IBM DOS Version 1.00

See one of our other IBM DOS 1.00 specimens by clicking here.

Label used with permission of IBM® Corporation
Label copyright © IBM® Corporation

Boot Screen:

Enter today's date (m-d-y):

The IBM Personal Computer DOS

Version 1.00 (C)Copyright IBM Corp 1981


Chkdsk Screen:


         40 disk files

     160256 bytes total disk space

       6144 bytes remain available

     654336 bytes total memory

     642192 bytes free


Package Contents:

Package images used with permission
IBM® Corporation
Outer Cover, P/N:6025146
Binder, P/N:6024001
User Manual, P/N:6172220
Product comment form, P/N:6172220 (4 enclosed)
Diskette, P/N:6172212
Diskette plastic binder holder, P/N:6172206

Collector's notes:
As the first commercial release of DOS from Microsoft®, IBM® Version 1.00 is the most historically critical to collectors and researchers alike. Considered to be the "Holy Grail" in terms of its collectible status, this version has the highest resale value of any version and continues to increase in price significantly more than rival versions in the early rare category.

We have been fortunate to buy and sell several of these releases over the years, but we have only seen a few for sale that were near-mint as this example represents. As media continues to age, it is the specimens of higher uncirculated/unused condition that remain viable into the future, and it is probable within the next five years only rankings of VG to Mint will survive the test of time. This will drive up price and drive down frequency of auction to perhaps only 1 every year or two for complete sets. Incomplete sets, disks only, or manuals only will continue to surface occasionally.

Rated: Prized.
Estimated Value (complete AND bootable):
Mint-$3000 VG-$1500 G-$1000
Disk only (bootable): Mint - $500 VG $250 G-$100
Manual First Edition: August, 1981
Manual First Ed. Revised: January, 1982

Vital Statistics:

Release Date: August, 1981
Disks in Set: 1
Diskette Form Factor:5.25", SS, SD 8 sectors per track
Capacity: 160k
Sector Size: 512 bytes
Track Size: 8 sectors
Disk Sides: 1
Total Tracks: 40
Total sectors: 319
File system: FAT12, sectors 1-2
Root directory capacity: 64 files, sectors 3-6
Data Area: sectors 7-319
Files on disk:40

Version string (sector 19, offset 1BAh)

00 B4 0E CD 21 E9 B9 FC 0D 0A 54 68 65 20 49 42 |           The IB

4D 20 50 65 72 73 6F 6E 61 6C 20 43 6F 6D 70 75 | M Personal Compu

74 65 72 20 44 4F 53 0D 0A 56 65 72 73 69 6F 6E | ter DOS  Version

20 31 2e 30 30 20 28 43 29 43 6f 70 79 72 69 67 | 1.00 (C) Copyrig

68 74 20 49 42 4D 20 43 6F 72 70 20 31 39 38 31 | ht IBM Corp 1981

0D 0A 24 4C 69 63 65 6E 73 65 64 20 4D 61 74 65 |   $Licensed Mate

72 69 61 6C 20 20 20 50 72 6F 67 72 61 6D 20 50 | rial - Program P

72 6F 70 65 72 74 79 20 6F 66 20 49 42 4D BA A1 | roperty of IBM

Notable Hex Editor contents:

Sector 00, offset 09h: "7-May-81"
Sector 00, offset 168h: "Robert O'Rear" (DOS programmer)
(also occurs at Sector 23, offset EAh)
Sector 07, offset 22h: "BIOS Version 1.00 22-July-81"
Sector 29, offset 8Ah: "David Litton" (author: disk utilities)
Sector 35, offset 88: "Mel Hallerman" (author: BASIC files)
Srctor 35, offset 9A: "Ron Heiney" (author: BASIC files)
Sector B2, offset 96h: "DEC-20 Downlink to Boca Raton [300-bps] 9-Apr-81"
Sector D3, offset 94h: "Glenn Stuwart Dardick" (author: BASIC files)

File Listing - Disk 1:

