I was always under the impression that DOS (or QDOS, if we want to pick nits) was essentially a clone of CP/M, even to the point of using CP/M code.
I know the historical record is muddy, and there are competing versions of the story, but I'm uncomfortable calling Tim Paterson the "original" author, when CP/M creator Gary Kildall was the one who really did so much from scratch.
EDIT: A very strong piece of evidence is the recent libel suit Paterson brought and lost against an author who called DOS a copy of CP/M:
"The Judge also agreed that Paterson copied CP/M's API, including the first 36 functions and the parameter passing mechanism, although Paterson renamed several of these. Kildall's "Read Sequential" function became "Sequential Read", for example, while "Read Random" became "Random Read"."
Did you read his blog? Because he addresses this very topic at some length.
Short version: he's never seen the CP/M code, and the similarity between the products isn't surprising, since they both are implementations of the same API.
He claims to have never seen the CP/M code, and I certainly don't have any inside knowledge as to whether that's true or not.
I've read claims that actual lines of CP/M could be found in QDOS. I've also read that Paterson "bought a CP/M manual and used it as the basis to write his operating system in six weeks."
Whatever the truth of the matter, it seems clear that QDOS got a real head start thanks to the existence of CP/M.
I'm not saying Paterson didn't do a lot of hard work, I'm just saying that the word "original" might be a stretch.
> I've read claims that actual lines of CP/M could be found in QDOS.
[citation needed]
Given the large differences in hardware, this seems pretty unlikely. But given they did implement the same API, I suspect that could be the source of some confusion.
> I've also read that Paterson "bought a CP/M manual and used it as the basis to write his operating system in six weeks."
Paterson owned a machine running CP/M and wrote software for it.
> Whatever the truth of the matter, it seems clear that QDOS got a real head start thanks to the existence of CP/M.
He actually attacks that notion head on in the blog, if you'd bothered to read that far. Basically he says that they needed an API and he thought using an existing one would pull developers in. If someone would have sued them right away they would have just changed the API--they weren't really wedded to it and it's not the most important part of the OS.
He also claims that if CP/M did anything it was that it proved that a "real" OS could be run on a microcomputer.
I know the historical record is muddy, and there are competing versions of the story, but I'm uncomfortable calling Tim Paterson the "original" author, when CP/M creator Gary Kildall was the one who really did so much from scratch.
EDIT: A very strong piece of evidence is the recent libel suit Paterson brought and lost against an author who called DOS a copy of CP/M:
"The Judge also agreed that Paterson copied CP/M's API, including the first 36 functions and the parameter passing mechanism, although Paterson renamed several of these. Kildall's "Read Sequential" function became "Sequential Read", for example, while "Read Random" became "Random Read"."
http://www.theregister.co.uk/2007/07/30/msdos_paternity_suit...