This could be the tech world’s version of a conviction being overturned by new DNA evidence.

A forensic analysis conducted for the latest issue of IEEE Spectrum magazine appears to have answered one of the biggest mysteries of the PC era: Was the landmark MS-DOS operating system that Bill Gates and Microsoft licensed to IBM an original piece of work, or stolen goods?

Sure, it’s ancient history, but it was a pivotal moment in the rise of the personal computer industry, and perhaps the most important business deal Microsoft ever made.

Gary Kildall, the late creator of the operating system CP/M, had accused Microsoft of profiting unfairly from his work, alleging that CP/M was copied by QDOS, the operating system that Microsoft acquired from Seattle Computer Products to create MS-DOS.

Not so, writes Bob Zeidman of Software Analysis and Forensic Engineering Corp., describing his analysis of CP/M and MS-DOS in IEEE Spectrum.

He concludes. “Every lead brought me not to Bill Gates but to a dead end. QDOS was absolutely not copied from CP/M, and MS-DOS showed no signs of copying either. Kildall’s accusations about Bill Gates were totally groundless.”

Read the full article here. It will be interesting to see if this finally puts the issue to rest.

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  • Terrence Andrew Davis

    I wrote all 135,000 lines of LoseThos.

  • Ferd

    um… QDOS was for the 8086, a16 bit chip. the “forensics” were done with the 8 bit 8080 version of CP/M. no wonder he found nothing in the object code.

  • Burning Granite

    I was skeptical but becoming convinced until I reached the end of the full article. When Zeidman suggested that DEC’s VMS could be an antecedent of MS/DOS he lost all credibility. VMS evolved from RSX (Dave Cutler’s first o/s, NT was his third; in those days I was doing kernel work on RSX), with totally different concepts than DOS. Unix also had totally different conceptual underpinnings. RT-11 was actually the model for both CP/M and the DOS variants. And it is quite possible that the design was copied without copying the code, which would still be a theft of intellectual property giving a tremendous leg up on time to market. It also would be difficult to litigate, or detect with Zeidman’s obviously limited knowledge and tools.

  • Aaron Evans

    Funny, Microsoft actually claimed to have bought QDOS and modified it for the IBM PC. It seems beyond credibility that the MSDOS code bore no trace of a resemblance to the QDOS code it was derived from. Either the tooling or the agenda of it’s user are flawed.

    Microsoft did this because IBM wanted a contract. They were very open about it. The only question was whether QDOS had stolen CP/M source code.

    • guest

      LOL. Don’t like the conclusion, so shoot the messenger. Trolls are so predictable.

      • you_know_it

        Like you.

  • Steven D. Brown


    MS-DOS/PC-DOS was intellectual property derived or cloned,if not outright duplicated from CP/M and QDOS based on the Intel 8080 microprocessor.

    Looks like Microsoft wants to rewrite history.

    Next they will be offering proof that Windows wasn’t ripped off from Xerox’s Palo Alto Research Center by Steve Jobs and Apple. And subsequently by Bill Gates and Microsoft.

    • guest

      Um, proof? He provides three pages of it in support of his conclusion. You offer nothing.

      • Steven D. Brown

        Were you there? Did you run CP/M, QDOS, MS-DOS, and PC-DOS? Doesn’t sound like it! How could you be taken in by such a blatant distortion of the truth!

        Editor’s Note: Upon publication, this article failed to properly
        disclose the connection between its author, Bob Zeidman, and Microsoft
        Corp., a key subject of the story. Mr. Zeidman is currently retained by Microsoft as an expert witness in Motorola Mobility v. Microsoft. IEEE Spectrum regrets the omission.

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