MS-DOS was *not* an illegal clone of CP/M

• cpmish

  15 332 8.6 Assembly

  An open source sort-of CP/M 2.2 distribution.

Huh. Lost my part-written comment somehow.

Anyway, hi, author/submitter here.

I have heard several versions of this story. Most seem to be unsubstantiated AFAICT.

The one that seems to add up is that Dr Kildall claimed that only he knew why some DOS APIs took the exact parameters they did.

Which ISTM is fair enough, if they were written using DR documentation. As I said, DR intended the API docs to be for app writers, but that didn't stop people using them to write compatible OSes, and lots of companies did.

That's how come David Given's amazing CPMish OS was possible:

https://github.com/davidgiven/cpmish

CPMish combines existing BDOS and BIOS replacements and other components. It puts together so many existing replacement parts for parts of CP/M-80 that nothing of the original was left. Theseus' ship, in software:

https://en.wikipedia.org/wiki/Ship_of_Theseus

There was a code investigation that looked for any DR code in the early MS-DOS binaries:

• InfluxDB

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