DeveloperSeattle Computer Products / Tim Paterson
Source modelClosed source
Initial release86-DOS 0.11
(August 1980)
Latest release86-DOS 1.14
(December 1981)
Supported platformsx86
Kernel typeMonolithic
User interfaceCommand-line interface

86-DOS, known internally as QDOS and occasionally in official documents as Seattle DOS and SCP-DOS,[1] is an operating system developed by Seattle Computer Products that was later licensed[2] and then bought[3] by Microsoft and used as the basis for IBM PC-DOS and MS-DOS.

History[edit | edit source]

Seattle Computer Products created and put up for sale one of the first 8086 computer kits, but its sales were minimal due to the lack of software written for it.[4] CP/M-86, expected to be the first venture into the 8086 software world, had been delayed since December 1979,[5][6] and by February 1980 they felt pressure to supply something for their devices.

Employee Tim Paterson, who had done hardware work at Seattle Computer Products prior to 1980 and only some software work in college,[7] got the idea of creating his own operating system during the time he was working on the company's 8086 board.[6] On or around February 6, 1980, Paterson had a board meeting with Rod Brock, owner of Seattle Computer Products, who gave him the go-ahead on his idea.[8] One of the primary goals of the operating system was translation compatibility with CP/M,[9][10] so most internal functions were reimplemented based on the CP/M-80 manual.[11] Another goal was a more efficient file system, reimplemented from his memory of an unfinished 8-bit operating system known as Microsoft Interrupt Driven Asynchronous System (MIDAS,[9] or MDOS[12] before 1980[a]), written by Marc McDonald,[9][12] which he learned about during the 1979 National Computer Conference.[7][b] Further inspiration was taken from North Star and Cromemco's variants of CP/M-80,[5] UCSD p-System, Unix,[7] CDC SCOPE, Cromemco RDOS, and the IMSAI 8080 Self-Contained System.[8]

Development officially began in April 1980,[4][c] with code written in MicroPro WordMaster[7][15] on on a Cromemco Z80 computer[15][16] running CDOS.[7] While some code was written in pure 8086 assembly, most was written in the more familiar Z80 assembly and then translated using Paterson's Z80 to 8086 translator, TRANS-86,[7][17] for testing on the Seattle Computer Products 8086 system.[18] The operating system was in a workable state by late July, with Paterson spending about half of his time on its development.[4][19] Though it wasn't completely finished, Paterson figured a quick release was more important than adding all the features.[20]

The very first 86-DOS advisement was submitted in July 1980 and appeared in the August 1980 issue of the BYTE Magazine[21] and the August 25 issue of Computer Business News[22]. It costed $95 for SCP hardware owners and $195 for other buyers at launch.[21] The advertisement was likely for 86-DOS 0.11, however due to press deadlines, it was submitted before 86-DOS 0.11 was ready, and hence the features described in the advertisement were Rod Brock's prediction.

Microsoft license[edit | edit source]

On the morning on September 22, 1980, about a month after 86-DOS 0.11 was released, Paul Allen of Microsoft called Rod Brock of Seattle Computer Products and told him they had an anonymous customer (IBM) interested in sublicensing 86-DOS.[23] The next day, they reached a verbal agreement, and on the 24th the terms of the nonexclusive sublicense were set in stone.[23] The license agreement was finally signed on January 6, 1981.

Microsoft purchase[edit | edit source]

Microsoft purchased 86-DOS in summer 1981 and renamed it to MS-DOS, shortly before the initial release of PC-DOS.

Lomas OEM[edit | edit source]

86-DOS is known to have been sold by Lomas Data Products with their LDP88, an 8088 processor, and LDP72, their floppy disk controller. 2 ads were posted for this OEM, with one being from October 1980[24] and another being from December 1980.[25][d] In both ads, the OEM was priced $195, having no markup on the original retail price.[24][25][26]

List of known versions[edit | edit source]

Preliminary versions[edit | edit source]

Final releases[edit | edit source]

See also[edit | edit source]

Notes[edit | edit source]

  1. The exact date of the name change is unknown, but drafts of the user manual from 1979 and 1980 give an approximate date.
  2. The implementation of MIDAS' file system failed on two fronts. First, the write order of the FAT and corresponding directory sector was flipped (so the FAT was written second), allowing for "orphan" files to be created. Second, Paterson forgot to implement a stopper indicating when there were no further directory entries in the track, causing a significant slowdown when only a small number of sectors needed to be read.[13]
  3. After his February board meeting, Paterson preemptively updated the 8086 monitor he wrote in 1979 (MON-86) to include a "trace" command.[14]
  4. The second ad, posted in December, was most likely submitted by October due to press deadlines.

