run-time library uses to perform input/output
on the port. In addition, the intrinsic (/Oi) versions of these functions do
not work unless you put the code in a segment that is marked with the IOPL
keyword in the .DEF file.
You cannot do IOPL from a regular code segment, so the run-time library has
declared a separate code segment called _IOSEG. In order to use inp, inpw,
outp, or outp in any of the protected mode run-time libraries (?LIBCP,
LLIBCDLL, LLIBCMT, or CDLLOBJS-based DLL), you must have a .DEF file with
this line in it:
SEGMENTS _IOSEG CLASS 'IOSEG_CODE' IOPL
Return Value
The functions return the data output. There is no error return.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
inp, inpw
Example
/* OUTP.C: This program uses inp and outp to make sound of variable tone
* and duration.
*/
#include <conio.h>
#include <stdio.h>
#include <time.h>
void Beep( unsigned duration, unsigned frequency ); /* Prototypes */
void Sleep( clock_t wait );
void main ()
{
Beep( 698, 700 );
Beep( 523, 500 );
}
/* Sounds the speaker for a time specified in microseconds by duration
* at a pitch specified in hertz by frequency.
*/
void Beep( unsigned frequency, unsigned duration )
{
int control;
/* If frequency is 0, Beep doesn't try to make a sound. */
if( frequency )
{
/* 75 is about the shortest reliable duration of a sound. */
if( duration < 75 )
duration = 75;
/* Prepare timer by sending 10111100 to port 43. */
outp( 0x43, 0xb6 );
/* Divide input frequency by timer ticks per second and
* write (byte by byte) to timer.
*/
frequency = (unsigned)(1193180L / frequency);
outp( 0x42, (char)frequency );
outp( 0x42, (char)(frequency >> 8) );
/* Save speaker control byte. */
control = inp( 0x61 );
/* Turn on the speaker (with bits 0 and 1). */
outp( 0x61, control | 0x3 );
}
Sleep( (clock_t)duration );
/* Turn speaker back on if necessary. */
if( frequency )
outp( 0x61, control );
}
/* Pauses for a specified number of microseconds. */
void Sleep( clock_t wait )
{
clock_t goal;
goal = wait + clock();
while( goal > clock() )
;
}
_outtext
────────────────────────────────────────────────────────────────────────────
Description
Prints text in graphics mode.
#include <graph.h>
void _far _outtext( unsigned char _far *text );
text Text string to output
Remarks
The _outtext function outputs the null-terminated string that text points
to. No formatting is provided, in contrast to the standard console I/O
library routines such as printf. This function will work in any screen mode.
Text output begins at the current text position.
To output text using special fonts, you must use the _outgtext function.
Return Value
None.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_outmem, _settextcolor, _settextposition, _settextwindow
Example
/* OUTTXT.C: This example illustrates text output functions:
* _gettextcolor _getbkcolor _gettextposition _outtext
* _settextcolor _setbkcolor _settextposition
*/
#include <conio.h>
#include <stdio.h>
#include <graph.h>
char buffer [80];
void main()
{
/* Save original foreground, background, and text position */
short blink, fgd, oldfgd;
long bgd, oldbgd;
struct rccoord oldpos;
/* Save original foreground, background, and text position. */
oldfgd = _gettextcolor();
oldbgd = _getbkcolor();
oldpos = _gettextposition();
_clearscreen( _GCLEARSCREEN );
/* First time no blink, second time blinking. */
for( blink = 0; blink <= 16; blink += 16 )
{
/* Loop through 8 background colors. */
for( bgd = 0; bgd < 8; bgd++ )
{
_setbkcolor( bgd );
_settextposition( (short)bgd + ((blink / 16) * 9) + 3, 1 );
_settextcolor( 7 );
sprintf(buffer, "Back: %d Fore:", bgd );
_outtext( buffer );
/* Loop through 16 foreground colors. */
for( fgd = 0; fgd < 16; fgd++ )
{
_settextcolor( fgd + blink );
sprintf( buffer, " %2d ", fgd + blink );
_outtext( buffer );
}
}
}
getch();
/* Restore original foreground, background, and text position. */
_settextcolor( oldfgd );
_setbkcolor( oldbgd );
_clearscreen( _GCLEARSCREEN );
_settextposition( oldpos.row, oldpos.col );
}
_pclose
────────────────────────────────────────────────────────────────────────────
Description
Waits for a child command and closes the stream on the associated pipe.
#include <stdio.h> Function declaration
int _pclose( FILE *stream );
stream File stream returned by previous call to
_popen
Remarks
The _pclose function waits for a child command and closes the stream on the
associated pipe. The argument stream is the return value from a previous
call to _popen. The _pclose function looks up the process ID of the child
command started by the associated _popen call, closes the stream, executes a
cwait call on the child command, and returns the exit status of the child
command. See _pipe for a general discussion of pipes in OS/2.
Return Value
The _pclose function returns the exit status of the child command. The
format of the return value is the same as that for cwait, with the exception
that the low-order and high-order bytes are swapped. If an error occurs, -1
is returned.
Compatibility
▼ ANSI ▼ DOS OS/2 UNIX XENIXA similar function (pclose) is
available in the XENIX and UNIX operating environments.
See Also
cwait, _pipe, _popen
Example
See the example for _popen.
perror
────────────────────────────────────────────────────────────────────────────
Description
Prints an error message.
#include <stdio.h> Required only for function declarations
void perror( const char *string );
string String message to print
Remarks
The perror function prints an error message to stderr. The string argument
is printed first, followed by a colon, then by the system error message for
the last library call that produced the error, and finally by a newline
character. If string is a null pointer or a pointer to a null string, perror
prints only the system error message.
The actual error number is stored in the variable errno (defined in
ERRNO.H). The system error messages are accessed through the variable
sys_errlist, which is an array of messages ordered by error number. The
perror function prints the appropriate error message by using the errno
value as an index to sys_errlist. The value of the variable sys_nerr is
defined as the maximum number of elements in the sys_errlist array.
To produce accurate results, perror should be called immediately after a
library routine returns with an error. Otherwise, the errno value may be
overwritten by subsequent calls.
Under DOS and OS/2, some of the errno values listed in ERRNO.H are not used.
These additional errno values are reserved for UNIX and XENIX use. See
Section 3.3, "_doserrno, errno, sys_errlist, sys_nerr," for a list of errno
values used on DOS and OS/2 and the corresponding error messages. The perror
function prints an empty string for any errno value not used under the
operating system.
Return Value
None.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
clearerr, ferror, strerror
Example
/* PERROR.C: This program attempts to open a file named NOSUCHF.ILE.
* Since this file probably doesn't exist, an error message is displayed.
* The same message is created using perror, strerror, and _strerror.
*/
#include <fcntl.h>
#include <sys\types.h>
#include <sys\stat.h>
#include <io.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
void main()
{
int fh;
if( (fh = open( "NOSUCHF.ILE", O_RDONLY )) == -1 )
{
/* Three ways to create error message: */
perror( "perror says open failed" );
printf( "strerror says open failed: %s\n", strerror( errno ) );
printf( _strerror( "_strerror says open failed" ) );
}
else
{
printf( "open succeeded on input file\n" );
close( fh );
}
}
Output
perror says open failed: No such file or directory
strerror says open failed: No such file or directory
_strerror says open failed: No such file or directory
_pg_analyzechart Functions
────────────────────────────────────────────────────────────────────────────
Description
Analyze a series of data.
#include <pgchart.h>
short _far _pg_analyzechart( chartenv _far *env, char _far * _far
*categories,
float _far *values, short n );
short _far _pg_analyzechartms( chartenv _far *env, char _far * _far
*categories,
float _far *values, short nseries, short n, short arraydim,
char _far * _far *serieslabels );
env Chart environment variable
categories Array of category variables
values Array of data values
nseries Number of series to chart
n Number of data values to chart
arraydim Row dimension of data array
serieslabels Array of labels for series
Remarks
The _pg_analyzechart routines analyze a single or multiple series of data
without actually displaying the presentation-graphic image.
The _pg_analyzechart function fills the chart environment with default
values for a single-series bar, column, or line chart, depending on the type
specified by the call to the _pg_defaultchart function. The variables
calculated by _pg_analyzechart reflect the data given in the arguments
categories and values. All arguments are the same as those used with the
_pg_chart function.
The _pg_analyzechartms function fills the chart environment with default
values for a multiseries bar, column, or line chart, depending on which type
is specified in the _pg_defaultchart function. The variables calculated by
_pg_analyzechartms reflect the data given in the arguments categories and
values. All arguments are the same as those used with the _pg_chartms
function.
Boolean flags in the chart environment, such as AUTOSCALE and LEGEND, should
be set to TRUE before calling either _pg_analyzechart function. This will
ensure that the function will calculate all defaults.
For a discussion of the chart environment and related topics, see Section
2.6.2, "Presentation-Graphics Functions."
Return Value
The _pg_analyzechart and _pg_analyzechartms functions return 0 if there were
no errors. A nonzero value indicates a failure.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_pg_chart functions, _pg_defaultchart, _pg_initchart
Example
/* PGACHART.C: This example illustrates presentation-graphics
* analyze functions.
* The example uses
* _pg_analyzechartms
* The same principles apply for
* _pg_analyzepie _pg_analyzechart
* _pg_analyzescatter _pg_analyzescatterms
*/
#include <conio.h>
#include <string.h>
#include <stdlib.h>
#include <graph.h>
#include <pgchart.h>
#define FALSE 0
#define TRUE 1
/* Note data declared as a single-dimension array. The multiseries
* chart functions expect only one dimension. See _pg_chartms
* example for alternate method using multidimension array.
*/
#define TEAMS 4
#define MONTHS 3
float _far values[TEAMS * MONTHS] = { .435, .522, .671,
.533, .431, .590,
.723, .624, .488,
.329, .226, .401 };
char _far *months[MONTHS] = { "May", "June", "July" };
char _far *teams[TEAMS] = { "Reds", "Sox", "Cubs", "Mets" };
void main()
{
chartenv env;
/* Find a valid graphics mode. */
if( !_setvideomode( _MAXRESMODE ) )
exit( 1 );
_pg_initchart(); /* Initialize chart system. */
/* Default multiseries bar chart */
_pg_defaultchart( &env, _PG_BARCHART, _PG_PLAINBARS );
strcpy( env.maintitle.title, "Little League Records - Default" );
_pg_chartms( &env, months, values, TEAMS, MONTHS, MONTHS, teams );
getch();
_clearscreen( _GCLEARSCREEN );
/* Analyze multiseries bar chart with autoscale. This sets all
* default scale values. We want y axis values to be automatic.
*/
_pg_defaultchart( &env, _PG_BARCHART, _PG_PLAINBARS );
strcpy( env.maintitle.title, "Little League Records - Customized" );
env.xaxis.autoscale = TRUE;
_pg_analyzechartms( &env, months, values, TEAMS, MONTHS, MONTHS, teams
);
/* Now customize some of the x axis values. Then draw the chart. */
env.xaxis.autoscale = FALSE;
env.xaxis.scalemax = 1.0; /* Make scale show 0.0 to 1.0. */
env.xaxis.ticinterval = 0.2; /* Don't make scale too crowded. */
env.xaxis.ticdecimals = 3; /* Show three decimals. */
strcpy( env.xaxis.scaletitle.title, "Win/Loss Percentage" );
_pg_chartms( &env, months, values, TEAMS, MONTHS, MONTHS, teams );
getch();
_setvideomode( _DEFAULTMODE );
}
_pg_analyzepie
────────────────────────────────────────────────────────────────────────────
Description
Analyzes a single series of data for a pie chart.
#include <pgchart.h>
short _far _pg_analyzepie( chartenv _far *env, char _far * _far
*categories,
float _far *values, short _far *explode, short n );
env Chart environment variable
categories Array of category variables
values Array of data values
explode Array of explode flags
n Number of data values to chart
Remarks
The _pg_analyzepie function analyzes a single series of data without
actually displaying the graphic image.
The _pg_analyzepie function fills the chart environment for a pie chart
using the data contained in the array values. All arguments are the same as
those used in the _pg_chartpie function.
For a discussion of the chart environment and related topics, see Section
2.6.2, "Presentation-Graphics Functions."
Return Value
The _pg_analyzepie function returns 0 if there were no errors. A nonzero
value indicates a failure.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_pg_chartpie, _pg_defaultchart, _pg_initchart
Example
See the example for _pg_analyzechart.
_pg_analyzescatter Functions
────────────────────────────────────────────────────────────────────────────
Description
Analyze a series of data for a scatter chart.
#include <pgchart.h>
short _far _pg_analyzescatter( chartenv _far *env, float _far *xvalues,
float _far *yvalues, short n );
short _far _pg_analyzescatterms( chartenv _far *env, float _far *xvalues,
float _far *yvalues, short nseries, short n, short rowdim,
char _far * _far *serieslabels );
env Chart environment structure
xvalues Array of x-axis data values
yvalues Array of y-axis data values
n Number of data values to chart
nseries Number of series to chart
rowdim Row dimension of data array
serieslabels Array of labels for series
Remarks
The _pg_analyzescatter set of routines analyzes a single or multiple series
of data without actually displaying the graphic image.
The _pg_analyzescatter function fills the chart environment for a
single-series scatter diagram. The variables calculated by this function
reflect the data given in the arguments xvalues and yvalues. All arguments
are the same as those used in the _pg_chartscatter function.
The _pg_analyzescatterms function fills the chart environment for a
multiseries scatter diagram. The variables calculated by
_pg_analyzescatterms reflect the data given in the arguments xvalues and
yvalues. All arguments are the same as those used in the function
_pg_chartscatterms.
Boolean flags in the chart environment, such as AUTOSCALE and LEGEND, should
be set to TRUE before calling _pg_analyzescatterms; this ensures that the
function will calculate all defaults.
For a discussion of the chart environment and related topics, see Section
2.6.2, "Presentation-Graphics Functions."
Return Value
The _pg_analyzescatter and _pg_analyzescatterms functions return 0 if there
were no errors. A nonzero value indicates a failure.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_pg_chartscatter functions, _pg_defaultchart, _pg_initchart
Example
See the example for _pg_analyzechart.
_pg_chart Functions
────────────────────────────────────────────────────────────────────────────
Description
Display single-series or multiseries charts.
#include <pgchart.h>
short _far _pg_chart( chartenv _far *env, char _far * _far *categories,
float _far *values, short n );
short _far _pg_chartms( chartenv _far *env, char _far * _far *categories,
float _far *values, short nseries, short n, short arraydim,
char _far * _far *serieslabels );
env Chart environment variable
categories Array of category variables
values Array of data values
n Number of data values to chart
nseries Number of series to chart
arraydim Row dimension of data array
serieslabels Array of labels for series
Remarks
The _pg_chart function displays a single-series bar, column, or line chart,
depending on the type specified in the chart environment variable (env).
The _pg_chartms function displays a multiseries bar, column, or line chart,
depending on the type specified in the chart environment. All the series
must contain the same number of data points, specified by the argument n.
The array values is a two-dimensional array containing all value data for
every series to be plotted on the chart. Each column of values represents a
single series. The parameter rowdim is the integer value used to dimension
rows in the array declaration for values.
For example, the following code fragment declares the identifier values to
be a twodimensional floating-point array with 20 rows and 10 columns:
#define ARRAYDIM 20
float values [ARRAYDIM][10];
short rowdim = ARRAYDIM;
Note that the number of columns in the values array cannot exceed 10, the
maximum number of data series on a single chart. Note also that rowdim
must be greater than or equal to the argument n, and the column dimension in
the array declaration must be greater than or equal to the argument nseries.
If n and nseries are set to values less than the full dimensional size of
the values array, only part of the data contained in values will be plotted.
The array serieslabels holds the labels used in the chart legend to identify
each series.
For a discussion of the chart environment and related topics, see Section
2.6.2, "Presentation-Graphics Functions."
Return Value
The _pg_chart and _pg_chartms functions return 0 if there were no errors. A
nonzero value indicates a failure.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_pg_analyzechart functions, _pg_defaultchart, _pg_initchart
Example
/* PGCHART.C: This example illustrates presentation-graphics support
* routines and single-series chart routines, including
* _pg_initchart _pg_defaultchart _pg_chart _pg_chartpie
*/
#include <conio.h>
#include <graph.h>
#include <string.h>
#include <stdlib.h>
#include <pgchart.h>
#define COUNTRIES 5
float _far value[COUNTRIES] = { 42.5, 14.3, 35.2, 21.3, 32.6
};
char _far *category[COUNTRIES] = { "USSR", "France","USA", "UK",
"Other" };
short _far explode[COUNTRIES] = { 0, 1, 0, 1, 0
};
void main()
{
chartenv env;
short mode = _VRES16COLOR;
/* Find a valid graphics mode. */
if( !_setvideomode( _MAXRESMODE ) )
exit( 1 );
_pg_initchart(); /* Initialize chart system. */
/* Single-series bar chart */
_pg_defaultchart( &env, _PG_BARCHART, _PG_PLAINBARS );
strcpy( env.maintitle.title, "Widget Production" );
_pg_chart( &env, category, value, COUNTRIES );
getch();
_clearscreen( _GCLEARSCREEN );
/* Single-series column chart */
_pg_defaultchart( &env, _PG_COLUMNCHART, _PG_PLAINBARS );
strcpy( env.maintitle.title, "Widget Production" );
_pg_chart( &env, category, value, COUNTRIES );
getch();
_clearscreen( _GCLEARSCREEN );
/* Pie chart */
_pg_defaultchart( &env, _PG_PIECHART, _PG_PERCENT );
strcpy( env.maintitle.title, "Widget Production" );
_pg_chartpie( &env, category, value, explode, COUNTRIES );
getch();
_setvideomode( _DEFAULTMODE );
}
_pg_chartscatter Functions
────────────────────────────────────────────────────────────────────────────
Description
Display scatter charts.
#include <pgchart.h>
short _far _pg_chartscatter( chartenv _far *env, float _far *xvalues,
float _far *yvalues, short n );
short _far _pg_chartscatterms( chartenv _far *env, float _far *xvalues,
float _far *yvalues, short nseries, short n, short rowdim,
char _far * _far *serieslabels );
env Chart environment structure
xvalues Array of x-axis data values
yvalues Array of y-axis data values
n Number of data values to chart
nseries Number of series to chart
rowdim Row dimension of data array
serieslabels Array of labels for series
Remarks
The _pg_chartscatter function displays a scatter diagram for a single series
of data.
The _pg_chartscatterms function displays a scatter diagram for more than one
series of data.
The arguments xvalues and yvalues are two-dimensional arrays containing data
for the x axis and y axis, respectively. Columns for each array hold data
for individual series; thus the first columns of xvalues and yvalues contain
plot data for the first series, the second columns contain plot data for the
second series, and so forth.
The n, rowdim, nseries, and serieslabels arguments fulfill the same purposes
as those used in the _pg_chartms function. See _pg_chartms for an
explanation of these arguments.
For a discussion of the chart environment and related topics, see Section
2.6.2, "Presentation-Graphics Functions."
Return Value
The _pg_chartscatter and _pg_chartscatterms functions return 0 if there were
no errors. A nonzero value indicates a failure.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_pg_analyzescatter functions, _pg_defaultchart, _pg_initchart
Example
See the example for _pg_chart.
_pg_chartpie
────────────────────────────────────────────────────────────────────────────
Description
Displays a pie chart.
#include <pgchart.h>
short _far _pg_chartpie( chartenv _far *env, char _far * _far *categories,
float _far *values, short _far *explode, short n );
env Chart environment structure
categories Array of category labels
values Array of data values
explode Array of explode flags
n Number of data values to chart
Remarks
The _pg_chartpie function displays a pie chart for the data contained in the
array values. Pie charts are formed from a single series of data─there is no
multiseries version of pie charts as there is for other chart types.
The array explode must be dimensioned so that its length is greater than or
equal to the argument n. All entries in explode are either 0 or 1. If an
entry is 1, the corresponding pie slice is displayed slightly removed from
the rest of the pie.
For example, if the explode array is initialized as
short explode[5] = {0, 1, 0, 0, 0};
the pie slice corresponding to the second entry of the categories array will
be displayed "exploded" from the other four slices.
For a discussion of the chart environment and related topics, see Section
2.6.2, "Presentation-Graphics Functions."
Return Value
The _pg_chartpie function returns 0 if there were no errors. A nonzero value
indicates a failure.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_pg_analyzepie, _pg_defaultchart, _pg_initchart
Example
See the example for _pg_chart.
_pg_defaultchart
────────────────────────────────────────────────────────────────────────────
Description
Initializes the chart environment.
#include <pgchart.h>
short _far _pg_defaultchart( chartenv _far *env, short charttype, short
chartstyle );
env Chart environment structure
charttype Chart type
chartstyle Chart style
Remarks
The _pg_defaultchart function initializes all necessary variables in the
chart environment for the chart type by the variable charttype.
All title fields in the environment structure are blanked. Titles should be
set in the proper fields after calling _pg_defaultchart.
The charttype variable can be set to one of the following manifest
constants:
Chart Type Description
────────────────────────────────────────────────────────────────────────────
_PG_BARCHART Bar chart
_PG_COLUMNCHART Column chart
_PG_LINECHART Line chart
_PG_PIECHART Pie chart
_PG_SCATTERCHART Scatter chart
The chartstyle variable specifies the style of the chart with either the
number "1" or the number "2." Each of the five types of
presentation-graphics charts can appear in two different chart styles, as
described below:
╓┌───────────┌───────────────────┌───────────────────────────────────────────╖
Chart Type Chart Style 1 Chart Style 2
────────────────────────────────────────────────────────────────────────────
Bar Side by side Stacked
Column Side by side Stacked
Line Points with lines Points only
Pie Percent No percent
Chart Type Chart Style 1 Chart Style 2
────────────────────────────────────────────────────────────────────────────
Scatter Points with lines Points only
In a pie chart, the pieces are "exploded" according to the explode array
argument in the _pg_chartpie function. In the "percent" format, percentages
are printed next to each slice. Bar and column charts have only one style
when displaying a single series of data. The styles "side by side" and
"stacked" are applicable only when more than one series appear on the same
chart. The first style arranges the bars or columns for the different series
side by side, showing relative heights or lengths. The stacked style
emphasizes relative sizes between bars and columns.
Return Value
The _pg_defaultchart function returns 0 if there were no errors. A nonzero
value indicates a failure.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_pg_getchardef, _pg_getpalette, _pg_getstyleset, _pg_hlabelchart,
_pg_initchart, _pg_resetpalette, _pg_resetstyleset, _pg_setchardef,
_pg_setpalette, _pg_setstyleset, _pg_vlabelchart
Example
See the example for _pg_chart.
_pg_getchardef
────────────────────────────────────────────────────────────────────────────
Description
Gets the pixel bit map for the specified character.
#include <pgchart.h>
short _far _pg_getchardef( short charnum, unsigned char _far *chardef );
charnum ASCII number of character
chardef Pointer to 8-by-8 bit map array
Remarks
The _pg_getchardef function retrieves the current 8-by-8 pixel bit map for
the character having the ASCII number charnum. The bit map is stored in the
chardef array.
Return Value
The _pg_getchardef function returns 0 if there were no errors. A nonzero
value indicates an error.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_pg_defaultchart, _pg_initchart, _pg_setchardef
_pg_getpalette
────────────────────────────────────────────────────────────────────────────
Description
Gets palette colors, line styles, and patterns.
#include <pgchart.h>
short _far _pg_getpalette( paletteentry _far *palette );
palette Pointer to first palette structure in
array
Remarks
The _pg_getpalette function retrieves palette colors, line styles, fill
patterns, and plot characters for all palettes. The pointer palette points
to an array of palette structures that will contain the desired palette
values.
The palette used by the presentation-graphics routines is independent of the
palette used by the low-level graphics routines.
Return Value
The function _pg_getpalette returns 0 if there were no errors, and it
returns the value _BADSCREENMODE if current palettes have not been
initialized by a previous call to _pg_setpalette.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_pg_defaultchart, _pg_initchart, _pg_resetpalette, _pg_setpalette
Example
/* PGGPAL.C: This example illustrates presentation-graphics palettes
* and the routines that modify them, including
* _pg_getpalette _pg_resetpalette _pg_setstyleset
* _pg_getstyleset _pg_resetstyleset _pg_vlabelchart
* _pg_hlabelchart _pg_setpalette
*/
#include <conio.h>
#include <string.h>
#include <stdlib.h>
#include <graph.h>
#include <pgchart.h>
#define TEAMS 2
#define MONTHS 3
float _far values[TEAMS][MONTHS] = { { .435, .522, .671 },
{ .533, .431, .401 } };
char _far *months[MONTHS] = { "May", "June", "July" };
char _far *teams[TEAMS] = { "Cubs", "Reds" };
fillmap fill1 = { 0x99, 0x33, 0x66, 0xcc, 0x99, 0x33, 0x66, 0xcc };
fillmap fill2 = { 0x99, 0xcc, 0x66, 0x33, 0x99, 0xcc, 0x66, 0x33 };
styleset styles;
palettetype pal;
void main()
{
chartenv env;
short mode = _VRES16COLOR;
/* Find a valid graphics mode. */
if( !_setvideomode( _MAXRESMODE ) )
exit( 1 );
_pg_initchart(); /* Initialize chart system.
*/
/* Modify global set of line styles used for borders, grids, and
* data connectors. Note that this change is used before
* _pg_defaultchart, which will use the style set.
*/
_pg_getstyleset( styles ); /* Get styles and modify
*/
styles[1] = 0x5555; /* style 1 (used for
*/
_pg_setstyleset( styles ); /* borders)─then set new.
*/
_pg_defaultchart( &env, _PG_BARCHART, _PG_PLAINBARS );
/* Modify palette for data lines, colors, fill patterns, and
* characters. Note that the line styles are set in the palette, not
* in the style set, so that only data connectors will be affected.
*/
_pg_getpalette( pal ); /* Get default palette.
*/
pal[1].plotchar = 16; /* Set to ASCII 16 and 17.
*/
pal[2].plotchar = 17;
memcpy( pal[1].fill, fill1, 8 ); /* Copy fill masks to
palette.*/
memcpy( pal[2].fill, fill2, 8 );
pal[1].color = 3; /* Change palette colors.
*/
pal[2].color = 4;
pal[1].style = 0xfcfc; /* Change palette line
styles.*/
pal[2].style = 0x0303;
_pg_setpalette( pal ); /* Put modified palette.
*/
/* Multiseries bar chart */
strcpy( env.maintitle.title, "Little League Records - Customized" );
_pg_chartms( &env, months, (float _far *)values,
TEAMS, MONTHS, MONTHS, teams );
getch();
_clearscreen( _GCLEARSCREEN );
/* Multiseries line chart */
_pg_defaultchart( &env, _PG_LINECHART, _PG_POINTANDLINE );
strcpy( env.maintitle.title, "Little League Records - Customized" );
_pg_chartms( &env, months, (float _far *)values,
TEAMS, MONTHS, MONTHS, teams );
/* Print labels. */
_pg_hlabelchart( &env, (short)(env.chartwindow.x2 * .75),
(short)(env.chartwindow.y2 * .10),
12, "Up and up!" );
_pg_vlabelchart( &env, (short)(env.chartwindow.x2 * .75),
(short)(env.chartwindow.y2 * .45),
13, "Sliding down!" );
getch();
_clearscreen( _GCLEARSCREEN );
_pg_resetpalette(); /* Restore default palette
*/
_pg_resetstyleset(); /* and style set.
*/
/* Multiseries bar chart */
_pg_defaultchart( &env, _PG_BARCHART, _PG_PLAINBARS );
strcpy( env.maintitle.title, "Little League Records - Default" );
_pg_chartms( &env, months, (float _far *)values,
TEAMS, MONTHS, MONTHS, teams );
getch();
_clearscreen( _GCLEARSCREEN );
/* Multiseries line chart */
_pg_defaultchart( &env, _PG_LINECHART, _PG_POINTANDLINE );
strcpy( env.maintitle.title, "Little League Records - Default" );
_pg_chartms( &env, months, (float _far *)values,
TEAMS, MONTHS, MONTHS, teams );
getch();
_setvideomode( _DEFAULTMODE );
}
_pg_getstyleset
────────────────────────────────────────────────────────────────────────────
Description
Gets the current styleset.
#include <pgchart.h>
void _far _pg_getstyleset( unsigned short _far *styleset );
styleset Pointer to current styleset
Remarks
The _pg_getstyleset function retrieves the contents of the current styleset.
Return Value
None.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_pg_defaultchart, _pg_initchart, _pg_resetstyleset, _pg_setstyleset
Example
See the example for _pg_getpalette.
_pg_hlabelchart
────────────────────────────────────────────────────────────────────────────
Description
Writes text horizontally on the screen.
#include <pgchart.h>
short _far _pg_hlabelchart( chartenv _far *env, short x, short y, short
color,
char _far *label );
env Chart environment structure
x x-coordinate for text
y Pixel y-coordinate for text
color Color code for text
label Label text
Remarks
The _pg_hlabelchart function writes text horizontally on the screen. The
arguments x and y are pixel coordinates for the beginning location of text
relative to the upper-left corner of the chart window.
Return Value
The _pg_hlabelchart functions return 0 if there were no errors. A nonzero
value indicates a failure.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_pg_defaultchart, _pg_initchart, _pg_vlabelchart
Example
See the example for _pg_getpalette.
_pg_initchart
────────────────────────────────────────────────────────────────────────────
Description
Initializes presentation graphics.
#include <pgchart.h>
short _far _pg_initchart( void );
Remarks
The _pg_initchart function initializes the presentation-graphics package. It
initializes the color and style pools, resets the chartline styleset, builds
default palette modes, and reads the presentation-graphics font definition
from the disk. This function is required in all programs that use
presentation graphics. The _pg_initchart function must be called before any
of the other functions in the presentation-graphics library.
The _pg_initchart function assumes a valid graphics mode has been
established. Therefore, it must be called only after a successful call to
the library function _setvideomode.
Return Value
The _pg_initchart functions return 0 if there were no errors. A nonzero
value indicates a failure.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_pg_defaultchart, _pg_getchardef, _pg_getpalette, _pg_getstyleset,
_pg_hlabelchart, _pg_resetpalette, _resetstyleset, _pg_setchardef,
_pg_setpalette, _pg_setstyleset, _pg_vlabelchart, _setvideomode
Example
See the example for _pg_chart.
_pg_resetpalette
────────────────────────────────────────────────────────────────────────────
Description
Resets palette colors, line styles, and patterns to default values.
#include <pgchart.h>
short _far _pg_resetpalette( void );
Remarks
The _pg_resetpalette function sets the palette colors, line styles, fill
patterns, and plot characters for the palette to the default for the current
screen mode.
The palette used by the presentation-graphics routines is independent of the
palette used by the low-level graphics routines.
Return Value
The _pg_resetpalette function returns 0 if there were no errors. If the
screen mode is not valid, the value _BADSCREENMODE is returned.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_pg_defaultchart, _pg_getpalette, _pg_initchart, _pg_setpalette
Example
See the example for _pg_getpalette.
_pg_resetstyleset
────────────────────────────────────────────────────────────────────────────
Description
Resets styleset to default values.
#include <pgchart.h>
void _far _pg_resetstyleset( void );
Remarks
The _pg_resetstyleset function reinitializes the styleset to the default
values for the current screen mode.
Return Value
None.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_pg_defaultchart, _pg_getstyleset, _pg_initchart, _pg_setstyleset
Example
See the example for _pg_getpalette.
_pg_setchardef
────────────────────────────────────────────────────────────────────────────
Description
Sets the pixel bit map for the specified character.
#include <pgchart.h>
short _far _pg_setchardef( short charnum, unsigned char _far *chardef );
charnum ASCII number of character
chardef Pointer to an 8-by-8 bit map array for
the character
Remarks
The _pg_setchardef function sets the 8-by-8 pixel bit map for the character
with the ASCII number charnum. The bit map is stored in the chardef array.
Return Value
The _pg_setchardef function returns 0 if there was no error. A nonzero value
indicates an error.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_pg_defaultchart, _pg_getchardef, _pg_initchart
_pg_setpalette
────────────────────────────────────────────────────────────────────────────
Description
Sets palette colors, line styles, and patterns.
#include <pgchart.h>
short _far _pg_setpalette( paletteentry _far *palette );
palette Pointer to first palette structure in
array
Remarks
The _pg_setpalette function sets palette colors, line styles, fill patterns,
and plot characters for all palettes. The pointer palette points to an array
of palette structures that contain the desired palette values.
The palette used by the presentation-graphics routines is independent of the
palette used by the low-level graphics routines.
Return Value
The _pg_setpalette function returns 0 if there were no errors. If the new
palettes are not valid, the value _BADSCREENMODE is returned.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_pg_defaultchart, _pg_getpalette, _pg_initchart, _pg_resetpalette
Example
See the example for _pg_getpalette.
_pg_setstyleset
────────────────────────────────────────────────────────────────────────────
Description
Sets the current styleset.
#include <pgchart.h>
void _far _pg_setstyleset( unsigned short _far *styleset );
styleset Pointer to new styleset
Remarks
The _pg_setstyleset function sets the current styleset.
Return Value
None.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_pg_defaultchart, _pg_getstyleset, _pg_initchart, _pg_resetstyleset
Example
See the example for _pg_getpalette.
_pg_vlabelchart
────────────────────────────────────────────────────────────────────────────
Description
Writes text vertically on the screen.
#include <pgchart.h>
short _far _pg_vlabelchart( chartenv _far *env, short x, short y, short
color,
char _far *label );
env Chart environment structure
x Pixel x coordinate for text
y Pixel y coordinate for text
color Color code for text
label Label text
Remarks
The _pg_vlabelchart function writes text vertically on the screen. The
arguments x and y are pixel coordinates for the beginning location of text
relative to the upper-left corner of the chart window.
Return Value
The _pg_vlabelchart function returns 0 if there were no errors. A nonzero
value indicates a failure.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_pg_defaultchart, _pg_hlabelchart, _pg_initchart
Example
See the example for _pg_getpalette.
_pie Functions
────────────────────────────────────────────────────────────────────────────
Description
Draw wedge-shaped figures.
#include <graph.h>
short _far _pie( short control, short x1, short y1, short x2, short y2,
short x3, short y3, short x4, short y4 );
short _far _pie_w( short control, double x1, double y1, double x2, double
y2,
double x3, double y3, double x4, double y4 );
short _far _pie_wxy( short control, struct _wxycoord _far *pwxy1,
struct _wxycoord _far *pwxy2, struct _wxycoord _far *pwxy3,
struct _wxycoord _far*pwxy4 );
control Fill-control constant
x1, y1 Upper-left corner of bounding rectangle
x2, y2 Lower-right corner of bounding rectangle
x3, y3 Start vector
x4, y4 End vector
pwxy1 Upper-left corner of bounding rectangle
pwxy2 Lower-right corner of bounding rectangle
pwxy3 Start vector
pwxy4 End vector
Remarks
The _pie functions draw a pie-shaped wedge by drawing an elliptical arc
whose center and two endpoints are joined by lines.
The _pie function uses the view coordinate system. The center of the arc is
the center of the bounding rectangle specified by the view coordinate points
(x1, y1) and (x2, y2). The arc starts where it intersects the vector defined
by (x3, y3) and ends where it intersects the vector (x4, y4).
The _pie_wxy and _pie_w functions use the window coordinate system. The
center of the arc is the center of the bounding rectangle specified by the
window coordinate pairs pwxy1 and pwxy2 for _pie_wxy, and by the points (x1,
y1) and (x2, y2) for _pie_w. The arc starts where it intersects the vector
defined by pwxy3 or (x3, y3) and ends where it intersects the vector defined
by pwxy4 or (x4, y4).
The _wxycoord structure is defined in GRAPH.H and contains the following
elements:
Element Description
────────────────────────────────────────────────────────────────────────────
double wx Window x coordinate
double wy Window y coordinate
The wedge is drawn using the current color moving in a counterclockwise
direction. The control parameter can be one of the following manifest
constants:
Constant Action
────────────────────────────────────────────────────────────────────────────
_GFILLINTERIOR Fills the figure using the current color
and fill mask
_GBORDER Does not fill the figure
The control option given by _GFILLINTERIOR is equivalent to a subsequent
call to the _floodfill function using the approximate center of the arc as
the starting point and the current color (set by _setcolor) as the boundary
color.
Return Value
These functions return a nonzero value if successful; otherwise, they return
0.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_arc functions, _ellipse functions, _floodfill, _getcolor, _lineto
functions, _rectangle functions, _setcolor, _setfillmask
Example
/* PIE.C: This program draws a pie-shaped figure. */
#include <stdlib.h>
#include <conio.h>
#include <graph.h>
void main()
{
/* Find a valid graphics mode. */
if( !_setvideomode( _MAXRESMODE ) )
exit( 1 );
_pie( _GBORDER, 80, 50, 240, 150, 240, 12, 0, 150 );
getch();
_setvideomode( _DEFAULTMODE );
}
_pipe
────────────────────────────────────────────────────────────────────────────
Description
Creates a pipe for reading and writing.
#include <fcntl.h> For O_BINARY and O_TEXT definitions
#include <errno.h> errno definitions
#include <io.h> Prototype declaration
int _pipe( int *phandles, unsigned int psize, int textmode );
phandles[2] Array to hold read and write handles
psize Amount of memory to reserve
textmode File mode
Remarks
A pipe is an artificial file-like I/O channel that a program can create and
use to pass information to other programs. A pipe is similar to a file in
that it has a file pointer or a file descriptor, or both, and can be read
from or written to using the input and output functions of the standard
library. Unlike a file, a pipe does not represent a specific file or device.
Instead, a pipe represents temporary storage in memory that is independent
of the program's own memory and is controlled entirely by the operating
system.
Pipes may be used to pass information between programs. For example, the
command processor in OS/2 creates a pipe when executing a command such as
PROGRAM1 | PROGRAM2
The standard output handle of PROGRAM1 is attached to the pipe's write
handle. The standard input handle of PROGRAM2 is attached to the pipe's read
handle. This eliminates the need for creating temporary files to pass
information to other programs.
The _pipe function creates a pipe. This function is similar to open but
opens the pipe for both reading and writing, returning two file handles
instead of one. The program can either use both sides of the pipe or close
the one it does not need. This function typically opens a pipe in
preparation for linking it to a child process.
The _pipe function opens a pipe and returns two handles to the pipe in the
phandles argument. The element phandles[0] contains the read handle, and the
element phandles[1] contains the write handle. Pipe file handles are used in
the same way as other file handles. (The low-level input and output
functions read and write can read from and write to a pipe.)
The psize argument specifies the amount of memory, in bytes, to reserve for
the pipe.
The textmode argument specifies the translation mode for the pipe. The
manifest constant O_TEXT specifies a text translation, and the constant
O_BINARY specifies binary translation. (See fopen for a description of text
and binary modes.) If the textmode argument is 0, the _pipe function uses
the default translation mode specified by the default-mode variable _fmode.
In multithread programs, no locking is performed. The handles returned are
newly opened and should not be referenced by any thread until after the
_pipe call is complete.
Under OS/2, a pipe is destroyed when all its handles have been closed. (If
all read handles on the pipe have been closed, writing to the pipe will
cause an error.) All read and write operations on the pipe wait until there
is enough data or enough buffer space to complete the I/O request.
Return Value
The _pipe function returns 0 if successful. A return value of -1 indicates
an error, and errno is set to one of the following values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
EMFILE No more file handles available (too many
open files)
ENFILE System file table overflow
Compatibility
▼ ANSI ▼ DOS OS/2 UNIX XENIX
A similar function (pipe) is available in the XENIX and UNIX operating
environments.
See Also
cwait, _pclose, _popen
Example
/* PIPE.C: This program uses _pipe to pass streams of text to
* child processes.
