DOS vs CP/M Dispute Comes Full Circle

The writer of DOS, Tim Paterson, had sued for libel after a book by Harold Evans claimed that DOS copied CP/M. Paterson lost his case.

Part of the evidence of copying is that the first 26 system calls worked the same in DOS as in CP/M.

The tragedy of CP/M's author, Gary Kildall, was the apocryphal story that, always denied by Kildall that, when IBM came to his company to license CP/M for the original IBM PC, Kildall was out flying his plane.

So IBM went to Bill Gates for an OS, and Gates bought DOS and licensed it to IBM and the rest is history.

Kildall, although a multi-millionaire, was a disappointed man, and died four years ago after cracking his head in a Monterey bar.

Kildall was plagued by what might have been, and by the fact that, whenever he met someone new, they would invariably ask: ‘Was it true you were out flying when IBM came calling?’