Oldest known version of DOS unearthed – MS-DOS ancestor 86-DOS version 0.1 C is now available on the Internet Archive

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Disk contains just nine files, two of them for a chess game.

86-DOS version 0.11
(Image credit: Archive.org / f15sim)

An incredibly early release of 86-DOS has been found, imaged, and shared on the Internet Archive. The disk appears to be an original release of version 0.1 C of 86-DOS from Seattle Computer Products (1980) and includes several utilities, along with a game. Moreover, according to the disk label, what we see is just the eleventh disk off the duplication line. This is an important finding, as 86-DOS is a direct ancestor of PC DOS and MS-DOS.

(Image credit: Archive.org / f15sim)

Archive.org member f15sim shared the early 86-DOS disk image on the Internet Archive’s site just ahead of the New Year.  We even get to see a photo of the disk in its paper sleeve, where “Serial #11” can be seen printed. Before this 86-DOS release was unearthed on its 5.25-inch floppy disk, the earliest version that had been saved for posterity was version 0.34.

PC operating system enthusiasts like NTDEV have already investigated and tested the ancient 86-DOS version 0.11. If you click to expand the Tweet, you'll see an exploration of the disk image contents and a short discussion of the OS, which was created to offer computer users and vendors a CP/M-like operating environment for 8086-based systems.

NTDEV highlights the Spartan nature of 86-DOS version 0.1 C. The OS is delivered as a floppy disk containing just nine files. The core OS standard COMMAND.COM was included, which interprets command line instructions like dir, copy, clear, and format. The disk also contained utilities for file and disk copying, a basic text editor, plus two or three development utilities.

The development utilities were important to 86-DOS releases as users would be short on software unless they sourced or translated existing 8-bit Z80 CP/M programs for the 8086 architecture. Thus, there was an assembly language program called ASM.COM, a code compiler app called HEX2BIN.COM, and a Z80 to 8086 translator dubbed TRANS.COM.

Last but not least, it is interesting to see that an OS as primitive as this release included a game. CHESS.COM was accompanied by instructions in CHESS.DOC, which would probably be essential reading on a no-graphics rendition of this complex strategic game.

To test 86-DOS yourself, you can grab the disk image directly from Archive.org and then follow the instructions provided here to get a working SIMH/AltairZ80 Simulator compatible with the disk image.

You can read much more about the history of 86-DOS, PC DOS, MS-DOS, and more on the Wikipedia page.

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Mark Tyson
Mark Tyson
News Editor

Mark Tyson is a news editor at Tom's Hardware. He enjoys covering the full breadth of PC tech; from business and semiconductor design to products approaching the edge of reason.

12 Comments Comment from the forums
  • abufrejoval
    When you wrote "Here is one of the earliest builds of what became Microsoft's darling.It's been compiled in July 1980, and less than 10 people had seen it.Until now." that immediately rang wrong, because compilation at the time was stricly applied to high level languages and I'm rather sure this was written in assembly code.

    In fact I'd hazard that pretty nearly all DOS variants like its CP/M brethren were written in assembly, which is why Unix was such a revolutionary approach when it was re-written in C.

    But even if the 8088 in fact allowed for the giant amount of 640KB of RAM, the first generation systems often had much less, wouldn't even have the full complement of 64KB. Pretty sure the original IBM-PC actually didn't take more than 64KB on the mainboard but at the time RAM expansion was still done via expansion cards.

    When you fight for every byte you didn't dare use a compiler for a DOS, even if you had one, which early on they obviously didn't.
    Reply
  • coromonadalix
    where's my Dolorean loll wow loll they still exist ... and the guy put other oldies on Archive. ...
    Reply
  • adamXpeter
    abufrejoval said:
    When you wrote "Here is one of the earliest builds of what became Microsoft's darling.It's been compiled in July 1980, and less than 10 people had seen it.Until now." that immediately rang wrong, because compilation at the time was stricly applied to high level languages and I'm rather sure this was written in assembly code.

    In fact I'd hazard that pretty nearly all DOS variants like its CP/M brethren were written in assembly, which is why Unix was such a revolutionary approach when it was re-written in C.

    But even if the 8088 in fact allowed for the giant amount of 640KB of RAM, the first generation systems often had much less, wouldn't even have the full complement of 64KB. Pretty sure the original IBM-PC actually didn't take more than 64KB on the mainboard but at the time RAM expansion was still done via expansion cards.

    When you fight for every byte you didn't dare use a compiler for a DOS, even if you had one, which early on they obviously didn't.
    Please note that assembly is not machine code, it is compiled, too.
    Reply
  • leoscott
    abufrejoval said:
    When you wrote "Here is one of the earliest builds of what became Microsoft's darling.It's been compiled in July 1980, and less than 10 people had seen it.Until now." that immediately rang wrong, because compilation at the time was stricly applied to high level languages and I'm rather sure this was written in assembly code.