*/
#include <stdlib.h>
#include <stdio.h>
#include <io.h>
#include <fcntl.h>
#include <process.h> /* _pipe */
#include <math.h>
enum PIPES { READ, WRITE }; /* Constants 0 and 1 for READ and WRITE */
#define NUMPROBLEM 8
void main( int argc, char *argv[] )
{
int hpipe[2];
char hstr[20];
int termstat, pid, problem, c;
/* If no arguments, this is the parent. */
if( argc == 1 )
{
/* Open a sets of pipes. */
if( _pipe( hpipe, 256, O_BINARY ) == -1 )
exit( 1 );
/* Convert pipe read handle to string and pass as argument to
* spawned child. Program spawns itself (argv[0]).
*/
itoa( hpipe[READ], hstr, 10 );
if( spawnl( P_NOWAIT, argv[0], argv[0], hstr, NULL ) == -1 )
printf( "Spawn failed" );
/* Put problem in write pipe. Since child is running
simultaneously,
* first solutions may be done before last problem is given.
*/
for( problem = 1000; problem <= NUMPROBLEM * 1000; problem += 1000
)
{
printf( "Son, what is the square root of %d?\n", problem );
write( hpipe[WRITE], (char *)&problem, sizeof( int ) );
}
/* Wait until child is done processing. */
wait( &termstat );
if( termstat & 0xff )
printf( "Child failed\n" );
close( hpipe[READ] );
close( hpipe[WRITE] );
}
/* If there is an argument, this must be the child. */
else
{
/* Convert passed string handle to integer handle. */
hpipe[READ] = atoi( argv[1] );
/* Read problem from pipe and calculate solution. */
for( c = 0; c < NUMPROBLEM; c++ )
{
read( hpipe[READ], (char *)&problem, sizeof( int ) );
printf( "Dad, the square root of %d is %3.2f.\n",
problem, sqrt( (double)problem ) );;
}
}
}
Output
Son, what is the square root of 1000?
Dad, the square root of 1000 is 31.62.
Son, what is the square root of 2000?
Son, what is the square root of 3000?
Dad, the square root of 2000 is 44.72.
Son, what is the square root of 4000?
Dad, the square root of 3000 is 54.77.
Son, what is the square root of 5000?
Dad, the square root of 4000 is 63.25.
Son, what is the square root of 6000?
Dad, the square root of 5000 is 70.71.
Son, what is the square root of 7000?
Dad, the square root of 6000 is 77.46.
Son, what is the square root of 8000?
Dad, the square root of 7000 is 83.67.
Dad, the square root of 8000 is 89.44.
_polygon Functions
────────────────────────────────────────────────────────────────────────────
Description
Draw polygon shapes.
#include <graph.h>
short _far _polygon( short control, struct xycoord _far *points, short
numpoints );
short _far _polygon_w( short control, double _far *points, short numpoints
);
short _far _polygon_wxy( short control, struct _wxycoord _far *points,
short numpoints );
control Fill flag
points Pointer to an array of structures
defining the polygon
numpoints Number of points
Remarks
The _polygon functions draw polygons. The border of the polygon is drawn in
the current color and line style. The _polygon routine uses the view
coordinate system (expressed in xycoord structures), and the _polygon_wxy
and _polygon_w routines use real-valued window coordinates (expressed in
_wxycoord structures and in pairs of double-precision floating-point values,
respectively).
The argument points is an array of xycoord or _wxycoord structures or pairs
of doubles, each of which specifies one of the polygon's vertices. (For
_polygon_w, points[0] and points[1] specify the x and y coordinates,
respectively, of the first point.) The argument numpoints indicates the
number of elements (the number of vertices) in the points array.
The control argument can be one of the following manifest constants:
Constant Action
────────────────────────────────────────────────────────────────────────────
_GFILLINTERIOR Fills the polygon using the current fill
mask
_GBORDER Does not fill the polygon
The _setwritemode, _setlinestyle, and _setfillmask functions all affect the
output from the_polygon functions.
Return Value
The _polygon functions return a nonzero value if the arc is successfully
drawn; otherwise, they return 0.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_ellipse functions, _floodfill, _lineto functions, _pie functions,
_rectangle functions, _setcolor, _setfillmask, _setlinestyle,
_setwritemode
Example
/* POLYGON.C: This program draws a star-shaped polygon. */
#include <conio.h>
#include <stdlib.h>
#include <graph.h>
#include <math.h>
#include <stdlib.h>
#define PI 3.1415
void main()
{
short side, radius = 90, x = 0, y = 0;
double radians;
struct xycoord polyside[5];
struct videoconfig vc;
/* Find a valid graphics mode. */
if( !_setvideomode( _MAXRESMODE ) )
exit( 1 );
_getvideoconfig( &vc );
_setvieworg( vc.numxpixels / 2, vc. numypixels / 2 );
/* Calculate points of star every 144 degrees, then connect them. */
for( side = 0; side < 5; side++ )
{
radians = 144 * PI / 180;
polyside[side].xcoord = x + (short)(cos( side * radians ) *
radius);
polyside[side].ycoord = y + (short)(sin( side * radians ) *
radius);
}
_polygon( _GFILLINTERIOR, polyside, 5 );
getch();
_setvideomode( _DEFAULTMODE );
}
_popen
────────────────────────────────────────────────────────────────────────────
Description
Creates a pipe and executes a command.
#include <stdio.h> Required for function declarations only
FILE *_popen( char *command, char *mode );
command Command to be executed
mode Mode of returned stream
Remarks
The _popen function creates a pipe and asynchronously executes a child copy
of the command processor with the specified command string command. See
_pipe for a general discussion of pipes in OS/2. The character string mode
specifies the type of access requested, as follows:
Type Description
────────────────────────────────────────────────────────────────────────────
"r" The calling process can read the child
command's standard output via the
returned stream.
"w" The calling process can write to the
child command's standard input via the
returned stream.
"b" Open in binary mode.
"t" Open in text mode.
See Section 2.7, "Input and Output," for a discussion of text and binary
modes.
Return Value
The _popen function returns a stream associated with one end of the created
pipe. The other end of the pipe is associated with the child command's
standard input or standard output. If an error occurs, NULL is returned.
Compatibility
▼ ANSI ▼ DOS OS/2 UNIX XENIX
A similar function (popen) is available in the XENIX and UNIX operating
environments.
See Also
_pclose, _pipe
Example
/* POPEN.C: This program uses _popen and _pclose to receive a stream
* of text from a child system process.
*/
#include <stdio.h>
#include <stdlib.h>
void main()
{
char buffer[128];
FILE *chkdsk;
/* Run CHKDSK so that it writes its output to a pipe. Open pipe
* with read text attribute so that we can read it like a text file.
*/
if( (chkdsk = _popen( "dir po*.c | sort | more", "rt" )) == NULL )
exit( 1 );
/* Read pipe until end of file. End of file indicates that CHKDSK
* closed its standard out (probably meaning it terminated).
*/
while( !feof( chkdsk ) )
{
if( fgets( buffer, 128, chkdsk ) != NULL )
printf( buffer );
}
/* Close pipe and print return value of CHKDSK. */
printf( "\nChild returned %d\n", _pclose( chkdsk ) );
}
Output
3 File(s) 12683264 bytes free
Directory of C:\LIBREF
The volume label in drive C is OS2.
POLYGON C 921 6-14-89 6:51p
POPEN C 845 6-19-89 2:48p
POW C 190 6-13-89 6:07p
Child returned 0
pow Functions
────────────────────────────────────────────────────────────────────────────
Description
Calculate x raised to the power of y.
#include <math.h>
double pow( double x, double y );
long double powl( long double x, long double y );
x Number to be raised
y Power of x
Remarks
The pow and powl functions compute x raised to the power of y.
The powl function is the 80-bit counterpart, and it uses an 80-bit, 10-byte
coprocessor form of arguments and return values. See the reference page on
the long double functions for more details on this data type.
Return Value
The pow and powl functions return the value of xy. If x is not 0.0 and y is
0.0, pow and powl return the value 1. If x is 0.0 and y is negative, pow and
powl set errno to EDOM and return 0.0. If both x and y are 0.0, or if x is
negative and y is not an integer, the function prints a DOMAIN error message
to stderr, sets errno to EDOM, and returns 0.0. If an overflow results, the
function sets errno to ERANGE and returns±HUGE_VAL. No message is printed on
overflow or underflow.
The pow function does not recognize integral floating-point values greater
than 264, such as 1.0E100.
Compatibility
pow
ANSI DOS OS/2 UNIX XENIX
powl
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
exp, log functions, sqrt
Example
/* POW.C */
#include <math.h>
#include <stdio.h>
void main()
{
double x = 2.0, y = 3.0, z;
z = pow( x, y );
printf( "%.1f to the power of %.1f is %.1f\n", x, y, z );
}
Output
2.0 to the power of 3.0 is 8.0
printf
────────────────────────────────────────────────────────────────────────────
Description
Prints formatted output to the standard output stream.
#include <stdio.h>
int printf( const char *format [[, argument]]... );
format Format control
argument Optional arguments
Remarks
The printf function formats and prints a series of characters and values to
the standard output stream, stdout. The format argument consists of ordinary
characters, escape sequences, and (if arguments follow format) format
specifications. The ordinary characters and escape sequences are copied to
stdout in order of their appearance. For example, the line
printf("Line one\n\t\tLine two\n");
produces the output
Line one
Line two
If arguments follow the format string, the format string must contain
specifications that determine the output format for the arguments.
Format specifications always begin with a percent sign (%) and are read left
to right. When the first format specification (if any) is encountered, the
value of the first argument after format is converted and output
accordingly. The second format specification causes the second argument to
be converted and output, and so on. If there are more arguments than there
are format specifications, the extra arguments are ignored. The results are
undefined if there are not enough arguments for all the format
specifications.
A format specification, which consists of optional and required fields, has
the following form:
%[[flags]] [[width]] [[.precision]] [[{F | N | h | l | L}]] type
Format Specification Fields
Each field of the format specification is a single character or a number
signifying a particular format option. The simplest format specification
contains only the percent sign and a type character (for example, %s). The
optional fields, which appear before the type character, control other
aspects of the formatting. The fields in a printf format specification are
described in the following list:
Field Description
────────────────────────────────────────────────────────────────────────────
type Required character that determines
whether the associated argument is
interpreted as a character, a string, or
a number. (See Table R.2.)
flags Optional character or characters that
control justification of output and
printing of signs, blanks, decimal
points, and octal and hexadecimal
prefixes. (See Table R.3.) More than one
flag can appear in a format
specification.
width Optional number that specifies minimum
number of characters output.
precision Optional number that specifies maximum
number of characters printed for all or
part of the output field, or minimum
number of digits printed for integer
values. (See Table R.4.)
F, N Optional prefixes that refer to the
"distance" to the object being printed (
near or far).
F and N are not part of the ANSI
definition for printf. They are
Microsoft extensions that should not be
used if ANSI portability is desired.
h, l, L Optional prefixes that determine the
size of the argument expected, as shown
below:
Prefix Use
────────────────────────────────────────────────────────────────────────────
h Used with the integer types
d, i, o, x, and X to specify
that the argument is short
int, or with u to specify
short unsigned int. If used
with %p, it indicates a
16-bit pointer.
l Used with d, i, o, x, and X
types to specify that the
argument is long int, or
with u to specify long
unsigned int; also used with
e, E, f, g, and G types to
specify double rather than
float. If used with %p, it
indicates a 32-bit pointer.
L Used with e, E, f, g, and G
types to specify long double
.
If a percent sign is followed by a character that has no meaning as a format
field, the character is copied to stdout. For example, to print a
percent-sign character, use %%.
Type Field Characters
The type character is the only required format field for the printf
function; it appears after any optional format fields. The type character
determines whether the associated argument is interpreted as a character, a
string, or a number. (See Table R.2.)
Table R.2 Type Characters for printf
╓┌──────────┌────────────┌───────────────────────────────────────────────────╖
Character Type Output Format
────────────────────────────────────────────────────────────────────────────
d int Signed decimal integer.
i int Signed decimal integer.
u int Unsigned decimal integer.
o int Unsigned octal integer.
x int Unsigned hexadecimal integer, using "abcdef."
X int Unsigned hexadecimal integer, using "ABCDEF."
Character Type Output Format
────────────────────────────────────────────────────────────────────────────
f double Signed value having the form [-]dddd.dddd, where
dddd is one or more decimal digits. The number of
digits before the decimal point depends on the
magnitude of the number, and the number of digits
after the decimal point depends on the requested
precision.
e double Signed value having the form [-]d.dddd e [sign]ddd
, where d is a single decimal digit, dddd is one
or more decimal digits, ddd is exactly three
decimal digits, and sign is + or -.
E double Identical to the e format, except that E, rather
than e, introduces the exponent.
g double Signed value printed in f or e format, whichever
is more compact for the given value and precision.
The e format is used only when the exponent of the
Character Type Output Format
────────────────────────────────────────────────────────────────────────────
The e format is used only when the exponent of the
value is less than - 4 or greater than or equal to
the precision argument. Trailing zeros are
truncated, and the decimal point appears only if
one or more digits follow it.
G double Identical to the g format, except that G, rather
than g, introduces the exponent (where
appropriate).
c int Single character.
s String Characters printed up to the first null character
('\0') or until the
precision value is reached.
n Pointer to Number of characters successfully written so far
integer to the stream or buffer; this value is stored in
the integer whose address is given as the
Character Type Output Format
────────────────────────────────────────────────────────────────────────────
the integer whose address is given as the
argument.
p Far pointer Prints the address pointed to by the argument in
to void the form xxxx:yyyy, where xxxx is the segment and
yyyy is the offset, and the digits x and y are
uppercase hexadecimal digits; %hp indicates a near
pointer and prints only the offset of the address.
────────────────────────────────────────────────────────────────────────────
Flag Directives
The first optional field of the format specification is flag. A flag
directive is a character that justifies output and prints signs, blanks,
decimal points, and octal and hexadecimal prefixes. More than one flag
directive may appear in a format specification. (See Table R.3.)
Table R.3 Flag Characters for printf
╓┌──────────────────────────┌──────────────────────────┌─────────────────────►
Flag(, Meaning , Default)
─────────────────────────────────────────────────────────────────────────────
- Left justify the result Right justify.
within the given field
width.
+ Prefix the output value Sign appears only for
with a sign negative signed values
(+ or -) if the output (-).
value is of a signed
type.
0 If width is prefixed with No padding.
0, zeros are added until
the minimum width is
reached. If 0 and -
Flag(, Meaning , Default)
─────────────────────────────────────────────────────────────────────────────
reached. If 0 and -
appear, the 0 is
ignored. If 0 is
specified with an
integer format (i, u, x,
X, o, d), the
0 is ignored.
blank (' ') Prefix the output value No blank appears.
with a blank if the
output value is signed
and positive; the blank
is ignored if both the
blank and + flags appear.
# When used with the o, x, No blank appears.
or X format, the # flag
prefixes any nonzero
output value with 0, 0x,
Flag(, Meaning , Default)
─────────────────────────────────────────────────────────────────────────────
output value with 0, 0x,
or 0X, respectively.
When used with the e, E, Decimal point appears
or f format, the # flag only if digits follow i
forces the output value
to contain a decimal
point in all cases.
When used with the g or G Decimal point appears
format, the # flag forces only if digits follow i
the output value to Trailing zeros are
contain a decimal point truncated.
in all cases and prevents
the truncation of
trailing zeros.
Ignored when used with c,
d, i, u, or s.
Flag(, Meaning , Default)
─────────────────────────────────────────────────────────────────────────────
d, i, u, or s.
─────────────────────────────────────────────────────────────────────────────
Width Specification
The second optional field of the format specification is the width
specification. The width argument is a non-negative decimal integer
controlling the minimum number of characters printed. If the number of
characters in the output value is less than the specified width, blanks are
added to the left or the right of the values─depending on whether the -
flag (for left justification) is specified─until the minimum width is
reached. If width is prefixed with 0, zeros are added until the minimum
width is reached (not useful for left-justified numbers).
The width specification never causes a value to be truncated. If the number
of characters in the output value is greater than the specified width, or
width is not given, all characters of the value are printed (subject to the
precision specification).
The width specification may be an asterisk (*), in which case an int
argument from the argument list supplies the value. The width argument must
precede the value being formatted in the argument list. A nonexistent or
small field width does not cause a truncation of a field; if the result of a
conversion is wider than the field width, the field expands to contain the
conversion result.
Precision Specification
The third optional field of the format specification is the precision
specification. It specifies a non-negative decimal integer, preceded by a
period (.), which specifies the number of characters to be printed, the
number of decimal places, or the number of significant digits. (See Table
R.4.) Unlike the width specification, the precision specification can cause
truncation of the output value, or rounding in the case of a floating-point
value. If precision is specified as zero and the value to be converted is
zero, the result is no characters output, as shown below:
printf( "%.0d", 0 ); /* No characters output */
The precision specification may be an asterisk (*), in which case an int
argument from the argument list supplies the value. The precision argument
must precede the value being formatted in the argument list.
The interpretation of the precision value and the default when precision is
omitted depend on the type, as shown in Table R.4.
Table R.4 How printf Precision Values Affect Type
╓┌─────────────────┌──────────────────────────────┌──────────────────────────►
Type Meaning Default
─────────────────────────────────────────────────────────────────────────────
d, i, u, o, x, X The precision specifies the If precision is 0 or omitted
minimum number of digits to entirely, or if the period (
be printed. If the number of ) appears without a number
digits in the argument is following it, the precision
less than precision, the is set to 1.
Type Meaning Default
─────────────────────────────────────────────────────────────────────────────
less than precision, the is set to 1.
output value is padded on the
left with zeros. The value is
not truncated when the number
of digits exceeds precision.
e, E The precision specifies the Default precision is 6; if
number of digits to be precision is 0 or the period
printed after the decimal (.) appears without a number
point. The last printed digit following it, no decimal
is rounded. point is printed.
f The precision value specifies Default precision is 6; if
the number of digits after precision is 0, or if the
the decimal point. If a period (.) appears without a
decimal point appears, at number following it, no
least one digit appears decimal point is printed.
before it. The value is
rounded to the appropriate
Type Meaning Default
─────────────────────────────────────────────────────────────────────────────
rounded to the appropriate
number of digits.
g, G The precision specifies the Six significant digits are
maximum number of significant printed, with any trailing
digits printed. zeros truncated.
c The precision has no effect. Character is printed.
s The precision specifies the Characters are printed until
maximum number of characters a null character is
to be printed. Characters in encountered.
excess of precision are not
printed.
─────────────────────────────────────────────────────────────────────────────
If the argument corresponding to a floating-point specifier is infinite,
indefinite, or not a number (NAN), the printf function gives the following
output:
Value Output
────────────────────────────────────────────────────────────────────────────
+ infinity 1.#INFrandom-digits
- infinity -1.#INFrandom-digits
Indefinite digit.#INDrandom-digits
NAN digit.#NANrandom-digits
Size and Distance Specification
For printf, the format specification fields F and N refer to the "distance"
to the object being read (near or far), and h and l refer to the "size" of
the object being read (16-bit short or 32-bit long). The following list
clarifies this use of F, N, h, l, and L:
Program Code Action
────────────────────────────────────────────────────────────────────────────
printf ("%Ns"); Print near string
printf ("%Fs"); Print far string
printf ("%Nn"); Store char count in near int
printf ("%Fn"); Store char count in far int
printf ("%hp"); Print a 16-bit pointer (xxxx)
printf ("%lp"); Print a 32-bit pointer (xxxx:xxxx)
printf ("%Nhn"); Store char count in near short int
printf ("%Nln"); Store char count in near long int
printf ("%Fhn"); Store char count in far short int
printf ("%Fln"); Store char count in far int
The specifications "%hs" and "%ls" are meaningless to printf. The
specifications "%Np" and "%Fp" are aliases for "%hp" and "%lp" for the sake
of compatibility with Microsoft C version 4.0.
Return Value
The printf function returns the number of characters printed, or a negative
value in the case of an error.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
fprintf, scanf, sprintf, vfprintf, vprintf, vsprintf
Example
/* PRINTF.C illustrates output formatting with printf. */
#include <stdio.h>
void main()
{
char ch = 'h', *string = "computer";
int count = -9234;
double fp = 251.7366;
/* Display integers. */
printf( "Integer formats:\n"
"\tDecimal: %d Justified: %.6d Unsigned: %u\n",
count, count, count, count );
printf( "Decimal %d as:\n\tHex: %Xh C hex: 0x%x Octal: %o\n",
count, count, count, count );
/* Display in different radixes. */
printf( "Digits 10 equal:\n\tHex: %i Octal: %i Decimal: %i\n",
0x10, 010, 10 );
/* Display characters. */
printf( "Characters in field:\n%10c %5c\n", ch, ch );
/* Display strings. */
printf( "Strings in field:\n%25s\n%25.4s\n", string, string );
/* Display real numbers. */
printf( "Real numbers:\n\t%f %.2f %e %E\n", fp, fp, fp, fp );
/* Display pointers. */
printf( "Address as:\n\tDefault: %p Near: %Np Far: %Fp\n",
&count, (int _near *)&count, (int _far *)&count );
/* Count characters printed. */
printf( "Display to here:\n" );
printf( "1234567890123456%n78901234567890\n", &count );
printf( "\tNumber displayed: %d\n\n", count );
}
Output
Integer formats:
Decimal: -9234 Justified: -009234 Unsigned: 56302
Decimal -9234 as:
Hex: DBEEh C hex: 0xdbee Octal: 155756
Digits 10 equal:
Hex: 16 Octal: 8 Decimal: 10
Characters in field:
h h
Strings in field:
computer
comp
Real numbers:
251.736600 251.74 2.517366e+002 2.517366E+002
Address as:
Default: 141C Near: 141C Far: 0087:141C
Display to here:
123456789012345678901234567890
Number displayed: 16
putc, putchar
────────────────────────────────────────────────────────────────────────────
Description
Writes a character to a stream (putc) or to stdout (putchar).
#include <stdio.h>
int putc( int c, FILE *stream );
int putchar( int c );
c Character to be written
stream Pointer to FILE structure
Remarks
The putc routine writes the single character c to the output stream at the
current position. The putchar routine is identical to putc(c, stdout).
These routines are implemented as both macros and functions. See Section
1.4, "Choosing Between Functions and Macros," for a discussion of how to
select between the macro and function forms.
Return Value
The putc and putchar routines return the character written, or EOF in the
case of an error. Any integer can be passed to putc, but only the lower 8
bits are written.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
fputc, fputchar, getc, getchar
Example
/* PUTC.C: This program uses putc to write buffer to a stream.
* If an error occurs, the program will stop before writing the
* entire buffer.
*/
#include <stdio.h>
void main()
{
FILE *stream;
char *p, buffer[] = "This is the line of output\n";
int ch;
/* Make standard out the stream and write to it. */
stream = stdout;
for( p = buffer; (ch != EOF) && (*p != '\0'); p++ )
ch = putc( *p, stream );
}
Output
This is the line of output
putch
────────────────────────────────────────────────────────────────────────────
Description
Writes a character to the console.
#include <conio.h> Required only for function declarations
int putch( int c );
c Character to be output
Remarks
The putch function writes the character c directly (without buffering) to
the console.
Return Value
The function returns c if successful, and EOF if not.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
cprintf, getch, getche
Example
/* GETCH.C: This program reads characters from the keyboard until it
* receives a 'Y' or 'y'.
*/
#include <conio.h>
#include <ctype.h>
void main()
{
int ch;
cputs( "Type 'Y' when finished typing keys: " );
do
{
ch = getch();
ch = toupper( ch );
} while( ch != 'Y' );
putch( ch );
putch( '\r' ); /* Carriage return */
putch( '\n' ); /* Line feed */
}
Output
Type 'Y' when finished typing keys: Y
putenv
────────────────────────────────────────────────────────────────────────────
Description
Creates new environment variables.
#include <stdlib.h> Required only for function declarations
int putenv( char *envstring );
envstring Environment-string definition
Remarks
The putenv function adds new environment variables or modifies the values of
existing environment variables. Environment variables define the environment
in which a process executes (for example, the default search path for
libraries to be linked with a program).
The envstring argument must be a pointer to a string with the form
varname=string
where varname is the name of the environment variable to be added or
modified and string is the variable's value. If varname is already part of
the environment, its value is replaced by string; otherwise, the new varname
variable and its string value are added to the environment. A variable can
be set to an empty value by specifying an empty string.
This function affects only the environment that is local to the currently
running process; it cannot be used to modify the command-level environment.
When the currently running process terminates, the environment reverts to
the level of the parent process (in most cases, the operating system level).
However, the environment affected by putenv can be passed to any child
processes created by spawn, exec, system, or (in OS/2 only) _popen, and
these child processes get any new items added by putenv.
Never free a pointer to an environment entry, because the environment
variable will then point to freed space. A similar problem can occur if you
pass putenv a pointer to a local variable, then exit the function in which
the variable is declared.
The putenv function operates only on data structures accessible to the
run-time library and not on the environment "segment" created for a process
by DOS or OS/2.
Note that environment-table entries must not be changed directly. If an
entry must be changed, use putenv. To modify the returned value without
affecting the environment table, use strdup or strcpy to make a copy of the
string.
The getenv and putenv functions use the global variable environ to access
the environment table. The putenv function may change the value of environ,
thus invalidating the envp argument to the main function. Therefore, it is
safer to use the environ variable to access the environment information.
Return Value
The putenv function returns 0 if it is successful. A return value of -1
indicates an error.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
getenv
Example
/* GETENV.C: This program uses getenv to retrieve the LIB environment
* variable and then uses putenv to change it to a new value.
*/
#include <stdlib.h>
#include <stdio.h>
main()
{
char *libvar;
/* Get the value of the LIB environment variable. */
libvar = getenv( "LIB" );
if( libvar != NULL )
printf( "Original LIB variable is: %s\n", libvar );
/* Attempt to change path. Note that this only affects the environment
* variable of the current process. The command processor's environment
* is not changed.
*/
putenv( "LIB=c:\\mylib;c:\\yourlib" );
/* Get new value. */
libvar = getenv( "LIB" );
if( libvar != NULL )
printf( "New LIB variable is: %s\n", libvar );
}
Output
Original LIB variable is: C:\LIB
New LIB variable is: c:\mylib;c:\yourlib
_putimage Functions
────────────────────────────────────────────────────────────────────────────
Description
Retrieve images from a buffer.
#include <graph.h>
void _far _putimage( short x, short y, char _huge *image, short action );
void _far _putimage_w( double wx, double wy, char _huge *image, short
action );
x, y Position of upper-left corner of image
image Stored image buffer
action Interaction with existing screen image
wx, wy Position of upper-left corner of image
Remarks
The _putimage function transfers to the screen the image stored in the
buffer that image points to.
In the _putimage function, the upper-left corner of the image is placed at
the view coordinate point (x, y). In the _putimage_w function, the
upper-left corner of the image is placed at the window coordinate point (wx,
wy).
The action argument defines the interaction between the stored image and the
one that is already on the screen. It may be any one of the following
manifest constants (defined in GRAPH.H):
Constant Meaning
────────────────────────────────────────────────────────────────────────────
_GAND Transfers the image over an existing
image on the screen. The resulting image
is the logical-AND product of the two
images: points that had the same color
in both the existing image and the new
one will remain the same color, while
points that have different colors are
joined by logical-AND.
_GOR Superimposes the image onto an existing
image. The new image does not erase the
previous screen contents.
_GPRESET Transfers the data point-by-point onto
the screen. Each point has the inverse
of the color attribute it had when it
was taken from the screen by _getimage,
producing a negative image.
_GPSET Transfers the data point-by-point onto
the screen. Each point has the exact
color attribute it had when it was taken
from the screen by _getimage.
_GXOR Causes the points on the screen to be
inverted where a point exists in the
image buffer. This behavior is exactly
like that of the cursor: when an image
is put against a complex background
twice, the background is restored
unchanged. This allows you to move an
object around without erasing the
background. The _GXOR constant is a
special mode often used for animation.
Return Value
None.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_getimage, _imagesize
Example
See the example for _getimage.
puts
────────────────────────────────────────────────────────────────────────────
Description
Writes a string to stdout.
#include <stdio.h>
int puts( const char *string );
string String to be output
Remarks
The puts function writes string to the standard output stream stdout,
replacing the string's terminating null character ('\0') with a newline
character (\n) in the output stream.
Return Value
The puts function returns a nonnegative value if it is successful. If the
function fails, it returns EOF.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
fputs, gets
Example
/* PUTS.C: This program uses puts to write a string to stdout. */
#include <stdio.h>
void main()
{
puts( "Hello world from puts!" );
}
Output
Hello world from puts!
putw
────────────────────────────────────────────────────────────────────────────
Description
Writes an integer to a stream.
#include <stdio.h>
int putw( int binint, FILE *stream );
binint Binary integer to be output
stream Pointer to FILE structure
Remarks
The putw function writes a binary value of type int to the current position
of stream. The putw function does not affect the alignment of items in the
stream, nor does it assume any special alignment.
The putw function is provided primarily for compatibility with previous
libraries. Note that portability problems may occur with putw, since the
size of an int and ordering of bytes within an int differ across systems.
Return Value
The putw function returns the value written. A return value of EOF may
indicate an error. Since EOF is also a legitimate integer value, ferror
should be used to verify an error.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
getw
Example
/* PUTW.C: This program uses putw to write a word to a stream,
* then performs an error check.
*/
#include <stdio.h>
#include <stdlib.h>
void main()
{
FILE *stream;
unsigned u;
if( (stream = fopen( "data.out", "wb" )) == NULL )
exit( 1 );
for( u = 0; u < 10; u++ )
{
putw( u + 0x2132, stdout );
putw( u + 0x2132, stream ); /* Write word to stream. */
if( ferror( stream ) ) /* Make error check. */
{
printf( "putw failed" );
clearerr( stream );
exit( 1 );
}
}
printf( "\nWrote ten words\n" );
fclose( stream );
}
Output
2!3!4!5!6!7!8!9!:!;!
Wrote ten words
qsort
────────────────────────────────────────────────────────────────────────────
Description
Performs a quick sort.
#include <stdlib.h> For ANSI compatibility
#include <search.h> Required only for function declarations
void qsort( void *base, size_t num, size_t width,
int( *compare ) ( const void *elem1, const void *elem2 ) );
base Start of target array
num Array size in elements
width Element size in bytes
compare Comparison function
elem1 Pointer to the key for the search
elem2 Pointer to the array element to be
compared with the key
Remarks
The qsort function implements a quick-sort algorithm to sort an array of num
elements, each of width bytes. The argument base is a pointer to the base of
the array to be sorted. The qsort function overwrites this array with the
sorted elements.
The argument compare is a pointer to a user-supplied routine that compares
two array elements and returns a value specifying their relationship. The
qsort function calls the compare routine one or more times during the sort,
passing pointers to two array elements on each call:
compare( (void *) elem1, (void *) elem2 );
The routine must compare the elements, then return one of the following
values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
< 0 elem1 less than elem2
= 0 elem1 equivalent to elem2
> 0 elem1 greater than elem2
The array is sorted in increasing order, as defined by the comparison
function. To sort an array in decreasing order, reverse the sense of
"greater than" and "less than" in the comparison function.
Return Value
None.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
bsearch, lsearch
Example
/* QSORT.C: This program reads the command-line parameters and
* uses qsort to sort them. It then displays the sorted arguments.
*/
#include <search.h>
#include <string.h>
#include <stdio.h>
int compare( char **arg1, char **arg2 ); /* Prototype */
void main( int argc, char **argv )
{
int i;
/* Eliminate argv[0] from sort: */
argv++;
argc─;
/* Sort remaining args using Quicksort algorithm: */
qsort( (void *)argv, (size_t)argc, sizeof( char * ), compare );
/* Output sorted list: */
for( i = 0; i < argc; ++i )
printf( "%s ", argv[i] );
printf( "\n" );
}
int compare( char **arg1, char **arg2 )
{
/* Compare all of both strings: */
return strcmpi( *arg1, *arg2 );
}
Output
[C:\LIBREF] qsort every good boy deserves favor
boy deserves every favor good
raise
────────────────────────────────────────────────────────────────────────────
Description
Sends a signal to the executing program.
#include <signal.h>
int raise( int sig );
sig Signal to be raised
Remarks
The raise function sends sig to the executing program. If a signal-handling
routine for sig has ben installed by a prior call to signal, raise causes
that routine to be executed. If no handler routine has been installed, the
default action (as listed below) is taken.
The signal value sig can be one of the following manifest constants:
╓┌──────────────────────┌──────────────────────────┌─────────────────────────►
Signal Meaning Default
─────────────────────────────────────────────────────────────────────────────
SIGABRT Abnormal termination. Terminates the calling
program with exit code 3.
SIGBREAK CTRL+ BREAK interrupt. Terminates the calling
program with exit code 3.
SIGFPE Floating-point error. Terminates the calling
program.
SIGILL Illegal instruction. This Terminates the calling
Signal Meaning Default
─────────────────────────────────────────────────────────────────────────────
SIGILL Illegal instruction. This Terminates the calling
signal is not generated program.
by DOS or OS/2, but is
supported for ANSI
compatibility.
SIGINT CTRL+ C interrupt. Issues INT23H.
SIGSEGV Illegal storage access. Terminates the calling
This signal is not program.
generated by DOS or OS/2,
but is supported for ANSI
compatiblity.
SIGTERM Termination request sent Ignores the signal.
to the program. This
signal is not generated
by DOS or OS/2, but is
supported for ANSI
Signal Meaning Default
─────────────────────────────────────────────────────────────────────────────
supported for ANSI
compatibility.
SIGUSR1 User-defined signals. Ignores the signal.
SIGUSR2
SIGUSR3
Return Value
If successful, the raise function returns 0. Otherwise, it returns a nonzero
value.
Compatibility
ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
abort, signal
Example
See the example for signal.
rand
────────────────────────────────────────────────────────────────────────────
Description
Generates a pseudorandom number.
#include <stdlib.h> Required only for function declarations
int rand( void );
Remarks
The rand function returns a pseudorandom integer in the range 0 to RAND_MAX.
The srand routine can be used to seed the pseudorandom-number generator
before calling rand.
Return Value
The rand function returns a pseudorandom number, as described above. There
is no error return.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
srand
Example
/* RAND.C: This program seeds the random-number generator with the
* time, then displays 20 random integers.
*/
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
void main()
{
int i;
/* Seed the random-number generator with current time so that
* the numbers will be different every time we run.
*/
srand( (unsigned)time( NULL ) );
/* Display 10 numbers. */
for( i = 0; i < 10; i++ )
printf( " %6d\n", rand() );
}
Output
19471
16395
8268
15582
6489
28356
27042
5276
23070
10930
read
────────────────────────────────────────────────────────────────────────────
Description
Reads data from a file.
#include <io.h> Required only for function declarations
int read( int handle, void *buffer, unsigned int count );
handle Handle referring to open file
buffer Storage location for data
count Maximum number of bytes
Remarks
The read function attempts to read count bytes into buffer from the file
associated with handle. The read operation begins at the current position of
the file pointer associated with the given file. After the read operation,
the file pointer points to the next unread character.
Return Value
The read function returns the number of bytes actually read, which may be
less than count if there are fewer than count bytes left in the file, or if
the file was opened in text mode (see below). The return value 0 indicates
an attempt to read at end-of-file. The return value -1 indicates an error,
and errno is set to the following value:
Value Meaning
────────────────────────────────────────────────────────────────────────────
EBADF The given handle is invalid; or the file
is not open for reading; or (DOS
versions 3.0 and later and OS/2 only)
the file is locked.
If you are reading more than 32K (the maximum size for type int) from a
file, the return value should be of type unsigned int (see the example that
follows). However, the maximum number of bytes that can be read from a file
in one operation is 65,534, since 65,535 (or 0xFFFF) is indistinguishable
from -1, and therefore cannot be distinguished from an error return.
If the file was opened in text mode, the return value may not correspond to
the number of bytes actually read. When text mode is in effect, each
carriage-return-line-feed (CR-LF) pair is replaced with a single line-feed
character. Only the single line-feed character is counted in the return
value. The replacement does not affect the file pointer.
Note that under DOS and OS/2, when files are opened in text mode, a CTRL+Z
character is treated as an end-of-file indicator. When the CTRL+Z is
encountered, the read terminates, and the next read returns 0 bytes. The
lseek function will clear the end-of-file indicator.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
creat, fread, open, write
Example
/* READ.C: This program opens a file named READ.C and tries to read 60,000
* bytes from that file using read. It then displays the actual
* number of bytes read from READ.C.
*/
#include <fcntl.h> /* Needed only for O_RDWR definition */
#include <io.h>
#include <stdlib.h>
#include <stdio.h>
char buffer[60000];
void main()
{
int fh;
unsigned int nbytes = 60000, bytesread;
/* Open file for input: */
if( (fh = open( "read.c", O_RDONLY )) == -1 )
{
perror( "open failed on input file" );
exit( 1 );
}
/* Read in input: */
if( ( bytesread = read( fh, buffer, nbytes ) ) <= 0 )
perror( "Problem reading file" );
else
printf( "Read %u bytes from file\n", bytesread );
close( fh );
}
Output
Read 747 bytes from file
realloc Functions
────────────────────────────────────────────────────────────────────────────
Description
#include <stdlib.h>
For ANSI compatibility (realloc only)
#include <malloc.h> Required only for function declarations
void *realloc( void *memblock, size_t size );
void _based( void ) *_brealloc( _segment seg, void _based( void )
*memblock,
size_t size );
void _far *_frealloc( void _far *memblock, size_t size );
void _near *_nrealloc( void _near *memblock, size_t size );
memblock Pointer to previously allocated memory
block
size New size in bytes
seg Segment selector
Remarks
The realloc family of functions changes the size of a previously allocated
memory block. The memblock argument points to the beginning of the memory
block. If memblock is NULL, realloc functions in the same way as malloc and
allocates a new block of size bytes. If memblock is not NULL, it should be a
pointer returned by calloc, malloc, or a prior call to realloc.
The size argument gives the new size of the block, in bytes. The contents of
the block are unchanged up to the shorter of the new and old sizes, although
the new block may be in a different location.
The memblock argument can also point to a block that has been freed, as long
as there has been no intervening call to the corresponding calloc, malloc,
_expand, or realloc function. If successful, the reallocated block is marked
in use.
In large data models (that is, compact-, large-, and huge-model programs),
realloc maps to _frealloc. In small data models (tiny-, small-, and
medium-model programs), realloc maps to _nrealloc.
The various realloc functions reallocate memory in the heap specified in the
following list:
Function Heap
────────────────────────────────────────────────────────────────────────────
realloc Depends on data model of program
_brealloc Based heap specified by seg value
_frealloc Far heap (outside default data segment)
_nrealloc Near heap (inside default data segment)
Return Value
The realloc functions return a void pointer to the reallocated (and possibly
moved) memory block.
The return value is NULL if the size is zero and the buffer argument is not
NULL, or if there is not enough available memory to expand the block to the
given size. In the first case, the original block is freed. In the second,
the original block is unchanged.
The storage space pointed to by the return value is guaranteed to be
suitably aligned for storage of any type of object. To get a pointer to a
type other than void, use a type cast on the return value.
Compatibility
realloc
ANSI DOS OS/2 UNIX XENIX
_brealloc, _frealloc, _nrealloc
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
calloc functions, free functions, malloc functions
Example
/* REALLOC.C: This program allocates a block of memory for buffer
* and then uses _msize to display the size of that block. Next, it
* uses realloc to expand the amount of memory used by buffer
* and then calls _msize again to display the new amount of
* memory allocated to buffer.
*/
#include <stdio.h>
#include <malloc.h>
#include <stdlib.h>
void main()
{
long *buffer;
size_t size;
if( (buffer = (long *)malloc( 1000 * sizeof( long ) )) == NULL )
exit( 1 );
size = _msize( buffer );
printf( "Size of block after malloc of 1000 longs: %u\n", size );
/* Reallocate and show new size: */
if( (buffer = realloc( buffer, size + (1000 * sizeof( long )) )) ==
NULL )
exit( 1 );
size = _msize( buffer );
printf( "Size of block after realloc of 1000 more longs: %u\n", size );
free( buffer );
}
Output
Size of block after malloc of 1000 longs: 4000
Size of block after realloc of 1000 more longs: 8000
_rectangle Functions
────────────────────────────────────────────────────────────────────────────
Description
Draw rectangles.
