So what? – Court ruling supports claims that Microsoft’s first OS was stolen — I didn’t even know this lawsuit was going on. I discuss the folklore of this story on today’s Tech5 podcast here. Look for the episode titled: Who Wrote DOS

Dismissing a defamation suit brought by the inventor of DOS against a British writer, a judge has left unchallenged computer industry lore that holds the operating system Microsoft licensed to IBM in the 1980s — thereby launching Bill Gates’ multibillion dollar software empire — was a knock off.

In a book on American innovation, author Sir Harold Evans wrote that DOS inventor Tim Paterson relied heavily on an existing OS called CP/M (Control Program/Monitor) created by a programmer who has since died. Microsoft in 1980 struck a licensing deal with Paterson’s company — Seattle Computer Products — to obtain access to DOS and resell it to IBM.

  1. Steve S says:

    And who says “Software engineering ain’t pretty”

  2. bobbo says:

    I recall a documentary on the telly regarding Bill Gates contracting with IBM for its OS when at the time he had nothing to sell. Bit vague then as to whether he ripped that guy off or bought it very cheaply as he arbitraged that OS with IBM.

    Isn’t all of software writing “kinda obvious” and very little of it should be patentable? I think so. Compete on consumer friendliness, not the nuts and bolts.

    Similarly, been looking for confirmation on the “Business Acumen” of Bill Gates. I read somewhere that Bill tried to sell his OS to IBM in the early days for about $75,000 but the lawyers at IBM said not to do it as they feared a vertical monopoly charge.—ie, all the so-called experts giving the wrong advice. Great story, but helps if it is true?

  3. iGlobalWarmer says:

    Hey John, are you trying to speak jive in your header summary”

    “One or two tidbits alone can make this the most important five minutes of you life.”

    Heh, heh….

  4. iGlobalWarmer says:

    #2 – the book wasn’t claiming Bill Gates ripped off Tim Paterson, it was claiming that Tim Paterson ripped off Gary Kildahl’s CP/M.

    Bill’s purchase from Paterson was perfectly above board (although a “steal” pricewise).

  5. Mark Derail says:

    What #5 said

    // oh noes agreeing with Global Warmer again…
    // (where’s those tofu chips!)

  6. TooMuchTravel says:

    The headline, while protected by free speech, is nonetheless slander and defamation itself. Microsoft stole nothing. It was legitimately purchased from Paterson, who later called it SeattleDOS. Where Paterson got it from was the contention point.

    The ruling has to due with a wrongful slander claim against the author, whose research is correct. CP/M is itself a derivative of features in DEC ooperating systems, and its source code became branched by many companies, ranging from Intertec to Microsoft themselves. Microsoft used to sell CP/M for the Apple II along with a Z80 CPU board.

    Microsoft in this case stole *nothing*. Shame on you.

  7. Peter Rodwell says:

    it was claiming that Tim Paterson ripped off Gary Kildahl’s CP/M

    I never saw Paterson’s original OS but I certainly remember both CP/M and the first (marketed) version of MS-DOS. Certainly the similarities were very many. Some of the MS-DOS error messages were slightly less user-hostile than those of CP/M and I’m almost certain that MS-DOS had sub-directory capabilities from the start while CP/M didn’t. Then to confuse things, DR brought out CP/M-86, which was just a 16-bit conversion of 8-bit CP/M and just as unfriendly…

  8. Ballenger says:

    Nice picture. Too bad there aren’t videos of those early meetings between MS and Big Blue. They must have scored as high on the not on the same page scale as Sacagawea trying to explain Lewis and Clark to the Shoshones.

  9. Joe says:


    “…and I’m almost certain that MS-DOS had sub-directory capabilities from the start while CP/M didn’t.”

    I don’t believe DOS 1.0 supported directories. That is the way I remember it anyway.


  10. Atomic Bitchwax says:

    I don’t believe DOS 1.0 supported directories. That is the way I remember it anyway.

    Nope. Directories didn’t come along until DOS 2.0, released along with the first IBM PC with a hard drive. (PC-XT). Without a hard drive, you didn’t really need directories.

  11. Dauragon88 says:


    Im so sorry…..I couldn’t help it……..

  12. Billabong says:

    I don’t see a bong in this picture it must be a fake.

  13. Les says:

    All of the BDOS function call are the same in DOS (Int 21) and CP/M (call 5).

    It pretty obvious.

  14. joshua says:

    OMG….it’s nothing short of a mircle that ANY of those people ever got laid… fact….I’ll bet some of them still haven’t….. 🙂

  15. Angel H. Wong says:


    Again, the difference between a gay nerd and a straight nerd is that a gay nerd is virgin by choice.

  16. edwinrogers says:

    Does this mean that everything MS have ever made and earned are proceeds and subsequent earnings of crime? Just curious about where this is going.

  17. Les says:

    DOS 2 had sub directories, and was quite different from CP/M. DOS 1 on the otherhand, was almost identical. Only the utilties were changed “to protect the inocent”. DDT became debug, PIP became copy, etc.

  18. Les says:

    Actualy CP/M had “user levels” which functioned as 16 seperate directories (although all files were stored in the same directory).

    Almost no CP/M users were aware of the user levels. New word allowed you to select user levels from inside the program.

  19. Lou says:

    Nothing to see here folks…. Supposedly gary kildal (CP/M) ripped off lots of syntax from a DEC PDP operating system.


    As a CP/M programmer (along with many other 70;s and 80;s OS’s), I do have a nostalgia for lean and mean OS’s (not that I ever want to write a printer driver again).

  20. tallwookie says:

    bah this is **OLD** news, ive known about this for years

    back in the 17th century, if you plagerized somone’s work it was considered a compliment to them – jebus, what 400 years can do

  21. Cinaedh says:

    I always thought CP/M stood for Control Program/Microcomputer. I learn something new every day on DU. Also, if you knew CP/M, you already knew DOS except for little confusing things like copy from – to instead of copy to – from.

  22. Frank IBC says:

    #12 – LOL!

  23. cheese says:

    What? DOS is ripped off from CP/M? Who would have guessed?

    I was always under the impression that:
    Unix | CPM | DOS

  24. Mr. Fusion says:

    #12, Dauragon

    Great one.

  25. MattD says:

    Alot of you are aware that PBS did a documentary detailing much of this is in a program called “Triumph of the Nerds”.

    The main page also includes a link to the transcript of the program:

    Much of this early DOS info (QDOS, PC-DOS 1.0) can be found in part two of the transcript:

    Patterson essentially admits to hacking CP/M as a personal project. MS was aware that this was a hacked version of CP/M at the time of purchase.

  26. oldoldguy says:

    $50k for QDOS was a big win for Seattle Computer Products.

    In 1981 $50k hard cash was a windfall profit for any engineering firm.

    SCP was selling computer boards, not even entire computers. They needed an 8086 OS in order to sell their 8086 boards. So SCP was looking at “giving away” the OS with every computer board.

    $50k was probably more profit than they would make with the entire company in two years.

    What is wrong with a “Copied CP/M”? Go back a few years and learn that CP/M is actually based on a Digital Equipment Corp (DEC) operating system. (TOPS-10) which used programs like PIP and a similar file naming system. (MS hired DEC’s VAX-VMS author, Dave Cutler, to lead the first version of Windows NT.) Microsoft renamed commands like “PIP” to “COPY” and did the world a big favor.

    Oh yeah, I read somewhere that IBM sold around 35k PCs in 1981-1982. Microsoft didnt exactly make back much of their MSDOS costs. Not until Mitch Kapor started shipping 1-2-3 for the IBM….. then the real fun started…


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