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pcjs/disks/pcx86/dos/compaq/1.11/README.md

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---
layout: page
title: COMPAQ MS-DOS 1.11
permalink: /disks/pcx86/dos/compaq/1.11/
machines:
- id: ibm5150-compaq111
type: pcx86
config: /devices/pcx86/machine/5150/mda/64kb/debugger/machine.xml
resume: 1
autoMount:
A:
name: COMPAQ MS-DOS 1.11
B:
name: None
autoType: $date\r$time\r
---
COMPAQ MS-DOS 1.11
------------------
Released in 1983 by COMPAQ Computer Corp, this early version of MS-DOS displays on startup:
The COMPAQ Personal Computer DOS
Version 1.11
(C) Copyright COMPAQ Computer Corp. 1982
(C) Copyright Microsoft 1981, 82
To learn more about this double-sided 320Kb diskette, see the
[Directory Listing](#directory-of-compaq-ms-dos-111-diskette) and [Boot Sector](#compaq-ms-dos-110-boot-sector) below.
{% include machine.html id="ibm5150-compaq111" %}
### Directory of COMPAQ MS-DOS 1.11 Diskette
Volume in drive A has no label
Directory of A:\
IOSYS COM 1998 05-13-83 12:00p
MSDOS COM 6136 05-13-83 12:00p
COMMAND COM 4959 05-13-83 12:00p
LINK EXE 41856 05-13-83 12:00p
EDLIN COM 2432 05-13-83 12:00p
SYS COM 645 05-13-83 12:00p
DEBUG COM 6619 05-13-83 12:00p
BASIC COM 549 05-13-83 12:00p
BASICA COM 547 05-13-83 12:00p
FORMAT COM 3296 05-13-83 12:00p
EXE2BIN EXE 1280 05-13-83 12:00p
DISKCOPY COM 1812 05-13-83 12:00p
DISKCOMP COM 1291 05-13-83 12:00p
MODE COM 1800 05-13-83 12:00p
CHKDSK COM 1720 05-13-83 12:00p
COMP COM 1484 05-13-83 12:00p
WORDS 1242 05-13-83 12:00p
BASICA EXE 54272 05-13-83 12:00p
TEST EXE 18560 05-13-83 12:00p
DEMO BAT 14 05-13-83 12:00p
DEMO BAS 7808 05-13-83 12:00p
DEMO1 BAS 17920 05-13-83 12:00p
DEMO2 BAS 17792 05-13-83 12:00p
DEMO3 BAS 21120 05-13-83 12:00p
DEMO4 BAS 6528 05-13-83 12:00p
JUGGLER DAT 16128 05-13-83 12:00p
USA DAT 16128 05-13-83 12:00p
INTEREST BAS 384 05-13-83 12:00p
28 file(s) 256320 bytes
Total files listed:
28 file(s) 256320 bytes
53248 bytes free
One curiosity regarding this disk are the BASIC files. **BASIC.COM** and **BASICA.COM** are nothing more than
tiny programs to load **BASICA.EXE**, a stand-alone version of BASIC that doesn't require any BASIC ROMs. And
**BASICA.EXE** reports a version number that differs from the DOS version:
The COMPAQ Personal Computer BASIC
Version 1.13
(C) Copyright COMPAQ Computer Corp. 1983
### COMPAQ MS-DOS 1.11 Boot Sector
The boot sector of the COMPAQ MS-DOS 1.11 disk image contains the following bytes:
00000000 fa bc e7 01 b8 c0 07 8e d0 fb 8e d8 8e c0 33 c0 |..............3.|
00000010 cd 13 b8 01 02 bb 00 02 b9 04 00 33 d2 e8 8b 00 |...........3....|
00000020 eb 1c bb da 00 8a 07 3c 24 74 0c 53 b4 0e bb 07 |.......<$t.S....|
00000030 00 cd 10 5b 43 eb ee 33 c0 cd 16 eb c3 c3 fc 8b |...[C..3........|
00000040 f3 bf c4 00 b9 0b 00 f3 a6 75 d7 83 c6 15 b9 0b |.........u......|
00000050 00 f3 a6 75 cd b8 01 02 bb 00 02 b9 02 00 33 d2 |...u..........3.|
00000060 e8 48 00 8a 27 80 fc fe be 26 01 74 0a 80 fc ff |.H..'....&.t....|
00000070 74 02 eb ae be 3c 01 b8 60 00 50 07 8b 04 33 db |t....<..`.P...3.|
00000080 8b 4c 02 8b 54 04 e8 22 00 8b 44 06 03 5c 08 8b |.L..T.."..D..\..|
00000090 4c 0a 8b 54 0c e8 13 00 8b 44 0e 03 5c 10 8b 4c |L..T.....D..\..L|
000000a0 12 8b 54 14 e8 04 00 ff 2e 52 01 bf 05 00 57 50 |..T......R....WP|
000000b0 cd 13 72 03 58 58 c3 33 c0 cd 13 58 5f 4f 75 ee |..r.XX.3...X_Ou.|
000000c0 58 e9 5e ff 49 4f 53 59 53 20 20 20 43 4f 4d 4d |X.^.IOSYS COMM|
000000d0 53 44 4f 53 20 20 20 43 4f 4d 0a 0d 4e 6f 6e 2d |SDOS COM..Non-|