#include <graph.h>
short _far _rectangle( short control, short x1, short y1, short x2, short
y2 );
short _far _rectangle_w( short control, double wx1, double wy1, double
wx2,
double wy2 );
short _far _rectangle_wxy( short control, struct _wxycoord _far *pwxy1,
struct _wxycoord _far *pwxy2 );
control Fill flag
x1, y1 Upper-left corner
x2, y2 Lower-right corner
wx1, wy1 Upper-left corner
wx2, wy2 Lower-right corner
pwxy1 Upper-left corner
pwxy2 Lower-right corner
Remarks
The _rectangle functions draw a rectangle with the current line style.
The _rectangle function uses the view coordinate system. The view coordinate
points (x1, y1) and (x2, y2) are the diagonally opposed corners of the
rectangle.
The _rectangle_w function uses the window coordinate system. The window
coordinate points (wx1, wy1) and (wx2, wy2) are the diagonally opposed
corners of the rectangle.
The _rectangle_wxy function uses the window coordinate system. The window
coordinate points (pwxy1) and (pwxy2) are the diagonally opposed corners of
the rectangle. The coordinates for the _rectangle_wxy routine are given in
terms of an _wxycoord structure (defined in GRAPH.H), which contains the
following elements:
Element Description
────────────────────────────────────────────────────────────────────────────
double wx window x coordinate
double wy window y coordinate
The control parameter can be one of the following manifest constants:
Constant Action
────────────────────────────────────────────────────────────────────────────
_GFILLINTERIOR Fills the figure with the current color
using the current fill mask
_GBORDER Does not fill the rectangle
If the current fill mask is NULL, no mask is used. Instead, the rectangle is
filled with the current color.
If you try to fill the rectangle with the _floodfill function, the rectangle
must be bordered by a solid line-style pattern.
Return Value
The function returns a nonzero value if the rectangle is drawn successfully,
or 0 if not.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_arc functions, _ellipse functions, _floodfill, _getcolor, _lineto
functions, _pie functions, _setcolor, _setfillmask
Example
/* RECT.C: This program draws a rectangle. */
#include <conio.h>
#include <stdlib.h>
#include <graph.h>
void main()
{
/* Find a valid graphics mode. */
if( !_setvideomode( _MAXRESMODE ) )
exit( 1 );
_rectangle( _GBORDER, 80, 50, 240, 150 );
getch();
_setvideomode( _DEFAULTMODE );
}
_registerfonts
────────────────────────────────────────────────────────────────────────────
Description
Initializes the fonts graphics system.
#include <graph.h>
short _far _registerfonts( unsigned char _far *pathname );
pathname Path name specifying .FON files to be
registered
Remarks
The _registerfonts function initializes the fonts graphics system. Font
files must be registered with the _registerfonts function before any other
font-related library function (_getgtextextent, _outgtext, _setfont,
_unregisterfonts) can be used.
The _registerfonts function reads the specified files and loads font header
information into memory. Each font header takes up about 140 bytes of
memory.
The pathname argument is the path specification and file name of valid .FON
files. The pathname can contain standard DOS wild-card characters.
The font functions affect only the output from the font output function
_outgtext; no other C run-time output functions are affected by font usage.
Return Value
The _registerfonts function returns a positive value which indicates the
number of fonts successfully registered. A negative return value indicates
failure. The following negative values may be returned:
Value Meaning
────────────────────────────────────────────────────────────────────────────
-1 No such file or directory.
-2 One or more of the .FON files was not a
valid, binary .FON file.
-3 One or more of the .FON files is
damaged.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_getfontinfo, _getgtextextent, _outgtext, _setfont, _unregisterfonts
Example
See the example for _outgtext.
_remapallpalette, _remappalette
────────────────────────────────────────────────────────────────────────────
Description
Remap all palette colors.
#include <graph.h>
short _far _remapallpalette( long _far *colors );
long _far _remappalette( short index, long color );
colors Color value array
index Color index to reassign
color Color value to assign color index to
Remarks
The _remapallpalette function remaps the entire color palette simultaneously
to the colors given in the colors array. The colors array is an array of
long integers where the size of the array varies from 16 to 64 to 256,
depending on the video mode. The number of colors mapped depends on the
number of colors supported by the current video mode. The _remapallpalette
function works in all video modes (except _ORESCOLOR mode), but only with
EGA, MCGA, or VGA hardware.
The default color values for a color text on 16-color graphics mode are
shown below:
╓┌───────┌─────────┌───────┌─────────────────────────────────────────────────╖
Number Color Number Color
────────────────────────────────────────────────────────────────────────────
0 Black 8 Dark gray
1 Blue 9 Light blue
Number Color Number Color
────────────────────────────────────────────────────────────────────────────
1 Blue 9 Light blue
2 Green 10 Light green
3 Cyan 11 Light cyan
4 Red 12 Light red
5 Magenta 13 Light magenta
6 Brown 14 Yellow
7 White 15 Bright white
The first array element specifies the new color value to be associated with
color index 0 (the background color in graphics modes). After the call to
_remapallpalette, calls to _setcolor will index into the new array of
colors. The mapping done by _remapallpalette affects the current display
immediately.
The colors array can be larger than the number of colors supported by the
current video mode, but only the first n elements are used, where n is the
number of colors supported by the current video mode, as indicated by the
numcolors element of the videoconfig structure.
The long color value is defined by specifying three bytes of data
representing the three component colors: red, green, and blue.
Each of the three bytes represents the intensity of one of the red, green,
or blue component colors, and must be in the range 0-31. In other words, the
low-order six bits of each byte specify the component's intensity and the
high-order two bits should be zero. The fourth (high-order) byte in the long
is unused and should be set to zero. The diagram below shows the ordering of
bytes within the long value.
For example, to create a lighter shade of blue, start with lots of blue, add
some green, and maybe a little bit of red. The three-byte color value would
be:
blue byte green byte red byte
00011111 00101111 00011111
high ───────────────-> low order
Manifest constants are defined in GRAPH.H for the default color values
corresponding to color indices 0-15 in color text modes and 16-color
graphics modes, as shown below:
╓┌──────┌──────────┌──────┌──────────────────────────────────────────────────╖
Index Constant Index Constant
────────────────────────────────────────────────────────────────────────────
0 _BLACK 8 _GRAY
1 _BLUE 9 _LIGHTBLUE
2 _GREEN 10 _LIGHTGREEN
3 _CYAN 11 _LIGHTCYAN
4 _RED 12 _LIGHTRED
Index Constant Index Constant
────────────────────────────────────────────────────────────────────────────
4 _RED 12 _LIGHTRED
5 _MAGENTA 13 _LIGHTMAGENTA
6 _BROWN 14 _YELLOW
7 _WHITE 15 _BRIGHTWHITE
The VGA supports a palette of 262,144 colors (256K) in color modes, and the
EGA supports a palette of only 64 different colors. Color values for EGA are
specified in exactly the same way as with the VGA; however, the low-order
four bits of each byte are simply ignored.
The _remappalette function assigns a new color value color to the color
index given by index. This remapping affects the current display
immediately.
The _remappalette function works in all graphics modes, but only with EGA,
MCGA, or VGA hardware. An error results if the function is called while
using any other configuration.
The color value used in _remappalette is defined and used exactly as noted
above for _remapallpalette. The range of color indices used with
_remappalette depends on the number of colors supported by the video mode.
The _remapallpalette and _remappalette functions do not affect the
presentation-graphics palettes, which are manipulated with the
_pg_getpalette, _pg_setpalette, and _pg_resetpalette functions.
If a VGA or MCGA adapter is connected to an analog monochrome monitor, the
color value is transformed into its gray-scale equivalent, based on the
weighted sum of its red, green, and blue components (30% red + 50% green +
11% blue). The original red, green, and blue values are lost.
Return Value
If successful, _remapallpalette returns -1 (short). In case of an error,
_remapallpalette returns 0 (short).
If successful, _remappalette returns the color value previously assigned to
index, or -1 if the function is inoperative (not EGA, VGA, or MCGA), or if
the color index is out of range.
Note that _remapallpalette returns a short value and _remappalette returns a
long value.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_selectpalette, _setbkcolor, _setvideomode
Example
/* RMPALPAL.C: This example illustrates functions for assigning
* color values to color indices. Functions illustrated include:
* _remappalette _remapallpalette
*/
#include <graph.h>
#include <conio.h>
#include <stdio.h>
#include <stdlib.h>
/* Macro for mixing Red, Green, and Blue elements of color */
#define RGB(r,g,b) (((long) ((b) << 8 | (g)) << 8) | (r))
long tmp, pal[256];
void main()
{
short red, blue, green;
short inc, i, mode, cells, x, y, xinc, yinc;
char buf[40];
struct videoconfig vc;
/* Make sure all palette numbers are valid. */
for( i = 0; i < 256; i++ )
pal[i] = _BLACK;
/* Loop through each graphics mode that supports palettes. */
for( mode = _MRES4COLOR; mode <= _MRES256COLOR; mode++ )
{
if( mode == _ERESNOCOLOR )
mode++;
if( !_setvideomode( mode ) )
continue;
/* Set variables for each mode. */
_getvideoconfig( &vc );
switch( vc.numcolors )
{
case 256: /* Active bits in this order: */
cells = 13;
inc = 12; /* ???????? ??bbbbbb ??gggggg ??rrrrrr */
break;
case 16:
cells = 4;
if( (vc.mode == _ERESCOLOR) || (vc.mode == _VRES16COLOR) )
inc = 16; /* ???????? ??bb???? ??gg???? ??rr???? */
else
inc = 32; /* ???????? ??Bb???? ??Gg???? ??Rr???? */
break;
case 4:
cells = 2;
inc = 32; /* ???????? ??Bb???? ??Gg???? ??Rr???? */
break;
default:
continue;
}
xinc = vc.numxpixels / cells;
yinc = vc.numypixels / cells;
/* Fill palette arrays in BGR order. */
for( i = 0, blue = 0; blue < 64; blue += inc )
for( green = 0; green < 64; green += inc )
for( red = 0; red < 64; red += inc )
{
pal[i] = RGB( red, green, blue );
/* Special case of using 6 bits to represent 16 colors.
* If both bits are on for any color, intensity is set.
* If one bit is set for a color, the color is on.
*/
if( inc == 32 )
pal[i + 8] = pal[i] | (pal[i] >> 1);
i++;
}
/* If palettes available, remap all palettes at once. */
if( !_remapallpalette( pal ) )
{
_setvideomode( _DEFAULTMODE );
_outtext( "Palettes not available with this adapter" );
exit( 1 );
}
/* Draw colored squares. */
for( i = 0, x = 0; x < ( xinc * cells ); x += xinc )
for( y = 0; y < ( yinc * cells); y += yinc )
{
_setcolor( i++ );
_rectangle( _GFILLINTERIOR, x, y, x + xinc, y + yinc );
}
/* Note that for 256-color mode, not all colors are shown. The
number
* of colors from mixing three base colors can never be the same as
* the number that can be shown on a two-dimensional grid.
*/
sprintf( buf, "Mode %d has %d colors", vc.mode, vc.numcolors );
_setcolor( vc.numcolors / 2 );
_outtext( buf );
getch();
/* Change each palette entry separately in GRB order. */
for( i = 0, green = 0; green < 64; green += inc )
for( red = 0; red < 64; red += inc )
for(blue = 0; blue < 64; blue += inc )
{
tmp = RGB( red, green, blue );
_remappalette( i, tmp );
if( inc == 32 )
_remappalette( i + 8, tmp | (tmp >> 1) );
i++;
}
getch();
}
_setvideomode( _DEFAULTMODE );
}
remove
────────────────────────────────────────────────────────────────────────────
Description
Deletes a file.
#include <stdio.h> Required for ANSI compatibility
#include <io.h> Use either IO.H or STDIO.H
int remove( const char *path );
path Path name of file to be removed
Remarks
The remove function deletes the file specified by path.
Return Value
The function returns 0 if the file is successfully deleted. Otherwise, it
returns -1 and sets errno to one of these values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
EACCES Path name specifies a read-only file.
ENOENT File or path name not found, or path
name specifies a directory.
Compatibility
ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
unlink
Example
/* REMOVE.C: This program uses remove to delete REMOVE.OBJ. */
#include <stdio.h>
void main()
{
if( remove( "remove.obj" ) == -1 )
perror( "Could not delete 'REMOVE.OBJ'" );
else
printf( "Deleted 'REMOVE.OBJ'\n" );
}
Output
Deleted 'REMOVE.OBJ'
rename
────────────────────────────────────────────────────────────────────────────
Description
Renames a file or directory.
#include <stdio.h> Required for ANSI compatibility
#include <io.h> Use either IO.H or STDIO.H
int rename( const char *oldname, const char *newname );
oldname Pointer to old name
newname Pointer to new name
Remarks
The rename function renames the file or directory specified by oldname to
the name given by newname. The old name must be the path name of an existing
file or directory. The new name must not be the name of an existing file or
directory.
The rename function can be used to move a file from one directory to another
by giving a different path name in the newname argument. However, files
cannot be moved from one device to another (for example, from drive A to
drive B). Directories can only be renamed, not moved.
Return Value
The rename function returns 0 if it is successful. On an error, it returns a
nonzero value and sets errno to one of the following values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
EACCES File or directory specified by newname
already exists or could not be created
(invalid path); or oldname is a
directory and newname specifies a
different path.
ENOENT File or path name specified by oldname
not found.
EXDEV Attempt to move a file to a different
device.
Compatibility
ANSI DOS OS/2 ▼ UNIX ▼ XENIX
Example
/* RENAMER.C: This program attempts to rename a file named RENAMER.OBJ to
* RENAMER.JBO. For this operation to succeed, a file named RENAMER.OBJ
* must exist and a file named RENAMER.JBO must not exist.
*/
#include <stdio.h>
void main()
{
int result;
char old[] = "RENAMER.OBJ", new[] = "RENAMER.JBO";
/* Attempt to rename file: */
result = rename( old, new );
if( result != 0 )
printf( "Could not rename '%s'\n", old );
else
printf( "File '%s' renamed to '%s'\n", old, new );
}
Output
File 'RENAMER.OBJ' renamed to 'RENAMER.JBO'
rewind
────────────────────────────────────────────────────────────────────────────
Description
Repositions the file pointer to the beginning of a file.
#include <stdio.h>
void rewind( FILE *stream );
stream Pointer to FILE structure
Remarks
The rewind function repositions the file pointer associated with stream to
the beginning of the file. A call to rewind is equivalent to
(void) fseek( stream, 0L, SEEK_SET );
except that rewind clears the error indicators for the stream, and fseek
does not. Both rewind and fseek clear the end-of-file indicator. Also, fseek
returns a value that indicates whether the pointer was successfully moved,
but rewind does not return any value.
You can also use the rewind function to clear the keyboard buffer. Use the
rewind function with the stream stdin, which is associated with the keyboard
by default.
Return Value
The rewind function has no return value.
Compatibility
ANSI DOS OS/2 UNIX XENIX
Example
/* REWIND.C: This program first opens a file named REWIND.OUT for input
and
* output and writes two integers to the file. Next, it uses rewind to
* reposition the file pointer to the beginning of the file and reads
* the data back in.
*/
#include <stdio.h>
void main()
{
FILE *stream;
int data1, data2;
data1 = 1;
data2 = -37;
if( (stream = fopen( "rewind.out", "w+" )) != NULL )
{
fprintf( stream, "%d %d", data1, data2 );
printf( "The values written are: %d and %d\n", data1, data2 );
rewind( stream );
fscanf( stream, "%d %d", &data1, &data2 );
printf( "The values read are: %d and %d\n", data1, data2 );
fclose( stream );
}
}
Output
The values written are: 1 and -37
The values read are: 1 and -37
rmdir
────────────────────────────────────────────────────────────────────────────
Description
Deletes a directory.
#include <direct.h> Required only for function declarations
int rmdir( char *dirname );
dirname Path name of directory to be removed
Remarks
The rmdir function deletes the directory specified by dirname. The directory
must be empty, and it must not be the current working directory or the root
directory.
Return Value
The rmdir function returns the value 0 if the directory is successfully
deleted. A return value of -1 indicates an error, and errno is set to one of
the following values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
EACCES The given path name is not a directory;
or the directory is not empty; or the
directory is the current working
directory or the root directory.
ENOENT Path name not found.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
chdir, mkdir
Example
/* MAKEDIR.C */
#include <direct.h>
#include <stdlib.h>
#include <stdio.h>
void main()
{
int result;
if( mkdir( "\\testtmp" ) == 0 )
{
printf( "Directory '\\testtmp' was successfully created\n" );
system( "dir \\testtmp" );
if( rmdir( "\\testtmp" ) == 0 )
printf( "Directory '\\testtmp' was successfully removed\n" );
else
printf( "Problem removing directory '\\testtmp'\n" );
}
else
printf( "Problem creating directory '\\testtmp'\n" );
}
Output
Directory '\testtmp' was successfully created
The volume label in drive C is OS2.
Directory of C:\TESTTMP
. <DIR> 6-19-89 11:20a
.. <DIR> 6-19-89 11:20a
2 File(s) 12730368 bytes free
Directory '\testtmp' was successfully removed
rmtmp
────────────────────────────────────────────────────────────────────────────
Description
Removes temporary files.
#include <stdio.h>
int rmtmp( void );
Remarks
The rmtmp function is used to clean up all the temporary files in the
current directory. The function removes only those files created by tmpfile
and should be used only in the same directory in which the temporary files
were created.
Return Value
The rmtmp function returns the number of temporary files closed and deleted.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
flushall, tmpfile, tmpnam
Example
/* TMPFILE.C: This program uses tmpfile to create a temporary file,
* then deletes this file with rmtmp.
*/
#include <stdio.h>
void main()
{
FILE *stream;
char tempstring[] = "String to be written";
int i;
/* Create temporary files. */
for( i = 1; i <= 10; i++ )
{
if( (stream = tmpfile()) == NULL )
perror( "Could not open new temporary file\n" );
else
printf( "Temporary file %d was created\n", i );
}
/* Remove temporary files. */
printf( "%d temporary files deleted\n", rmtmp() );
}
Output
Temporary file 1 was created
Temporary file 2 was created
Temporary file 3 was created
Temporary file 4 was created
Temporary file 5 was created
Temporary file 6 was created
Temporary file 7 was created
Temporary file 8 was created
Temporary file 9 was created
Temporary file 10 was created
10 temporary files deleted
_rotl, _rotr
────────────────────────────────────────────────────────────────────────────
Description
Rotate bits to the left (_rotl) or right (_rotr).
#include <stdlib.h>
unsigned int _rotl( unsigned int value, int shift );
unsigned int _rotr( unsigned int value, int shift );
value Value to be rotated
shift Number of bits to shift
Remarks
The _rotl and _rotr functions rotate the unsigned value by shift bits. The
_rotl function rotates the value left. The _rotr function rotates the value
right. Both functions "wrap" bits rotated off one end of value to the other
end.
Return Value
Both functions return the rotated value. There is no error return.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_lrotl, _lrotr
Example
/* ROT.C: This program uses _rotr and _rotl with different shift
* values to rotate an integer.
*/
#include <stdlib.h>
#include <stdio.h>
void main()
{
unsigned val = 0x0fd93;
printf( "0x%4.4x rotated left three times is 0x%4.4x\n",
val, _rotl( val, 3 ) );
printf( "0x%4.4x rotated right four times is 0x%4.4x\n",
val, _rotr( val, 4 ) );
}
Output
0xfd93 rotated left three times is 0xec9f
0xfd93 rotated right four times is 0x3fd9
scanf
────────────────────────────────────────────────────────────────────────────
Description
Reads formatted data from the standard input stream.
#include <stdio.h>
int scanf( const char *format [[,argument]]... );
format Format control
argument Optional argument
Remarks
The scanf function reads data from the standard input stream stdin into the
locations given by argument. Each argument must be a pointer to a variable
with a type that corresponds to a type specifier in format. The format
controls the interpretation of the input fields. The format can contain one
or more of the following:
■ White-space characters: blank (' '); tab (\t); or newline (\n). A
white-space character causes scanf to read, but not store, all
consecutive white-space characters in the input up to the next
non-white-space character. One white-space character in the format
matches any number (including 0) and combination of white-space
characters in the input.
■ Non-white-space characters, except for the percent sign (%). A
non-white-space character causes scanf to read, but not store, a
matching non-white-space character. If the next character in stdin
does not match, scanf terminates.
■ Format specifications, introduced by the percent sign (%). A format
specification causes scanf to read and convert characters in the input
into values of a specified type. The value is assigned to an argument
in the argument list.
The format is read from left to right. Characters outside format
specifications are expected to match the sequence of characters in stdin;
the matching characters in stdin are scanned but not stored. If a character
in stdin conflicts with the format specification, scanf terminates. The
character is left in stdin as if it had not been read.
When the first format specification is encountered, the value of the first
input field is converted according to this specification and stored in the
location that is specified by the first argument. The second format
specification causes the second input field to be converted and stored in
the second argument, and so on through the end of the format string.
An input field is defined as all characters up to the first white-space
character (space, tab, or newline), or up to the first character that cannot
be converted according to the format specification, or until the field width
(if specified) is reached. If there are too many arguments for the given
specifications, the extra arguments are evaluated but ignored. The results
are unpredictable if there are not enough arguments for the format
specification.
A format specification has the following form:
%[[*]] [[width]] [[{F | N}]] [[{h | l}]]type
Each field of the format specification is a single character or a number
signifying a particular format option. The type character, which appears
after the last optional format field, determines whether the input field is
interpreted as a character, a string, or a number. The simplest format
specification contains only the percent sign and a type character (for
example, %s ).
Each field of the format specification is discussed in detail below. If a
percent sign (%) is followed by a character that has no meaning as a
format-control character, that character and the following characters (up to
the next percent sign) are treated as an ordinary sequence of
characters─that is, a sequence of characters that must match the input. For
example, to specify that a percent-sign character is to be input, use %%.
An asterisk (*) following the percent sign suppresses assignment of the next
input field, which is interpreted as a field of the specified type. The
field is scanned but not stored.
The width is a positive decimal integer controlling the maximum number of
characters to be read from stdin. No more than width characters are
converted and stored at the corresponding argument. Fewer than width
characters may be read if a white-space character (space, tab, or newline)
or a character that cannot be converted according to the given format occurs
before width is reached.
The optional F and N prefixes allow the user to specify whether the argument
is far or near, respectively. F should be prefixed to an argument pointing
to a far object, while N should be prefixed to an argument pointing to a
near object. Note also that the F and N prefixes are not part of the ANSI
definition for scanf, but are instead Microsoft extensions, which should not
be used when ANSI portability is desired.
The optional prefix l indicates that the long version of the following type
is to be used, while the prefix h indicates that the short version is to be
used. The corresponding argument should point to a long or double object
(with the l character) or a short object (with the h character). The l and h
modifiers can be used with the d, i, n, o, x, and u type characters. The l
modifier can also be used with the e, f, and g type characters. The l and h
modifiers are ignored if specified for any other type.
For scanf, N and F refer to the "distance" to the object being read in (near
or far) and h and l refer to the "size" of the object being read in (16-bit
short or 32-bit long). The list below clarifies this use of N, F, l, and h:
Program Code Action
────────────────────────────────────────────────────────────────────────────
scanf( "%Ns", &x ); Read a string into near memory
scanf( "%Fs", &x ); Read a string into far memory
scanf( "%Nd", &x ); Read an int into near memory
scanf( "%Fd", &x ); Read an int into far memory
scanf( "%Nld", &x ); Read a long int into near memory
scanf( "%Fld", &x ); Read a long int into far memory
scanf( "%Nhp", &x ); Read a 16-bit pointer into near memory
scanf( "%Nlp", &x ); Read a 32-bit pointer into near memory
scanf( "%Fhp", &x ); Read a 16-bit pointer into far memory
scanf( "%Flp", &x ); Read a 32-bit pointer into far memory
The type characters and their meanings are described in Table R.5.
To read strings not delimited by space characters, a set of characters in
brackets ([ ]) can be substituted for the s (string) type character. The
corresponding input field is read up to the first character that does not
appear in the bracketed character set. If the first character in the set is
a caret (^), the effect is reversed: the input field is read up to the first
character that does appear in the rest of the character set.
Note that %[a-z] and %[z-a] are interpreted as equivalent to %[abcde...z].
This is a common scanf extension, but note that it is not required by the
ANSI specification.
To store a string without storing a terminating null character ('\0'), use
the specification %nc, where n is a decimal integer. In this case, the c
type character indicates that the argument is a pointer to a character
array. The next n characters are read from the input stream into the
specified location, and no null character ('\0') is appended. If n is not
specified, the default value for it is 1.
The scanf function scans each input field, character by character. It may
stop reading a particular input field before it reaches a space character
for a variety of reasons: the specified width has been reached; the next
character cannot be converted as specified; the next character conflicts
with a character in the control string that it is supposed to match; or the
next character fails to appear in a given character set. For whatever
reason, when scanf stops reading an input field, the next input field is
considered to begin at the first unread character. The conflicting
character, if there is one, is considered unread and is the first character
of the next input field or the first character in subsequent read operations
on stdin.
Table R.5 Type Characters for scanf
╓┌──────────────────────────┌──────────────────────────┌─────────────────────►
Character Type of Input Expected Type of Argument
─────────────────────────────────────────────────────────────────────────────
d Decimal integer Pointer to int
o Octal integer Pointer to int
x Hexadecimal integer(1) Pointer to int
Character Type of Input Expected Type of Argument
─────────────────────────────────────────────────────────────────────────────
i Decimal, hexadecimal, or Pointer to int
octal integer
u Unsigned decimal integer Pointer to unsigned int
U Unsigned decimal integer Pointer to unsigned lon
e, E Floating-point value Pointer to float
f consisting of an optional
g, G sign (+ or -), a series
of one or more decimal
digits containing a
decimal point, and an
optional exponent ("e" or
"E") followed by an
optionally signed integer
value.
Character Type of Input Expected Type of Argument
─────────────────────────────────────────────────────────────────────────────
c Character. White-space Pointer to char
characters that are
ordinarily skipped are
read when c is specified;
to read the next
non-white-space
character, use %1s.
s String Pointer to character
array large enough for
input field plus a
terminating null
character ('\0'), which
is automatically
appended.
n No input read from stream Pointer to int, into
or buffer. which is stored the
Character Type of Input Expected Type of Argument
─────────────────────────────────────────────────────────────────────────────
or buffer. which is stored the
number of characters
successfully read from
the stream or buffer up
to that point in the
current call to scanf.
p Value in the form xxxx: Pointer to far pointer
yyyy, where the digits x void
and y are uppercase
hexadecimal digits.
─────────────────────────────────────────────────────────────────────────────
1 Since the input for a %x format specifier is always interpreted as a
hexadecimal number, the input should not include a leading 0x. (If 0x is
included, the 0 is interpreted as a hexadecimal input value.)
Return Value
The scanf function returns the number of fields that were successfully
converted and assigned. The return value may be less than the number
requested in the call to scanf. The return value does not include fields
that were read but not assigned.
The return value is EOF if the end-of-file or end-of-string is encountered
in the first attempt to read a character.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
fscanf, printf, sscanf, vfprintf, vprintf, vsprintf
Example
/* SCANF.C: This program receives formatted input using scanf. */
#include <stdio.h>
void main()
{
int i;
float fp;
char c, s[81];
int result;
printf( "Enter an integer, a floating-point number, "
"a character and a string:\n" );
result = scanf( "%d %f %c %s", &i, &fp, &c, s );
printf( "\nThe number of fields input is %d\n", result );
printf( "The contents are: %d %f %c %s\n", i, fp, c, s );
}
Output
Enter an integer, a floating-point number, a character and a string:
71
98.6
h
White space stops input
The number of fields input is 4
The contents are: 71 98.599998 h White
_scrolltextwindow
────────────────────────────────────────────────────────────────────────────
Description
Scrolls the text in a text window.
#include <graph.h>
void _far _scrolltextwindow( short lines );
lines Number of lines to scroll
Remarks
The _scrolltextwindow function scrolls the text in a text window (previously
defined by the _settextwindow function). The lines argument specifies the
number of lines to scroll. A positive value of lines scrolls the window up
(the usual direction); a negative value scrolls the window down. Specifying
a number larger than the height of the current text window is equivalent to
calling _clearscreen( _GWINDOW ). A value of 0 for lines has no effect on
the text.
Return Value
None.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_gettextposition, _outmem, _outtext, _settextposition, _settextwindow
Example
/* SCRTXWIN.C: This program displays text in text windows and then
* scrolls, inserts, and deletes lines.
*/
#include <stdio.h>
#include <conio.h>
#include <graph.h>
void deleteline( void );
void insertline( void );
void status( char *msg );
void main()
{
short row;
char buf[40];
/* Set up screen for scrolling, and put text window around scroll area.
*/
_settextrows( 25 );
_clearscreen( _GCLEARSCREEN );
for( row = 1; row <= 25; row++ )
{
_settextposition( row, 1 );
sprintf( buf, "Line %c %2d", row + 'A' - 1, row );
_outtext( buf );
}
getch();
_settextwindow( 1, 1, 25, 10 );
/* Delete some lines. */
_settextposition( 11, 1 );
for( row = 12; row < 20; row++ )
deleteline();
status( "Deleted 8 lines" );
/* Insert some lines. */
_settextposition( 5, 1 );
for( row = 1; row < 6; row++ )
insertline();
status( "Inserted 5 lines" );
/* Scroll up and down. */
_scrolltextwindow( -7 );
status( "Scrolled down 7 lines" );
_scrolltextwindow( 5 );
status( "Scrolled up 5 lines" );
_setvideomode( _DEFAULTMODE );
}
/* Delete lines by scrolling them off the top of the current text window.
* Save and restore original window.
*/
void deleteline()
{
short left, top, right, bottom;
struct rccoord rc;
_gettextwindow( &top, &left, &bottom, &right );
rc = _gettextposition();
_settextwindow( rc.row, left, bottom, right );
_scrolltextwindow( _GSCROLLUP );
_settextwindow( top, left, bottom, right );
_settextposition( rc.row, rc.col );
}
/* Insert some lines by scrolling in blank lines from the top of the
* current text window. Save and restore original window.
*/
void insertline()
{
short left, top, right, bottom;
struct rccoord rc;
_gettextwindow( &top, &left, &bottom, &right );
rc = _gettextposition();
_settextwindow( rc.row, left, bottom, right );
_scrolltextwindow( _GSCROLLDOWN );
_settextwindow( top, left, bottom, right );
_settextposition( rc.row, rc.col );
}
/* Display and clear status in its own window. */
void status( char *msg )
{
short left, top, right, bottom;
struct rccoord rc;
_gettextwindow( &top, &left, &bottom, &right );
_settextwindow( 1, 50, 2, 80 );
_outtext( msg );
getch();
_clearscreen( _GWINDOW );
_settextwindow( top, left, bottom, right );
}
_searchenv
────────────────────────────────────────────────────────────────────────────
Description
Searches for a file using environment paths.
#include <stdlib.h>
void _searchenv( char *filename, char *varname, char *pathname );
filename Name of file to search for
varname Environment to search
pathname Buffer to store complete path
Remarks
The _searchenv routine searches for the target file in the specified domain.
The varname variable can be any environment variable which specifies a list
of directory paths, such as PATH, LIB, INCLUDE, or other user-defined
variables. It is most often PATH, which searches for filename on all paths
specified in the PATH variable. The _searchenv function is case-sensitive,
so the varname variable should match the case of the environment variable.
The routine first searches for the file in the current working directory. If
it doesn't find the file, it next looks through the directories specified by
the environment variable.
If the target file is found in one of the directories, the newly created
path is copied into the buffer pointed to by pathname. You must ensure that
there is sufficient space for the constructed path name. If the filename
file is not found, pathname will contain an empty null-terminated string.
Return Value
The _searchenv function does not return a value.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
getenv, putenv
Example
/* SEARCHEN.C: This program searches for a file in a directory
* specified by an environment variable.
*/
#include <stdlib.h>
#include <stdio.h>
void main()
{
char pathbuffer[_MAX_PATH];
char searchfile[] = "CL.EXE";
char envvar[] = "PATH";
/* Search for file in PATH environment variable: */
_searchenv( searchfile, envvar, pathbuffer );
if( *pathbuffer != '\0' )
printf( "Path for %s: %s\n", searchfile, pathbuffer );
else
printf( "%s not found\n", searchfile );
}
Output
Path for CL.EXE: C:\BIN\CL.EXE
segread
────────────────────────────────────────────────────────────────────────────
Description
Gets the current values of segment registers.
#include <dos.h>
void segread( struct SREGS *segregs );
segregs Segment-register values
Remarks
The segread function fills the structure pointed to by segregs with the
current contents of the segment registers. The SREGS union is described in
the reference section for int86x. This function is intended to be used with
the intdosx and int86x functions to retrieve segment-register values for
later use.
Return Value
None.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
FP_SEG, intdosx, int86x
Example
/* SEGREAD.C: This program gets the current segment values with segread.
*/
#include <dos.h>
#include <stdio.h>
void main()
{
struct SREGS segregs;
unsigned cs, ds, es, ss;
/* Read the segment register values */
segread( &segregs );
cs = segregs.cs;
ds = segregs.ds;
es = segregs.es;
ss = segregs.ss;
printf( "CS = 0x%.4x DS = 0x%.4x ES = 0x%.4x SS = 0x%.4x\n",
cs, ds, es, ss );
}
Output
CS = 0x0047 DS = 0x0067 ES = 0x0067 SS = 0x0067
CS = 0x2bcc DS = 0x2ce8 ES = 0x2ba3 SS = 0x2ce8
_selectpalette
────────────────────────────────────────────────────────────────────────────
Description
Selects a graphics palette.
#include <graph.h>
short _far _selectpalette( short number );
number Palette number
Remarks
The _selectpalette function works only under the video modes _MRES4COLOR and
_MRESNOCOLOR. A palette consists of a selectable background color (Color 0)
and three set colors. Under the _MRES4COLOR mode, the number argument
selects one of the four predefined palettes shown in Table R.6.
Table R.6 _MRES4COLOR Palette Colors
╓┌───────────────┌─────────────┌───────────────┌─────────────────────────────╖
────────────────────────────────────────────────────────────────────────────
Palette Number Color 1 Color 2 Color 3
────────────────────────────────────────────────────────────────────────────
Palette Number Color 1 Color 2 Color 3
0 Green Red Brown
1 Cyan Magenta Light gray
2 Light green Light red Yellow
3 Light cyan Light magenta White
────────────────────────────────────────────────────────────────────────────
The _MRESNOCOLOR video mode is used with black-and-white displays, producing
palettes consisting of various shades of gray. It will also produce color
when used with a color display. The number of palettes available depends
upon whether a CGA or EGA hardware package is employed. Under a CGA
configuration, only the two palettes shown in Table R.7 are available.
Table R.7 _MRESNOCOLOR Mode CGA Palette Colors
╓┌───────────────┌─────────────┌──────────────┌──────────────────────────────╖
────────────────────────────────────────────────────────────────────────────
Palette Color 1 Color 2 Color 3
Number
0 Blue Red Light gray
1 Light blue Light red White
────────────────────────────────────────────────────────────────────────────
Under the EGA configuration, the three palettes shown in Table R.8 are
available in the _MRESNOCOLOR video mode.
Table R.8 _MRESNOCOLOR Mode EGA Palette Colors
╓┌───────────────┌─────────────┌─────────────┌───────────────────────────────╖
────────────────────────────────────────────────────────────────────────────
Palette Color 1 Color 2 Color 3
Number
0 Green Red Brown
1 Light green Light red Yellow
2 Light cyan Light red Yellow
────────────────────────────────────────────────────────────────────────────
Note that with an EGA in _MRESNOCOLOR video mode, Palette 3 is identical to
Palette 1.
Return Value
The function returns the value of the previous palette. There is no error
return.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_getvideoconfig, _setbkcolor, _setvideomode
Example
/* SELPAL.C: This program changes the current CGA palette. */
#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#include <graph.h>
long bkcolor[8] = { _BLACK, _BLUE, _GREEN, _CYAN,
_RED, _MAGENTA, _BROWN, _WHITE };
char *bkname [] = { "BLACK", "BLUE", "GREEN", "CYAN",
"RED", "MAGENTA", "BROWN", "WHITE" };
void main()
{
int i, j, k;
if ( !_setvideomode( _MRES4COLOR ) )
{
printf( "No palettes available" );
exit( 1 );
}
for( i = 0; i < 4; i++ ) /* Palette loop */
{
_selectpalette( i );
for( k = 0; k < 8; k++ ) /* Background color loop */
{
_clearscreen( _GCLEARSCREEN );
_setbkcolor( bkcolor[k] );
_settextposition( 1, 1 );
printf( "Background: %s\tPalette: %d", bkname[k], i );
for( j = 1; j < 4; j++ ) /* Foreground color loop */
{
_setcolor( j );
_ellipse( _GFILLINTERIOR, 100, j * 30, 220, 80 + (j * 30)
);
}
getch();
}
}
_setvideomode( _DEFAULTMODE );
}
_setactivepage
────────────────────────────────────────────────────────────────────────────
Description
Sets the active page.
#include <graph.h>
short _far _setactivepage( short page );
page Memory page number
Remarks
For hardware and mode configurations with enough memory to support multiple
screen pages, _setactivepage specifies the area in memory in which graphics
output is written. The page argument selects the current active page. The
default page number is 0.
Screen animation can be done by alternating the graphics pages displayed.
Use the _setvisualpage function to display a completed graphics page while
executing graphics statements in another active page.
These functions can also be used to control text output if you use the text
functions _gettextcursor, _settextcursor, _outtext, _settextposition,
_gettextposition, _settextcolor, _gettextcolor, _settextwindow, and
_wrapon instead of the standard C-language I/O functions.
The CGA hardware configuration has only 16K of RAM available to support
multiple video pages, and only in the text mode. The EGA and VGA
configurations may be equipped with up to 256K of RAM for multiple video
pages in graphics mode.
Return Value
If successful, the function returns the page number of the previous active
page. If the function fails, it returns a negative value.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_getactivepage, _getvisualpage, _setvisualpage
Example
/* PAGE.C illustrates video page functions including:
* _getactivepage _getvisualpage _setactivepage _setvisualpage
*/
#include <conio.h>
#include <graph.h>
#include <stdlib.h>
void main()
{
short oldvpage, oldapage, page, row, col, line;
struct videoconfig vc;
char buf[80];
_getvideoconfig( &vc );
if( vc.numvideopages < 4 )
exit( 1 ); /* Fail for OS/2 or monochrome */
oldapage = _getactivepage();
oldvpage = _getvisualpage();
_displaycursor( _GCURSOROFF );
/* Draw arrows in different place on each page. */
for( page = 1; page < 4; page++ )
{
_setactivepage( page );
_settextposition( 12, 16 * page );
_outtext( ">>>>>>>>" );
}
while( !kbhit() )
/* Cycle through pages 1 to 3 to show moving image. */
for( page = 1; page < 4; page++ )
_setvisualpage( page );
getch();
/* Restore original page (normally 0) to restore screen. */
_setactivepage( oldapage );
_setvisualpage( oldvpage );
_displaycursor( _GCURSORON );
}
_setbkcolor
────────────────────────────────────────────────────────────────────────────
Description
Sets the current background color.
#include <graph.h>
long _far _setbkcolor( long color );
color Desired color
Remarks
The _setbkcolor function sets the current background color to the color
value color.
In a color text mode (such as _TEXTC80), _setbkcolor accepts (and
_getbkcolor returns) a color index. The value for the default colors is
given in a table in the description of the _settextcolor function. For
example, _setbkcolor(2L) sets the background color to color index 2. The
actual color displayed depends on the palette mapping for color index 2. The
default is green in a color text mode.
In a color graphics mode (such as _ERESCOLOR), _setbkcolor accepts (and
_getbkcolor returns) a color value. The value for the background color is
given by the manifest constants defined in the GRAPH.H include file. For
example, _setbkcolor( _GREEN) sets the background color in a graphics mode
to green. These manifest constants are provided as a convenience in defining
and manipulating the most common colors. The actual range of colors is, in
general, much greater.
