Toby's correct. dknoll, what you're probably thinking about is that IBM had approached Gary Kildall about using CP/M as the operating system, and he either took too long getting back to them, wanted too much money for the deal, or something... I forget the specifics... but CP/M-86 could have been the OS of the 80's, and instead Digital Research ended up bankrupt.
there were some accusations back in the 80s that DOS was copied from CP/M, but those have been rebutted by several people. MS-DOS has always been a unique operating system, but it was designed to look like CP/M and to use a similar “interrupt” API system.
Interestingly enough, Microsoft also created an operating system for MSX computers called MSX-DOS... and it actually is compatible with CP/M. It can run many CP/M programs, and if you’re going to accuse an OS of being a clone, MSX-DOS is closer to being one than MS-DOS.