References[edit | edit source]

  1. United States District Court for the Western District of Washington (25 July 2007). Paterson v. Little, Brown, and Co., et al. - Order. Seattle Times. Case 2:05-cv-01719-TSZ Document 29.
  2. Brock, Rod; Allen, Paul (6 January 1981); Iowa District Court for Polk County. 86-DOS License Agreement with Microsoft; Plaintiff's Exhibit #1, Comes v. Microsoft.
  3. Brock, Rod; Allen, Paul (27 July 1981); Iowa District Court for Polk County. 86-DOS Agreement of Sale with Microsoft; Plaintiff's Exhibit #2, Comes v. Microsoft.
  4. 4.0 4.1 4.2 Hunter, David (March 1983). The Roots of DOS: Tim Paterson. Softalk for the IBM Personal Computer. p. 12-15.
  5. 5.0 5.1 Paterson, Tim (30 September 2007). Design of DOS. DosMan Drivel.
  6. 6.0 6.1 Bornstein, Howard (1986). MS-DOS (Versions 1.0-3.2) Technical Reference Encyclopedia. Microsoft Press. p. 8. ISBN 0-914845-69-1.
  7. 7.0 7.1 7.2 7.3 7.4 7.5 Paterson, Tim (4 August 2018). VCF West XIII -- Tim Paterson -- Original DOS and the old days. Vintage Computer Federation.
  8. 8.0 8.1 United States District Court for the Western District of Washington (18 January 2007). Paterson v. Little, Brown, and Co., et al. - Deposition Upon Oral Examination of Tim Paterson. Case 2:05-cv-01719-TSZ Document 14-2.
  9. 9.0 9.1 9.2 Manes, Stephen; Andrews, Paul (1993). Gates: How Microsoft's Mogul Reinvented an Industry—and Made Himself the Richest Man in America. Doubleday. p. 280-281. ISBN 0-385-42075-7.
  10. Välimäki, Mikko (2005). The Rise of Open Source Licensing. Turre. p. 88. ISBN 952-91-8779-3.
  11. Cringely, Robert (June 1996). Triumph of the Nerds: The Rise of Accidental Empires (Season 1). PBS.
  12. 12.0 12.1 Duncan, Ray (1988). The MS-DOS Encyclopedia. Microsoft Press. ISBN 1-55615-049-0.
  13. Personal communication to Marc McDonald, February 12, 2022.
  14. Paterson, Tim (February 18, 1980). 8086 Monitor Version 1.4A Instruction Manual. PatersonTech.
  15. 15.0 15.1 Glatzer, Hal (March 1984). Reflections on Past and Future With the Man From MS-DOS. Software News. p. 44 & 46.
  16. Watt, Peggy (7 April 1986). MS-DOS creator Tim Paterson earns place in industry annals. Computerworld. p. 54.
  17. Microsoft Macro Assembler (MASM) Unofficial Changelist. BytePointer.
  18. Paterson, Tim (24 November 2007). The First DOS Machine. DosMan Drivel.
  19. Rojas, Raúl (April 2001). Encyclopedia of Computers and Computer History (A-L). Fitzroy Dearborn. ISBN 1-57958-235-4.
  20. Watt, Peggy (12 August 1991). PC-DOS, also 10, has its own storied past. Infoworld. p. 48.
  21. 21.0 21.1 Seattle Computer Products (August 1980). BYTE Ad. BYTE Magazine. p. 173.
  22. Seattle Computer Products (25 August 1980). Computer Business News Ad. Computer Business World. p. 16 & 18.
  23. 23.0 23.1 Manes, Stephen; Andrews, Paul (1993). Gates: How Microsoft's Mogul Reinvented an Industry—and Made Himself the Richest Man in America. Doubleday. p. 285-286. ISBN 0-385-42075-7.
  24. 24.0 24.1 Lomas Data Products (October 1980). BYTE Ad. BYTE Magazine.
  25. 25.0 25.1 Lomas Data Products (December 1980). BYTE Ad. BYTE Magazine.
  26. Seattle Computer Products (November 1980). BYTE Ad. BYTE Magazine.