In general, whenever an argument is long, it refers to a color value, and
whenever it is short, it refers to a color index. The two exceptions are
_setbkcolor and _getbkcolor.
Since the background color is color index 0, the _remappalette function will
act identically to the _setbkcolor function. Unlike _remappalette, however,
_setbkcolor does not require an EGA or VGA environment.
In a text mode, the _setbkcolor function does not affect anything already
appearing on the display; only the subsequent output is affected. In a
graphics mode, it immediately changes all background pixels.
Return Value
In text modes, _setbkcolor returns the color index of the old background
color. In graphics modes, _setbkcolor returns the old color value of color
index 0. There is no error return.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_getbkcolor, _remappalette, _selectpalette
Example
See the example for _getcolor.
setbuf
────────────────────────────────────────────────────────────────────────────
Description
Controls stream buffering.
#include <stdio.h>
void setbuf( FILE *stream, char *buffer );
stream Pointer to FILE structure
buffer User-allocated buffer
Remarks
The setbuf function allows the user to control buffering for stream. The
stream argument must refer to an open file that has not been read or
written. If the buffer argument is NULL, the stream is unbuffered. If not,
the buffer must point to a character array of length BUFSIZ, where BUFSIZ is
the buffer size as defined in STDIO.H. The user-specified buffer, instead of
the default system-allocated buffer for the given stream, is used for I/O
buffering.
The stderr and (in DOS only) stdaux streams are unbuffered by default, but
may be assigned buffers with setbuf.
The setbuf function has been subsumed by the setvbuf function, which should
be the preferred routine for new code. The setbuf function is retained for
compatibility with existing code.
Return Value
None.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
fclose, fflush, fopen, setvbuf
Example
/* SETBUF.C: This program first opens files named DATA1 and DATA2.
* Then it uses setbuf to give DATA1 a user-assigned buffer
* and to change DATA2 so that it has no buffer.
*/
#include <stdio.h>
void main()
{
char buf[BUFSIZ];
FILE *stream1, *stream2;
if( ((stream1 = fopen( "data1", "a" )) != NULL) &&
((stream2 = fopen( "data2", "w" )) != NULL) )
{
/* "stream1" uses user-assigned buffer: */
setbuf( stream1, buf );
printf( "stream1 set to user-defined buffer at: %Fp\n", buf );
/* "stream2" is unbuffered */
setbuf( stream2, NULL );
printf( "stream2 buffering disabled\n" );
fcloseall();
}
Output
stream1 set to user-defined buffer at: 0298:0DF2
stream2 buffering disabled
_setcliprgn
────────────────────────────────────────────────────────────────────────────
Description
Sets the clipping region for graphics.
#include <graph.h>
void _far _setcliprgn( short x1, short y1, short x2, short y2 );
x1, y1 Upper-left corner of clip region
x2, y2 Lower-right corner of clip region
Remarks
The _setcliprgn function limits the display of subsequent graphics output
and font text output to an area of the screen called the "clipping region."
The physical points (x1, y1) and (x2, y2) are the diagonally opposed sides
of a rectangle that defines the clipping region. This function does not
change the view coordinate system. Rather, it merely masks the screen.
Note that the _setcliprgn function affects graphics and font text output
only. To mask the screen for text output, use the _settextwindow function.
Return Value
None.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_settextwindow, _setvieworg, _setviewport, _setwindow
Example
/* SCLIPRGN.C */
#include <stdlib.h>
#include <conio.h>
#include <graph.h>
void main()
{
/* Find a valid graphics mode. */
if( !_setvideomode( _MAXRESMODE ) )
exit( 1 );
/* Set clip region, then draw and ellipse larger than the region. */
_setcliprgn( 0, 0, 200, 125 );
_ellipse( _GFILLINTERIOR, 80, 50, 240, 190 );
getch();
_setvideomode( _DEFAULTMODE );
}
_setcolor
────────────────────────────────────────────────────────────────────────────
Description
Sets the current color.
#include <graph.h>
short _far _setcolor( short color );
color Desired color index
Remarks
The _setcolor function sets the current color index to color. The color
parameter is masked but always within range. The following graphics
functions use the current color: _arc, _ellipse, _floodfill, _lineto,
_outgtext, _pie, _rectangle, and _setpixel.
The _setcolor function accepts an int value as an argument. It is a color
index.
The default color index is the highest numbered color index in the current
palette.
Note that the _setcolor function does not affect the output of the
presentation-graphics functions.
Return Value
This function returns the previous color. If the function fails (e.g., if
used in a text mode), it returns -1.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_arc functions, _ellipse functions, _floodfill, _getcolor, _lineto
functions, _outgtext, _pie functions, _rectangle functions,
_selectpalette, _setpixel functions
Example
/* GPIXEL.C: This program assigns different colors to randomly
* selected pixels.
*/
#include <conio.h>
#include <stdlib.h>
#include <graph.h>
void main()
{
short xvar, yvar;
struct videoconfig vc;
/* Find a valid graphics mode. */
if( !_setvideomode( _MAXCOLORMODE ) )
exit( 1 );
_getvideoconfig( &vc );
/* Draw filled ellipse to turn on certain pixels. */
_ellipse( _GFILLINTERIOR, vc.numxpixels / 6, vc.numypixels / 6,
vc.numxpixels / 6 * 5, vc.numypixels / 6 * 5
);
/* Draw random pixels in random colors... */
while( !kbhit() )
{
/* ...but only if they are already on (inside the ellipse). */
xvar = rand() % vc.numxpixels;
yvar = rand() % vc.numypixels;
if( _getpixel( xvar, yvar ) != 0 )
{
_setcolor( rand() % 16 );
_setpixel( xvar, yvar );
}
}
getch(); /* Throw away the keystroke. */
_setvideomode( _DEFAULTMODE );
}
_setfillmask
────────────────────────────────────────────────────────────────────────────
Description
Sets the fill mask.
#include <graph.h>
void _far _setfillmask( unsigned char _far *mask );
mask Mask array
Remarks
The _setfillmask function sets the current fill mask, which determines the
fill pattern. The mask is an 8-by-8 array of bits in which each bit
represents a pixel. A 1 bit sets the corresponding pixel to the current
color, while a 0 bit leaves the pixel unchanged. The pattern is repeated
over the entire fill area.
If no fill mask is set (mask is NULL─the default), only the current color is
used in fill operations.
Return Value
None.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_ellipse functions, _floodfill, _getfillmask, _pie functions, _rectangle
functions
Example
/* GFILLMSK.C: This program illustrates _getfillmask and _setfillmask. */
#include <conio.h>
#include <stdlib.h>
#include <graph.h>
void ellipsemask( short x1, short y1, short x2, short y2, char _far
*newmask );
unsigned char mask1[8] = { 0x43, 0x23, 0x7c, 0xf7, 0x8a, 0x4d, 0x78, 0x39
};
unsigned char mask2[8] = { 0x18, 0xad, 0xc0, 0x79, 0xf6, 0xc4, 0xa8, 0x23
};
char oldmask[8];
void main()
{
int loop;
/* Find a valid graphics mode. */
if( !_setvideomode( _MAXRESMODE ) )
exit( 1 );
/* Set first fill mask and draw rectangle. */
_setfillmask( mask1 );
_rectangle( _GFILLINTERIOR, 20, 20, 100, 100 );
getch();
/* Call routine that saves and restores mask. */
ellipsemask( 60, 60, 150, 150, mask2 );
getch();
/* Back to original mask. */
_rectangle( _GFILLINTERIOR, 120, 120, 190, 190 );
getch();
_setvideomode( _DEFAULTMODE );
}
/* Draw an ellipse with a specified fill mask. */
void ellipsemask( short x1, short y1, short x2, short y2, char _far
*newmask )
{
unsigned char savemask[8];
_getfillmask( savemask ); /* Save mask */
_setfillmask( newmask ); /* Set new mask */
_ellipse( _GFILLINTERIOR, x1, y1, x2, y2 ); /* Use new mask */
_setfillmask( savemask ); /* Restore original */
}
_setfont
────────────────────────────────────────────────────────────────────────────
Description
Finds a single font.
#include <graph.h>
short _far _setfont( unsigned char _far *options );
options String describing font characteristics
Remarks
The _setfont function finds a single font, from the set of registered fonts,
that has the characteristics specified by the options string. If a font is
found, it is made the current font. The current font is used in all
subsequent calls to the _outgtext function. There can be only one active
font at any time.
The options string is a set of characters that specifies the desired
characteristics of the font. The _setfont function searches the list of
registered fonts for a font matching the specified characteristics.
The characteristics that may be specified in the options string are shown in
the list below. Characteristics specified in the options string are not
case- or position-sensitive.
Characteristic Description
────────────────────────────────────────────────────────────────────────────
t'fontname' Typeface.
hx Character height, where x is the number
of pixels.
wy Character width, where y is the number
of pixels.
f Find only a fixed-space font (should not
be used with the
p characteristic).
p Find only a proportionally spaced font
(should not be used with the f
characteristic).
v Find only a vector font (should not be
used with the r
characteristic).
r Find only a raster-mapped (bit-mapped)
font (should not be used with the v
characteristic).
b Select a best fit font.
nx Select font number x, where x is less
than or equal to the value returned by
the _registerfonts function. Use this
option to "step through" an entire set
of fonts.
You can request as many options as desired, except with nx, which should be
used alone. If mutually exclusive options are requested (such as the pair
f/p or r/v), the _setfont function ignores them. There is no error detection
for incompatible parameters used with nx.
Options can be separated by blanks in the options string. Any other
character is ignored by _setfont.
The t (the typeface specification) in options is specified as a "t" followed
by fontname in single quotes. Choose fontname from the following list:
Fontname Description
────────────────────────────────────────────────────────────────────────────
Courier Fixed-width bit-mapped font with serifs
Helv Sans serif proportional bit-mapped font
Tms Rmn Proportional bit-mapped font with serifs
Script Proportional vector-mapped font of
slanted characters formed from nearly
continuous lines
Modern Proportional vector-mapped font without
serifs
Roman Proportional vector-mapped font with
serifs
A b in the options field causes the _setfont routine to automatically select
the "best fit" font that matches the other characteristics you have
specified. If the b parameter is spec-ified and at least one font is
registered, _setfont will always be able to set a font and will return 0 to
indicate success.
In selecting a font, the _setfont routine uses the following precedence
(rated from highest precedence to lowest):
1. Pixel height
2. Typeface
3. Pixel width
4. Fixed or proportional font
You can also specify a pixel width and height for fonts. If a nonexistent
value is chosen for either, and the b option is specified, the _setfont
function will chose the closest match. A smaller font size has precedence
over a larger size. If _setfont requests Helv 12 with best fit, and only
Helv 10 and Helv 14 are available, _setfont will select Helv 10.
If a nonexistent value is chosen for pixel height and width, the _setfont
function will apply a magnification factor to a vector-mapped font to obtain
a suitable font size. This automatic magnification does not apply if the r
(raster-mapped font) option is specified, or if a specific typeface is
requested and no best fit (b) option is specified.
If you specify the nx parameter, _setfont will ignore any other specified
options and supply only the font number corresponding to x.
Note that the font functions affect only the output from the font output
function _outgtext; no other C run-time output functions are affected by
font usage.
Return Value
The _setfont function returns a 0 to indicate success and a -1 to indicate
an error. An error occurs if a request for a specific font fails and the b
option was not specified, or if fonts have not yet been registered.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_getfontinfo, _getgtextextent, _outgtext, _registerfonts,
_unregisterfonts
Example
See the example for _outgtext.
_setgtextvector
────────────────────────────────────────────────────────────────────────────
Description
Changes the orientation of font text output.
#include <graph.h>
struct xycoord _far _setgtextvector( short x, short y );
x, y Integers specifying font rotation
Remarks
The _setgtextvector function sets the current orientation for font text
output to the vector specified by x and y. The current orientation is used
in calls to the _outgtext function.
The values of x and y define the vector which determines the direction of
rotation of font text on the screen. The text-rotation options are shown
below:
(x, y) Text Orientation
────────────────────────────────────────────────────────────────────────────
(0, 0) Unchanged
(1, 0) Horizontal text (default)
(0, 1) Rotated 90 degrees counterclockwise
(-1, 0) Rotated 180 degrees
(0, -1) Rotated 270 degrees counterclockwise
If other values are input, only the sign of the input is used. For example,
(-3, 0) is interpreted as (-1, 0).
Return Value
The _setgtextvector function returns the previous vector in a structure of
xycoord type. If you pass the _setgtextvector function the values (0, 0),
the function returns the current vector values in the xycoord structure.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_getfontinfo, _getgtextextent, _grstatus, _outgtext, _registerfonts,
_setfont, _unregisterfonts
Example
See the example for _outgtext.
setjmp
────────────────────────────────────────────────────────────────────────────
Description
Saves the current state of the program.
#include <setjmp.h>
int setjmp( jmp_buf env );
env Variable in which environment is stored
Remarks
The setjmp function saves a stack environment that can be subsequently
restored using longjmp. Used together this way, setjmp and longjmp provide a
way to execute a "non-local goto." They are typically used to pass execution
control to error-handling or recovery code in a previously called routine
without using the normal calling or return conventions.
A call to setjmp causes the current stack environment to be saved in env. A
subsequent call to longjmp restores the saved environment and returns
control to the point just after the corresponding setjmp call. All variables
(except register variables) accessible to the routine receiving control
contain the values they had when setjmp was called.
Return Value
The setjmp function returns 0 after saving the stack environment. If setjmp
returns as a result of a longjmp call, it returns the value argument of
longjmp, or, if the value argument of longjmp is 0, setjmp returns 1. There
is no error return.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
longjmp
Example
See the example for _fpreset.
_setlinestyle
────────────────────────────────────────────────────────────────────────────
Description
Sets the line style.
#include <graph.h>
void _far _setlinestyle( unsigned short mask );
mask Desired line-style mask
Remarks
Some graphics routines ( _lineto and _rectangle) draw straight lines on the
screen. The type of line is controlled by the current line-style mask.
The _setlinestyle function selects the mask used for line drawing. The mask
argument is a 16-bit array, where each bit represents a pixel in the line
being drawn. If a bit is 1, the corresponding pixel is set to the color of
the line (the current color). If a bit is 0, the corresponding pixel is left
unchanged. The template is repeated for the entire length of the line.
The default mask is 0xFFFF (a solid line).
Return Value
None.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_getlinestyle, _lineto functions, _rectangle functions
Example
See the example for _getlinestyle.
setlocale
────────────────────────────────────────────────────────────────────────────
Description
Defines the locale.
#include <locale.h>
char *setlocale( int category, const char *locale );
category Category affected by locale
locale Name of the locale that will control the
specified category
Remarks
The setlocale function sets the categories specified by category to the
locale specified by locale. The "locale" refers to the locality (country)
for which certain aspects of your program can be customized. Some
locale-dependent aspects include the formatting of dates and the display
format for monetary values.
The setlocale function is used to set or get the program's current entire
locale or simply portions of the locale information. The category argument
specifies which portion of a program's locale information will be used. The
manifest constants used for the category argument are listed below:
Category Parts of Program Affected
────────────────────────────────────────────────────────────────────────────
LC_ALL All categories listed below.
LC_COLLATE The strcoll and strxfrm functions.
LC_CTYPE The character-handling functions (except
for isdigit and isxdigit, which are
unaffected).
LC_MONETARY Monetary formatting information returned
by the localeconv function.
LC_NUMERIC Decimal point character for the
formatted output routines (such as
printf), for the data conversion
routines, and for
the nonmonetary formatting information
returned by the
localeconv function.
LC_TIME The strftime function.
The locale argument is a pointer to a string that specifies the name of the
locale. If locale points to an empty string, the locale is the
implementation-defined native environment. A value of "C" specifies the
minimal ANSI conforming environment for C translation. This is the only
locale supported in Microsoft C, version 6.0.
If the locale argument is a null pointer, setlocale returns a pointer to the
string associated with the category of the program's locale. The program's
current locale setting is not changed.
Return Value
If a valid locale and category are given, _setlocale returns a pointer to
the string associated with the specified category for the new locale. If the
locale or category is invalid, the setlocale function returns a null pointer
and the program's current locale settings are not changed.
The pointer to a string returned by setlocale can be used in subsequent
calls to restore that part of the program's locale information. Later calls
to setlocale will overwrite the string.
Compatibility
ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
localeconv, strcoll, strftime, strxfrm
setmode
────────────────────────────────────────────────────────────────────────────
Description
Sets the file translation mode.
#include <fcntl.h>
#include <io.h> Required only for function declarations
int setmode ( int handle, int mode );
handle File handle
mode New translation mode
Remarks
The setmode function sets to mode the translation mode of the file given by
handle. The mode must be one of the following manifest constants:
Constant Meaning
────────────────────────────────────────────────────────────────────────────
O_TEXT Sets text (translated) mode.
Carriage-return-line-feed (CR-LF)
combinations are translated into a
single line-feed (LF) character on
input. Line-feed characters are
translated into CR-LF combinations on
output.
O_BINARY Sets binary (untranslated) mode. The
above translations are suppressed.
The setmode function is typically used to modify the default translation
mode of stdin, stdout, stderr, stdaux, and stdprn, but can be used on any
file. If setmode is applied to the file handle for a stream, the setmode
function should be called before any input or output operations are
performed on the stream.
Return Value
If successful, setmode returns the previous translation mode. A return value
of -1 indicates an error, and errno is set to one of the following values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
EBADF Invalid file handle
EINVAL Invalid mode argument (neither O_TEXTnor
O_BINARY )
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
creat, fopen, open
Example
/* SETMODE.C: This program uses setmode to change stdin from text
* mode to binary mode.
*/
#include <stdio.h>
#include <fcntl.h>
#include <io.h>
void main()
{
int result;
/* Set "stdin" to have binary mode: */
result = setmode( fileno( stdin ), O_BINARY );
if( result == -1 )
perror( "Cannot set mode" );
else
printf( "'stdin' successfully changed to binary mode\n" );
}
Output
Output
'stdin' successfully changed to binary mode
_setpixel Functions
────────────────────────────────────────────────────────────────────────────
Description
Set a pixel to the current color.
#include <graph.h>
short _far _setpixel( short x, short y );
short _far _setpixel_w( double wx, double wy );
x, y Target pixel
wx, wy Target pixel
Remarks
The _setpixel and the _setpixel_w functions set a pixel at a specified
location to the current color.
The _setpixel function sets the pixel at the view-coordinate point (x, y) to
the current color.
The _setpixel_w function sets the pixel at the window-coordinate point (wx,
wy) to the current color.
Return Value
The function returns the previous value of the target pixel. If the function
fails (for example, the point lies outside of the clipping region), it will
return -1.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_getpixel functions, _setcolor
Example
/* GPIXEL.C: This program assigns different colors to randomly
* selected pixels.
*/
#include <conio.h>
#include <stdlib.h>
#include <graph.h>
void main()
{
short xvar, yvar;
struct videoconfig vc;
/* Find a valid graphics mode. */
if( !_setvideomode( _MAXCOLORMODE ) )
exit( 1 );
_getvideoconfig( &vc );
/* Draw filled ellipse to turn on certain pixels. */
_ellipse( _GFILLINTERIOR, vc.numxpixels / 6, vc.numypixels / 6,
vc.numxpixels / 6 * 5, vc.numypixels / 6 * 5
);
/* Draw random pixels in random colors... */
while( !kbhit() )
{
/* ...but only if they are already on (inside the ellipse). */
xvar = rand() % vc.numxpixels;
yvar = rand() % vc.numypixels;
if( _getpixel( xvar, yvar ) != 0 )
{
_setcolor( rand() % 16 );
_setpixel( xvar, yvar );
}
}
getch(); /* Throw away the keystroke. */
_setvideomode( _DEFAULTMODE );
}
_settextcolor
────────────────────────────────────────────────────────────────────────────
Description
Sets the current text color.
#include <graph.h>
short _far _settextcolor( short index );
index Desired color index
Remarks
The _settextcolor function sets the current text color to the color index
specified by index. The default text color is the same as the maximum color
index.
The _settextcolor routine sets the color for the _outtext and _outmem
functions only. It does not affect the color of the printf function or the
color of text output with the _outgtext font routine. Use the _setcolor
function to change the color of font output.
In text color mode, you can specify a color index in the range 0 -31. The
colors in the range 0 -15 are interpreted as normal (non-blinking). The
normal color range is defined below:
╓┌───────┌─────────┌──────┌──────────────────────────────────────────────────╖
Index Color Index Color
────────────────────────────────────────────────────────────────────────────
0 Black 8 Dark gray
1 Blue 9 Light blue
2 Green 10 Light green
3 Cyan 11 Light cyan
4 Red 12 Light red
Index Color Index Color
────────────────────────────────────────────────────────────────────────────
4 Red 12 Light red
5 Magenta 13 Light magenta
6 Brown 14 Yellow
7 White 15 Bright white
Blinking is selected by adding 16 to the normal color value.
In every text mode, including monochrome, _getvideoconfig returns the value
32 for the number of available colors. The value 32 indicates the range of
values (0 -31) accepted by the _settextcolor function. This includes sixteen
normal colors (0 -15) and sixteen blinking colors (16 -31). Monochrome text
mode has fewer unique display attributes, so some color values are
redundant. However, because blinking is selected in the same manner,
monochrome text mode has the same range (0 -31) as other text modes.
Return Value
The function returns the color index of the previous text color. There is no
error return.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_gettextcolor, _outtext
Example
/* OUTTXT.C: This example illustrates text output functions:
* _gettextcolor _getbkcolor _gettextposition _outtext
* _settextcolor _setbkcolor _settextposition
*/
#include <conio.h>
#include <stdio.h>
#include <graph.h>
char buffer [80];
void main()
{
/* Save original foreground, background, and text position */
short blink, fgd, oldfgd;
long bgd, oldbgd;
struct rccoord oldpos;
/* Save original foreground, background, and text position. */
oldfgd = _gettextcolor();
oldbgd = _getbkcolor();
oldpos = _gettextposition();
_clearscreen( _GCLEARSCREEN );
/* First time no blink, second time blinking. */
for( blink = 0; blink <= 16; blink += 16 )
{
/* Loop through 8 background colors. */
for( bgd = 0; bgd < 8; bgd++ )
{
_setbkcolor( bgd );
_settextposition( (short)bgd + ((blink / 16) * 9) + 3, 1 );
_settextcolor( 7 );
sprintf(buffer, "Back: %d Fore:", bgd );
_outtext( buffer );
/* Loop through 16 foreground colors. */
for( fgd = 0; fgd < 16; fgd++ )
{
_settextcolor( fgd + blink );
sprintf( buffer, " %2d ", fgd + blink );
_outtext( buffer );
}
}
}
getch();
/* Restore original foreground, background, and text position. */
_settextcolor( oldfgd );
_setbkcolor( oldbgd );
_clearscreen( _GCLEARSCREEN );
_settextposition( oldpos.row, oldpos.col );
}
_settextcursor
────────────────────────────────────────────────────────────────────────────
Description
Sets the current cursor attribute.
#include <graph.h>
short _far _settextcursor( short attr );
attr Cursor attribute
Remarks
The _settextcursor function sets the cursor attribute (i.e., the shape) to
the value specified by attr. The high-order byte of attr determines the top
line of the cursor within the character cell. The low-order byte of attr
determines the bottom line of the cursor.
The _settextcursor function uses the same format as the BIOS routines in
setting the cursor. Typical values for the cursor attribute are listed
below:
Attribute Cursor Shape
────────────────────────────────────────────────────────────────────────────
0x0707 Underline
0x0007 Full block cursor
0x0607 Double underline
0x2000 No cursor
Note that this function works only in text video modes.
Return Value
The function returns the previous cursor attribute, or -1 if an error occurs
(such as calling the function in a graphics screen mode).
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_displaycursor, _gettextcursor
Example
/* DISCURS.C: This program changes the cursor shape using _gettextcursor
* and _settextcursor, and hides the cursor using _displaycursor.
*/
#include <conio.h>
#include <graph.h>
void main()
{
short oldcursor;
short newcursor = 0x007; /* Full block cursor */
/* Save old cursor shape and make sure cursor is on. */
oldcursor = _gettextcursor();
_clearscreen( _GCLEARSCREEN );
_displaycursor( _GCURSORON );
_outtext( "\nOld cursor shape: " );
getch();
/* Change cursor shape. */
_outtext( "\nNew cursor shape: " );
_settextcursor( newcursor );
getch();
/* Restore original cursor shape. */
_outtext( "\n" );
_settextcursor( oldcursor );
}
_settextposition
────────────────────────────────────────────────────────────────────────────
Description
Sets the text position.
#include <graph.h>
struct rccoord _far _settextposition( short row, short column );
row, column New output start position
Remarks
The _settextposition function sets the current text position to the display
point (row, column). The _outtext and _outmem functions (and standard
console I/O routines, such as printf) output text at that point.
The rccoord structure, defined in GRAPH.H, contains the following elements:
Element Description
────────────────────────────────────────────────────────────────────────────
short row Row coordinate
short col Column coordinate
Return Value
The function returns the previous text position in an rccoord structure,
defined in GRAPH.H.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_gettextposition, _outtext, _settextwindow
Example
/* OUTTXT.C: This example illustrates text output functions:
* _gettextcolor _getbkcolor _gettextposition _outtext
* _settextcolor _setbkcolor _settextposition
*/
#include <conio.h>
#include <stdio.h>
#include <graph.h>
char buffer [80];
void main()
{
/* Save original foreground, background, and text position */
short blink, fgd, oldfgd;
long bgd, oldbgd;
struct rccoord oldpos;
/* Save original foreground, background, and text position. */
oldfgd = _gettextcolor();
oldbgd = _getbkcolor();
oldpos = _gettextposition();
_clearscreen( _GCLEARSCREEN );
/* First time no blink, second time blinking. */
for( blink = 0; blink <= 16; blink += 16 )
{
/* Loop through 8 background colors. */
for( bgd = 0; bgd < 8; bgd++ )
{
_setbkcolor( bgd );
_settextposition( (short)bgd + ((blink / 16) * 9) + 3, 1 );
_settextcolor( 7 );
sprintf(buffer, "Back: %d Fore:", bgd );
_outtext( buffer );
/* Loop through 16 foreground colors. */
for( fgd = 0; fgd < 16; fgd++ )
{
_settextcolor( fgd + blink );
sprintf( buffer, " %2d ", fgd + blink );
_outtext( buffer );
}
}
}
getch();
/* Restore original foreground, background, and text position. */
_settextcolor( oldfgd );
_setbkcolor( oldbgd );
_clearscreen( _GCLEARSCREEN );
_settextposition( oldpos.row, oldpos.col );
}
_settextrows
────────────────────────────────────────────────────────────────────────────
Description
Sets the number of screen rows for text modes.
#include <graph.h>
short _far _settextrows( short rows );
rows Number of text rows
Remarks
The _settextrows function specifies the number of screen rows to be used in
text modes.
If the constant _MAXTEXTROWS is specified for the rows argument, the
function will choose the maximum number of rows available. In text modes,
this is 50 rows on VGA, 43 on EGA, and 25 on others. In graphics modes that
support 30 or 60 rows, _MAXTEXTROWS specifies 60 rows.
Return Value
This function returns the numbers of rows set. The function returns 0 if an
error occurred.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_getvideoconfig, _setvideomode, _setvideomoderows
Example
/* STXTROWS.C: This program attempts to set the screen height. It returns
* an errorlevel code of 1 (fail) or 0 (success) that could be tested in
* a batch file.
*/
#include <graph.h>
#include <stdlib.h>
void main( int argc, char **argv )
{
short rows;
if( !(rows = atoi( argv[1] )) )
{
_outtext( "\nSyntax: STXTROWS [ 25 | 43 | 50 ]\n" );
exit( 1 );
}
/* Make sure new rows are the same as requested rows. */
if( _settextrows( rows ) != rows )
{
_outtext( "\nInvalid rows\n" );
exit( 1 );
}
else
exit( 0 );
}
_settextwindow
────────────────────────────────────────────────────────────────────────────
Description
Creates a text window.
#include <graph.h>
void _far _settextwindow( short r1, short c1, short r2, short c2 );
r1, c1 Upper-left corner of window
r2, c2 Lower-right corner of window
Remarks
The _settextwindow function specifies a window in row and column coordinates
where all text output to the screen is displayed. The arguments (r1, c1)
specify the upper-left corner of the text window, and the arguments (r2, c2)
specify the lower-right corner of the text window.
Text is output from the top of the text window down. When the text window is
full, the uppermost line scrolls up out of it.
Note that this function does not affect the output of presentation-graphics
text (e.g., labels, axis marks, etc.). It also does not affect the output of
the font display routine _outgtext. Use the _setviewport function to control
the display area for presentation graphics or fonts.
Return Value
None.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_gettextposition, _gettextwindow, _outtext, _settextposition
Example
See the example for _scrolltextwindow.
setvbuf
────────────────────────────────────────────────────────────────────────────
Description
Controls stream buffering and buffer size.
#include <stdio.h>
int setvbuf( FILE *stream, char *buffer, int mode, size_t size );
stream Pointer to FILE structure
buffer User-allocated buffer
mode Mode of buffering: _IOFBF (full
buffering), _IOLBF (line buffering), _
IONBF (no buffer)
size Size of buffer
Remarks
The setvbuf function allows the program to control both buffering and buffer
size for stream. The stream must refer to an open file that has not been
read from or written to since it was opened. The array pointed to by buffer
is used as the buffer, unless it is NULL, and an automatically allocated
buffer size bytes long is used.
The mode must be _IOFBF, _IOLBF, or _IONBF. If mode is _IOFBF or _IOLBF,
then size is used as the size of the buffer. If mode is _IONBF, the stream
is unbuffered and size and buffer are ignored.
Values for mode and their meanings are:
Type Meaning
────────────────────────────────────────────────────────────────────────────
_IOFBF Full buffering; that is, buffer is used
as the buffer and size is used as the
size of the buffer. If buffer is NULL,
an automatically allocated buffer size
bytes long is used.
_IOLBF Under DOS and OS/2, the same as _IOFBF.
_IONBF No buffer is used, regardless of buffer
or size.
The legal values for size are greater than 0 and less than 32,768.
Return Value
The return value for setvbuf is 0 if successful, and a nonzero value if an
illegal type or buffer size is specified.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
fclose, fflush, fopen, setbuf
Example
/* SETVBUF.C: This program opens two streams named stream1 and stream2.
* It then uses setvbuf to give stream1 a user-defined buffer of 1024
* bytes and stream2 no buffer.
*/
#include <stdio.h>
void main()
{
char buf[1024];
FILE *stream1, *stream2;
if( ((stream1 = fopen( "data1", "a" )) != NULL) &&
((stream2 = fopen( "data2", "w" )) != NULL) )
{
if( setvbuf( stream1, buf, _IOFBF, sizeof( buf ) ) != 0 )
printf( "Incorrect type or size of buffer for stream1\n" );
else
printf( "'stream1' now has a buffer of 1024 bytes\n" );
if( setvbuf( stream2, NULL, _IONBF, 0 ) != 0 )
printf( "Incorrect type or size of buffer for stream2\n" );
else
printf( "'stream2' now has no buffer\n" );
fcloseall();
}
}
Output
'stream1' now has a buffer of 1024 bytes
'stream2' now has no buffer
_setvideomode
────────────────────────────────────────────────────────────────────────────
Description
Sets the video mode.
#include <graph.h>
short _far _setvideomode( short mode );
mode Desired mode
Remarks
The _setvideomode function selects a screen mode appropriate for a
particular hardware/display configuration. The mode argument can be one of
the manifest constants shown in Table R.9 and defined in GRAPH.H.
Table R.9 Manifest Constants for Screen Mode
╓┌────────────────────┌──────────────────┌──────────────────┌──────────┌─────►
Mode Type(1) Size(2) Colors(3) Adapter
─────────────────────────────────────────────────────────────────────────────
_DEFAULTMODE Hardware default
mode
_MAXRESMODE Highest
resolution in
graphics mode
_MAXCOLORMODE Maximum colors in
graphics mode
_TEXTBW40 M/T 40 x 25 16 CGA
_TEXTC40 C/T 40 x 25 16 CGA
_TEXTBW80 M/T 80 x 25 16 CGA
_TEXTC80 C/T 80 x 25 6 CGA
Mode Type(1) Size(2) Colors(3) Adapter
─────────────────────────────────────────────────────────────────────────────
_TEXTC80 C/T 80 x 25 6 CGA
_MRES4COLOR C/G 320 x 200 4 CGA
_MRESNOCOLOR M/G 320 x 200 4 CGA
_HRESBW M/G 640 x 200 2 CGA
_TEXTMONO M/T 80 x 25 1 MDPA
_HERCMONO(5) Hercules graphics 720 x 348 1 HGC
_MRES16COLOR C/G 320 x 200 16 EGA
_HRES16COLOR C/G 640 x 200 16 EGA
_ERESNOCOLOR M/T 640 x 350 1 EGA
_ERESCOLOR C/G 640 x 350 16 EGA
Mode Type(1) Size(2) Colors(3) Adapter
─────────────────────────────────────────────────────────────────────────────
_ERESCOLOR C/G 640 x 350 16 EGA
_VRES2COLOR C/G 640 x 480 2 VGA
_VRES16COLOR C/G 640 x 480 16 VGA
_MRES256COLOR C/G 320 x 200 256 VGA
_ORESCOLOR C/G 640 x 400 1 of 16 OLIV
─────────────────────────────────────────────────────────────────────────────
1. M indicates monochrome, C indicates color output, T indicates text, and G
indicates graphics generation.
2. For text modes, size is given in characters (columns x rows). For
graphics modes, size is given in pixels (horizontal x vertical).
3. For monochrome displays, the number of colors is the number of gray
shades.
4. Adapters are the IBM (and compatible) Monochrome Adapter (MDPA), Color
Graphics Adapter (CGA), Enhanced Graphics Adapter (EGA), Video Graphics
Array (VGA), Hercules-compatible adapter (HGC), and Olivetti-compatible
adapter (OLIV).
5. In _HERCMONO mode, the text dimensions are 80 columns by 25 rows, with a
9 by 14 character box. The bottom two scan lines of row 25 are not
visible.
Note that only standard hardware is described here, but display hardware
that is strictly compatible with IBM, Hercules, or Olivetti hardware should
also work as described.
_MAXRESMODE and _MAXCOLORMODE
The two special modes _MAXRESMODE and _MAXCOLORMODE select the highest
resolution or greatest number of colors available with the current hardware,
respectively. These two modes fail for adapters that do not support graphics
modes.
Table R.10 lists the video mode selected for different adapter and monitor
combinations when _MAXRESMODE or _MAXCOLORMODE is specified:
Table R.10 Modes Selected by _MAXRESMODE and _MAXCOLORMODE
╓┌────────────────┌─────────────┌────────────────────────────────────────────╖
Adapter/Monitor _MAXRESMODE _MAXCOLORMODE
────────────────────────────────────────────────────────────────────────────
MDPA fails fails
HGC _HERCMONO _HERCMONO
CGA color* _HRESBW _MRES4COLOR
CGA noncolor* _HRESBW _MRESNOCOLOR
OCGA _ORESCOLOR _MRES4COLOR
OEGA color _ORESCOLOR _ERESCOLOR
Adapter/Monitor _MAXRESMODE _MAXCOLORMODE
────────────────────────────────────────────────────────────────────────────
EGA color 256K _HRES16COLOR _HRES16COLOR
EGA color 64K _HRES16COLOR _HRES16COLOR
EGA ecd 256K _ERESCOLOR _ERESCOLOR
EGA ecd 64K _ERESCOLOR _HRES16COLOR
EGA mono _ERESNOCOLOR _ERESNOCOLOR
MCGA _VRES2COLOR _MRES256COLOR
VGA _VRES16COLOR _MRES256COLOR
OVGA _VRES16COLOR _MRES256COLOR
────────────────────────────────────────────────────────────────────────────
Adapter/Monitor _MAXRESMODE _MAXCOLORMODE
────────────────────────────────────────────────────────────────────────────
* Color monitor is assumed if the start-up text mode was TEXTC80 or TEXTC40
or if the start-up mode was graphics mode. Composite or other noncolor CGA
monitor is assumed if start-up mode was TEXTBW80 or TEXTBW40.
Hercules Support
You must install the Hercules driver MSHERC.COM before running your program.
Type MSHERC to load the driver. This can be done from an AUTOEXEC.BAT file.
If you have both a Hercules monochrome card and a color video card, you
should install MSHERC.COM with the /H (/HALF) option. The /H option causes
the driver to use one instead of two graphics pages. This prevents the two
video cards from attempting to use the same memory. You do not have to use
the /H option if you have only a Hercules card. See your Hercules hardware
manuals for more details of compatibility.
To use a mouse, you must follow special instructions for Hercules cards in
Microsoft Mouse Programmer's Reference Guide. (This is sold separately; it
is not supplied with either Microsoft C or the mouse package.)
Return Value
The function returns the number of text rows if the function is successful.
If an error is encountered (that is, the mode selected is not supported by
the current hardware configuration), the function returns 0.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
In OS/2, only text video modes may be selected by _setvideomode.
See Also
_getvideoconfig, _settextrows, _setvideomoderows
Example
/* SVIDMODE.C: This program sets a video mode from a string given on the
* command line.
*/
#include <graph.h>
#include <stdlib.h>
#include <string.h>
short modes[] = { _TEXTBW40, _TEXTC40, _TEXTBW80,
_TEXTC80, _MRES4COLOR, _MRESNOCOLOR,
_HRESBW, _TEXTMONO, _HERCMONO,
_MRES16COLOR, _HRES16COLOR, _ERESNOCOLOR,
_ERESCOLOR, _VRES2COLOR, _VRES16COLOR,
_MRES256COLOR, _ORESCOLOR
};
char *names[] = { "TEXTBW40", "TEXTC40", "TEXTBW80",
"TEXTC80", "MRES4COLOR", "MRESNOCOLOR",
"HRESBW", "TEXTMONO", "HERCMONO",
"MRES16COLOR", "HRES16COLOR", "ERESNOCOLOR",
"ERESCOLOR", "VRES2COLOR", "VRES16COLOR",
"MRES256COLOR","ORESCOLOR"
};
void error( char *msg );
void main( int argc, char *argv[] )
{
short i, num = sizeof( modes ) / sizeof( short );
struct videoconfig vc;
if( argc < 2 )
error( "No argument given" );
/* If matching name found, change to corresponding mode. */
for( i = 0; i < num; i++ )
{
if( !strcmpi( argv[1], names[i] ) )
{
_setvideomode( modes[i] );
_outtext( "New mode is: " );
_outtext( names[i] );
exit( 0 );
}
}
error( "Invalid mode string" );
}
void error( char *msg )
{
_outtext( msg );
exit( 1 );
}
_setvideomoderows
────────────────────────────────────────────────────────────────────────────
Description
Sets the video mode and number of text rows for text modes.
#include <graph.h>
short _far _setvideomoderows( short mode, short rows );
mode Desired mode
rows Number of text rows
Remarks
The _setvideomoderows function selects a screen mode for a particular
hardware/display combination. The manifest constants for the screen mode are
given in the reference pages for _setvideomode. The _setvideomoderows
function also specifies the number of text rows to be used in a text mode.
If the constant _MAXTEXTROWS is specified for the rows argument, the
function will choose the maximum number of rows available. In text modes,
this is 50 rows on VGA, 43 on EGA, and 25 on others. In graphics modes that
support 30 or 60 rows, _MAXTEXTROWS specifies 60 rows.
Return Value
The setvideomoderows function returns the numbers of rows set. The function
returns 0 if an error occurred (e.g., if the mode is not supported).
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
In OS/2, only text video modes may be selected by _setvideomoderows.