IBMBIO   COM	     1,920 07-23-81  12:00a SH

IBMDOS   COM	     6,400 08-13-81  12:00a SH

COMMAND  COM         3,231 08-04-81  12:00a

FORMAT   COM         2,560 08-04-81  12:00a

CHKDSK   COM         1,395 08-04-81  12:00a

SYS      COM           896 08-04-81  12:00a

DISKCOPY COM         1,216 08-04-81  12:00a

DISKCOMP COM         1,124 08-04-81  12:00a

COMP     COM         1,620 08-04-81  12:00a

DATE     COM           252 08-04-81  12:00a

TIME     COM           250 08-04-81  12:00a

MODE     COM           860 08-04-81  12:00a

EDLIN    COM         2,392 08-04-81  12:00a

DEBUG    COM         6,049 08-04-81  12:00a

LINK     EXE        43,264 08-04-81  12:00a

BASIC    COM        10,880 08-04-81  12:00a

BASICA   COM        16,256 08-04-81  12:00a

ART      BAS         1,920 08-04-81  12:00a

SAMPLES  BAS         2,432 08-04-81  12:00a

MORTGAGE BAS         6,272 08-04-81  12:00a

COLORBAR BAS         1,536 08-04-81  12:00a

BUG      BAS           640 08-04-81  12:00a

CALENDAR BAS         3,840 08-04-81  12:00a

MUSIC    BAS         4,224 08-04-81  12:00a

DONKEY   BAS         3,584 08-04-81  12:00a

BLUE     BAS         1,152 08-04-81  12:00a

HUMOR    BAS           640 08-04-81  12:00a

POP      BAS           768 08-04-81  12:00a

FORTY    BAS           768 08-04-81  12:00a

DANDY    BAS           640 08-04-81  12:00a

MARCH    BAS           768 08-04-81  12:00a

STARS    BAS           768 08-04-81  12:00a

HAT      BAS           768 08-04-81  12:00a

SCALES   BAS           640 08-04-81  12:00a

SAKURA   BAS           512 08-04-81  12:00a

CIRCLE   BAS         1,664 08-04-81  12:00a

PIECHART BAS         2,304 08-04-81  12:00a

SPACE    BAS         1,920 08-04-81  12:00a

BALL     BAS         2,048 08-04-81  12:00a

COMM     BAS         4,352 08-04-81  12:00a

       40 file(s)        136,405 bytes

                           6,144 bytes free

      160,256 bytes total disk space

        8,704 bytes in 2 hidden files

      145,408 bytes in 38 user files

        6,144 bytes available on disk

          512 bytes in each allocation unit

          313 total allocation units on disk

           12 available allocation units on disk

MD5 Signatures:

IBMBIO.COM 5F01E2438448C2FCBFCF296352CD5ACD IBMDOS.COM 3A1B572EC8958A796CD15BBAA99CEFBA COMMAND.COM D572C3DF143808773A0B0939FB9DA381 VER command: not available until IBM DOS 2.00

Version History:

The original release of the disk operating system for the PC as we know it today. Historically, this version is a critical point of departure for Microsoft®. IBM® discontinued providing release announcements for all software products prior to 1983, so our research efforts were careful to track down our information. There were some initial reports that version 1.00 was a pre-release not meant for public use and only saw distribution to dealers. This has taken on common assumption as fact across the Internet and elsewhere in the collector community, who have come to assume IBM DOS 1.10 was first.

But, in fact, version 1.00 was the first official release, pre-dating 1.10 by more than 8 months and it was available in conjunction with the first PC release on August 12, 1981. The original hardware product release bulletin states the 5150 came with "IBM Personal Computer DOS", and this version was referenced in several publications from the day. To determine the validity of this, we searched for the original programmer, Robert O'Rear, who was kind enough to communicate with us and provide information. We were also fortunate in finding a developer from the era through our network of contacts, who gave us first a person account of buying version 1.00 with his first PC for $40 at the product launch.

The mystery of no Microsoft copyright on IBM DOS 1.00 recently surfaced as an issue. As it turns out, the original release of this version, while copyright by IBM®, was entirely Microsoft® in origin as several publications eluded to (specifically the MS-DOS Encyclopedia by Ray Duncan). There has been no specific proof this was the case however until we were fortunate enough to have someone point out to us that they thought IBM® had written this release because it lacked a Microsoft copyright. Caught off guard, we immediately got in touch with Robert O'Rear and Tim Paterson who both validated our suspicion IBM® had requested it that way. Starting with version 1.10 the licensing agreement between IBM® and Microsoft® changed and both copyrights were present on the media.

With that controversy addressed, we can focus on the facts and start with this: this was a FAT12 file system with only a root directory - it did not support sub-directories. This version did not support any type of fixed disk. Version 1.00 was the first to logically infer two drive letters to one physical device, and it supported I/O redirection to reserved filenames. It required 8k of RAM memory to operate. IBM DOS version 1.00 was the finished prototype of Microsoft's® development efforts working with 86-DOS version 0.3 from December of 1980.

The Version 1.00 service life was short-lived, with only an 8 month period of exclusive circulation. The forensic datestamp of the latest file on the disk is IBMDOS at 8-13-81. We had the good fortune to receive information from senior Microsoft® insiders who were on the original team that IBM's decision was to flip datestamp bits to reflect the desired release date, vs. the physical date the version went to market. This means that the August, 1981 announcement date was not as tight relative to the physical release of the media from the lab as we first suspected.