PC-DOS 0.90

There was no PC-DOS 0.90 product per se. It has been dubbed version 0.90 simply because it predates PC-DOS 1.00 by several months. More information about this preliminary version of PC-DOS can be found at the OS/2 Museum.

Below is an IBM PC (Model 5150) with an original IBM ROM BIOS and Color (CGA) Display that will boot PC-DOS 0.90. The machine is configured to run at 4.77Mhz, so the ROM BIOS memory test has been disabled, since a PC with 256Kb was rather slow to boot. A similar configuration with Monochrome Display and Debugger is also available.

[PCx86 Machine]

PC-DOS 0.90 files were distributed on one single-sided (160Kb) diskette. A directory listing of the disk is provided below.

Directory of PC-DOS 0.90 Diskette

 Volume in drive A has no label
 Directory of A:\

IBMBIO   COM      2560 05-29-81  12:00a
IBMDOS   COM      5566 05-29-81  12:00a
COMMAND  COM      2576 05-29-81  12:00a
DEBUG    COM      5450 05-27-81  12:00a
TIME     COM       243 05-19-81  12:00a
DATE     COM       245 05-20-81  12:00a
ASM      COM      6389 05-15-81  12:00a
FORMAT   COM      2048 05-29-81  12:00a
HEX2BIN  COM       483 05-07-81  12:00a
BASIC    COM     11008 06-04-81  12:00a
CHKDSK   COM      1224 05-30-81  12:00a
EDLIN    COM      2231 05-29-81  12:00a
MODE     COM       675
COMMENTS          3561 06-05-81  12:00a
MOVBAS   COM       128 04-23-81  12:00a
BAS18    COM     11008 06-04-81  12:00a
BASICA   COM     14976 06-04-81  12:00a
AUTOEXEC BAK        24
SYS      COM       896 06-03-81  12:00a
BAS18A   COM     14976 06-04-81  12:00a
COMMENTS BAK      3560 06-05-81  12:00a
FCOMP    COM      1408 04-13-81  12:00a
DISKCOPY COM      1211 06-04-81  12:00a
CONVERT  COM      3200 04-15-81  12:00a
COMP     COM       256 04-15-81  12:00a
KILO     BAS       768 04-23-81  12:00a
20HAL    COM      1792 04-24-81  12:00a
SPCWAR   BAS      5120 05-22-81  12:00a
TTY      ASC      2432 05-22-81  12:00a
VCOPY    BAT        26 04-24-81  12:00a
SHIPS    MAC      1792 06-01-81  12:00a
CIRCLE   MAC       384 06-01-81  12:00a
RBAS     COM     32768 04-25-81  12:00a
THREED   BAS      3072
CUBE     DAT       402 04-30-81  12:00a
       35 file(s)     144458 bytes
                        8192 bytes free

The boot sector of the original PC-DOS 0.90 disk image contained the following bytes:

00000000  eb 2f 14 00 00 00 60 00  20 37 2d 4d 61 79 2d 38  |./....`. 7-May-8|
00000010  31 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |1...............|
00000020  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000030  00 fa 8c c8 8e d8 ba 00  00 8e d2 bc 00 7c fb a1  |.............|..|
00000040  06 7c 8e d8 8e c0 ba 00  00 8b c2 cd 13 72 41 e8  |.|...........rA.|
00000050  58 00 72 fb 2e 8b 0e 02  7c 51 bb 00 00 33 d2 b9  |X.r.....|Q...3..|
00000060  08 00 be 01 00 56 b0 01  b4 02 cd 13 72 22 5e 58  |.....V......r"^X|
00000070  e8 e7 00 2b c6 74 14 fe  c5 b1 01 be 08 00 3b c6  |...+.t........;.|
00000080  73 04 8b f0 eb 01 96 56  50 eb dd 2e ff 2e 04 7c  |s......VP......||
00000090  be 44 7d b8 42 7d 50 32  ff ac 24 7f 74 0b 56 b4  |.D}.B}P2..$.t.V.|
000000a0  0e bb 07 00 cd 10 5e eb  f0 c3 bb 00 00 b9 04 00  |......^.........|
000000b0  b8 01 02 cd 13 1e 72 34  8c c8 8e d8 bf 00 00 b9  |......r4........|
000000c0  0b 00 26 80 0d 20 26 80  8d 20 00 20 47 e2 f3 bf  |..&.. &.. . G...|
000000d0  00 00 be 76 7d b9 0b 00  fc f3 a6 75 0f bf 20 00  |...v}......u.. .|
000000e0  be 82 7d b9 0b 00 f3 a6  75 02 1f c3 be f9 7c e8  |..}.....u.....|.|
000000f0  a5 ff b4 00 cd 16 1f f9  c3 0d 0a 4e 6f 6e 2d 53  |...........Non-S|
00000100  79 73 74 65 6d 20 64 69  73 6b 20 6f 72 20 64 69  |ystem disk or di|
00000110  73 6b 20 65 72 72 6f f2  0d 0a 52 65 70 6c 61 63  |sk erro...Replac|
00000120  65 20 61 6e 64 20 73 74  72 69 6b 65 20 61 6e 79  |e and strike any|
00000130  20 6b 65 79 20 77 68 65  6e 20 72 65 61 64 f9 0d  | key when read..|
00000140  0a 00 cd 18 0d 0a 44 69  73 6b 20 42 6f 6f 74 20  |......Disk Boot |
00000150  66 61 69 6c 75 72 e5 0d  0a 00 50 52 8b c6 bf 00  |failur....PR....|
00000160  02 f7 e7 03 d8 5a 58 c3  52 6f 62 65 72 74 20 4f  |.....ZX.Robert O|
00000170  27 52 65 61 72 20 69 62  6d 62 69 6f 20 20 63 6f  |'Rear ibmbio  co|
00000180  6d b0 69 62 6d 64 6f 73  20 20 63 6f 6d b0 c9 00  |m.ibmdos  com...|
00000190  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001a0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001b0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001c0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001d0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001e0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001f0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|

Note that if you download the disk image from the PCjs website (using the “Save” button on a PCjs machine), the following boot sector bytes will differ:

00000000  eb 2f 14 00 00 00 60 00  20 37 2d 00 02 01 01 00  |./....`. 7-.....|
00000010  02 40 00 40 01 fe 01 00  08 00 01 00 00 00 00 00  |[email protected]@............|

This is simply a side-effect of the DiskDump utility that’s used to prepare disk images for the PCjs website. It automatically adds a BPB to the boot sector if the BPB is missing or incorrect, making it easier for modern operating systems to mount the disk image.