See Also
_getvideoconfig, _settextrows, _setvideomode
Example
/* SVMROWS.C */
#include <stdlib.h>
#include <conio.h>
#include <graph.h>
void main()
{
struct videoconfig config;
/* Set 43-line graphics mode if available. */
if( !_setvideomoderows( _ERESCOLOR, 43 ) )
{
_outtext( "EGA or VGA required" );
exit( 1 );
}
_getvideoconfig( &config );
/* Set logical origin to center and draw a rectangle. */
_setlogorg( config.numxpixels / 2 - 1, config.numypixels / 21 );
_rectangle( _GBORDER, -80, -50, 80, 50 );
getch();
_setvideomode( _DEFAULTMODE );
}
_setvieworg
────────────────────────────────────────────────────────────────────────────
Description
Moves the view-coordinate origin to the specified physical point.
#include <graph.h>
struct xycoord _far _setvieworg( short x, short y );
x, y New origin point
Remarks
The _setvieworg function moves the view-coordinate origin (0, 0) to the
physical point (x, y). All other view-coordinate points move the same
direction and distance.
The xycoord structure, defined in GRAPH.H, contains the following elements:
Element Description
────────────────────────────────────────────────────────────────────────────
short xcoord x coordinate
short ycoord y coordinate
────────────────────────────────────────────────────────────────────────────
C 5.1 Difference
This function replaces the _setlogorg function.
────────────────────────────────────────────────────────────────────────────
Return Value
The function returns the physical coordinates of the previous view origin in
an xycoord structure, defined in GRAPH.H.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_getphyscoord, _getviewcoord, _getwindowcoord, _setcliprgn, _setviewport
Example
/* SVORG.C: This program sets the view origin to the center of
* the screen, then draws a rectangle using the new origin.
*/
#include <stdlib.h>
#include <conio.h>
#include <graph.h>
void main()
{
struct videoconfig config;
/* Find a valid graphics mode. */
if( !_setvideomode( _MAXRESMODE ) )
exit( 1 );
_getvideoconfig( &config );
/* Set view origin to the center of the screen. */
_setvieworg( config.numxpixels / 2, config.numypixels / 2 );
_rectangle( _GBORDER, -80, -50, 80, 50 );
getch();
_setvideomode( _DEFAULTMODE );
}
_setviewport
────────────────────────────────────────────────────────────────────────────
Description
Creates a viewport.
#include <graph.h>
void _far _setviewport( short x1, short y1, short x2, short y2 );
x1, y1 Upper-left corner of viewport
x2, y2 Lower-right corner of viewport
Remarks
The _setviewport function redefines the graphics viewport. The _setviewport
function defines a clipping region in exactly the same manner as
_setcliprgn, and then sets the view-coordinate origin to the upper-left
corner of the region. The physical points (x1, y1) and (x2, y2) are the
diagonally opposed corners of the rectangular clipping region. Any window
transformation done with the _setwindow function applies only to the
viewport and not to the entire screen.
Return Value
None.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_setcliprgn, _setvieworg, _setwindow
Example
/* SVIEWPRT.C: This program sets a viewport and then draws a rectangle
* around it and an ellipse in it.
*/
#include <conio.h>
#include <stdlib.h>
#include <graph.h>
void main()
{
/* Find a valid graphics mode. */
if( !_setvideomode( _MAXRESMODE ) )
exit( 1 );
_setviewport( 100, 100, 200, 200 );
_rectangle( _GBORDER, 0, 0, 100, 100 );
_ellipse( _GFILLINTERIOR, 10, 10, 90, 90 );
getch();
_setvideomode( _DEFAULTMODE );
}
_setvisualpage
────────────────────────────────────────────────────────────────────────────
Description
Sets the visual page.
#include <graph.h>
short _far _setvisualpage( short page );
page Visual page number
Remarks
For hardware configurations that have an EGA or a VGA and enough memory to
support multiple-screen pages, the _setvisualpage function selects the
current visual page. The page argument specifies the current visual page.
The default page number is 0.
Return Value
The function returns the number of the previous visual page. If the function
fails, it returns a negative value.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_getactivepage, _getvisualpage, _setactivepage, _setvideomode
Example
See the example for _setactivepage.
_setwindow
────────────────────────────────────────────────────────────────────────────
Description
Defines a graphics window.
#include <graph.h>
short _far _setwindow( short finvert, double wx1, double wy1, double wx2,
double wy2 );
finvert Invert flag
wx1, wy1 Upper-left corner of window
wx2, wy2 Lower-right corner of window
Remarks
The _setwindow function defines a window bounded by the specified
coordinates. The arguments (wx1, wy1) specify the upper-left corner of the
window, and the arguments (wx2, wy2) specify the lower-right corner of the
window.
The finvert argument specifies the direction of the coordinates. If finvert
is TRUE, the y axis increases from the screen bottom to the screen top
(Cartesian coordinates). If finvert is FALSE, the y axis increases from the
screen top to the screen bottom (screen coordinates).
Any window transformation done with the _setwindow function applies only to
the viewport and not to the entire screen.
If wx1 equals wx2 or wy1 equals wy2, the function will fail.
Note that this function does not affect the output of presentation-graphics
text (e.g., labels, axis marks, etc.). It also does not affect the output of
the font display routine _outgtext.
Return Value
The function returns a nonzero value if successful. If the function fails
(e.g., if it is not in a graphics mode), it returns 0.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_setviewport
Example
/* SWINDOW.C: This program illustrates translation between window,
* view, and physical coordinates. Functions used include:
* _setwindow _getwindowcoord
* _getphyscoord _getviewcoord_wxy
*/
#include <conio.h>
#include <stdlib.h>
#include <graph.h>
enum boolean { FALSE, TRUE };
enum display { MOVE, DRAW, ERASE };
void main()
{
struct xycoord view, phys;
struct _wxycoord oldwin, newwin;
struct videoconfig vc;
double xunit, yunit, xinc, yinc;
short color, key, fintersect = FALSE, fdisplay = TRUE;
/* Find a valid graphics mode. */
if( !_setvideomode( _MAXRESMODE ) )
exit( 1 );
_getvideoconfig( &vc );
/* Set a window using real numbers. */
_setwindow( FALSE, -125.0, -100.0, 125.0, 100.0 );
/* Calculate the size of one pixel in window coordinates.
* Then get the current window coordinates and color.
*/
oldwin = _getwindowcoord( 1, 1 );
newwin = _getwindowcoord( 2, 2 );
xunit = xinc = newwin.wx - oldwin.wx;
yunit = yinc = newwin.wy - oldwin.wy;
newwin = oldwin = _getcurrentposition_w();
color = _getcolor();
while( 1 )
{
/* Set flag according to whether current pixel is on, then
* turn pixel on.
*/
if( _getpixel_w( oldwin.wx, oldwin.wy ) == color )
fintersect = TRUE;
else
fintersect = FALSE;
_setcolor( color );
_setpixel_w( oldwin.wx, oldwin.wy );
/* Get and test key. */
key = getch();
switch( key )
{
case 27: /* ESC Quit */
_setvideomode( _DEFAULTMODE );
exit( 0 );
case 32: /* SPACE Move no color */
fdisplay = MOVE;
continue;
case 0: /* Extended code - get next */
key = getch();
switch( key )
{
case 72: /* UP -y */
newwin.wy -= yinc;
break;
case 77: /* RIGHT +x */
newwin.wx += xinc;
break;
case 80: /* DOWN +y */
newwin.wy += yinc;
break;
case 75: /* LEFT -x */
newwin.wx -= xinc;
break;
case 82: /* INS Draw white */
fdisplay = DRAW;
continue;
case 83: /* DEL Draw black */
fdisplay = ERASE;
continue;
}
break;
}
/* Translate window coordinates to view, view to physical.
* Then check physical to make sure we're on screen. Update screen
* and position if we are. Ignore if not.
*/
view = _getviewcoord_wxy( &newwin );
phys = _getphyscoord( view.xcoord, view.ycoord );
if( (phys.xcoord >= 0) && (phys.xcoord < vc.numxpixels) &&
(phys.ycoord >= 0) && (phys.ycoord < vc.numypixels) )
{
/* If display on, draw to new position, else move to new. */
if( fdisplay != MOVE )
{
if( fdisplay == ERASE )
_setcolor( 0 );
_lineto_w( newwin.wx, newwin.wy );
}
else
{
_setcolor( 0 );
_moveto_w( newwin.wx, newwin.wy );
/* If there was no intersect, erase old pixel. */
if( !fintersect )
_setpixel_w( oldwin.wx, oldwin.wy );
}
oldwin = newwin;
}
else
newwin = oldwin;
}
}
_setwritemode
────────────────────────────────────────────────────────────────────────────
Description
Sets the current logical mode for line drawing.
#include <graph.h>
short _far _setwritemode( short action );
action Interaction with existing screen image
Remarks
The _setwritemode function sets the current logical write mode, which is
used when drawing lines with the _lineto and _rectangle functions.
The action argument defines the write mode. The possible values are _GAND,
_GOR, _GPRESET, _GPSET, and _GXOR. See the description of the _putimage
function for more details on these manifest constants.
Return Value
The _setwritemode function returns the previous write mode, or -1 if an
error occurs.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_getwritemode, _grstatus, _lineto functions, _putimage functions,
_rectangle functions, _setcolor, _setlinestyle
Example
See the example for _getwritemode.
signal
────────────────────────────────────────────────────────────────────────────
Description
Sets interrupt signal handling.
#include <signal.h>
void ( *signal( int sig, void( *func )( int sig [[, int subcode ]] ) ) ) (
int sig );
sig Signal value
func Function to be executed
subcode Optional subcode to the signal number
Remarks
The signal function allows a process to choose one of several ways to handle
an interrupt signal from the operating system.
The sig argument must be one of the manifest constants described in Table
R.11 and defined in SIGNAL.H.
Table R.11 Signals and Responses
╓┌──────────┌────────────────┌──────────────────────┌────────────────────────╖
Value Modes Meaning Default Action
────────────────────────────────────────────────────────────────────────────
SIGABRT Real, Abnormal termination Terminates the calling
protected program with exit code
3
SIGBREAK Protected CTRL+BREAK signal Terminates the calling
program with exit code
3
SIGFPE Real, Floating-point error Terminates the calling
protected program with exit code
3
Value Modes Meaning Default Action
────────────────────────────────────────────────────────────────────────────
3
SIGILL Real, Illegal instruction Terminates the calling
protected program with exit code
3
SIGINT Real, CTRL+C signal Terminates the calling
protected program with exit code
3
SIGSEGV Real, Illegal storage Terminates the calling
protected access program with exit code
3
SIGTERM Real, Termination request Terminates the calling
protected program with exit code
3
SIGUSR1 Protected OS/2 process flag A Signal is ignored
Value Modes Meaning Default Action
────────────────────────────────────────────────────────────────────────────
SIGUSR1 Protected OS/2 process flag A Signal is ignored
SIGUSR2 Protected OS/2 process flag B Signal is ignored
SIGUSR3 Protected OS/2 process flag C Signal is ignored
────────────────────────────────────────────────────────────────────────────
SIGUSR1, SIGUSR2, and SIGUSR3 are user-defined signals which can be sent by
means of DosFlagProcess. For details, see Microsoft Operating System/2
Programmer's Reference.
Note that SIGILL, SIGSEGV, and SIGTERM are not generated under DOS and
SIGSEGV is not generated under OS/2. They are included for ANSI
compatibility. Thus, you may set signal handlers for these signals via
signal, and you may also explicitly generate these signals by calling raise.
Note also that signal settings are not preserved in child processes created
by calls to exec or spawn. The signal settings are reset to the default in
the child process.
The action taken when the interrupt signal is received depends on the value
of func. The func argument must be either a function address or one of the
manifest constants defined in SIGNAL.H and listed below:
Value Meaning
────────────────────────────────────────────────────────────────────────────
SIG_ACK Acknowledges receipt of a signal (OS/2
only). This constant is valid only if a
user-defined signal handler is
installed. Once a process receives a
given signal, the operating system does
not send any more signals of this type
until it receives a SIG_ACK
acknowledgment from the process. The
operating system does not queue up
signals of a given type; therefore, if
more than one signal of a given type
accumulates before the process returns a
SIG_ACK value, only the most recent
signal is sent to the process after the
SIG_ACK value is received by the
operating system. This option has no
effect on which handler is installed for
a given signal. The manifest constant
SIG_ACK is not supported for SIGFPE
signals.
SIG_DFL Uses system-default response. The
system-default response for all signals
except SIGUSR1, SIGUSR2, and SIGUSR3 is
to abort the calling program. The
calling process is terminated with exit
code 3, and control returns to DOS or
OS/2. If the
calling program uses stream I/O, buffers
created by the run-time library are not
flushed, but buffers created by the
operating system are flushed. The
default response for SIGUSR1, SIGUSR2,
and SIGUSR3 is to ignore the signal.
SIG_ERR Ignores interrupt signal (OS/2 only).
This constant is equivalent to SIG_IGN,
except that any process that tries to
send this signal receives an error. A
process may use the raise function to
send a signal to itself. A different
process may send a signal by means of
the function DosFlagProcess (if the
signal is SIGUSR1, SIGUSR2, or SIGUSR3)
or by means of
DosKillProcess (if the signal is SIGTERM
).
SIG_IGN Ignores interrupt signal. This value
should never be given for SIGFPE, since
the floating-point state of the process
is left
undefined.
Function address Installs the specified function as the
handler for the given
signal.
For all signals except SIGFPE and SIGUSR
X, the function is passed the sig
argument SIGINT and executed.
For SIGFPE signals, the function is
passed two arguments; namely SIGFPE and
the floating-point error code
identifying the type of exception that
occurred.
For SIGUSR1, SIGUSR2, and SIGUSR3, the
function is passed two arguments: the
signal number and the argument furnished
by the DosFlagProcess function.
For SIGFPE, the function pointed to by func is passed two arguments, SIGFPE
and an integer error subcode, FPE_xxx; then the function is executed. (See
the include file FLOAT.H for definitions of the FPE_xxx subcodes.) The value
of func is not reset upon receiving the signal. To recover from
floating-point exceptions, use setjmp in conjunction with longjmp. (See the
example under _fpreset.) If the function returns, the calling process
resumes execution with the floating-point state of the process left
undefined.
If the function returns, the calling process resumes execution immediately
following the point at which it received the interrupt signal. This is true
regardless of the type of signal or operating mode.
Before the specified function is executed under DOS versions 3.x or earlier,
the value of func is set to SIG_DFL. The next interrupt signal is treated as
described above for SIG_DFL, unless an intervening call to signal specifies
otherwise. This allows the program to reset signals in the called function.
Under OS/2, the signal handler is not reset to the system-default response.
Instead, no signals of a given type are received by a process until the
process sends a SIG_ACK value to the operating system. The program can
restore the system-default response from the handler by first sending
SIG_DFL and then sending SIG_ACK to the operating system.
Since signal-handler routines are normally called asynchronously when an
interrupt occurs, it is possible that your signal-handler function will get
control when a C run-time operation is incomplete and in an unknown state.
Certain restrictions therefore apply to the C functions that can be used in
your signal-handler routine:
1. Do not issue low-level or standard input and output routines (e.g.,
printf, read, write, and fread).
2. Do not call heap routines or any routine that uses the heap routines
(e.g., malloc, strdup, putenv).
3. Do not use any C function that generates a system call (e.g., getcwd,
time).
4. Do not use the longjmp function unless the interrupt is caused by a
floating-point exception (i.e., sig is SIGFPE). In this case, the
program should first reinitialize the floating-point package by means
of a call to _fpreset.
5. Do not use any overlay routines.
Return Value
The signal function returns the previous value of func associated with the
given signal. For example, if the previous value of func was SIG_IGN, the
return value will be SIG_IGN. The one exception to this rule is SIG_ACK,
which returns the address of the currently installed handler.
A return value of -1 indicates an error, and errno is set to EINVAL. The
possible error causes are an invalid sig value, an invalid func value (that
is, a value that is less than SIG_ACK but not defined), or a func value of
SIG_ACK used when no handler is currently installed.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
abort, exec functions, exit, _exit, _fpreset, spawn functions
Example
/* SIGNAL.C illustrates setting up signal interrupt routines. Functions
* illustrated include signal and raise.
*
* Since C I/O functions are not safe inside signal routines, the code
* uses conditionals to use system-level DOS and OS/2 services. Another
* option is to set global flags and do any I/O operations outside the
* signal handler. To compile the OS/2 version, define the symbol OS2.
*/
#include <stdio.h>
#include <conio.h>
#include <signal.h>
#include <process.h>
#include <stdlib.h>
#if defined( OS2 )
#define INCL_NOCOMMON
#define INCL_NOPM
#define INCL_VIO
#define INCL_KBD
#include <os2.h>
#include <string.h>
#else
#include <dos.h>
#include <bios.h>
#endif
void ctrlchandler( void ); /* Prototypes */
void safeout( char *str );
int safein( void );
void main()
{
int ch;
/* Modify CTRL+C behavior. */
if( signal( SIGINT, ctrlchandler ) == SIG_ERR )
{
fprintf( stderr, "Couldn't set SIGINT\n" );
abort();
}
/* Input loop illustrates results. */
do
{
ch = getch();
if( ch == 0 )
{
ch = getch();
if( ch == 46 ) /* Treat ALT+C like CTRL+C */
raise( SIGINT );
else
printf( "Extended code: %X\n", ch );
}
else
printf( "ASCII code: %X\n", ch );
} while( ch != 27 ); /* ESC code */
}
/* Handles SIGINT (CTRL+C) interrupt. */
void ctrlchandler()
{
int c;
char str[] = " ";
/* Disallow CTRL+C during handler. */
signal( SIGINT, SIG_IGN );
safeout( "User break - abort processing? " );
c = safein();
str[0] = c;
safeout( str );
safeout( "\r\n" );
if( (c == 'y') || (c == 'Y') )
abort();
else
/* The CTRL+C interrupt must be reset to our handler since
* by default it is reset to the system handler.
*/
signal( SIGINT, ctrlchandler );
}
/* Outputs a string using system level calls. */
void safeout( char *str )
{
#if defined( OS2 )
VioWrtTTY( str, strlen( str ), 0 );
#else
union REGS inregs, outregs;
inregs.h.ah = 0x0e;
while( *str )
{
inregs.h.al = *str++;
int86( 0x10, &inregs, &outregs );
}
#endif
}
/* Inputs a character using system level calls. */
int safein()
{
#if defined( OS2 )
KBDKEYINFO kki;
KbdCharIn( &kki, IO_WAIT, 0 );
return kki.chChar;
#else
return _bios_keybrd( _KEYBRD_READ ) & 0xff;
#endif
}
Output
ASCII code: 74
ASCII code: 68
ASCII code: 65
^C
User break - abort processing? n
ASCII code: 62
ASCII code: 1B
sin Functions
────────────────────────────────────────────────────────────────────────────
Description
Calculate sines and hyperbolic sines.
#include <math.h>
double sin( double x );
double sinh( double x );
long double sinl( long double x );
long double sinhl( long double x );
x Angle in radians
Remarks
The sin and sinh functions find the sine and hyperbolic sine of x,
respectively. The sinl and sinhl functions are the 80-bit counterparts and
use an 80-bit, 10-byte coprocessor form of arguments and return values. See
the reference page on the long double functions for more details on this
data type.
Return Value
The sin functions return the sine of x. If x is large, a partial loss of
significance in the result may occur, and sin generates a PLOSS error. If x
is so large that significance is completely lost, the sin function prints a
TLOSS message to stderr and returns 0. In both cases, errno is set to
ERANGE.
The sinh function returns the hyperbolic sine of x. If the result is too
large, sinh sets errno to ERANGE and returns ±HUGE_VAL.
Compatibility
sin, sinh
ANSI DOS OS/2 UNIX XENIX
sinl, sinhl
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
acos functions, asin functions, atan functions, cos functions, tan functions
Example
/* SINCOS.C: This program displays the sine, hyperbolic sine, cosine,
* and hyperbolic cosine of pi / 2.
*/
#include <math.h>
#include <stdio.h>
void main()
{
double pi = 3.1415926535;
double x, y;
x = pi / 2;
y = sin( x );
printf( "sin( %f ) = %f\n", x, y );
y = sinh( x );
printf( "sinh( %f ) = %f\n",x, y );
y = cos( x );
printf( "cos( %f ) = %f\n", x, y );
y = cosh( x );
printf( "cosh( %f ) = %f\n",x, y );
}
Output
sin( 1.570796 ) = 1.000000
sinh( 1.570796 ) = 2.301299
cos( 1.570796 ) = 0.000000
cosh( 1.570796 ) = 2.509178
sopen
────────────────────────────────────────────────────────────────────────────
Description
Opens a file for file sharing.
#include <fcntl.h>
#include <sys\types.h>
#include <sys\stat.h>
#include <share.h>
#include <io.h> Required only for function declarations
int sopen( char *filename, int oflag, int shflag [[, int pmode ]] );
filename File name
oflag Type of operations allowed
shflag Type of sharing allowed
pmode Permission setting
Remarks
The sopen function opens the file specified by filename and prepares the
file for subsequent shared reading or writing, as defined by oflag and
shflag. The integer expression oflag is formed by combining one or more of
the following manifest constants, defined in the file FCNTL.H. When two or
more constants are used to form the argument oflag, the constants are
combined with the OR operator ( | ).
Constant Meaning
────────────────────────────────────────────────────────────────────────────
O_APPEND Repositions the file pointer to the end
of the file before every write
operation.
O_BINARY Opens file in binary (untranslated)
mode. (See fopen for a description of
binary mode.)
O_CREAT Creates and opens a new file. This has
no effect if the file specified by
filename exists.
O_EXCL Returns an error value if the file
specified by filename exists. This
applies only when used with O_CREAT.
O_RDONLY Opens file for reading only. If this
flag is given, neither the O_RDWR flag
nor the O_WRONLY flag can be given.
O_RDWR Opens file for both reading and writing.
If this flag is given, neither O_RDONLY
nor O_WRONLY can be given.
O_TEXT Opens file in text (translated) mode.
(See fopen for a description of text
mode.)
O_TRUNC Opens and truncates an existing file to
0 bytes. The file must have write
permission; the contents of the file are
destroyed.
O_WRONLY Opens file for writing only. If this
flag is given, neither O_RDONLY nor
O_RDWR can be given.
The argument shflag is a constant expression consisting of one of the
following manifest constants, defined in SHARE.H. If SHARE.COM (or SHARE.EXE
for some versions of DOS) is not installed, DOS ignores the sharing mode.
(See your system documentation for detailed information about sharing
modes.)
Constant Meaning
────────────────────────────────────────────────────────────────────────────
SH_COMPAT Sets compatibility mode (not available
in OS/2). This is the sharing mode used
in the open function in DOS.
SH_DENYRW Denies read and write access to file.
SH_DENYWR Denies write access to file.
SH_DENYRD Denies read access to file.
SH_DENYNO Permits read and write access. This is
the sharing mode used in the open
function in OS/2.
The sopen function should be used only under OS/2 and DOS versions 3.0 and
later. Under earlier versions of DOS, the shflag argument is ignored.
The pmode argument is required only when O_CREAT is specified. If the file
does not exist, pmode specifies the file's permission settings, which are
set when the new file is closed for the first time. Otherwise, the pmode
argument is ignored. The pmode argument is an integer expression that
contains one or both of the manifest constants S_IWRITE and S_IREAD, defined
in SYS\STAT.H. When both constants are given, they are combined with the OR
operator ( | ). The meaning of the pmode argument is as follows:
Value Meaning
────────────────────────────────────────────────────────────────────────────
S_IWRITE Writing permitted
S_IREAD Reading permitted
S_IREAD | S_IWRITE Reading and writing permitted
If write permission is not given, the file is read-only. Under DOS and OS/2,
all files are readable; it is not possible to give write-only permission.
Thus, the modes S_IWRITE and S_IREAD | S_IWRITE are equivalent.
Note that under DOS versions 3.x with SHARE installed, a problem occurs when
opening a new file with sopen under the following sets of conditions:
■ With oflag set to O_CREAT | O_RDONLY or O_CREAT | WRONLY, pmode set to
S_IREAD, and shflag set to SH_COMPAT.
■ With oflag set to any combination that includes O_CREAT | O_RDWR,
pmode set to S_IREAD, and shflag set to anything other than SH_COMPAT.
In either case, the operating system will prematurely close the file during
system calls made within sopen, or the system will generate a sharing
violation (INT 24H). To avoid the problem, open the file with pmode set to
S_IWRITE. After closing the file, call chmod and change the mode back to
S_IREAD. Another solution is to open the file with pmode set to S_IREAD,
oflag set to O_CREAT | O_RDWR, and shflag set to SH_COMPAT.
The sopen function applies the current file-permission mask to pmode before
setting the permissions (see umask).
Return Value
The sopen function returns a file handle for the opened file. A return value
of -1 indicates an error, and errno is set to one of the following values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
EACCES Given path name is a directory; or the
file is read-only but an open for
writing was attempted; or a sharing
violation occurred (the file's sharing
mode does not allow the specified
operations; OS/2 and DOS versions 3.0
and later only).
EEXIST The O_CREAT and O_EXCL flags are
specified, but the named file already
exists.
EINVAL An invalid oflag or shflag argument was
given.
EMFILE No more file handles available (too many
open files).
ENOENT File or path name not found.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
close, creat, fopen, _fsopen, open, umask
Example
See the example for locking.
spawn Functions
────────────────────────────────────────────────────────────────────────────
Description
Create and execute a new child process.
#include <stdio.h>
#include <process.h>
int spawnl( int mode, char *cmdname, char *arg0, char *arg1, ... char
*argn, NULL );
int spawnle( int mode, char *cmdname, char *arg0, char *arg1, ... char
*argn, NULL, char **envp );
int spawnlp( int mode, char *cmdname, char *arg0, char *arg1, ... char
*argn, NULL );
int spawnlpe( int mode, char *cmdname, char *arg0, char *arg1, ... char
*argn, NULL, char **envp );
int spawnv( int mode, char *cmdname, char **argv );
int spawnve( int mode, char *cmdname, char **argv, char **envp );
int spawnvp( int mode, char *cmdname, char **argv );
int spawnvpe( int mode, char *cmdname, char **argv, char **envp );
mode Execution mode for parent process
cmdname Path name of file to be executed
arg0, ... argn List of pointers to arguments
argv Array of pointers to arguments
envp Array of pointers to environment
settings
Remarks
The spawn family of functions creates and executes a new child process.
Enough memory must be available for loading and executing the child process.
The mode argument determines the action taken by the parent process before
and during spawn. The following values for mode are defined in PROCESS.H:
Value Meaning
────────────────────────────────────────────────────────────────────────────
P_DETACH Continues to execute the parent process;
child process is run in the background
with no access to the console or
keyboard. Calls to wait and cwait
against the child process will fail.
This is an asynchronous detached spawn
and is valid only in OS/2 protected
mode.
P_NOWAIT Continues to execute parent process
concurrently with child process
(asynchronous spawn, valid only in
protected mode).
P_NOWAITO Continues to execute parent process and
ignores wait and cwait calls against
child process (asynchronous spawn, valid
only in protected mode).
P_OVERLAY Overlays parent process with child,
destroying the parent (same effect as
exec calls).
P_WAIT Suspends parent process until execution
of child process is complete
(synchronous spawn).
The cmdname argument specifies the file which will be executed as the child
process, and can specify a full path (from the root), a partial path (from
the current working directory), or just a file name. If cmdname does not
have a file-name extension or does not end with a period (.), the spawn
function first tries the .COM extension, then the .EXE extension, and
finally the .BAT extension (or, in OS/2 protected mode, the .CMD extension).
This ability to spawn batch files is a new feature in Microsoft C version
6.0.
If cmdname has an extension, only that extension is used. If cmdname ends
with a period, the spawn calls search for cmdname with no extension. The
spawnlp, spawnlpe, spawnvp, and spawnvpe routines search for cmdname (using
the same procedures) in the directories specified by the PATH environment
variable.
If cmdname contains a drive specifier or any slashes (i.e., if it is a
relative path name), the spawn call searches only for the specified file and
no path searching is done.
Arguments for the Child Process
Arguments are passed to the child process by giving one or more pointers to
character strings as arguments in the spawn call. These character strings
form the argument list for the child process. The combined length of the
strings forming the argument list for the child process must not exceed 128
bytes in real mode. The terminating null character ('\0') for each string is
not included in the count, but space characters (automatically inserted to
separate arguments) are included.
The argument pointers may be passed as separate arguments (spawnl, spawnle,
spawnlp, and spawnlpe) or as an array of pointers (spawnv, spawnve, spawnvp,
and spawnvpe). At least one argument, arg0 or argv[0], must be passed to the
child process. By convention, this argument is the name of the program as it
might be typed on the command line by the user. (A different value will not
produce an error.) In real mode, the argv[0] value is supplied by the
operating system and is the fully qualified path name of the executing
program. In protected mode, it is usually the program name as it would be
typed on the command line.
The spawnl, spawnle, spawnlp, and spawnlpe calls are typically used in cases
where the number of arguments is known in advance. The arg0 argument is
usually a pointer to cmdname. The arguments arg1 through argn are pointers
to the character strings forming the new argument list. Following argn,
there must be a NULL pointer to mark the end of the argument list.
The spawnv, spawnve, spawnvp, and spawnvpe calls are useful when the number
of arguments to the child process is variable. Pointers to the arguments are
passed as an array, argv. The argument argv[0] is usually a pointer to a
path name in real mode or to the program name in protected mode, and argv[1]
through argv[n] are pointers to the character strings forming the new
argument list. The argument argv[n+1] must be a NULL pointer to mark the end
of the argument list.
Environment of the Child Process
Files that are open when a spawn call is made remain open in the child
process. In the spawnl, spawnlp, spawnv, and spawnvp calls, the child
process inherits the environment of the parent. The spawnle, spawnlpe,
spawnve, and spawnvpe calls allow the user to alter the environment for the
child process by passing a list of environment settings through the envp
argument. The argument envp is an array of character pointers, each element
of which (except for the final element) points to a null-terminated string
defining an environment variable. Such a string usually has the form
NAME=value
where NAME is the name of an environment variable and value is the string
value to which that variable is set. (Note that value is not enclosed in
double quotation marks.) The final element of the envp array should be NULL.
When envp itself is NULL, the child process inherits the environment
settings of the parent process.
The spawn functions can pass the child process all information about open
files, including the translation mode, through the C_FILE_INFO entry in the
environment that is passed in real mode (_C_FILE_INFO in protected mode).
The C start-up code normally processes this entry and then deletes it from
the environment. However, if a spawn function spawns a non-C process (such
as CMD.EXE), this entry remains in the environment. Printing the environment
shows graphics characters in the definition string for this entry, since the
environment information is passed in binary form in real mode. It should not
have any other effect on normal operations. In protected mode, the
environment information is passed in text form and therefore contains no
graphics characters.
You must explicitly flush (using fflush or flushall) or close any stream
prior to the spawn function call.
Starting with Microsoft C version 6.0, you can control whether or not the
open file information of a process will be passed to its child processes.
The external variable _fileinfo (declared in STDLIB.H) controls the passing
of C_FILE_INFO information. If _fileinfo is 0, the C_FILE_INFO information
is not passed to the child processes. If _fileinfo is not 0, C_FILE_INFO is
passed to child processes.
By default, _fileinfo is 0 and thus the C_FILE_INFO information is not
passed to child processes. There are two ways to modify the default value of
_fileinfo:
■ Link the supplied object file FILEINFO.OBJ into your program. Use the
/NOE option to avoid multiple symbol definitions.
■ Set the _fileinfo variable to a nonzero value directly within your C
program.
Return Value
The return value from a synchronous spawn (P_WAIT specified for mode) is the
exit status of the child process.
The return value from an asynchronous spawn (P_NOWAIT or P_NOWAITO specified
for mode) is the process ID. To obtain the exit code for a process spawned
with P_NOWAIT, you must call the wait or cwait function and specify the
process ID. The exit code cannot be obtained for a process spawned with
P_NOWAITO.
The exit status is 0 if the process terminated normally. The exit status can
be set to a nonzero value if the child process specifically calls the exit
routine with a nonzero argument. If the child process did not explicitly set
a positive exit status, a positive exit status indicates an abnormal exit
with an abort or an interrupt. A return value of -1 indicates an error (the
child process is not started). In this case, errno is set to one of the
following values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
E2BIG In DOS, the argument list exceeds 128
bytes, or the space
required for the environment information
exceeds 32K. In OS/2, the argument list
and the space required for environment
information combined exceed 32K.
EINVAL The mode argument is invalid.
ENOENT The file or path name is not found.
ENOEXEC The specified file is not executable or
has an invalid
executable-file format.
ENOMEM Not enough memory is available to
execute the child process.
Note that signal settings are not preserved in child processes created by
calls to spawn routines. The signal settings are reset to the default in the
child process.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
The spawn functions, with P_OVERLAY mode, will not work in OS/2
DOScompatibility mode in programs which are bound with FAPI for dual-mode
execution.
Programs linked as DOS mode .EXE files will work, and protected-mode
programs will work. The restriction applies only to bound programs in real
mode.
In order to ensure proper overlay initialization and termination, do not use
the setjmp or longjmp functions to enter or leave an overlay routine.
See Also
abort, atexit, exec functions, exit, _exit, onexit, system
Example
/* SPAWN.C: This program accepts a number in the range 18 from the
* command line. Based on the number it receives, it executes one of the
* eight different procedures that spawn the process named child. For
* some of these procedures, the CHILD.EXE file must be in the
* same directory; for others, it only has to be in the same path.
*/
#include <stdio.h>
#include <process.h>
char *my_env[] =
{
"THIS=environment will be",
"PASSED=to child.exe by the",
"SPAWNLE=and",
"SPAWNLPE=and",
"SPAWNVE=and",
"SPAWNVPE=functions",
NULL
};
void main( int argc, char *argv[] )
{
char *args[4];
int result;
/* Set up parameters to be sent: */
args[0] = "child";
args[1] = "spawn??";
args[2] = "two";
args[3] = NULL;
switch (argv[1][0]) /* Based on first letter of argument */
{
case '1':
spawnl( P_WAIT, argv[2], argv[2], "spawnl", "two", NULL );
break;
case '2':
spawnle( P_WAIT, argv[2], argv[2], "spawnle", "two",
NULL, my_env );
break;
case '3':
spawnlp( P_WAIT, argv[2], argv[2], "spawnlp", "two", NULL );
break;
case '4':
spawnlpe( P_WAIT, argv[2], argv[2], "spawnlpe", "two",
NULL, my_env );
break;
case '5':
spawnv( P_OVERLAY, argv[2], args );
break;
case '6':
spawnve( P_OVERLAY, argv[2], args, my_env );
break;
case '7':
spawnvp( P_OVERLAY, argv[2], args );
break;
case '8':
spawnvpe( P_OVERLAY, argv[2], args, my_env );
break;
default:
printf( "SYNTAX: SPAWN <1-8> <childprogram>\n" );
exit( 1 );
}
printf( "\n\nReturned from SPAWN!\n" );
}
_splitpath
────────────────────────────────────────────────────────────────────────────
Description
Breaks a path name into components.
#include <stdlib.h>
void _splitpath( char *path, char *drive, char *dir, char *fname, char
*ext );
path Full path name
drive Drive letter
dir Directory path
fname File name
ext File extension
Remarks
The _splitpath routine breaks a full path name into its four components. The
path argument should point to a buffer containing the complete path name.
The maximum size necessary for each buffer is specified by the manifest
constants _MAX_DRIVE, _MAX_DIR, _MAX_FNAME, and _MAX_EXT, defined in
STDLIB.H. The other arguments point to the buffers used to store the
path-name elements:
Buffer Description
────────────────────────────────────────────────────────────────────────────
drive Contains the drive letter followed by a
colon (:) if a drive is specified in
path.
dir Contains the path of subdirectories, if
any, including the trailing slash.
Forward slashes ( / ), backslashes ( \
), or both may be present in path.
fname Contains the base file name without any
extensions.
ext Contains the file-name extension, if
any, including the leading period (.).
The return parameters will contain empty strings for any path-name
components not found in path.
Return Value
None.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_fullpath, _makepath
Example
/* MAKEPATH.C */
#include <stdlib.h>
#include <stdio.h>
void main()
{
char path_buffer[_MAX_PATH];
char drive[_MAX_DRIVE];
char dir[_MAX_DIR];
char fname[_MAX_FNAME];
char ext[_MAX_EXT];
_makepath( path_buffer, "c", "\\c60\\clibref\\", "makepath", "c" );
printf( "Path created with _makepath: %s\n\n", path_buffer );
_splitpath( path_buffer, drive, dir, fname, ext );
printf( "Path extracted with _splitpath:\n" );
printf( " Drive: %s\n", drive );
printf( " Dir: %s\n", dir );
printf( " Filename: %s\n", fname );
printf( " Ext: %s\n", ext );
}
Output
Path created with _makepath: c:\c60\clibref\makepath.c
Path extracted with _splitpath:
Drive: c:
Dir: \c60\clibref\
Filename: makepath
Ext: .c
sprintf
────────────────────────────────────────────────────────────────────────────
Description
Writes formatted data to a string.
#include <stdio.h>
int sprintf( char *buffer, const char *format [[, argument]]...);
buffer Storage location for output
format Format-control string
argument Optional arguments
Remarks
The sprintf function formats and stores a series of characters and values in
buffer. Each argument (if any) is converted and output according to the
corresponding format specification in the format. The format consists of
ordinary characters and has the same form and function as the format
argument for the printf function. (See printf for a description of the
format and arguments.) A null character is appended to the end of the
characters written, but is not counted in the return value.
Return Value
The sprintf function returns the number of characters stored in buffer, not
counting the terminating null character.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
fprintf, printf, sscanf
Example
/* SPRINTF.C: This program uses sprintf to format various data and
* place them in the string named buffer.
*/
#include <stdio.h>
void main()
{
char buffer[200], s[] = "computer", c = 'l';
int i = 35, j;
float fp = 1.7320534;
/* Format and print various data: */
j = sprintf( buffer, "\tString: %s\n", s );
j += sprintf( buffer + j, "\tCharacter: %c\n", c );
j += sprintf( buffer + j, "\tInteger: %d\n", i );
j += sprintf( buffer + j, "\tReal: %f\n", fp );
printf( "Output:\n%s\ncharacter count = %d\n", buffer, j );
}
Output
Output:
String: computer
Character: l
Integer: 35
Real: 1.732053
character count = 71
sqrt, sqrtl
────────────────────────────────────────────────────────────────────────────
Description
Calculates the square root.
#include <math.h>
double sqrt( double x );
long double sqrtl( long double x );
x Nonnegative floating-point value
Remarks
The sqrt functions calculate the square root of x. The sqrtl function is the
80-bit counterpart and uses an 80-bit, 10-byte coprocessor form of arguments
and return values.
Return Value
The sqrt functions return the square-root result. If x is negative, the
function prints a DOMAIN error message to stderr, sets errno to EDOM, and
returns 0.
Error handling can be modified by using the matherr or _matherrl routine.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
exp, log, matherr, pow
Example
/* SQRT.C: This program calculates a square root. */
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
void main()
{
double question = 45.35, answer;
answer = sqrt( question );
if( errno == EDOM )
printf( "Domain error\n" );
else
printf( "The square root of %.2f is %.2f\n", question, answer );
}
Output
The square root of 45.35 is 6.73
srand
────────────────────────────────────────────────────────────────────────────
Description
Sets a random starting point.
#include <stdlib.h> Required only for function declarations
void srand( unsigned int seed );
seed Seed for random-number generation
Remarks
The srand function sets the starting point for generating a series of
pseudorandom integers. To reinitialize the generator, use 1 as the seed
argument. Any other value for seed sets the generator to a random starting
point.
The rand function is used to retrieve the pseudorandom numbers that are
generated. Calling rand before any call to srand will generate the same
sequence as calling srand with seed passed as 1.
Return Value
None.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
rand
Example
/* RAND.C: This program seeds the random number generator with the
* time, then displays 20 random integers.
*/
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
void main()
{
int i;
/* Seed the random number generator with current time so that
* the numbers will be different every time we run.
*/
srand( (unsigned)time( NULL ) );
/* Display 10 numbers. */
for( i = 0; i < 10; i++ )
printf( " %6d\n", rand() );
}
Output
19471
16395
8268
15582
6489
28356
27042
5276
23070
10930
sscanf
────────────────────────────────────────────────────────────────────────────
Description
Reads formatted data from a string.
