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The MS-DOS Encyclopedia
Appendix C: Extended Error Codes
The extended error codes used by Interrupt 21H functions consist of
four separate codes in the AX, BH, BL, and CH registers. These codes
give as much detail as possible about the error and suggest how the
issuing program should respond.
AX--Extended Error Code
If an error condition occurs in response to an Interrupt 21H function
call, the carry flag is set and one of the following error codes is
returned in AX:
╓┌──────────────┌────────────────────────────────────────────────────────────╖
Error Description
──────────────────────────────────────────────────────────────────
01H Invalid function code
02H File not found
03H Path not found
04H Too many open files (no handles left)
05H Access denied
06H Invalid handle
07H Memory control blocks destroyed
08H Insufficient memory
09H Invalid memory block address
0AH Invalid environment
0BH Invalid format
0CH Invalid access code
0DH Invalid data
0EH Reserved
0FH Invalid drive
10H Attempt to remove the current directory
11H Not same device
12H No more files
13H Disk is write-protected
14H Bad disk unit
15H Drive not ready
16H Invalid disk command
17H CRC error
18H Invalid length (disk operation)
19H Seek error
1AH Not an MS-DOS disk
1BH Sector not found
1CH Out of paper
1DH Write fault
1EH Read fault
1FH General failure
20H Sharing violation
21H Lock violation
22H Wrong disk
23H FCB unavailable
24H Sharing buffer overflow
25-31H Reserved
32H Network request not supported
33H Remote computer not listening
34H Duplicate name on network
35H Network path not found
36H Network busy
37H Network device no longer exists
38H Net BIOS command limit exceeded
39H Network adapter hardware error
3AH Incorrect response from network
3BH Unexpected network error
3CH Incompatible remote adapter
3DH Print queue full
3EH Print queue not full
3FH Print file was canceled (not enough space)
40H Network name was deleted
41H Access denied
42H Network device type incorrect
43H Network name not found
44H Network name limit exceeded
45H Net BIOS session limit exceeded
46H Sharing temporarily paused
47H Network request not accepted
48H Print or disk redirection paused
49-4FH Reserved
50H File exists
51H Reserved
52H Cannot make directory entry
53H Fail on Interrupt 24H
54H Out of network structures
55H Device already assigned
56H Invalid password
57H Invalid parameter
58H Network data fault
BH--Error Class
BH returns a code that describes the class of error that occurred:
╓┌──────────────┌────────────────────────────────────────────────────────────╖
Class Description
──────────────────────────────────────────────────────────────────
01H Out of a resource, such as storage or channels
02H Not an error, but a temporary situation (such as a locked
region in a file) that can be expected to end
03H Authorization problem
04H An internal error in system software
05H Hardware failure
06H A system software failure not the fault of the active
process (could be caused by missing or incorrect
configuration files, for example)
07H Application program error
08H File or item not found
09H File or item of invalid format or type or otherwise invalid
or unsuitable
0AH File or item interlocked
0BH Wrong disk in drive, bad spot on disk, or other problem with
storage medium
0CH Other error
BL--Suggested Action
BL returns a code that suggests how the program should respond to the
error:
╓┌──────────────┌────────────────────────────────────────────────────────────╖
Action Description
──────────────────────────────────────────────────────────────────
01H Retry, then prompt user.
02H Retry after a pause.
03H If the user entered data such as a drive letter or filename,
prompt for it again.
04H Terminate with cleanup.
05H Terminate immediately. The system is so unhealthy that the
program should exit as soon as possible without taking the
time to close files and update indexes.
06H Error is informational.
07H Prompt the user to perform some action, such as changing
disks, then retry the operation.
CH--Locus
CH returns a code that provides additional information to help locate
the area involved in the failure. This code is particularly useful for
hardware failures (BH = 05H).
╓┌──────────────┌────────────────────────────────────────────────────────────╖
Locus Description
──────────────────────────────────────────────────────────────────
01H Unknown
02H Related to random-access block devices, such as a disk drive
03H Related to network
04H Related to serial-access character devices, such as a
printer
05H Related to random-access memory
Procedure
Programs should handle errors by noting the error returned in AX from
the original system call and then invoking Interrupt 21H Function 59H
to get the extended error information. If no extended error
information is provided, the program should respond to the original
error code.
The Function 59H system call is available during Interrupt 24H.
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