000000e0 53 79 73 74 65 6d 20 64 69 73 6b 20 6f 72 20 64 |System disk or d|
000000f0 69 73 6b 20 65 72 72 6f 72 0a 0d 52 65 70 6c 61 |isk error..Repla|
00000100 63 65 20 61 6e 64 20 73 74 72 69 6b 65 20 61 6e |ce and strike an|
00000110 79 20 6b 65 79 20 77 68 65 6e 20 72 65 61 64 79 |y key when ready|
00000120 0a 0d 24 47 41 53 01 02 08 00 00 00 08 02 00 02 |..$GAS..........|
00000130 01 01 00 00 08 02 00 10 01 02 00 00 06 02 03 00 |................|
00000140 00 01 08 02 00 0c 01 01 00 00 03 02 00 10 01 01 |................|
00000150 00 01 00 00 60 00 28 43 29 43 6f 70 79 72 69 67 |....`.(C)Copyrig|
00000160 68 74 20 43 4f 4d 50 41 51 20 43 6f 6d 70 75 74 |ht COMPAQ Comput|
00000170 65 72 20 43 6f 72 70 6f 72 61 74 69 6f 6e 20 31 |er Corporation 1|
00000180 39 38 32 00 00 00 00 00 00 00 00 00 00 00 00 00 |982.............|
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 the disk cannot be mounted by a modern operating system (e.g., macOS), because it lacks a proper
BPB at offset 0x000B.
To resolve the mounting problem, one solution is to use the [DiskDump](/modules/diskdump/) utility's *--forceBPB*
option, which creates a mountable disk image by making the following boot sector modifications:
00000000 eb fe 90 50 43 4a 53 2e 4f 52 47 00 02 02 01 00 |...PCJS.ORG.....|
00000010 02 70 00 80 02 ff 01 00 08 00 02 00 00 00 00 00 |.p..............|
00000020 00 00 00 00 00 8a 07 3c 24 74 0c 53 b4 0e bb 07 |.......<$t.S....|
The following (hex) byte ranges are modified:
- 0000-0002: 2-byte Intel x86 JMP instruction followed by 1-byte x86 NOP
- 0003-000A: 8-byte OEM signature string (we use the fake "PCJS.ORG" OEM signature)
- 000B-001D: 19-byte BPB describing a 320Kb diskette image with 8 sectors/track and 2 heads
Ordinarily, only the 19-byte BPB would be required, but it turns out that macOS won't mount the disk image
unless the boot sector *also* begins with an Intel x86 JMP instruction. So the *--forceBPB* option updates all
30 bytes at the beginning of the boot sector, making the disk image mountable, but also rendering it unbootable --
which is OK if all you want to do is mount the image and copy files from it.
One common misconception is that the last word of a mountable boot sector must also contain 0xAA55 (ie, the low
byte at offset 0x1FE must be 0x55 and the high byte at offset 0x1FF must be 0xAA). This claim is often backed up
by pointing out that some (newer) ROMs will not boot from a disk if that signature is missing.
However, that evidence is misleading, because those ROMs check only *hard disk* boot sectors for the 0xAA55 signature,
not diskettes. Which makes sense, because hard disk support didn't exist in DOS until version 2.0 -- the same version
of DOS that also introduced BPBs and boot sector signatures.
Here's how you can use [DiskDump](/modules/diskdump/) to a mountable disk. Note that *two* DiskDump commands are
required, because BPB modification only happens when converting an IMG file to a JSON file; the second DiskDump command
converts the modified JSON back into an IMG file.
diskdump --disk=COMPAQ-DOS111.img --format=json --forceBPB --output=COMPAQ-DOS111-BPB.json
warning: BPB has been updated
327680-byte disk image saved to COMPAQ-DOS111-BPB.json
diskdump --disk=COMPAQ-DOS111.json --format=img --output=COMPAQ-DOS111-BPB.img
327680-byte disk image saved to COMPAQ-DOS111-BPB.img
chmod -w COMPAQ-DOS111-BPB.img
open COMPAQ-DOS111-BPB.img
mkdir COMPAQ-DOS111
cp -pr /Volumes/Untitled/ COMPAQ-DOS111
[Return to [COMPAQ MS-DOS Disks](/disks/pcx86/dos/compaq/)]
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