#include <stdio.h>
int sscanf( const char *buffer, const char *format [[, argument ]] ... );
buffer Stored data
format Format-control string
argument Optional arguments
Remarks
The sscanf function reads data from buffer into the locations given by each
argument. Every argument must be a pointer to a variable with a type that
corresponds to a type specifier in format. The format controls the
interpretation of the input fields and has the same form and function as the
format argument for the scanf function; see scanf for a complete description
of format.
Return Value
The sscanf function returns the number of fields that were successfully
converted and assigned. The return value does not include fields that were
read but not assigned.
The return value is EOF for an attempt to read at end-of-string. A return
value of 0 means that no fields were assigned.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
fscanf, scanf, sprintf
Example
/* SSCANF.C: This program uses sscanf to read data items from
* a string named tokenstring, then displays them.
*/
#include <stdio.h>
void main()
{
char tokenstring[] = "15 12 14...";
char s[81];
char c;
int i;
float fp;
/* Input various data from tokenstring: */
sscanf( tokenstring, "%s", s );
sscanf( tokenstring, "%c", &c );
sscanf( tokenstring, "%d", &i );
sscanf( tokenstring, "%f", &fp );
/* Output the data read */
printf( "String = %s\n", s );
printf( "Character = %c\n", c );
printf( "Integer: = %d\n", i );
printf( "Real: = %f\n", fp );
}
Output
String = 15
Character = 1
Integer: = 15
Real: = 15.000000
stackavail
────────────────────────────────────────────────────────────────────────────
Description
Gets the size of the stack available.
#include <malloc.h> Required only for function declarations
size_t stackavail( void );
Remarks
The stackavail function returns the approximate size (in bytes) of the stack
space available for dynamic memory allocation with alloca.
Return Value
The stackavail function returns the size in bytes as an unsigned integer
value.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
Example
/* ALLOCA.C: This program checks the stack space available before
* and after using the alloca function to allocate space on the stack.
*/
#include <malloc.h>
#include <stdio.h>
void main()
{
char *buffer;
printf( "Bytes available on stack: %u\n", stackavail() );
/* Allocate memory for string. */
buffer = alloca( 120 * sizeof( char ) );
printf( "Enter a string: " );
gets( buffer );
printf( "You entered: %s\n", buffer );
printf( "Bytes available on stack: %u\n", stackavail() );
}
Output
Bytes available on stack: 2028
Enter a string: How much stack space will this string take?
You entered: How much stack space will this string take?
Bytes available on stack: 1902
stat
────────────────────────────────────────────────────────────────────────────
Description
Gets status information on a file.
#include <sys\stat.h>
#include <sys\types.h>
int stat( char *pathname, struct stat *buffer );
pathname Path name of existing file
buffer Pointer to structure that receives
results
Remarks
The stat function obtains information about the file or directory specified
by pathname and stores it in the structure pointed to by buffer. The stat
structure, defined in the file SYS\STAT.H, includes the following fields:
Field Value
────────────────────────────────────────────────────────────────────────────
st_atime Time of last modification of file (same
as st_mtime and st_ctime).
st_ctime Time of last modification of file (same
as st_atime and st_mtime).
st_dev Drive number of the disk containing the
file (same as st_rdev). Real mode only.
st_mode Bit mask for file-mode information. The
S_IFDIR bit is set if pathname specifies
a directory; the S_IFREG bit is set if
pathname specifies an ordinary file.
User read/write bits are set according
to the file's permission mode; user
execute bits are set according to the
file-name extension.
st_mtime Time of last modification of file (same
as st_atime and st_ctime).
st_nlink Always 1.
st_rdev Drive number of the disk containing the
file (same as st_dev). Real mode only.
st_size Size of the file in bytes.
Note that if pathname refers to a device, the size and time fields in the
stat structure are not meaningful.
Return Value
The stat function returns the value 0 if the file-status information is
obtained. A return value of -1 indicates an error; also, errno is set to
ENOENT, indicating that the file name or path name could not be found.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
access, fstat
Example
/* STAT.C: This program uses the stat function to report information
* about the file named STAT.C.
*/
#include <time.h>
#include <sys\types.h>
#include <sys\stat.h>
#include <stdio.h>
void main()
{
struct stat buf;
int fh, result;
char buffer[] = "A line to output";
/* Get data associated with "stat.c": */
result = stat( "stat.c", &buf );
/* Check if statistics are valid: */
if( result != 0 )
perror( "Problem getting information" );
else
{
/* Output some of the statistics: */
printf( "File size : %ld\n", buf.st_size );
printf( "Drive : %c:\n", buf.st_dev + 'A' );
printf( "Time modified : %s", ctime( &buf.st_atime ) );
}
}
Output
File size : 761
Drive : C:
Time modified : Wed Jun 14 12:20:08 1989
_status87
────────────────────────────────────────────────────────────────────────────
Description
Gets the floating-point status word.
#include <float.h>
unsigned int _status87( void );
Remarks
The _status87 function gets the floating-point status word. The status word
is a combination of the 8087/80287/80387 status word and other conditions
detected by the 8087/80287/80387 exception handler, such as floating-point
stack overflow and underflow.
Return Value
The bits in the value returned indicate the floating-point status. See the
FLOAT.H include file for a complete definition of the bits returned by
_status87.
Note that many of the math library functions modify the 8087/80287 status
word, with unpredictable results. Return values from _clear87 and _status87
become more reliable as fewer floating-point operations are performed
between known states of the floating-point status word.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_clear87, _control87
Example
/* STATUS87.C: This program creates various floating-point errors and
* then uses _status87 to display messages indicating these problems.
*/
#include <stdio.h>
#include <float.h>
void main()
{
double a = 1e-40, b;
float x, y;
printf( "Status = %.4x - clear\n",_status87() );
/* Assignment into y is inexact & underflows: */
y = a;
printf( "Status = %.4x - inexact, underflow\n", _status87() );
/* y is denormal: */
b = y;
printf( "Status = %.4x - inexact underflow, denormal\n", _status87() );
/* Clear user 8087: */
_clear87();
}
Output
Status = 0000 - clear
Status = 0030 - inexact, underflow
Status = 0032 - inexact underflow, denormal
strcat, _fstrcat
────────────────────────────────────────────────────────────────────────────
Description
Append a string.
#include <string.h> Required only for function declarations
char *strcat( char *string1, const char *string2 );
char _far * _far _fstrcat( char _far *string1, const char _far *string2 );
string1 Destination string
string2 Source string
Remarks
The strcat and _fstrcat functions append string2 to string1, terminate the
resulting string with a null character, and return a pointer to the
concatenated string (string1).
The strcat and _fstrcat functions operate on null-terminated strings. The
string arguments to these functions are expected to contain a null character
('\0') marking the end of the string. No overflow checking is performed when
strings are copied or appended.
The _fstrcat function is a model-independent (large-model) form of the
strcat function. The behavior and return value of _fstrcat are identical to
those of the model-dependent function strcat, with the exception that the
arguments and return values are far pointers.
Return Value
The return values for these functions are described above.
Compatibility
strcat
ANSI DOS OS/2 UNIX XENIX
_fstrcat
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
strncat, strncmp, strncpy, strnicmp, strrchr, strspn
Example
/* STRCPY.C: This program uses strcpy and strcat to build a phrase. */
#include <string.h>
#include <stdio.h>
void main()
{
char string[80];
strcpy( string, "Hello world from " );
strcat( string, "strcpy " );
strcat( string, "and " );
strcat( string, "strcat!" );
printf( "String = %s\n", string );
}
Output
String = Hello world from strcpy and strcat!
strchr, _fstrchr
────────────────────────────────────────────────────────────────────────────
Description
Find a character in a string.
#include <string.h> Required only for function declarations
char *strchr( const char *string, int c );
char _far * _far _fstrchr( const char _far *string, int c );
string Source string
c Character to be located
Remarks
The strchr and _fstrchr functions return a pointer to the first occurrence
of c in string. The character c may be the null character ('\0'); the
terminating null character of string is included in the search. The function
returns NULL if the character is not found.
The strchr and _fstrchr functions operate on null-terminated strings. The
string arguments to these functions are expected to contain a null character
('\0') marking the end of the string.
The _fstrchr function is a model-independent (large-model) form of the
strchr function. The behavior and return value of _fstrchr are identical to
those of the model-dependent function strchr, with the exception that the
arguments and return values are far.
Return Value
The return values for these functions are described above.
Compatibility
strchr
ANSI DOS OS/2 UNIX XENIX
_fstrchr
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
strcspn, strncat, strncmp, strncpy, strnicmp, strpbrk, strrchr, strspn,
strstr
Example
/* STRCHR.C: This program illustrates searching for a character with
* strchr (search forward) or strrchr (search backward).
*/
#include <string.h>
#include <stdio.h>
int ch = 'r';
char string[] = "The quick brown dog jumps over the lazy fox";
char fmt1[] = " 1 2 3 4 5";
char fmt2[] = "12345678901234567890123456789012345678901234567890";
void main()
{
char *pdest;
int result;
printf( "String to be searched: \n\t\t%s\n", string );
printf( "\t\t%s\n\t\t%s\n\n", fmt1, fmt2 );
printf( "Search char:\t%c\n", ch );
/* Search forward. */
pdest = strchr( string, ch );
result = pdest - string + 1;
if( pdest != NULL )
printf( "Result:\tfirst %c found at position %d\n\n", ch, result );
else
printf( "Result:\t%c not found\n" );
/* Search backward. */
pdest = strrchr( string, ch );
result = pdest - string + 1;
if( pdest != NULL )
printf( "Result:\tlast %c found at position %d\n\n", ch, result );
else
printf( "Result:\t%c not found\n" );
}
Output
String to be searched:
The quick brown dog jumps over the lazy fox
1 2 3 4 5
12345678901234567890123456789012345678901234567890
Search char: r
Result: first r found at position 12
Result: last r found at position 30
strcmp, _fstrcmp
────────────────────────────────────────────────────────────────────────────
Description
Compare strings.
#include <string.h> Required only for function declarations
int strcmp( const char *string1, const char *string2 );
int _far _fstrcmp( const char _far *string1, const char _far *string2 );
string1 String to compare
string2 String to compare
Remarks
The strcmp and _fstrcmp functions compare string1 and string2
lexicographically and return a value indicating their relationship, as
follows:
Value Meaning
────────────────────────────────────────────────────────────────────────────
< 0 string1 less than string2
= 0 string1 identical to string2
> 0 string1 greater than string2
The strcmp and _fstrcmp functions operate on null-terminated strings. The
string arguments to these functions are expected to contain a null character
('\0') marking the end of the string.
The _fstrcmp function is a model-independent (large-model) form of the
strcmp function. The behavior and return value of _fstrcmp are identical to
those of the model-dependent function strcmp, with the exception that the
arguments are far pointers.
The strcmpi and stricmp functions are case-insensitive versions of strcmp.
Return Value
The return values for these functions are described above.
Compatibility
strcmp
ANSI DOS OS/2 UNIX XENIX
_fstrcmp
▼ ANSI DOS OS/2 ▼ UNIX XENIX
See Also
memcmp, memicmp, strncat, strncmp, strncpy, strnicmp, strrchr, strspn
Example
/* STRCMP.C */
#include <string.h>
#include <stdio.h>
char string1[] = "The quick brown dog jumps over the lazy fox";
char string2[] = "The QUICK brown dog jumps over the lazy fox";
void main()
{
char tmp[20];
int result;
/* Case sensitive */
printf( "Compare strings:\n\t%s\n\t%s\n\n", string1, string2 );
result = strcmp( string1, string2 );
if( result > 0 )
strcpy( tmp, "greater than" );
else if( result < 0 )
strcpy( tmp, "less than" );
else
strcpy( tmp, "equal to" );
printf( "\tstrcmp: String 1 is %s string 2\n", tmp );
/* Case insensitive (could use equivalent stricmp) */
result = strcmpi( string1, string2 );
if( result > 0 )
strcpy( tmp, "greater than" );
else if( result < 0 )
strcpy( tmp, "less than" );
else
strcpy( tmp, "equal to" );
printf( "\tstrcmpi: String 1 is %s string 2\n", tmp );
}
Output
Compare strings:
The quick brown dog jumps over the lazy fox
The QUICK brown dog jumps over the lazy fox
strcmp: String 1 is greater than string 2
strcmpi: String 1 is equal to string 2
strcmpi
────────────────────────────────────────────────────────────────────────────
Description
Compares strings without regard to case.
#include <string.h> Required only for function declarations
int strcmpi( const char *string1, const char *string2 );
string1 String to compare
string2 String to compare
Remarks
The strcmpi function compares string1 and string2 lexicographically and
returns a value indicating their relationship, as follows:
Value Meaning
────────────────────────────────────────────────────────────────────────────
< 0 string1 less than string2
= 0 string1 identical to string2
> 0 string1 greater than string2
The strcmp function is a case-sensitive version of strcmpi.
The strcmpi function operates on null-terminated strings. The string
arguments to these functions are expected to contain a null character ('\0')
marking the end of the string.
Return Value
The return values for these functions are described above.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
memcmp, memicmp, strncat, strncmp, strncpy, strnicmp, strrchr, strspn
Example
See the example for strcmp.
strcoll
────────────────────────────────────────────────────────────────────────────
Description
Compares strings using locale-specific information.
#include <string.h> Required only for function declarations
int strcoll( const char *string1, const char *string2 );
string1 String to compare
string2 String to compare
Remarks
The strcoll function compares string1 and string2 lexicographically and
returns a value indicating their relationship, as follows:
Value Meaning
────────────────────────────────────────────────────────────────────────────
< 0 string1 less than string2
= 0 string1 identical to string2
> 0 string1 greater than string2
The strcoll function operates on null-terminated strings. The string
arguments to these functions are expected to contain a null character ('\0')
marking the end of the string.
The strcoll function differs from strcmp in that it uses locale-specific
information to provide locale-specific collating sequences.
Return Value
The return value for this function is described above.
Compatibility
ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
localeconv, setlocale, strcmp, strncmp, strxfrm
strcpy, _fstrcpy
────────────────────────────────────────────────────────────────────────────
Description
Copy a string.
#include <string.h> Required only for function declarations
char *strcpy( char *string1, const char *string2 );
char _far * _far _fstrcpy( char _far *string1, const char _far *string2 );
string1 Destination string
string2 Source string
Remarks
The strcpy function copies string2, including the terminating null
character, to the location specified by string1, and returns string1.
The strcpy and _fstrcpy functions operate on null-terminated strings. The
string arguments to these functions are expected to contain a null character
('\0') marking the end of the string. No overflow checking is performed when
strings are copied or appended.
The _fstrcpy function is a model-independent (large-model) form of the
strcpy function. The behavior and return value of _fstrcpy are identical to
those of the model-dependent function strcpy, with the exception that the
arguments and return values are far pointers.
Return Value
The return values for these functions are described above.
Compatibility
strcpy
ANSI DOS OS/2 UNIX XENIX
_fstrcpy
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
strcat, strcmp, strncat, strncmp, strncpy, strnicmp, strrchr, strspn
Example
/* STRCPY.C: This program uses strcpy and strcat to build a phrase. */
#include <string.h>
#include <stdio.h>
void main()
{
char string[80];
strcpy( string, "Hello world from " );
strcat( string, "strcpy " );
strcat( string, "and " );
strcat( string, "strcat!" );
printf( "String = %s\n", string );
}
Output
String = Hello world from strcpy and strcat!
strcspn, _fstrcspn
────────────────────────────────────────────────────────────────────────────
Description
Find a substring in a string.
#include <string.h> Required only for function declarations
size_t strcspn( const char *string1, const char *string2 );
size_t _far _fstrcspn( const char _far *string1, const char _far *string2
);
string1 Source string
string2 Character set
Remarks
The strcspn functions return the index of the first character in string1
belonging to the set of characters specified by string2. This value is
equivalent to the length of the initial substring of string1 consisting
entirely of characters not in string2. Terminating null characters are not
considered in the search. If string1 begins with a character from string2,
strcspn returns 0.
The strcspn and _fstrcspn functions operate on null-terminated strings. The
string arguments to these functions are expected to contain a null character
('\0') marking the end of the string.
The _fstrcspn function is a model-independent (large-model) form of the
strcspn function. The behavior and return value of _fstrcspn are identical
to those of the modeldependent function strcspn, with the exception that the
arguments and return values are far.
Return Value
The return values for these functions are described above.
Compatibility
strcspn
ANSI DOS OS/2 UNIX XENIX
_fstrcspn
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
strncat, strncmp, strncpy, strnicmp, strrchr, strspn
Example
/* STRCSPN.C */
#include <string.h>
#include <stdio.h>
void main()
{
char string[] = "xyzabc";
int pos;
pos = strcspn( string, "abc" );
printf( "First a, b or c in %s is at character %d\n", string, pos );
}
Output
First a, b or c in xyzabc is at character 3
_strdate
────────────────────────────────────────────────────────────────────────────
Description
Copies a date to a buffer.
#include <time.h>
char *_strdate( char *datestr );
datestr Current date
Remarks
The _strdate function copies the date to the buffer pointed to by datestr,
formatted
mm/dd/yy
where mm is two digits representing the month, dd is two digits
representing the day of the month, and yy is the last two digits of the
year. For example, the string
12/05/88
represents December 5, 1988.
The buffer must be at least nine bytes long.
Return Value
The _strdate function returns a pointer to the resulting text string
datestr.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
asctime, ctime, gmtime, localtime, mktime, time, tzset
Example
/* STRTIME.C */
#include <time.h>
#include <stdio.h>
void main()
{
char dbuffer [9];
char tbuffer [9];
_strdate( dbuffer );
printf( "The current date is %s \n", dbuffer );
_strtime( tbuffer );
printf( "The current time is %s \n", tbuffer );
}
Output
The current date is 06/20/89
The current time is 09:33:13
strdup Functions
────────────────────────────────────────────────────────────────────────────
Description
Duplicate strings.
#include <string.h> Required only for function declarations
char *strdup( const char *string );
char _far * _far _fstrdup( const char _far *string );
char _near * _far _nstrdup( const char _far *string );
string Source string
Remarks
The strdup function allocates storage space (with a call to malloc) for a
copy of string and returns a pointer to the storage space containing the
copied string. The function returns NULL if storage cannot be allocated.
The _fstrdup and _nstrdup functions provide complete control over the heap
used for string duplication. The strdup function returns a pointer to a copy
of the string argument. The space for the string is allocated from the heap
specified by the memory model in use. In large-data models (that is,
compact-, large-, and huge-model programs), strdup allocates space from the
far heap. In small-data models (tiny-, small-, and medium-model programs),
strdup allocates space from the near heap.
The strdup, _fstrdup, and _nstrdup functions operate on null-terminated
strings. The string arguments to these functions are expected to contain a
null character ('\0') marking the end of the string.
The _fstrdup function returns a far pointer to a copy of the string
allocated in far memory (the far heap). As with the other model-independent
functions, the syntax and semantics of these functions correspond to those
of strdup except for the sizes of the arguments and return values. The
_nstrdup function returns a near pointer to a copy of the string allocated
in the near heap (in the default data segment).
Return Value
The return values for these functions are described above.
Compatibility
strdup, _fstrdup, _nstrdup
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
strcat, strcmp, strncat, strncmp, strncpy, strnicmp, strrchr, strspn
Example
/* STRDUP.C */
#include <string.h>
#include <stdio.h>
#include <conio.h>
#include <dos.h>
void main()
{
char buffer[] = "This is the buffer text";
char *newstring;
printf( "Original: %s\n", buffer );
newstring = strdup( buffer );
printf( "Copy: %s\n", newstring );
}
Output
Original: This is the buffer text
Copy: This is the buffer text
strerror, _strerror
────────────────────────────────────────────────────────────────────────────
Description
Gets a system error message (strerror) or prints a user-supplied error
message (_strerror).
#include <string.h> Required only for function declarations
char *strerror( int errnum );
char *_strerror( char *string );
errnum Error number
string User-supplied message
Remarks
The strerror function maps errnum to an error-message string, returning a
pointer to the string. The function itself does not actually print the
message; for that, you need to call an output function such as printf.
If string is passed as NULL, _strerror returns a pointer to a string
containing the system error message for the last library call that produced
an error. The error-message string is terminated by the newline character
('\n').
If string is not equal to NULL, then _strerror returns a pointer to a string
containing (in order) your string message, a colon, a space, the system
error message for the last library call producing an error, and a newline
character. Your string message can be a maximum of 94 bytes long.
Unlike perror, _strerror alone does not print any messages. To print the
message returned by _strerror to stderr, your program will need an fprintf
statement, as shown in the following lines:
if ((access("datafile",2)) == -1)
fprintf(_strerror(NULL));
The actual error number for _strerror is stored in the variable errno, which
should be declared at the external level. The system error messages are
accessed through the variable sys_errlist, which is an array of messages
ordered by error number. The _strerror function accesses the appropriate
error message by using the errno value as an index to the variable
sys_errlist. The value of the variable sys_nerr is defined as the maximum
number of elements in the sys_errlist array.
To produce accurate results, _strerror should be called immediately after a
library routine returns with an error. Otherwise, the errno value may be
overwritten by subsequent calls.
Note that the _strerror function under Microsoft C version 5.0 is identical
to the version 4.0 strerror function. The name was altered to permit the
inclusion in Microsoft C version 5.0 of the ANSI-conforming strerror
function. The _strerror function is not part of the ANSI definition but is
instead a Microsoft extension to it; it should not be used where portability
is desired. For ANSI compatibility, use strerror instead.
Return Value
The strerror function returns a pointer to the error-message string. The
string can be overwritten by subsequent calls to strerror.
The _strerror function returns no value.
Compatibility
strerror
ANSI DOS OS/2 ▼ UNIX ▼ XENIX
_strerror
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
clearerr, ferror, perror
Example
See the example for perror.
strftime
────────────────────────────────────────────────────────────────────────────
Description
Formats a time string.
#include <time.h> Required only for function declarations
size_t strftime( char *string, size_t maxsize, const char *format,
const struct tm *timeptr );
string Output string
maxsize Maximum length of string
format Format control string
timeptr tm data structure
Remarks
The strftime function formats the tm time value in timeptr according to the
supplied format argument and stores the result in the buffer string. At
most, maxsize characters are placed in the string.
The format argument consists of one or more codes; as in printf, the
formatting codes are preceded by a % sign. Characters that do not begin with
a % sign are copied unchanged to string. The LC_TIME category of the current
locale affects the output formatting of strftime.
The formatting codes for strftime are listed below:
Format Description
────────────────────────────────────────────────────────────────────────────
%a Abbreviated weekday name
%A Full weekday name
%b Abbreviated month name
%B Full month name
%c Date and time representation appropriate
for the locale
%d Day of the month as a decimal number (01
- 31)
%H Hour in 24-hour format (00 - 23)
%I Hour in 12-hour format (01 - 12)
%j Day of the year as a decimal number (001
- 366)
%m Month as a decimal number (01 - 12)
%M Minute as a decimal number (00 - 59)
%p Current locale's AM/PM indicator for a
12-hour clock
%S Second as a decimal number (00 - 61)
%U Week of the year as a decimal number;
Sunday is taken as the first day of the
week (00 - 53)
%w Weekday as a decimal number (0 - 6;
Sunday is 0)
%W Week of the year as a decimal number;
Monday is taken as the first day of the
week (00 - 53)
%x Date representation for current locale
%X Time representation for current locale
%y Year without the century as a decimal
number (00 - 99)
%Y Year with the century as a decimal
number
%z Time zone name or abbreviation; no
characters if time zone is unknown
%% Percent sign
Return Value
The strftime function returns the number of characters placed in string if
the total number of resulting characters, including the terminating null, is
not more than maxsize.
Otherwise, strftime returns 0, and the contents of the string are
indeterminate.
Compatibility
ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
localeconv, setlocale, strxfrm
Example
See the example for perror.
stricmp, _fstricmp
────────────────────────────────────────────────────────────────────────────
Description
Compare strings without regard to case.
#include <string.h> Required only for function declarations
int stricmp( const char *string1, const char *string2 );
int _far _fstricmp( const char _far *string1, const char _far *string2 );
string1 String to compare
string2 String to compare
Remarks
The stricmp and _fstricmp functions compare string1 and string2
lexicographically and return a value indicating their relationship, as
follows:
Value Meaning
────────────────────────────────────────────────────────────────────────────
< 0 string1 less than string2
= 0 string1 identical to string2
> 0 string1 greater than string2
The stricmp and _fstricmp functions operate on null-terminated strings. The
string arguments to these functions are expected to contain a null character
('\0') marking the end of the string.
The _fstricmp function is a model-independent (large-model) form of the
stricmp function. The behavior and return value of _fstricmp are identical
to those of the modeldependent function stricmp, with the exception that the
arguments are far pointers.
The strcmp function is a case-sensitive version of stricmp.
Return Value
The return values for these functions are described above.
Compatibility
stricmp
▼ ANSI DOS OS/2 UNIX XENIX_fstricmp
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
memcmp, memicmp, strcat, strcpy, strncat, strncmp, strncpy, strnicmp,
strrchr, strset, strspn
Example
See the example for strcmp.
strlen, _fstrlen
────────────────────────────────────────────────────────────────────────────
Description
Get the length of a string.
#include <string.h> Required only for function declarations
size_t strlen( const char *string );
size_t _fstrlen( const char _far *string );
string Null-terminated string
Remarks
The strlen and _fstrlen functions return the length in bytes of string, not
including the terminating null character ('\0').
The _fstrlen function is a model-independent (large-model) form of the
strlen function. The behavior and return value of _fstrlen are identical to
those of the model-dependent function strlen, with the exception that the
argument is a far pointer.
Return Value
These functions return the string length. There is no error return.
Compatibility
strlen
ANSI DOS OS/2 UNIX XENIX
_fstrlen
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
Example
/* STRLEN.C */
#include <string.h>
#include <stdio.h>
#include <conio.h>
#include <dos.h>
void main()
{
char buffer[61] = "How long am I?";
int len;
len = strlen( buffer );
printf( "'%s' is %d characters long\n", buffer, len );
}
Output
'How long am I?' is 14 characters long
strlwr, _fstrlwr
────────────────────────────────────────────────────────────────────────────
Description
Convert a string to lowercase.
#include <string.h> Required only for function declarations
char *strlwr( char *string );
char _far * _far _fstrlwr( char _far *string );
string String to be converted
Remarks
The strlwr and _fstrlwr functions convert any uppercase letters in the given
nullterminated string to lowercase. Other characters are not affected.
The _fstrlwr function is a model-independent (large-model) form of the
strlwr function. The behavior and return value of _fstrlwr are identical to
those of the model-dependent function strlwr, with the exception that the
argument and return values are far pointers.
Return Value
These functions return a pointer to the converted string. There is no error
return.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
strupr
Example
/* STRLWR.C: This program uses strlwr and strupr to create
* uppercase and lowercase copies of a mixed-case string.
*/
#include <string.h>
#include <stdio.h>
void main()
{
char string[100] = "The String to End All Strings!";
char *copy1, *copy2;
copy1 = strlwr( strdup( string ) );
copy2 = strupr( strdup( string ) );
printf( "Mixed: %s\n", string );
printf( "Lower: %s\n", copy1 );
printf( "Upper: %s\n", copy2 );
}
Output
Mixed: The String to End All Strings!
Lower: the string to end all strings!
Upper: THE STRING TO END ALL STRINGS!
strncat, _fstrncat
────────────────────────────────────────────────────────────────────────────
Description
Appends characters of a string.
#include <string.h> Required only for function declarations
char *strncat( char *string1, const char *string2, size_t count );
char _far * _far _fstrncat( char _far *string1, const char _far *string2,
size_t count );
string1 Destination string
string2 Source string
count Number of characters appended
Remarks
The strncat and _fstrncat functions append, at most, the first count
characters of string2 to string1, terminate the resulting string with a null
character ('\0'), and return a pointer to the concatenated string (string1).
If count is greater than the length of string2, the length of string2 is
used in place of count.
The _fstrncat function is a model-independent (large-model) form of the
strncat function. The behavior and return value of _fstrncat are identical
to those of the model-dependent function strncat, with the exception that
all the pointer arguments and return values are far pointers.
Return Value
The return values for these functions are described above.
Compatibility
strncat
ANSI DOS OS/2 UNIX XENIX
_fstrncat
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
strcat, strcmp, strcpy, strncmp, strncpy, strnicmp, strrchr, strset, strspn
Example
/* STRNCAT.C */
#include <string.h>
#include <stdio.h>
void main()
{
char string[80] = "This is the initial string!";
char suffix[] = " extra text to add to the string...";
/* Combine strings with no more than 19 characters of suffix: */
printf( "Before: %s\n", string );
strncat( string, suffix, 19 );
printf( "After: %s\n", string );
}
Output
Before: This is the initial string!
After: This is the initial string! extra text to add
strncmp, _fstrncmp
────────────────────────────────────────────────────────────────────────────
Description
Compare characters of two strings.
#include <string.h> Required only for function declarations
int strncmp( const char *string1, const char *string2, size_t count );
int _far _fstrncmp( const char _far *string1, const char _far *string2,
size_t count );
string1 String to compare
string2 String to compare
count Number of characters compared
Remarks
The strncmp and _fstrncmp functions lexicographically compare, at most, the
first count characters of string1 and string2 and return a value indicating
the relationship between the substrings, as listed below:
Value Meaning
────────────────────────────────────────────────────────────────────────────
< 0 string1 less than string2
= 0 string1 equivalent to string2
> 0 string1 greater than string2
The strnicmp function is a case-insensitive version of strncmp.
The _fstrncmp function is a model-independent (large-model) form of the
strncmp function. The behavior and return value of _fstrncmp are identical
to those of the model-dependent function strncmp, with the exception that
all the arguments and return values are far.
Return Value
The return values for these functions are described above.
Compatibility
strncmp
ANSI DOS OS/2 UNIX XENIX
_fstrncmp
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
strcat, strcmp, strcpy, strncat, strncpy, strrchr, strset, strspn
Example
/* STRNCMP.C */
#include <string.h>
#include <stdio.h>
char string1[] = "The quick brown dog jumps over the lazy fox";
char string2[] = "The QUICK brown fox jumps over the lazy dog";
void main()
{
char tmp[20];
int result;
printf( "Compare strings:\n\t\t%s\n\t\t%s\n\n", string1, string2 );
printf( "Function:\tstrncmp (first 10 characters only)\n" );
result = strncmp( string1, string2 , 10 );
if( result > 0 )
strcpy( tmp, "greater than" );
else if( result < 0 )
strcpy( tmp, "less than" );
else
strcpy( tmp, "equal to" );
printf( "Result:\t\tString 1 is %s string 2\n\n", tmp );
printf( "Function:\tstrnicmp (first 10 characters only)\n" );
result = strnicmp( string1, string2, 10 );
if( result > 0 )
strcpy( tmp, "greater than" );
else if( result < 0 )
strcpy( tmp, "less than" );
else
strcpy( tmp, "equal to" );
printf( "Result:\t\tString 1 is %s string 2\n\n", tmp );
}
Output
Compare strings:
The quick brown dog jumps over the lazy fox
The QUICK brown fox jumps over the lazy dog
Function: strncmp (first 10 characters only)
Result: String 1 is greater than string 2
Function: strnicmp (first 10 characters only)
Result: String 1 is equal to string 2
strncpy, _fstrncpy
────────────────────────────────────────────────────────────────────────────
Description
Copy characters of one string to another.
#include <string.h> Required only for function declarations
char *strncpy( char *string1, const char *string2, size_t count );
char _far * _far _fstrncpy( char _far *string1, const char _far *string2,
size_t count );
string1 Destination string
string2 Source string
count Number of characters copied
Remarks
The strncpy and _fstrncpy functions copy count characters of string2 to
string1 and return string1. If count is less than the length of string2, a
null character ('\0') is not appended automatically to the copied string. If
count is greater than the length of string2, the string1 result is padded
with null characters ('\0') up to length count.
Note that the behavior of strncpy and _fstrncpy is undefined if the address
ranges of the source and destination strings overlap.
The _fstrncpy function is a model-independent (large-model) form of the
strncpy function. The behavior and return value of _fstrncpy are identical
to those of the model- dependent function strncpy, with the exception that
all the arguments and return values are far.
Return Value
The return values for these functions are described above.
Compatibility
strncpy
ANSI DOS OS/2 UNIX XENIX
_fstrncpy
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
strcat, strcmp, strcpy, strncat, strncmp, strnicmp, strrchr, strset, strspn
Example
/* STRNCPY.C */
#include <string.h>
#include <stdio.h>
void main()
{
char string[100] = "Cats are nice usually";
printf("Before: %s\n", string );
strncpy( string, "Dogs", 4 );
strncpy( string + 9, "mean", 4 );
printf("After: %s\n", string );
}
Output
Before: Cats are nice usually
After: Dogs are mean usually
strnicmp, _fstrnicmp
────────────────────────────────────────────────────────────────────────────
Description
Compare characters of two strings without regard to case.
#include <string.h> Required only for function declarations
int strnicmp( const char *string1, const char *string2, size_t count );
int _far _fstrnicmp( const char _far *string1, const char _far *string2,
size_t count );
string1 String to compare
string2 String to compare
count Number of characters compared
Remarks
The strnicmp and _fstrnicmp functions lexicographically compare (without
regard to case), at most, the first count characters of string1 and string2
and return a value indicating the relationship between the substrings, as
listed below:
Value Meaning
────────────────────────────────────────────────────────────────────────────
< 0 string1 less than string2
= 0 string1 equivalent to string2
> 0 string1 greater than string2
The strncmp function is a case-sensitive version of strnicmp.
The _fstrnicmp function is a model-independent (large-model) form of the
strnicmp function. The behavior and return value of _fstrnicmp are identical
to those of the model-dependent function strnicmp, with the exception that
all the arguments and return values are far.
Return Value
The return values for these functions are described above.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
strcat, strcmp, strcpy, strncat, strncpy, strrchr, strset, strspn
Example
See the example for strncmp.
strnset, _fstrnset
────────────────────────────────────────────────────────────────────────────
Description
Initialize characters of a string to a given character.
#include <string.h> Required only for function declarations
char *strnset( char *string, int c, size_t count );
char _far * _far _fstrnset( char _far *string, int c, size_t count );
string String to be initialized
c Character setting
count Number of characters set
Remarks
The strnset and _fstrnset functions set, at most, the first count characters
of string to the character c and return a pointer to the altered string. If
count is greater than the length of string, the length of string is used in
place of count.
The _fstrnset function is a model-independent (large-model) form of the
strnset function. The behavior and return value of _fstrnset are identical
to those of the model-dependent function strnset, with the exception that
all the arguments and return values are far.
Return Value
The return values for these functions are described above.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
strcat, strcmp, strcpy, strset
Example
/* STRNSET.C */
#include <string.h>
#include <stdio.h>
void main()
{
char string[15] = "This is a test";
/* Set not more than 4 characters of string to be *'s */
printf( "Before: %s\n", string );
strnset( string, '*', 4 );
printf( "After: %s\n", string );
}
Output
Before: This is a test
After: **** is a test
strpbrk, _fstrpbrk
────────────────────────────────────────────────────────────────────────────
Description
Scan strings for characters in specified character sets.
#include <string.h> Required only for function declarations
char *strpbrk( const char *string1, const char *string2 );
char _far * _far _fstrpbrk( const char _far *string1, const char _far
*string2 );
string1 Source string
string2 Character set
Remarks
The strpbrk function finds the first occurrence in string1 of any character
from string2. The terminating null character ('\0') is not included in the
search.
The _fstrpbrk function is a model-independent (large-model) form of the
strpbrk function. The behavior and return value of _fstrpbrk are identical
to those of the model- dependent function strpbrk, with the exception that
all the arguments and return values are far.
Return Value
These functions return a pointer to the first occurrence of any character
from string2 in string1. A NULL return value indicates that the two string
arguments have no characters in common.
Compatibility
strpbrk
ANSI DOS OS/2 UNIX XENIX
_fstrpbrk
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
strchr, strrchr
Example
/* STRPBRK.C */
#include <string.h>
#include <stdio.h>
void main()
{
char string[100] = "The 3 men and 2 boys ate 5 pigs\n";
char *result;
/* Return pointer to first 'a' or 'b' in "string" */
printf( "1: %s\n", string );
result = strpbrk( string, "0123456789" );
printf( "2: %s\n", result++ );
result = strpbrk( result, "0123456789" );
printf( "3: %s\n", result++ );
result = strpbrk( result, "0123456789" );
printf( "4: %s\n", result );
}
Output
1: The 3 men and 2 boys ate 5 pigs
2: 3 men and 2 boys ate 5 pigs
3: 2 boys ate 5 pigs
4: 5 pigs
strrchr, _fstrrchr
────────────────────────────────────────────────────────────────────────────
Description
Scan a string for the last occurrence of a character.
#include <string.h> Required only for function declarations
char *strrchr( const char *string, int c );
char _far * _far _fstrrchr( const char _far *string, int c );
string Searched string
c Character to be located
Remarks
The strrchr function finds the last occurrence of the character c in string.
The string's terminating null character ('\0') is included in the search.
(Use strchr to find the first occurrence of c in string.)
The _fstrrchr function is a model-independent (large-model) form of the
strrchr function. The behavior and return value of _fstrrchr are identical
to those of the modeldependent function strrchr, with the exception that all
the pointer arguments and return values are far pointers.
Return Value
These functions return a pointer to the last occurrence of the character in
the string. A NULL pointer is returned if the given character is not found.
Compatibility
strrchr
ANSI DOS OS/2 UNIX XENIX
_fstrrchr
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
strchr, strcspn, strncat, strncmp, strncpy, strnicmp, strpbrk, strspn
Example
/* STRCHR.C: This program illustrates searching for a character with
* strchr (search forward) or strrchr (search backward).
*/
#include <string.h>
#include <stdio.h>
int ch = 'r';
char string[] = "The quick brown dog jumps over the lazy fox";
char fmt1[] = " 1 2 3 4 5";
char fmt2[] = "12345678901234567890123456789012345678901234567890";
void main()
{
char *pdest;
int result;
printf( "String to be searched: \n\t\t%s\n", string );
printf( "\t\t%s\n\t\t%s\n\n", fmt1, fmt2 );
printf( "Search char:\t%c\n", ch );
/* Search forward. */
pdest = strchr( string, ch );
result = pdest - string + 1;
if( pdest != NULL )
printf( "Result:\tfirst %c found at position %d\n\n", ch, result );
else
printf( "Result:\t%c not found\n" );
/* Search backward. */
pdest = strrchr( string, ch );
result = pdest - string + 1;
if( pdest != NULL )
printf( "Result:\tlast %c found at position %d\n\n", ch, result );
else
printf( "Result:\t%c not found\n" );
}
Output
String to be searched:
The quick brown dog jumps over the lazy fox
1 2 3 4 5
12345678901234567890123456789012345678901234567890
Search char: r
Result: first r found at position 12
Result: last r found at position 30
strrev, _fstrrev
────────────────────────────────────────────────────────────────────────────
Description
Reverses characters of a string.
#include <string.h> Required only for function declarations
char *strrev( char *string );
char _far * _far _fstrrev( char _far *string );
string String to be reversed
Remarks
The strrev function reverses the order of the characters in string. The
terminating null character ('\0') remains in place.
The _fstrrev function is a model-independent (large-model) form of the
strrev function. The behavior and return value of _fstrrev are identical to
those of the model-dependent function strrev, with the exception that the
argument and return value are far pointers.
Return Value
These functions return a pointer to the altered string. There is no error
return.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
strcpy, strset
Example
/* STRREV.C: This program checks an input string to see whether it is a
* palindrome: that is, whether it reads the same forward and backward.