    In fact I'd hazard that pretty nearly all DOS variants like its CP/M brethren were written in assembly, which is why Unix was such a revolutionary approach when it was re-written in C.

    But even if the 8088 in fact allowed for the giant amount of 640KB of RAM, the first generation systems often had much less, wouldn't even have the full complement of 64KB. Pretty sure the original IBM-PC actually didn't take more than 64KB on the mainboard but at the time RAM expansion was still done via expansion cards.

    When you fight for every byte you didn't dare use a compiler for a DOS, even if you had one, which early on they obviously didn't.
    Memory16 KB – 256 KB (motherboard)
    Reply
  • Joseph_138
    I would fully expect Microsoft to send in the lawyers. Technically, DOS is still under copyright protection, as it isn't old enough, yet. The first Mickey Mouse cartoon has only just passed out of copyright protection, and that was released in 1928.
    Reply
  • Korgz
    adamXpeter said:
    Please note that assembly is not machine code, it is compiled, too.
    Except it isn't. Assembly language is "Assembled" by either a single pass or multi-pass assembler. Note: if it was actually compiled then it would indicate a level of portability that Assembly simply does not have. Before commenting I would recommend you do a few tutorials or actually try writing your own assembly code as it would teach you the basics of how opcodes, operands from an assembly language etc get assembled into machine code.
    Reply
  • abufrejoval
    adamXpeter said:
    Please note that assembly is not machine code, it is compiled, too.
    That interpretation might have held true at about 1952 when Grace Hopper first used the term for A-0.

    But that changed already in 1957 when the first Fortran compiler was finished by John Backus & al.

    Grace then sure pushed for much higher abstraction levels with the Common Business oriented Language aka COBOL in 1959. She redefined the term she created to imply an abstraction level of the code which was above machine code.

    That's not the case for assembly.

    Nobody would have called CP/M ASM or MS-DOS MASM compilers and I have no idea what Seattle computers used, perhaps some type of Intel MDS-80 Blu Box with an Intel furnished assembler and linker.

    And in case you haven't had a chance to enjoy Grace, please have a look here. She sure was a lot of character in a tiny body!
    Reply
  • abufrejoval
    leoscott said:

    Memory16 KB – 256 KB (motherboard)
    Early revisions of the IBM PC had 16KB soldered and allowed expansion to 64KB via DIL sockets using 16Kbit RAM chips.
    Later revisions featured 64KBit RAM chips, had 64KB soldered and could be expanded to 256KB on the mainboard.

    The first one I used at work was already an IBM PC-XT, probably with 128KB.

    I should really remember, because IBM PCs used hardware parity for RAM, which had to be initialized on a cold start. So I remember staring at the top right, where RAM was being checked and parity was initialized for quite a few seconds with RAM amount counting upward before the system would finally boot.

    It also had a Hercules graphics card for 720x348 monochrome bitmapped graphics, which was the main justification for the purchase of that system over using time shared mainframes.

    Of course it had this giant 5 1/4" 10MB full height hard disk, which was still called a "Winchester Drive" and it ran PC-DOS 2.0 with subdirectories to manage it.

    I ran quite a few variants of CP/M on my own Z-80A and Z-80B systems at home before and during that time until I could afford an 80286.

    I don't know where I got the CP/M 2.2 -3.0 assembly source code, but I did have it and read it "cover-to-cover" at the time. Just like Unix v6, written in C, where we went through the full source code at university.
    Reply
  • dmitche31958
    Admin said:
    An incredibly early release of 86-DOS has been found, imaged, and shared on the Internet Archive. This is an important find as it is a direct ancestor to PC DOS and MS-DOS.

    Oldest known version of DOS unearthed – MS-DOS ancestor 86-DOS version 0.11 is now available on the Internet Archive : Read more
    I'm sorry but this is so not interesting that I have to respond. This is not similar to finding a "direct ancestor", but simply an earlier, undeveloped work-in-progress. No one will be jumping through hoops to download and use it. There is no new found information here, other than to show what hadn't been developed into the OS at this point in time.
    Reply
  • JeffreyP55
    Admin said:
    An incredibly early release of 86-DOS has been found, imaged, and shared on the Internet Archive. This is an important find as it is a direct ancestor to PC DOS and MS-DOS.

    Oldest known version of DOS unearthed – MS-DOS ancestor 86-DOS version 0.11 is now available on the Internet Archive : Read more
    Not very excited. Taught myself DOS way back in the Pleistocene. No need to revisit it. A minimalist few commands still in windows.
    Reply