*/
#include <string.h>
#include <stdio.h>
void main()
{
char string[100];
int result;
printf( "Input a string and I will tell you if it is a palindrome:\n"
);
gets( string );
/* Reverse string and compare (ignore case): */
result = strcmpi( string, strrev( strdup( string ) ) );
if( result == 0 )
printf( "The string \"%s\" is a palindrome\n\n", string );
else
printf( "The string \"%s\" is not a palindrome\n\n", string );
}
Output
Input a string and I will tell you if it is a palindrome:
Able was I ere I saw Elba
The string "Able was I ere I saw Elba" is a palindrome
strset, _fstrset
────────────────────────────────────────────────────────────────────────────
Description
Set characters of a string to a character.
#include <string.h> Required only for function declarations
char *strset( char *string, int c );
char _far * _far _fstrset( char _far *string, int c );
string String to be set
c Character setting
Remarks
The strset function sets all of the characters of string to c, except the
terminating null character ('\0').
The _fstrset function is a model-independent (large-model) form of the
strset function. The behavior and return value of _fstrset are identical to
those of the model-dependent function strset, with the exception that the
pointer arguments and return value are far pointers.
Return Value
These functions return a pointer to the altered string. There is no error
return.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
memset, strcat, strcmp, strcpy, strnset
Example
/* STRSET.C */
#include <string.h>
#include <stdio.h>
void main()
{
char string[] = "Fill the string with something";
printf( "Before: %s\n", string );
strset( string, '*' );
printf( "After: %s\n", string );
}
Output
Before: Fill the string with something
After: ******************************
strspn, _fstrspn
────────────────────────────────────────────────────────────────────────────
Description
Find the first substring.
#include <string.h> Required only for function declarations
size_t strspn( const char *string1, const char *string2 );
size_t _far _fstrspn( const char _far *string1, const char _far *string2
);
string1 Searched string
string2 Character set
Remarks
The strspn function returns the index of the first character in string1 that
does not belong to the set of characters specified by string2. This value is
equivalent to the length of the initial substring of string1 that consists
entirely of characters from string2. The null character ('\0') terminating
string2 is not considered in the matching process. If string1 begins with a
character not in string2, strspn returns 0.
The _fstrspn function is a model-independent (large-model) form of the
strspn function. The behavior and return value of _fstrspn are identical to
those of the model-dependent function strspn, with the exception that the
arguments are far pointers.
Return Value
These functions return an integer value specifying the length of the segment
in string1 consisting entirely of characters in string2.
Compatibility
strspn
ANSI DOS OS/2 UNIX XENIX
_fstrspn
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
strcspn, strncat, strncmp, strncpy, strnicmp, strrchr
Example
/* STRSPN.C: This program uses strspn to determine the length of
* the segment in the string "cabbage" consisting of a's, b's, and c's.
* In other words, it finds the first non-abc letter.
*/
#include <string.h>
#include <stdio.h>
void main()
{
char string[] = "cabbage";
int result;
result = strspn( string, "abc" );
printf( "The portion of '%s' containing only a, b, or c "
"is %d bytes long\n", string, result );
}
Output
The portion of 'cabbage' containing only a, b, or c is 5 bytes long
strstr, _fstrstr
────────────────────────────────────────────────────────────────────────────
Description
Find a substring.
#include <string.h> Required only for function declarations
char *strstr( const char *string1, const char *string2 );
char _far * _far _fstrstr( const char _far *string1, const char _far
*string2 );
string1 Searched string
string2 String to search for
Remarks
The strstr function returns a pointer to the first occurrence of string2 in
string1.
The _fstrstr function is a model-independent (large-model) form of the
strstr function. The behavior and return value of _fstrstr are identical to
those of the model-dependent function strstr, with the exception that the
arguments and return value are far pointers.
Return Value
These functions return either a pointer to the first occurrence of string2
in string1, or NULL if they do not find the string.
Compatibility
strstr
ANSI DOS OS/2 ▼ UNIX ▼ XENIX
_fstrstr
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
strcspn, strncat, strncmp, strncpy, strnicmp, strpbrk, strrchr, strspn
Example
/* STRSTR.C */
#include <string.h>
#include <stdio.h>
char str[] = "lazy";
char string[] = "The quick brown dog jumps over the lazy fox";
char fmt1[] = " 1 2 3 4 5";
char fmt2[] = "12345678901234567890123456789012345678901234567890";
void main()
{
char *pdest;
int result;
printf( "String to be searched:\n\t%s\n", string );
printf( "\t%s\n\t%s\n\n", fmt1, fmt2 );
pdest = strstr( string, str );
result = pdest - string + 1;
if( pdest != NULL )
printf( "%s found at position %d\n\n", str, result );
else
printf( "%s not found\n", str );
}
Output
String to be searched:
The quick brown dog jumps over the lazy fox
1 2 3 4 5
12345678901234567890123456789012345678901234567890
lazy found at position 36
_strtime
────────────────────────────────────────────────────────────────────────────
Description
Copies the time to a buffer.
#include <time.h>
char *_strtime( char *timestr );
timestr Time string
Remarks
The _strtime function copies the current time into the buffer pointed to by
timestr. The time is formatted
hh:mm:ss
where hh is two digits representing the hour in 24-hour notation, mm is
two digits representing the minutes past the hour, and ss is two digits
representing seconds. For example, the string
18:23:44
represents 23 minutes and 44 seconds past 6:00 PM.
The buffer must be at least nine bytes long.
Return Value
The _strtime function returns a pointer to the resulting text string
timestr.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
asctime, ctime, gmtime, localtime, mktime, time, tzset
Example
/* STRTIME.C */
#include <time.h>
#include <stdio.h>
void main()
{
char dbuffer [9];
char tbuffer [9];
_strdate( dbuffer );
printf( "The current date is %s \n", dbuffer );
_strtime( tbuffer );
printf( "The current time is %s \n", tbuffer );
}
Output
The current date is 06/20/89
The current time is 09:33:13
strtod, strtol, _strtold, strtoul
────────────────────────────────────────────────────────────────────────────
Description
Convert strings to a double-precision (strtod, _strtold), long-integer
(strtol), or unsigned long-integer (strtoul) value.
#include <stdlib.h>
double strtod( const char *nptr, char **endptr );
long strtol( const char *nptr, char **endptr, int base );
long double _strtold( const char *nptr, char **endptr );
unsigned long strtoul( const char *nptr, char **endptr, int base );
nptr String to convert
endptr End of scan
base Number base to use
Remarks
The strtod, _strtold, strtol, and strtoul functions convert a character
string to a double-precision value, a long-double value, a long-integer
value, or an unsigned long-integer value, respectively. The input string is
a sequence of characters that can be interpreted as a numerical value of the
specified type. If the strtod or _strtold function appears in a compact-,
large-, or huge-model program, nptr can be a maximum of 100 characters.
These functions stop reading the string at the first character they cannot
recognize as part of a number. This may be the null character ('\0') at the
end of the string. With strtol or strtoul, this terminating character can
also be the first numeric character greater than or equal to base. If endptr
is not NULL, a pointer to the character that stopped the scan is stored at
the location pointed to by endptr. If no conversion could be performed (no
valid digits were found or an invalid base was specified), the value of nptr
is stored at the location pointed to by endptr.
The strtod and _strtold functions expect nptr to point to a string with the
following form:
[[whitespace]] [[sign]] [[digits]] [[.digits]] [[ {d | D | e |
E}[[sign]]digits]]
The first character that does not fit this form stops the scan.
The strtol function expects nptr to point to a string with the following
form:
[[whitespace]] [[sign]] [[0]] [[{ x | X }]] [[digits]]
The strtoul function expects nptr to point to a string having this form:
[[whitespace]] [[{ + | -}]] [[0]] [[{ x | X }]] [[digits]]
If base is between 2 and 36, then it is used as the base of the number. If
base is 0, the initial characters of the string pointed to by nptr are used
to determine the base. If the first character is 0 and the second character
is not 'x' or 'X', then the string is interpreted as an octal integer;
otherwise, it is interpreted as a decimal number. If the first character is
'0' and the second character is 'x' or 'X', then the string is interpreted
as a hexadecimal integer. If the first character is '1' through '9', then
the string is interpreted as a decimal integer. The letters 'a' through 'z'
(or 'A' through 'Z') are assigned the values 10 through 35; only letters
whose assigned values are less than base are permitted.
The strtoul function allows a plus (+) or minus (-) sign prefix; a leading
minus sign indicates that the return value is negated.
Return Value
The strtod and _strtold functions return the value of the floating-point
number, except when the representation would cause an overflow, in which
case it returns ±HUGE_VAL. The functions return 0 if no conversion could be
performed or an underflow occurred.
The strtol function returns the value represented in the string, except when
the representation would cause an overflow, in which case it returns
LONG_MAX or LONG_MIN. The function returns 0 if no conversion could be
performed.
The strtoul function returns the converted value, if any. If no conversion
can be performed, the function returns 0. The function returns ULONG_MAX on
overflow. In all four functions, errno is set to ERANGE if overflow or
underflow occurs.
Compatibility
strtod, strtol, _strtold
ANSI DOS OS/2 UNIX XENIX
strtoul
ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
atof, atol
Example
/* STRTOD.C: This program uses strtod to convert a string to a
* double-precision value; strtol to convert a string to long
* integer values; and strtoul to convert a string to unsigned
* long-integer values.
*/
#include <stdlib.h>
#include <stdio.h>
void main()
{
char *string, *stopstring;
double x;
long l;
int base;
unsigned long ul;
string = "3.1415926This stopped it";
x = strtod( string, &stopstring );
printf( "string = %s\n", string );
printf(" strtod = %f\n", x );
printf(" Stopped scan at: %s\n\n", stopstring );
string = "-10110134932This stopped it";
l = strtol( string, &stopstring, 10 );
printf( "string = %s\n", string );
printf(" strtol = %ld\n", l );
printf(" Stopped scan at: %s\n\n", stopstring );
string = "10110134932";
printf( "string = %s\n", string );
/* Convert string using base 2, 4, and 8: */
for( base = 2; base <= 8; base *= 2 )
{
/* Convert the string: */
ul = strtoul( string, &stopstring, base );
printf( " strtol = %ld (base %d)\n", ul, base );
printf( " Stopped scan at: %s\n", stopstring );
}
}
Output
string = 3.1415926This stopped it
strtod = 3.141593
Stopped scan at: This stopped it
string = -10110134932This stopped it
strtol = -2147483647
Stopped scan at: This stopped it
string = 10110134932
strtol = 45 (base 2)
Stopped scan at: 34932
strtol = 4423 (base 4)
Stopped scan at: 4932
strtol = 2134108 (base 8)
Stopped scan at: 932
strtok, _fstrtok
────────────────────────────────────────────────────────────────────────────
Description
Find the next token in a string.
#include <string.h> Required only for function declarations
char *strtok( char *string1, const char *string2 );
char _far * _far _fstrtok( char _far *string1, const char _far *string2 );
string1 String containing token(s)
string2 Set of delimiter characters
Remarks
The strtok function reads string1 as a series of zero or more tokens and
string2 as the set of characters serving as delimiters of the tokens in
string1. The tokens in string1 may be separated by one or more of the
delimiters from string2.
The tokens can be broken out of string1 by a series of calls to strtok. In
the first call to strtok for string1, strtok searches for the first token in
string1, skipping leading delimiters. A pointer to the first token is
returned. To read the next token from string1, call strtok with a NULL value
for the string1 argument. The NULL string1 argument causes strtok to search
for the next token in the previous token string. The set of delimiters may
vary from call to call, so string2 can take any value.
The _fstrtok function is a model-independent (large-model) form of the
strtok function. The behavior and return value of _fstrtok are identical to
those of the model-dependent function strtok, with the exception that the
arguments and return value are far pointers.
Note that calls to these functions will modify string1, since each time
strtok is called it inserts a null character ('\0') after the token in
string1.
Return Value
The first time strtok is called, it returns a pointer to the first token in
string1. In later calls with the same token string, strtok returns a pointer
to the next token in the string. A NULL pointer is returned when there are
no more tokens. All tokens are null-terminated.
Compatibility
strtok
ANSI DOS OS/2 UNIX XENIX
_fstrtok
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
strcspn, strspn
Example
/* STRTOK.C: In this program, a loop uses strtok to print all the tokens
* (separated by commas or blanks) in the string named "string".
*/
#include <string.h>
#include <stdio.h>
char string[] = "A string\tof ,,tokens\nand some more tokens";
char seps[] = " ,\t\n";
char *token;
void main()
{
printf( "%s\n\nTokens:\n", string );
/* Establish string and get the first token: */
token = strtok( string, seps );
while( token != NULL )
{
/* While there are tokens in "string" */
printf( " %s\n", token );
/* Get next token: */
token = strtok( NULL, seps );
}
}
Output
A string of ,,tokens
and some more tokens
Tokens:
A
string
of
tokens
and
some
more
tokens
strupr, _fstrupr
────────────────────────────────────────────────────────────────────────────
Description
Convert a string to uppercase.
#include <string.h> Required only for function declarations
char *strupr( char *string );
char _far * _far _fstrupr( char _far *string );
string String to be capitalized
Remarks
These functions convert any lowercase letters in the string to uppercase.
Other characters are not affected.
The _fstrupr function is a model-independent (large-model) form of the
strupr function. The behavior and return value of _fstrupr are identical to
those of the model-dependent function strupr, with the exception that the
argument and return value are far pointers.
Return Value
These functions return a pointer to the converted string. There is no error
return.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
strlwr
Example
/* STRLWR.C: This program uses strlwr and strupr to create
* uppercase and lowercase copies of a mixed-case string.
*/
#include <string.h>
#include <stdio.h>
void main()
{
char string[100] = "The String to End All Strings!";
char *copy1, *copy2;
copy1 = strlwr( strdup( string ) );
copy2 = strupr( strdup( string ) );
printf( "Mixed: %s\n", string );
printf( "Lower: %s\n", copy1 );
printf( "Upper: %s\n", copy2 );
}
Output
Mixed: The String to End All Strings!
Lower: the string to end all strings!
Upper: THE STRING TO END ALL STRINGS!
strxfrm
────────────────────────────────────────────────────────────────────────────
Description
Transforms a string based on locale-specific information.
#include <string.h> Required only for function declarations
size_t strxfrm( char *string1, const char *string2, size_t count );
string1 String to which transformed version of
string2 is returned
string2 String to transform
count Maximum number of characters to be
placed in string1
Remarks
The strxfrm function transforms the string pointed to by string2 into a new
form that is stored in string1. No more than count characters (including the
null character) are transformed and placed into the resulting string.
The transformation is made using the information in the locale-specific
LC_COLLATE macro.
After the transformation, a call to strcmp with the two transformed strings
will yield identical results to a call to strcoll applied to the original
two strings.
The value of the following expression is the size of the array needed to
hold the transformation of the source string:
1 + strxfrm( NULL, string, 0 )
Currently, the C libraries support the "C" locale only; thus strxfrm is
equivalent to the following:
strncpy( _string1, _string2, _count );
return( strlen( _string2 ) );
Return Value
The strxfrm function returns the length of the transformed string, not
counting the terminating null character. If the return value is greater than
or equal to count, the contents of string1 are unpredictable.
Compatibility
ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
localeconv, setlocale, strncmp
swab
────────────────────────────────────────────────────────────────────────────
Description
Swaps bytes.
#include <stdlib.h> Required only for function declarations
void swab( char *src, char *dest, int n );
src Data to be copied and swapped
dest Storage location for swapped data
n Number of bytes to be copied and swapped
Remarks
The swab function copies n bytes from src, swaps each pair of adjacent
bytes, and stores the result at dest. The integer n should be an even number
to allow for swapping. The swab function is typically used to prepare binary
data for transfer to a machine that uses a different byte order.
Return Value
None.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
Example
/* SWAB.C */
#include <stdlib.h>
#include <stdio.h>
char from[] = "BADCFEHGJILKNMPORQTSVUXWZY";
char to[] = "..........................";
void main()
{
printf( "Before:\t%s\n\t%s\n\n", from, to );
swab( from, to, sizeof( from ) );
printf( "After:\t%s\n\t%s\n\n", from, to );
}
Output
Before: BADCFEHGJILKNMPORQTSVUXWZY
..........................
After: BADCFEHGJILKNMPORQTSVUXWZY
ABCDEFGHIJKLMNOPQRSTUVWXYZ
system
────────────────────────────────────────────────────────────────────────────
Description
Executes a command.
#include <process.h> Required only for function declarations
#include <stdlib.h> Use STDLIB.H for ANSI compatibility
int system( const char *command );
command Command to be executed
Remarks
The system function passes command to the command interpreter, which
executes the string as an operating-system command. The system function
refers to the COMSPEC and PATH environment variables that locate the
command-interpreter file (the file named COMMAND.COM in DOS or CMD.EXE in
OS/2). If command is a pointer to an empty string, the function simply
checks to see whether or not the command interpreter exists.
Return Value
If command is NULL and the command interpreter is found, the function
returns a nonzero value. If the command interpreter is not found, it returns
the value 0 and sets errno to ENOENT. If command is not NULL, the system
function returns the value 0 if the command interpreter is successfully
started. Under OS/2, the system function returns the exit status from the
command interpreter.
A return value of -1 indicates an error, and errno is set to one of the
following values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
E2BIG In DOS, the argument list exceeds 128
bytes, or the space required for the
environment information exceeds 32K. In
OS/2, the combined argument list and
space required for environment
information exceed 32K.
ENOENT The command interpreter cannot be found.
ENOEXEC The command-interpreter file has an
invalid format and is not executable.
ENOMEM Not enough memory is available to
execute the command; or the available
memory has been corrupted; or an invalid
block exists, indicating that the
process making the call was not
allocated properly.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
exec functions, exit, _exit, spawn functions
Example
/* SYSTEM.C: This program uses system to TYPE its source file. */
#include <process.h>
void main()
{
system( "type system.c" );
}
Output
/* SYSTEM.C: This program uses system to TYPE its source file. */
#include <process.h>
void main()
{
system( "type system.c" );
}
tan Functions
────────────────────────────────────────────────────────────────────────────
Description
Calculate the tangent (tan and tanl) and hyperbolic tangent (tanh and
tanhl).
#include <math.h>
double tan( double x );
double tanh( double x );
long double tanl( long double x );
long double tanhl( long double x );
x Angle in radians
Remarks
The tan functions return the tangent or hyperbolic tangent of their
arguments. The list below describes the differences between the various
tangent functions:
Function Description
────────────────────────────────────────────────────────────────────────────
tan Calculates tangent of x
tanh Calculates hyperbolic tangent of x
tanl Calculates tangent of x (80-bit version)
tanhl Calculates hyperbolic tangent of x
(80-bit version)
The tanl and tanhl functions are the 80-bit counterparts and use an 80-bit,
10-byte coprocessor form of arguments and return values. See the reference
page on the long double functions for more details on this data type.
Return Value
The tan function returns the tangent of x. If x is large, a partial loss of
significance in the result may occur; in this case, tan sets errno to ERANGE
and generates a PLOSS error. If x is so large that significance is totally
lost, tan prints a TLOSS error message to stderr, sets errno to ERANGE, and
returns 0.
There is no error return for tanh.
Compatibility
tan, tanh
ANSI DOS OS/2 UNIX XENIX
tanl, tanhl
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
acos functions, asin functions, atan functions, cos functions, sin functions
Example
/* TAN.C: This program displays the tangent of pi / 4 and the hyperbolic
* tangent of the result.
*/
#include <math.h>
#include <stdio.h>
void main()
{
double pi = 3.1415926535;
double x, y;
x = tan( pi / 4 );
y = tanh( x );
printf( "tan( %f ) = %f\n", x, y );
printf( "tanh( %f ) = %f\n", y, x );
}
Output
tan( 1.000000 ) = 0.761594
tanh( 0.761594 ) = 1.000000
tell
────────────────────────────────────────────────────────────────────────────
Description
Gets the position of the file pointer.
#include <io.h> Required only for function declarations
long tell( int handle );
handle Handle referring to open file
Remarks
The tell function gets the current position of the file pointer (if any)
associated with the handle argument. The position is expressed as the number
of bytes from the beginning of the file.
Return Value
A return value of -1L indicates an error, and errno is set to EBADF to
indicate an invalid file-handle argument. On devices incapable of seeking,
the return value is undefined.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
ftell, lseek
Example
/* TELL.C: This program uses tell to tell the file pointer position
* after a file read.
*/
#include <io.h>
#include <stdio.h>
#include <fcntl.h>
void main()
{
int fh;
long position;
char buffer[500];
if( (fh = open( "tell.c", O_RDONLY )) != -1 )
{
if( read( fh, buffer, 500 ) > 0 )
printf( "Current file position is: %d\n", tell( fh ) );
close( fh );
}
}
Output
Current file position is: 425
tempnam, tmpnam
────────────────────────────────────────────────────────────────────────────
Description
Create temporary file names.
#include <stdio.h>
char *tempnam( char *dir, char *prefix );
char *tmpnam( char *string );
string Pointer to temporary name
dir Target directory to be used if TMP not
defined
prefix File-name prefix
Remarks
The tmpnam function generates a temporary file name that can be used to open
a temporary file without overwriting an existing file. This name is stored
in string. If string is NULL, then tmpnam leaves the result in an internal
static buffer. Thus, any subsequent calls destroy this value. If string is
not NULL, it is assumed to point to an array of at least L_tmpnam bytes (the
value of L_tmpnam is defined in STDIO.H). The function will generate unique
file names for up to TMP_MAX calls.
The character string that tmpnam creates consists of the path prefix,
defined by the entry P_tmpdir in the file STDIO.H, followed by a sequence
consisting of the digit characters '0' through '9'; the numerical value of
this string can range from 1 to 65,535. Changing the definitions of L_tmpnam
or P_tmpdir in STDIO.H does not change the operation of tmpnam.
The tempnam function allows the program to create a temporary file name for
use in another directory. This file name will be different from that of any
existing file. The prefix argument is the prefix to the file name. The
tempnam function uses malloc to allocate space for the file name; the
program is responsible for freeing this space when it is no longer needed.
The tempnam function looks for the file with the given name in the following
directories, listed in order of precedence:
Directory Used Conditions
────────────────────────────────────────────────────────────────────────────
Directory specified by TMP TMP environment variable is set, and
directory specified by TMP exists.
dir argument to tempnam TMP environment variable is not set, or
directory specified by TMP does not
exist.
P_tmpdir in STDIO.H The dir argument is NULL, or diris name
of nonexistent directory.
Current working directory P_tmpdir does not exist.
If the search through the locations listed above fails, tempnam returns the
value NULL.
Return Value
The tmpnam and tempnam functions both return a pointer to the name
generated, unless it is impossible to create this name or the name is not
unique. If the name cannot be created or if a file with that name already
exists, tmpnam and tempnam return the value NULL.
Compatibility
tmpnam
ANSI DOS OS/2 UNIX XENIX
tempnam
▼ ANSI DOS OS/2 UNIX XENIX
See Also
tmpfile
Example
/* TEMPNAM.C: This program uses tmpnam to create a unique file name in
* the current working directory, then uses tempnam to create a unique
* file name with a prefix of stq.
*/
#include <stdio.h>
void main()
{
char *name1, *name2;
/* Create a temporary file name for the current working directory: */
if( ( name1 = tmpnam( NULL ) ) != NULL )
printf( "%s is safe to use as a temporary file.\n", name1 );
else
printf( "Cannot create a unique file name\n" );
/* Create a temporary file name in temporary directory with the
* prefix "stq". The actual destination directory may vary depending
* on the state of the TMP environment variable and the global variable
* P_tmpdir.
*/
if( ( name2 = tempnam( "c:\\tmp", "stq" ) ) != NULL )
printf( "%s is safe to use as a temporary file.\n", name2 );
else
printf( "Cannot create a unique file name\n" );
}
Output
\2 is safe to use as a temporary file.
C:\TMP\stq2 is safe to use as a temporary file.
time
────────────────────────────────────────────────────────────────────────────
Description
Gets the system time.
#include <time.h> Required only for function declarations
time_t time( time_t *timer );
timer Storage location for time
Remarks
The time function returns the number of seconds elapsed since 00:00:00
Greenwich mean time (GMT), January 1, 1970, according to the system clock.
The system time is adjusted according to the timezone system variable, which
is explained in the tzset reference section.
The return value is stored in the location given by timer. This parameter
may be NULL, in which case the return value is not stored.
Return Value
The time function returns the time in elapsed seconds. There is no error
return.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
asctime, ftime, gmtime, localtime, tzset, utime
Example
/* CTIME.C: This program gets the current time in time_t form, then uses
* ctime to display the time in string form.
*/
#include <time.h>
#include <stdio.h>
void main()
{
time_t ltime;
time( <ime );
printf( "The time is %s\n", ctime( <ime ) );
}
Output
The time is Thu Jun 15 16:08:18 1989
tmpfile
────────────────────────────────────────────────────────────────────────────
Description
Creates a temporary file.
#include <stdio.h>
FILE *tmpfile( void );
Remarks
The tmpfile function creates a temporary file and returns a pointer to that
stream. If the file cannot be opened, tmpfile returns a NULL pointer.
This temporary file is automatically deleted when the file is closed, when
the program terminates normally, or when rmtmp is called, assuming that the
current working directory does not change. The temporary file is opened in
w+b (binary read/write) mode.
Return Value
If successful, the tmpfile function returns a stream pointer. Otherwise, it
returns a NULL pointer.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
rmtmp, tempnam, tmpnam
Example
/* TMPFILE.C: This program uses tmpfile to create a temporary file,
* then deletes this file with rmtmp.
*/
#include <stdio.h>
void main()
{
FILE *stream;
char tempstring[] = "String to be written";
int i;
/* Create temporary files. */
for( i = 1; i <= 10; i++ )
{
if( (stream = tmpfile()) == NULL )
perror( "Could not open new temporary file\n" );
else
printf( "Temporary file %d was created\n", i );
}
/* Remove temporary files. */
printf( "%d temporary files deleted\n", rmtmp() );
}
Output
Temporary file 1 was created
Temporary file 2 was created
Temporary file 3 was created
Temporary file 4 was created
Temporary file 5 was created
Temporary file 6 was created
Temporary file 7 was created
Temporary file 8 was created
Temporary file 9 was created
Temporary file 10 was created
10 temporary files deleted
toascii, tolower, toupper Functions
────────────────────────────────────────────────────────────────────────────
Description
Convert characters.
#include <ctype.h>
int toascii( int c );
int tolower( int c );
int _tolower( int c );
int toupper( int c );
int _toupper( int c );
c Character to be converted
Remarks
The toascii, tolower, _tolower, toupper, and _toupper routines convert a
single character, as described below:
Function Description
────────────────────────────────────────────────────────────────────────────
toascii Converts c to ASCII character
tolower Converts c to lowercase if appropriate
_tolower Converts c to lowercase
toupper Converts c to uppercase if appropriate
_toupper Converts c to uppercase
The toascii routine sets all but the low-order 7 bits of c to 0, so that the
converted value represents a character in the ASCII character set. If c
already represents an ASCII character, c is unchanged.
The tolower and _tolower routines convert c to lowercase if c represents an
uppercase letter. Otherwise, c is unchanged. The _tolower routine is a
version of tolower to be used only when c is known to be uppercase. The
result of _tolower is undefined if c is not an uppercase letter.
The toupper and _toupper routines convert c to uppercase if c represents a
lowercase letter. Otherwise, c is unchanged. The _toupper routine is a
version of toupper to be used only when c is known to be lowercase. The
result of _toupper is undefined if c is not a lowercase letter.
Note that these routines are implemented both as functions and as macros. To
conform with the ANSI specification, the tolower and toupper routines are
also implemented as functions. The function versions can be used by removing
the macro definitions through #undef directives or by not including CTYPE.H.
Function declarations of tolower and toupper are given in STDLIB.H.
If the -Za compile option is used, the macro form of toupper or tolower is
not used because it evaluates its argument more than once. Since the
arguments are evaluated more than once, arguments with side effects would
produce potentially bad results.
Return Value
The toascii, tolower, _tolower, toupper, and _toupper routines return the
converted character c. There is no error return.
Compatibility
toascii, _tolower, _toupper
▼ ANSI DOS OS/2 UNIX XENIX
tolower, toupper
ANSI DOS OS/2 UNIX XENIX
See Also
is functions
Example
/* TOUPPER.C: This program uses toupper and tolower to analyze all
* characters between 0x0 and 0x7F. It also applies _toupper and _tolower
* to any code in this range for which these functions make sense.
*/
#include <conio.h>
#include <ctype.h>
#include <string.h>
char msg[] = "Some of THESE letters are Capitals\r\n";
char *p;
void main()
{
cputs( msg );
/* Reverse case of message. */
for( p = msg; p < msg + strlen( msg ); p++ )
{
if( islower( *p ) )
putch( _toupper( *p ) );
else if( isupper( *p ) )
putch( _tolower( *p ) );
else
putch( *p );
}
}
Output
Some of THESE letters are Capitals
sOME OF these LETTERS ARE cAPITALS
tzset
────────────────────────────────────────────────────────────────────────────
Description
Sets time environment variables.
#include <time.h> Required only for function declarations
void tzset( void );
int daylight; Global variables set by function
long timezone;
char *tzname[2]
Remarks
The tzset function uses the current setting of the environment variable TZ
to assign values to three global variables: daylight, timezone, and tzname.
These variables are used by the ftime and localtime functions to make
corrections from Greenwich mean time (GMT) to local time, and by time to
compute GMT from system time.
The value of the environment variable TZ must be a three-letter time-zone
name, such as PST, followed by an optionally signed number giving the
difference in hours between GMT and local time. The number may be followed
by a three-letter daylight-saving-time (DST) zone, such as PDT. For example,
"PST8PDT" represents a valid TZ value for the Pacific time zone. If DST is
never in effect, as is the case in certain states and localities, TZ should
be set without a DST zone.
If the TZ value is not currently set, the default is PST8PDT, which
corresponds to the Pacific time zone.
Based on the TZ environment variable value, the following values are
assigned to the variables daylight, timezone, and tzname when tzset is
called:
Variable Value
────────────────────────────────────────────────────────────────────────────
daylight Nonzero value if a daylight-saving-time
zone is specified in the TZ setting;
otherwise, 0
timezone Difference in seconds between GMT and
local time
tzname[0] String value of the three-letter
time-zone name from the TZ setting
tzname[1] String value of the daylight-saving-time
zone, or an empty string if the
daylight-saving-time zone is omitted
from the TZ setting
The default for daylight is 1; for timezone, 28,800; for tzname[0], PST; and
for tzname[1], PDT. This corresponds to "PST8PDT."
If the DST zone is omitted from the TZ settings, the daylight variable will
be 0 and the ftime, gmtime, and localtime functions will return 0 for their
DST flags.
Return Value
None.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
asctime, ftime, gmtime, localtime, time
Example
/* TZSET.C: This program first sets up the time zone by placing the
variable
* named TZ=EST5 in the environment table. It then uses tzset to set the
* global variables named daylight, timezone, and tzname.
*/
#include <time.h>
#include <stdlib.h>
#include <stdio.h>
void main()
{
if( putenv( "TZ=EST5EDT" ) == -1 )
{
printf( "Unable to set TZ\n" );
exit( 1 );
}
else
{
tzset();
printf( "daylight = %d\n", daylight );
printf( "timezone = %ld\n", timezone );
printf( "tzname[0] = %s\n", tzname[0] );
}
}
Output
daylight = 1
timezone = 18000
tzname[0] = EST
ultoa
────────────────────────────────────────────────────────────────────────────
Description
Converts an unsigned long integer to a string.
#include <stdlib.h> Required only for function declarations
char *ultoa( unsigned long value, char *string, int radix );
value Number to be converted
string String result
radix Base of value
Remarks
The ultoa function converts value to a null-terminated character string and
stores the result (up to 33 bytes) in string. No overflow checking is
performed. The radix argument specifies the base of value; it must be in the
range 2-36.
Return Value
The ultoa function returns a pointer to string. There is no error return.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
itoa, ltoa
Example
/* ITOA.C: This program converts integers of various sizes to strings
* in various radixes.
*/
#include <stdlib.h>
#include <stdio.h>
void main()
{
char buffer[20];
int i = 3445;
long l = -344115L;
unsigned long ul = 1234567890UL;
itoa( i, buffer, 10 );
printf( "String of integer %d (radix 10): %s\n", i, buffer );
itoa( i, buffer, 16 );
printf( "String of integer %d (radix 16): 0x%s\n", i, buffer );
itoa( i, buffer, 2 );
printf( "String of integer %d (radix 2): %s\n", i, buffer );
ltoa( l, buffer, 16 );
printf( "String of long int %ld (radix 16): 0x%s\n", l, buffer );
ultoa( ul, buffer, 16 );
printf( "String of unsigned long %lu (radix 16): 0x%s\n", ul, buffer );
}
Output
String of integer 3445 (radix 10): 3445
String of integer 3445 (radix 16): 0xd75
String of integer 3445 (radix 2): 110101110101
String of long int -344115 (radix 16): 0xfffabfcd
String of unsigned long 1234567890 (radix 16): 0x499602d2
umask
────────────────────────────────────────────────────────────────────────────
Description
Sets the default file-permission mask.
#include <sys\types.h>
#include <sys\stat.h>
#include <io.h> Required only for function declarations
int umask( int pmode );
pmode Default permission setting
Remarks
The umask function sets the file-permission mask of the current process to
the mode specified by pmode. The file-permission mask is used to modify the
permission setting of new files created by creat, open, or sopen. If a bit
in the mask is 1, the corresponding bit in the file's requested permission
value is set to 0 (disallowed). If a bit in the mask is 0, the corresponding
bit is left unchanged. The permission setting for a new file is not set
until the file is closed for the first time.
The argument pmode is a constant expression containing one or both of the
manifest constants S_IREAD and S_IWRITE, defined in SYS\STAT.H. When both
constants are given, they are joined with the bitwise-OR operator ( | ). The
meaning of the pmode argument is as follows:
Value Meaning
────────────────────────────────────────────────────────────────────────────
S_IREAD Reading not allowed (file is write-only)
S_IWRITE Writing not allowed (file is read-only)
For example, if the write bit is set in the mask, any new files will be
read-only.
Note that under DOS and OS/2, all files are readable─it is not possible to
give write-only permission. Therefore, setting the read bit with umask has
no effect on the file's modes.
Return Value
The umask function returns the previous value of pmode. There is no error
return.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
chmod, creat, mkdir, open
Example
/* UMASK.C: This program uses umask to set the file-permission mask so
* that all future files will be created as read-only files. It also
* displays the old mask.
*/
#include <sys\types.h>
#include <sys\stat.h>
#include <io.h>
#include <stdio.h>
void main()
{
int oldmask;
/* Create read-only files: */
oldmask = umask( S_IWRITE );
printf( "Oldmask = 0x%.4x\n", oldmask );
}
Output
Oldmask = 0x0000
ungetc
────────────────────────────────────────────────────────────────────────────
Description
Pushes a character back onto the stream.
#include <stdio.h>
int ungetc( int c, FILE *stream );
c Character to be pushed
stream Pointer to FILE structure
Remarks
The ungetc function pushes the character c back onto stream and clears the
end-of-file indicator. The stream must be open for reading. A subsequent
read operation on the stream starts with c. An attempt to push EOF onto the
stream using ungetc is ignored. The ungetc function returns an error value
if nothing has yet been read from stream or if c cannot be pushed back.
Characters placed on the stream by ungetc may be erased if fflush, fseek,
fsetpos, or rewind is called before the character is read from the stream.
The file-position indicator will have the same value it had before the
characters were pushed back. On a successful ungetc call against a text
stream, the file-position indicator is unspecified until all the pushed-back
characters are read or discarded. On each successful ungetc call against a
binary stream, the file-position indicator is stepped down; if its value was
0 before a call, the value is undefined after the call.
Results are unpredictable if the ungetc function is called twice without a
read operation between the two calls. After a call to the fscanf function, a
call to ungetc may fail unless another read operation (such as the getc
function) has been performed. This is because the fscanf function itself
calls the ungetc function.
Return Value
The ungetc function returns the character argument c. The return value EOF
indicates a failure to push back the specified character.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
getc, getchar, putc, putchar
Example
/* UNGETC.C: This program first converts a character representation of an
* unsigned integer to an integer. If the program encounters a character
* that is not a digit, the program uses ungetc to replace it in the
stream.
*/
#include <stdio.h>
#include <ctype.h>
void main()
{
int ch;
int result = 0;
printf( "Enter an integer: " );
/* Read in and convert number: */
while( ((ch = getchar()) != EOF) && isdigit( ch ) )
result = result * 10 + ch - '0'; /* Use digit. */
if( ch != EOF )
ungetc( ch, stdin ); /* Put non-digit back. */
printf( "Number = %d\nNext character in stream = '%c'\n",
result, getchar() );
}
Output
Enter an integer: 521a
Number = 521
Next character in stream = 'a'
ungetch
────────────────────────────────────────────────────────────────────────────
Description
Pushes back the last character read from the console.
#include <conio.h> Required only for function declarations
int ungetch( int c );
c Character to be pushed
Remarks
The ungetch function pushes the character c back to the console, causing c
to be the next character read by getch or getche. The ungetch function fails
if it is called more than once before the next read. The c argument may not
be EOF.
Return Value
The ungetch function returns the character c if it is successful. A return
value of EOF indicates an error.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
cscanf, getch, getche
Example
/* UNGETCH.C: In this program, a white-space delimited token is read
* from the keyboard. When the program encounters a delimiter,
* it uses ungetch to replace the character in the keyboard buffer.
*/
#include <conio.h>
#include <ctype.h>
#include <stdio.h>
void main()
{
char buffer[100];
int count = 0;
int ch;
ch = getche();
while( isspace( ch ) ) /* Skip preceding white space. */
ch = getche();
while( count < 99 ) /* Gather token. */
{
if( isspace( ch ) ) /* End of token. */
break;
buffer[count++] = ch;
ch = getche();
}
ungetch( ch ); /* Put back delimiter. */
buffer[count] = '\0'; /* Null terminate the token. */
printf( "\ntoken = %s\n", buffer );
}
Output
White
token = White
unlink
────────────────────────────────────────────────────────────────────────────
Description
Deletes a file.
#include <io.h> Required only for function declarations
#include <stdio.h> Use either IO.H or STDIO.H
int unlink( const char *filename );
filename Name of file to remove
Remarks
The unlink function deletes the file specified by filename.
Return Value
If successful, unlink returns 0; otherwise, it returns -1 and sets errno to
one of the following constants:
Value Meaning
────────────────────────────────────────────────────────────────────────────
EACCES Path name specifies a read-only file
ENOENT File or path name not found, or path
name specified a directory
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
close, remove
Example
/* UNLINK.C: This program uses unlink to delete UNLINK.OBJ. */
#include <stdio.h>
void main()
{
if( unlink( "unlink.obj" ) == -1 )
perror( "Could not delete 'UNLINK.OBJ'" );
else
printf( "Deleted 'UNLINK.OBJ'\n" );
}
Output
Deleted 'UNLINK.OBJ'
_unregisterfonts
────────────────────────────────────────────────────────────────────────────
Description
Frees memory used by fonts.
#include <graph.h>
void _far _unregisterfonts( void );
Remarks
The _unregisterfonts function frees memory previously allocated and used by
the _registerfonts function. The _unregisterfonts function removes the
header information for all fonts and unloads the currently selected font
data from memory.
Any attempt to use the _setfont or _outgtext function after calling
_unregisterfonts results in an error.
Return Value
None.
Compatibility
▼ ANSI DOS ▼ OS/2 ▼ UNIX ▼ XENIX
See Also
_getfontinfo, _getgtextextent, _outgtext, _registerfonts, _setfont
Example
See the example for _outgtext.
utime
────────────────────────────────────────────────────────────────────────────
Description
Sets the file modification time.
#include <sys\types.h>
#include <sys\utime.h>
int utime( char *filename, struct utimbuf *times );
filename File name
times Pointer to stored time values
Remarks
The utime function sets the modification time for the file specified by
filename. The process must have write access to the file; otherwise, the
time cannot be changed.
Although the utimbuf structure contains a field for access time, only the
modification time is set under DOS and OS/2 . If times is a NULL pointer,
the modification time is set to the current time. Otherwise, times must
point to a structure of type utimbuf, defined in SYS\UTIME.H. The
modification time is set from the modtime field in this structure.
Return Value
The utime function returns the value 0 if the file-modification time was
changed. A return value of -1 indicates an error, and errno is set to one of
the following values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
EACCES Path name specifies directory or
read-only file
EINVAL Invalid argument; the times argument is
invalid
EMFILE Too many open files (the file must be
opened to change its modification time)
ENOENT File or path name not found
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
asctime, ctime, fstat, ftime, gmtime, localtime, stat, time
Example
/* UTIME.C: This program uses utime to set the file-modification time to
* the current time.
*/
#include <stdio.h>
#include <stdlib.h>
#include <sys\types.h>
#include <sys\utime.h>
void main()
{
/* Show file time before and after. */
system( "dir utime.c" );
if( utime( "utime.c", NULL ) == -1 )
perror( "utime failed\n" );
else
printf( "File time modified\n" );
system( "dir utime.c" );
}
Output
The volume label in drive C is OS2.
Directory of C:\LIBREF
UTIME C 397 6-20-89 2:11p
1 File(s) 12974080 bytes free
File time modified
The volume label in drive C is OS2.
Directory of C:\LIBREF
UTIME C 397 6-20-89 2:12p
1 File(s) 12974080 bytes free
va_arg, va_end, va_start
────────────────────────────────────────────────────────────────────────────
Description
Access variable-argument lists.
#include <stdarg.h> Required for ANSI compatibility
#include <varargs.h> Required for UNIX V compatibility
#include <stdio.h>
type va_arg( va_list arg_ptr, type );
void va_end( va_list arg_ptr );
void va_start( va_list arg_ptr ); UNIX version
void va_start( va_list arg_ptr, prev_param ); ANSI
arg_ptr Pointer to list of arguments
prev_param Parameter preceding first optional
argument (ANSI only)
type Type of argument to be retrieved
Remarks
The va_arg, va_end, and va_start macros provide a portable way to access the
arguments to a function when the function takes a variable number of
arguments. Two versions of the macros are available: the macros defined in
STDARG.H conform to the proposed ANSI C standard, and the macros defined in
VARARGS.H are compatible with the UNIX System V definition. The macros are
listed below:
Macro Description
────────────────────────────────────────────────────────────────────────────
va_alist Name of parameter to called function
(UNIX version only)
va_arg Macro to retrieve current argument
va_dcl Declaration of va_alist (UNIX version
only)
va_end Macro to reset arg_ptr
va_list The typedef for the pointer to list of
arguments
va_start Macro to set arg_ptr to beginning of
list of optional arguments (UNIX version
only)
Both versions of the macros assume that the function takes a fixed number of
required arguments, followed by a variable number of optional arguments. The
required arguments are declared as ordinary parameters to the function and
can be accessed through the param-eter names. The optional arguments are
accessed through the macros in STDARG.H or VARARGS.H, which set a pointer to
the first optional argument in the argument list, retrieve arguments from
the list, and reset the pointer when argument processing is completed.
The proposed ANSI C standard macros, defined in STDARG.H, are used as
follows:
1. All required arguments to the function are declared as parameters in
the usual way. The va_dcl macro is not used with the STDARG.H macros.
2. The va_start macro sets arg_ptr to the first optional argument in the
list of arguments passed to the function. The argument arg_ptr must
have va_list type. The argument prev_param is the name of the required
parameter immediately preceding the first optional argument in the
argument list. If prev_param is declared with the register storage
class, the macro's behavior is undefined. The va_start macro must be
used before va_arg is used for the first time.
3. The va_arg macro does the following:
■ Retrieves a value of type from the location given by arg_ptr
■ Increments arg_ptr to point to the next argument in the list,
using the size of type to determine where the next argument starts
The va_arg macro can be used any number of times within the function
to retrieve arguments from the list.
4. After all arguments have been retrieved, va_end resets the pointer to
NULL.
The UNIX System V macros, defined in VARARGS.H, operate in a slightly
different manner, as follows:
1. Any required arguments to the function can be declared as parameters
in the usual way.
2. The last (or only) parameter to the function represents the list of
optional arguments. This parameter must be named va_alist (not to be
confused with va_list, which is defined as the type of va_alist).
3. The va_dcl macro appears after the function definition and before the
opening left brace of the function. This macro is defined as a
complete declaration of the va_alist parameter, including the
terminating semicolon; therefore, no semicolon should follow va_dcl.
4. Within the function, the va_start macro sets arg_ptr to the beginning
of the list of optional arguments passed to the function. The va_start
macro must be used before va_arg is used for the first time. The
argument arg_ptr must have va_list type.
5. The va_arg macro does the following:
■ Retrieves a value of type from the location given by arg_ptr
■ Increments arg_ptr to point to the next argument in the list,
using the size of type to determine where the next argument starts
The va_arg macro can be used any number of times within the function
to retrieve the arguments from the list.
6. After all arguments have been retrieved, va_end resets the pointer to
NULL.
Return Value
The va_arg macro returns the current argument; va_start and va_end do not
return values.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
vfprintf, vprintf, vsprintf
Example
/* VA.C: The program below illustrates passing a variable number of
arguments
* using the following macros:
* va_start va_arg va_end
* va_list va_decl (UNIX only)
*/
#include <stdio.h>
#define ANSI /* Comment out for UNIX version */
#ifdef ANSI /* ANSI compatible version */
#include <stdarg.h>
int average( int first, ... );
#else /* UNIX compatible version */
#include <varargs.h>
int average( va_list );
#endif
void main()
{
/* Call with 3 integers (-1 is used as terminator). */
printf( "Average is: %d\n", average( 2, 3, 4, -1 ) );
/* Call with 4 integers. */
printf( "Average is: %d\n", average( 5, 7, 9, 11, -1 ) );
/* Call with just -1 terminator. */
printf( "Average is: %d\n", average( -1 ) );
}
/* Returns the average of a variable list of integers. */
#ifdef ANSI /* ANSI compatible version */
int average( int first, ... )
{
int count = 0, sum = 0, i = first;
va_list marker;
va_start( marker, first ); /* Initialize variable arguments. */
while( i != -1 )
{
sum += i;
count++;
i = va_arg( marker, int);
}
va_end( marker ); /* Reset variable arguments. */
return( sum ? (sum / count) : 0 );
}
#else /* UNIX compatible version must use old-style definition. */
int average( va_alist )
va_dcl
{
int i, count, sum;
va_list marker;
va_start( marker ); /* Initialize variable arguments. */
for( sum = count = 0; (i = va_arg( marker, int)) != -1; count++ )
sum += i;
va_end( marker ); /* Reset variable arguments. */
return( sum ? (sum / count) : 0 );
}
#endif
Output
Average is: 3
Average is: 8
Average is: 0
vfprintf, vprintf, vsprintf
────────────────────────────────────────────────────────────────────────────
Description
Write formatted output using a pointer to a list of arguments.
#include <stdio.h>
#include <varargs.h> Required for compatibility with UNIX
System V
#include <stdarg.h> Required for compatibility with the ANSI
C standard
int vfprintf( FILE *stream, const char *format, va_list argptr );
int vprintf( const char *format, va_list argptr );
int vsprintf( char *buffer, const char *format, va_list argptr );
stream Pointer to FILE structure
format Format control
argptr Pointer to list of arguments
buffer Storage location for output
Remarks
The vfprintf, vprintf, and vsprintf functions format data and output data to
the file specified by stream, to standard output, and to the memory pointed
to by buffer, respectively. These functions are similar to their
counterparts fprintf, printf, and sprintf, but each accepts a pointer to a
list of arguments instead of an argument list.
The format argument has the same form and function as the format argument
for the printf function; see printf for a description of format.
The argptr parameter has type va_list, which is defined in the include files
VARARGS.H and STDARG.H. The argptr parameter points to a list of arguments
that are converted and output according to the corresponding format
specifications in the format.
Return Value
The return value for vprintf and vsprintf is the number of characters
written, not counting the terminating null character. If successful, the
vfprintf return value is the number of characters written. If an output
error occurs, it is a negative value.
Compatibility
ANSI DOS OS/2 UNIX XENIX
See Also
fprintf, printf, sprintf, va_arg, va_end, va_start
Example
/* VPRINTF.C shows how to use vprintf functions to write new versions
* of printf. The vsprintf function is used in the example.
*/
#include <stdio.h>
#include <graph.h>
#include <string.h>
#include <stdarg.h>
#include <malloc.h>
int wprintf( short row, short col, short clr, long bclr, char *fmt, ... );
void main()
{
short fgd = 0;
long bgd = 0L;
_clearscreen( _GCLEARSCREEN );
_outtext( "Color text example:\n\n" );
/* Loop through 8 background colors. */
for( bgd = 0L; bgd < 8; bgd++ )
{
wprintf( (int)bgd + 3, 1, 7, bgd, "Back: %d Fore:", bgd );
/* Loop through 16 foreground colors. */
for( fgd = 0; fgd < 16; fgd++ )
wprintf( -1, -1, fgd, -1L, " %2d ", fgd );
}
}
/* Full-screen window version of printf that takes row, column, textcolor,
* and background color as its first arguments, followed by normal printf
* format strings (except that \t is not handled). You can specify -1 for
* any of the first arguments to use the current value. The function
returns
* the number of characters printed, or a negative number for errors.
*/
int wprintf( short row, short col, short clr, long bclr, char *fmt, ... )
{
struct rccoord tmppos;
short ret, size;
va_list marker;
char *buffer;
/* It's probably safe to use a buffer length of 512 bytes or five times
* the length of the format string.
*/
size = strlen( fmt );
size = (size > 512) ? 512 : size * 5;
if( (buffer = (char *)malloc( size )) == NULL )
return -1;
/* Set text position. */
tmppos = _gettextposition();
if( row < 1 )
row = tmppos.row;
if( col < 1 )
col = tmppos.col;
_settextposition( row, col );
/* Set foreground and background colors. */
if( clr >= 0 )
_settextcolor( clr );
if( bclr >= 0 )
_setbkcolor( bclr );
/* Write text to a string and output the string. */
va_start( marker, fmt );
ret = vsprintf( buffer, fmt, marker );
va_end( marker );
_outtext( buffer );
free( buffer );
return ret;
}
wait
────────────────────────────────────────────────────────────────────────────
Description
Suspends the calling process.
#include <process.h>
int wait( int *termstat );
termstat Termination-status word and return code
for terminated child process
Remarks
The wait function suspends the calling process until any of the caller's
immediate child processes terminate. If all of the caller's children have
terminated before it calls the wait function, the function returns
immediately.
If not NULL, termstat points to a buffer containing a termination-status
word and return code for the child process. The status word indicates
whether or not the child process ended normally by calling the OS/2 DosExit
function. Supply NULL if you do not need the child's termination-status
word.
If the child process did terminate normally, the low-order and high-order
bytes of the termination-status word are as follows:
Byte Contents
────────────────────────────────────────────────────────────────────────────
Low order 0
High order Low-order byte of the result code passed
by the child process to DosExit. The
DosExit function is called if the child
process called exit or _exit, if it
returned from main, or if it reached the
end of main. The low-order byte of the
result code is either the low-order byte
of the argument to _exit or exit, the
low-order byte of the return value from
main, or a random value if the child
process reached the end of main.
Note that the OS/2 DosExit function allows programs to return a 16-bit
result code. However, the wait and cwait functions will return only the
low-order byte of that result code.
If the child process terminated for any other reason, the high-order and
low-order bytes of the termination-status word are as follows:
Byte Contents
────────────────────────────────────────────────────────────────────────────
Low order Termination code from DosWait:
Code Meaning
────────────────────────────────────────────────────────────────────────────
1 Hard-error abort
2 Trap operation
3 SIGTERM intercepted
signal not
High order 0
Return Value
If wait returns after normal termination of a child process, it returns the
child's process ID.
If wait returns after abnormal termination of a child process, it returns
the number -1 and sets errno to EINTR.
Otherwise, wait returns -1 immediately and sets errno to ECHILD, indicating
that no child processes exist for the calling process.
Compatibility
▼ ANSI ▼ DOS OS/2 UNIX XENIX
See Also
cwait, exit, _exit
Example
/* WAIT.C: This program launches several child processes and waits for
* the first to finish.
*/
#define INCL_NOPM
#define INCL_NOCOMMON
#define INCL_DOSPROCESS
#include <os2.h> /* DosSleep */
#include <process.h> /* wait */
#include <stdlib.h>
#include <stdio.h>
#include <time.h>
/* Macro to get a random integer within a specified range */
#define getrandom( min, max ) ((rand() % (int)(((max) + 1) - (min))) +
(min))
struct CHILD
{
int pid;
char name[10];
} child[4] = { { 0, "Ann" }, { 0, "Beth" }, { 0, "Carl" }, { 0, "Dave" }
};
void main( int argc, char *argv[] )
{
int termstat, pid, c, tmp;
srand( (unsigned)time( NULL ) ); /* Seed randomizer */
/* If no arguments, this is the parent. */
if( argc == 1 )
{
/* Spawn children in random order with a random delay. */
tmp = getrandom( 0, 3 );
for( c = tmp; c < tmp + 4; c++ )
child[c % 4].pid = spawnl( P_NOWAIT, argv[0], argv[0],
child[c % 4].name, NULL );
/* Wait for the first children. Only get ID of first. */
printf( "Who's first?\n" );
pid = wait( &termstat );
for( c = 0; c < 3; c++ )
wait( &termstat );
/* Check IDs to see who was first. */
for( c = 0; c < 4; c++ )
if( pid == child[c].pid )
printf( "%s was first\n\n", child[c].name );
}
/* If there are arguments, this must be a child. */
else
{
/* Delay for random time. */
srand( (unsigned)time( NULL ) * argv[1][0] );
DosSleep( getrandom( 1, 5) * 1000L );
printf( "Hi, dad. It's %s.\n", argv[1] );
}
}
Output
Who's first?
Hi, dad. It's Carl.
Hi, dad. It's Ann.
Hi, dad. It's Beth.
Hi, dad. It's Dave.
Carl was first
_wrapon
────────────────────────────────────────────────────────────────────────────
Description
Controls word wrap.
#include <graph.h>
short _far _wrapon( short option );
option Wrap condition
Remarks
The _wrapon function controls whether text output with the _outtext function
wraps to a new line or is simply clipped when the text output reaches the
edge of the defined text window. The option argument can be one of the
following manifest constants:
Constant Meaning
────────────────────────────────────────────────────────────────────────────
_GWRAPOFF Truncates lines at window border
_GWRAPON Wraps lines at window border
Note that this function does not affect the output of presentation-graphics
routines or font routines.
Return Value
The function returns the previous value of option. There is no error return.
Compatibility
▼ ANSI DOS OS/2 ▼ UNIX ▼ XENIX
See Also
_outtext, _settextwindow
Example
/* WRAPON.C */
#include <conio.h>
#include <graph.h>
void main()
{
_wrapon( _GWRAPON );
while( !kbhit() )
_outtext( "Wrap on! " );
getch();
_outtext( "\n\n" );
_wrapon( _GWRAPOFF );
while( !kbhit() )
_outtext( "Wrap off! " );
getch();
_outtext( "\n\n" );
}
Output
Wrap on! Wrap on! Wrap on! Wrap on! Wrap on! Wrap on! Wrap on! Wrap
on! Wrap on! Wrap on! Wrap on! Wrap on! Wrap on! Wrap on! Wrap on!
Wrap on! Wrap on! Wrap on! Wrap on! Wrap on! Wrap on! Wrap on! Wr
ap on! Wrap on! Wrap on! Wrap on! Wrap on! Wrap on! Wrap on! Wrap o
n! Wrap on! Wrap on!
Wrap off! Wrap off! Wrap off! Wrap off! Wrap off! Wrap off! Wrap off! Wrap
write
────────────────────────────────────────────────────────────────────────────
Description
Writes data to a file.
#include <io.h> Required only for function declarations
int write( int handle, void *buffer, unsigned int count );
handle Handle referring to open file
buffer Data to be written
count Number of bytes
Remarks
The write function writes count bytes from buffer into the file associated
with handle. The write operation begins at the current position of the file
pointer (if any) associated with the given file. If the file is open for
appending, the operation begins at the current end of the file. After the
write operation, the file pointer is increased by the number of bytes
actually written.
Return Value
The write function returns the number of bytes actually written. The return
value may be positive but less than count (for example, when write runs out
of disk space before count bytes are written).
A return value of -1 indicates an error. In this case, errno is set to one
of the following values:
Value Meaning
────────────────────────────────────────────────────────────────────────────
EBADF Invalid file handle or file not opened
for writing
ENOSPC No space left on device
If you are writing more than 32K (the maximum size for type int) to a file,
the return value should be of type unsigned int. (See the example that
follows.) However, the maximum number of bytes that can be written to a file
at one time is 65,534, since 65,535 (or 0xFFFF) is indistinguishable from -1
and would return an error.
If the file is opened in text mode, each line-feed character is replaced
with a carriagereturn-line-feed pair in the output. The replacement does not
affect the return value.
When writing to files opened in text mode, the write function treats a
CTRL+Z character as the logical end-of-file. When writing to a device, write
treats a CTRL+Z character in the buffer as an output terminator.
Compatibility
▼ ANSI DOS OS/2 UNIX XENIX
See Also
fwrite, open, read
Example
/* WRITE.C: This program opens a file for output and uses write to
* write some bytes to the file.
*/
#include <io.h>
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys\types.h>
#include <sys\stat.h>
char buffer[] = "This is a test of 'write' function";
void main()
{
int fh;
unsigned byteswritten;
if( (fh = open( "write.o", O_RDWR | O_CREAT, S_IREAD | S_IWRITE )) !=
-1 )
{
if( (byteswritten = write( fh, buffer, sizeof( buffer ) )) == -1 )
perror( "Write failed" );
else
printf( "Wrote %u bytes to file\n", byteswritten );
close( fh );
}
}
Output
Wrote 35 bytes to file
INDEX
──────────────────────────────────────────────────────────────────────────
A
abort
abs
Absolute value
abs
cabs
cabsl
fabs
fabsl
labs
Access mode
access
acos
acosl
alloca
Allocation
see Memory allocation; see
_amblksiz variable
Appending
constants
streams
_arc, _arc_w, _arc_wxy
description
use
Arccosine function
Arcsine function
Arctangent function
Arguments
singularity
type checking
variable-length number
asctime
asin
asinl
assert
Assertions
atan, atan2
atanl, atan2l
atanl, _atan2l
atexit
atof, atoi, atol, _atold
_atold
Attributes
B
_bcalloc
bdos
_beginthread
Bessel functions
described
j0, j1, jn;
y0, y1, yn;
_j0l, _j1l, _jnl;
_y0l, _y1l, _ynl;
_bexpand
_bfree
_bfreeseg
_bheapadd
_bheapchk
_bheapmin
_bheapseg
_bheapset
_bheapwalk
Binary
format, conversion to IEEE
double precision
int
reading
writing
mode
fdopen
fopen
freopen
open
setmode
sopen
vs. text mode
_fmode
_fsopen
search
BINMODE.OBJ
_bios_disk
_bios_equiplist
_bios_keybrd}bios_keybrd
_bios_memsize
_bios_printer
_bios_serialcom
_bios_timeofday
_bmalloc
_bmsize
Bold type, use of
Brackets, double, use of
_brealloc
bsearch
Buffer manipulation
memccpy
memchr
memcmp
memcpy
memicmp
memmove
memset
routines and uses (list)
_fmemccpy
_fmemchr
_fmemcmp
_fmemcpy
_fmemicmp
_fmemmove
_fmemset
Buffering
described
preopened streams
using
Buffers
assigning
comparing
copying
flushing
searching
setting characters
BUFSIZ constant
Byte order, swapping
C
cabs
cabsl
calloc
Carry flag
bdos
int86
int86x
intdos
intdosx
ceil
Ceiling function
ceill
_cexit, _c_exit
cgets
_chain_intr
Character classification and conversion functions
include files
isalnum
iscntrl
isdigit
isgraph
islower
isprint
ispunct
isspace
isupper
isxdigit
toascii
tolower, _tolower
toupper, _toupper
Characters
converting. See Character classification and conversion functions
device
reading
fgetc, fgetchar
from console
from port
getc, getchar
read function
ungetting
writing
fputc, fputchar
putc, putchar
to console
to port
write function
chdir
_chdrive
Child process
cwait
signal settings
termination-status word
exec
floating-point state of parent
spawn
wait
chmod
chsize
_clear87
clearerr
_clearscreen
Clipping regions
clock
clock_t type
close
Comparison
max macro
min macro
Compatibility mode
complex type
CONIO.H
Console, ungetting characters from
_control87
Conversion
characters. See Character classification and conversion functions
data. See Data conversion
floating-point numbers
to integers and fractions
to strings
floating-point numbers
IEEE double to MS binary double
integers to strings
long integers to strings
strings to
floating-point values
lowercase
uppercase
time. See Time, conversion
cos, cosh
Cosine
cosl, coshl
cprintf
cputs
creat
cscanf
ctime
CTYPE.H routines
cwait
D
Data conversion
see also Conversion; see also
atof, atol
atof, atol, _atold
atoi
ecvt
fcvt
gcvt
include files
itoa
ltoa
strtod, strtol, strtoul
ultoa
Data items
reading
writing
Date routines
see Time, routines; see
Daylight variable
Default translation mode
child process, used in
O_TEXT
setmode
sopen
_fmode
_fopen
_fsopen
dexpl
dieeetomsbin, dmsbintoieee
difftime
DIRECT.H
Directories
creating
deleting
getting current
renaming
Directory control
chdir
chmod
getcwd
include files
mkdir
remove
rmdir
unlink
_getdcwd
_disable
diskfree_t structure
diskinfo_t structure
_displaycursor
div
Division
div
ldiv
div_t type
Document conventions
DOMAIN
DOS commands, execution within programs
DOS error codes
DOS interface routines
and uses (list)
bdos
dosexterr
FP_OFF
harderr, _hardresume, _hardretn
include files
int86
int86x
intdos
intdosx
segread
_bios_disk
_bios_equiplist
_bios_keybrd
_bios_memsize
_bios_printer
_bios_timeofday
_chain_intr
_dos_allocmem
_dos_close
_dos_creat, _dos_creatnew
_dos_findnext
_dos_freemem
_dos_getdate
_dos_getdiskfree
_dos_getdrive
_dos_getfileattr
_dos_getftime
_dos_gettime
_dos_getvect
_dos_keep
_dos_open
_dos_read
_dos_setblock
_dos_setdate
_dos_setdrive
_dos_setfileattr
_dos_setftime
_dos_settime
_dos_setvect
_dos_write
_enable
DOS interrupts, invoking
DOS system calls
error handling
invoking
_bios_serialcom
DOS version number, detection
DOS.H
dosdate_t structure, dostime_t structure
_doserrnovariable
DOSERROR type
dosexterr
_dos_allocmem
_dos_close
_dos_creat
_dos_creatnew
_dos_findfirst
_dos_findnext
_dos_freemem
_dos_getdate
_dos_getdiskfree
_dos_getdrive
_dos_getfileattr
_dos_getftime
_dos_gettime
_dos_getvect
_dos_keep
_dos_open
_dos_read
_dos_setblock
_dos_setdate
_dos_setdrive
_dos_setfileattr
_dos_setftime
_dos_settime
_dos_setvect
_dos_write
Drive routines
_chdrive
_getdrive
dup, dup2
Dynamic allocation
see Memory allocation; see
E
E2BIG
EACCES
EBADF
ecvt
EDEADLOCK
EDOM
EEXIST
EINVAL
_ellipse, _ellipse_w, _ellipse_wxy
Ellipses
EMFILE
_enable
End-of-file
indicators
low-level I/O
stream I/O
clearing
described
_endthread
ENOENT
ENOEXEC
ENOMEM
ENOSPC
environ variable
Environment variables
described
getenv
putenv
EOF constant
eof
ERANGE
errno variable
described
error numbers
I/O routines
Error handling
DOS error codes
DOS system calls
logic errors
perror
strerror, _strerror
Error indicator
described
ferror
Error messages, user supplied
Euclidean distance
exception type
EXDEV
exec family
exit, _exit
Exiting processes
exp
_expand
expl
Exponential functions
exp
expl
frexp
frexpl
ldexp
ldexpl
log, log10
logl, log10
pow
powl
sqrt
sqrtl
F
fabs
fabsl
Far pointers
_fcalloc
fclose, fcloseall
fcvt
fdopen
feof
ferror
_fexpand
fflush
_ffree
fgetc, fgetchar
fgetpos
fgets
_fheapchk
_fheapmin
_fheapset
_fheapwalk
fieeetomsbin, fmsbintoieee
File handles
duplication
functions
predefined
stream
File handling
access
chmod
chsize
filelength
fstat
includefiles
isatty
locking
mktemp
remove
rename
setmode
stat
umask
unlink
File permission mask
see Permission setting; see
File pointers
defined
positioning
fgetpos
fseek
fsetpos
ftell
lseek
read and write operations
rewind
tell
File status information
FILE
pointer
structure
type
filelength
fileno
Files
changing size
closing
creating
deleting
determining length
locking
modifying names
obtaining status
opening
creat
input and ouput
open
sopen
reading characters
renaming
setting modification time
writing characters
find_t structure
Floating point
control word
errors
math package
reinitialization
_clear87
_control87
_fpreset
_status87
numbers, conversion to strings
status word
_floodfill, _floodfill_w
floor
floorl
flushall
Flushing buffers
_fmalloc
_fmemccpy
_fmemchr
_fmemcmp
_fmemcpy
_fmemicmp
_fmemmove
_fmemset
fmod
_fmode variable
fmodl
_fmsize
Fonts
bit-mapped
functions (list)
fopen
Formatted I/O
cprintf
cscanf
fprintf
fscanf
printf
scanf
sprintf
sscanf
vfprintf, vprintf, vsprintf
fpos_t type
_fpreset
fprintf
fputc, fputchar
fputs
FP_OFF, FP_SEG
fread
_frealloc
free
_freect
freopen
frexp
frexpl
fscanf
fseek
fsetpos
_fsopen
fstat
_fstrcat
_fstrchr
_fstrcmp
_fstrcpy
_fstrcspn
_fstrdup
_fstricmp
_fstrlen
_fstrlwr
_fstrncat
_fstrncmp
_fstrncpy
_fstrnicmp
_fstrnset
_fstrpbrk
_fstrrchr
_fstrrev
_fstrset
_fstrspn
_fstrstr
_fstrtok
_fstrupr
ftell
ftime
_fullpath
fwrite
G
gcvt
_getactivepage
_getarcinfo
_getbkcolor
getc, getchar
getch, getche
_getcolor
_getcurrentposition, _getcurrentposition_w
getcwd
_getdcwd
_getdrive
getenv
_getfillmask
_getfontinfo
_getgtextextent
_getimage, _getimage_w, _getimage_wxy
_getlinestyle
_getphyscoord
getpid
_getpixel, _getpixel_w
gets
_gettextcolor
_gettextcursor
_gettextposition
_gettextwindow
_getvideoconfig
_getviewcoord, _getviewcoord_w, _getviewcoord_wxy
_getvisualpage
getw
_getwindowcoord
_getwritemode
Global variables
accessing
daylight
environ
errno
described
perror
strerror
sys_errlist
described
perror
strerror
sys_nerr
timezone
tzname
_amblksiz
_doserrno
_fmode
_osmajor
_osminor
_psp
gmtime
Goto, nonlocal
Graphics
attributes
color selection
configuration
coordinates
font functions (list)
image transfer
low-level palettes
output
parameters
presentation graphics
text output
text support
_gettextwindow
_scrolltextwindow
_settextrows
_settextwindow
_setvideomoderows
_setwindow
_wrapon
Greenwich mean time
_grstatus
H
halloc
Handle
see File handles; see
_harderr
_hardresume
_hardretn
Heap consistency check
_bheapchk
_bheapmin
_fheapchk, _heapchk, _nheapchk
_fheapmin, _heapmin, _nheapmin
_heapadd
_heapchk
_heapmin
_heapset
_heapwalk
hfree
Hyperbolic
cosine
sine
tangent
hypot
Hypotenuse
hypotl
I
I/O
buffered
console and port
cgets
cprintf
cputs
cscanf
described
getch, getche
include files
inp, inpw
kbhit
outp, outpw
putch
ungetch
low-level
close
creat
described
dup, dup2
eof
error handling
include files
lseek
open
read
sopen
tell
write
stream
IEEE format, converting double-precision to Microsoft binary
_imagesize, _imagesize_w, _imagesize_wxy
Include files
buffer manipulation routines
character classification, conversion
console and port I/O
data conversion
directory control
DOS interface routines
file handling
low-level I/O
math routines
memory allocation
naming conventions
process control
processor calls
searching and sorting
stream I/O
string manipulation
time routines
inp, inpw
int86
int86x
intdos
intdosx
Integers
conversion to strings
long, conversion to strings
Interrupt signals
Interrupts
see DOS interrupts, invoking; see
IO.H
isalnum, isdigit, isgraph
isalpha, isascii, iscntrl
isatty
isdigit
islower, isupper, isxdigit
isprint
ispunct
isspace
Italic letters, use of
itoa
J
j0, j1, jn
_j0l, _j1l, _jnl
jmp_buf type
K
kbhit
Keystroke, testing
L
labs
ldexpl
ldiv
ldiv_t type
lfind
Lines
reading
writing
_lineto
_lineto_w
Local time corrections
localeconv
Localization
localeconv
setlocale
localtime
locking
log, log10
Logarithmic functions
logl, log10l
Long integers, conversion to strings
longjmp
Low-level graphics
see also individual function names; see also
color selection
configuration
coordinates
font functions. See Fonts
image transfer
output
_arc, _arc_w, _arc_wxy
_ellipse, _ellipse_w, _ellipse_wxy
_getarcinfo
_getwritemode
_grstatus
_lineto, _lineto_w
_pie, _pie_w, _pie_wxy
_polygon, _polygon_w, _polygon_wxy
_rectangle, _rectangle_w, _rectangle_wxy
_setwritemode
palettes
parameters
physical coordinates
text support (list)
view coordinates
window coordinates
_lrotl
_lrotr
lsearch
lseek
ltoa
M
_makepath
malloc
MALLOC.H
Mask
see Permission setting; see
MATH.H
matherr
described
use
matherrl
max
_memavl
memccpy
memchr
memcmp
memcpy
memicmp
_memmax
memmove
Memory allocation
available memory, determination
calloc
free
halloc
hfree
malloc
realloc
routines and uses (list)
stackavail
_amblksiz
_bcalloc
_bfree
_bfreeseg
_bheapadd
_bheapchk
_bheapmin
_bheapseg
_bheapset
_bheapwalk
_bmalloc
_bmsize
_brealloc
_expand
_fcalloc
_ffree
_fheapchk
_fheapmin
_fheapset
_fheapwalk
_fmalloc
_fmsize
_frealloc
_freect
_heapadd
_heapchk
_heapmin
_heapset
_heapwalk
_memavl
_memmax
_msize
_ncalloc
_nfree
_nheapchk
_nheapmin
_nheapset
_nheapwalk
_nmalloc
_nmsize
_nrealloc
MEMORY.H
memset
Microsoft Windows
min
mkdir
mktemp
mktime
Model-independent memory routines
modf
modfl
Modification time
Monofont, use of
movedata
_moveto
_moveto_w
MS C 4.0, differences
fputs
puts
_msize
N
_ncalloc
NDEBUG
_nexpand
_nfree
_nheapchk
_nheapmin
_nheapset
_nheapwalk
_nmalloc
_nmsize
Nonlocal goto
_nrealloc
_nstrdup
Null pointer
O
oflag
see Open flag; see
onexit
Open flag
open
Optional items
_osmajor variable
_osminor variable
_outgtext
_outmem
outp, outpw
Output
see I/O; see
_outtext
OVERFLOW
Overlapping moves
Overlay, of parent process
O_BINARY
P
Palettes, low-level
Parameters, variable-length number
Parent process
cwait
described
overlay and suspension
wait
_pclose
Permission setting
access
changing
described
mask
open
sopen
umask
perror
_pg_analyzechart
_pg_analyzechartms
_pg_analyzepie
_pg_analyzescatter
_pg_analyzescatterms
_pg_chart
_pg_chartms
_pg_chartpie
_pg_chartscatter
_pg_chartscatterms
_pg_defaultchart
_pg_getchardef
_pg_getpalette
_pg_getstyleset
_pg_hlabelchart
_pg_initchart
_pg_resetpalette
_pg_resetstyleset
_pg_setchardef
_pg_setpalette
_pg_setstyleset
_pg_vlabelchart
_pie, _pie_w, _pie_wxy
_pipe
Pipes
_pclose
_pipe
_popen
PLOSS
Pointers, long
_polygon, _polygon_w, _polygon_wxy
_popen
Port I/O
see I/O, console and port; see
pow
Predefined
handles
stream pointers
types. See Standard types
printf
Printing
see Write operations; see
Process control
abort
atexit
cwait
exec family
exit, _exit
getpid
include files
onexit
raise
signal
spawn family
system
wait
_cexit, _c_exit
Process ID
PROCESS.H
Processor calls, include files
Program segment prefix (PSP)
Pseudorandom integers
_psp
putc, putchar
putch
putenv
_putimage, _putimage_w
puts
putw
Q
qsort
Quick sort algorithm
Quotation marks, use of
R
R eallocation
_freal loc
raise
rand
Random access
fgetpos
fseek
fsetpos
ftell
lseek
rewind
tell
Random number generator
Read access
see Permission setting; see
Read operations
binary int value
characters
from file
from stdin
from stream
formatted
cscanf
fscanf
scanf
sscanf
from console
cgets
cscanf
getch
keystroke checking
from port
line
from stdin
from stream
read
realloc
Reallocation
realloc
_brealloc
_expand
_frealloc Reallocate memory blocks.
HO = @L2C1 =
_nrealloc
_rectangle, _rectangle_w, _rectangle_wxy
Redirection
_registerfonts
REGS type
Remainder function
_remapallpalette
_remappalette
remove
rename
Reversing strings
rewind
rmdir
rmtmp
_rotl
_rotr
S
scanf
Scanning
see Read operations; see
_scrolltextwindow
SEARCH.H
_searchenv
Searching and sorting
bsearch
include files
lfind
lfind, lsearch
lsearch
qsort
seed
Segment registers
segread
_selectpalette
_setactivepage
_setbkcolor
setbuf
_setcliprgn
_setcolor
_setfillmask
_setfont
_setgtextvector
setjmp
_setlinestyle
setlocale
setmode
_setpixel, _setpixel_w
_settextcolor
_settextcursor
_settextposition
_settextrows
_settextwindow
setvbuf
_setvideomode
_setvideomoderows
_setvieworg
_setviewport
_setvisualpage
_setwindow
_setwritemode
SIGNAL.H
signal
described
Signal
raise
sin, sinh
Sine
SING
sinl, sinhl
size_t type
Small capital letters, use of
sopen
Sorting
see Searching and sorting; see
spawn family
argument-type-checking limitations
described
use
_splitpath
sprintf
sqrt
sqrtl
Square-root function
srand
SREGS type
sscanf
described
use
Stack environment
restoring
saving
stackavail
Standard auxiliary
see stdaux; see
Standard error
see stderr; see
Standard input
see stdin; see
Standard output
see stdout; see
Standard print
see stdprn; see
Standard types
clock_t
complex
diskfree_t
diskinfo_t
div_t
dosdate_t
DOSERROR
dostime_t
exceptions
FILE
find_t
fpos_t
jmp_buf
ldiv_t
listed
REGS
size_t
SREGS
stat
timeb
time_t
tm
utimbuf
va_list
stat routine
described
use
stat type
described
fstat
_status87
stdaux, stderr, stdin
buffering
described
file handle
translation mode, changing
STDIO.H
stdout, stdprn
buffering
described
file handle
translation mode, changing
strcat
strchr
strcmp
strcoll
strcpy
strcspn
_strdate
strdup
Stream I/O
see also I/O, console and port; see also
buffering
clearerr
described
error handling
fclose, fcloseall
fdopen
feof
ferror
fflush
fgetc, fgetchar
fgetpos
fgets
fileno
flushall
fopen
fprintf
fputc, fputchar
fputs
fread
freopen
fscanf
fseek
fsetpos
ftell
fwrite
getc, getchar
gets
getw
printf
putc, putchar
putw
rewind
routines and uses (list)
scanf
setbuf
sprintf
sscanf
tempnam, tmpnam
ungetc
vfprintf, vprintf, vsprintf
_fsopen
Stream pointer
Streams
appending
buffering
clearing errors
closing
file handles for
file pointer position
fseek
fsetpos
ftell
getpos
rewind
formatted I/O
printf
scanf
sprintf
sscanf
stream
vprintf
opening
reading
binary int value
characters
data items
lines
reopening
rewinding
stdaux, stderr, stdin
stdout, stdprn
translation mode. See Binary, mode
ungetting characters
writing
binary int value
characters
data items
lines
strings
strerror
_strerror
strftime
stricmp
String manipulation
routines and uses (list)
strcat
strchr
strcmp
strcoll
strcpy
strcspn
strdup
stricmp
strlwr
strncat
strncmp
strncpy
strnicmp
strnset
strpbrk
strrchr
strrev
strset
strspn
strstr
strtok
strupr
strxfrm
_fstrcat
_fstrchr
_fstrcmp
_fstrcpy
_fstrcspn
_fstrdup
_fstricmp
_fstrlwr
_fstrncat
_fstrncmp
_fstrncpy
_fstrnicmp
_fstrnset
_fstrpbrk
_fstrrchr
_fstrrev
_fstrset
_fstrspn
_fstrstr
_fstrtok
_fstrupr
_nstrdup
STRING.H
Strings
comparing
concatenating
converting
to floating-point values
to lowercase
to uppercase
copying
initializing
reading from console
reversing
searching
strchr
strcspn
strpbrk
strrchr
strspn
strstr
strtok
_fstrchr
_fstrcspn
_fstrpbrk
_fstrrchr
_fstrspn
_fstrstr
_fstrtok
writing
to console
to stream
strlen
strlwr
strncat
strncmp
strncpy
strnicmp
strnset
strpbrk
strrchr
strrev
strset
strspn
strstr
_strtime
strtod
strtok
strtol
_strtold
strtoul
strupr
strxfrm
swab
System calls
see DOS system calls; see
System time
see Time; see
system
SYS\STAT.H
SYS\TIMEB.H
SYS\TYPES
SYS\UTIME.H
sys_errlist
described
system error messages
sys_nerr
T
tan, tanh
Tangent
tanl, tanhl
tell
tempnam, tmpnam
Terminal capabilities
Text mode
described
setmode
sopen
stream I/O
vs. binary
Threads
DosExit
termination
_beginthread
_endthread
time function
TIME.H
Time
conversion
long integer to string
long integer to structure
structure to string
time
functions
Time
global variables, setting
local time, correcting
obtaining
routines
(list)
asctime
clock
ctime
difftime
ftime
gmtime
localtime
mktime
time
tzset
utime
time differences, computing
timeb type
timezone variable
time_t type
TLOSS
tm type
tmpfile
tmpnam
toascii
Tokens, finding in strings
_tolower
tolower, toupper
_toupper
Trigonometric functions
acos
acosl
asin
asinl
atan, atan2
atanl, atan2
cos, cosh
hypot
hypotl
sin, sinh
sinl, sinhl
tan, tanh
tanl, tanhl
TZ environment variable
default value
localtime
tzset
tzname variable
tzset
U
ultoa
umask
UNDERFLOW
ungetc
ungetch
Universal Coordinated Time
unlink
_unregisterfonts
Update
Uppercase, use of
utimbuf type
utime
V
va_arg, va_end, va_start
va_list type
Version number (DOS)
vfprintf, vprintf, vsprintf
W
wait
Word
see Binary, int; see
_wrapon
Write access
see Permission setting; see
Write operations
binary int value to stream
character
to console
to file
to stdout
to stream
data items from stream
formatted
cprintf
printf
sprintf
stream I/O
vprintf
line to stream
string to stream
to console
to port
write
Y
y0, y1, yn
_y0l, _y1l, _ynl
_y1l
_ynl