CP/M and DOS

CP/M, as many people know, was written by Gary Kildall and based on his earlier microcomputer work, GK had done, namely PL/M. CP/M denotes Control Program for Microcomputers, PL/M denotes Programming Language for Microcomputers. The best story I know - about him, CP/M and his company Digital Research - is here.

CP/M86, which everybody thought to become the standard OS for the Intel side of the micropocessor world was not ready to ship plus it's probably true that Gary snubbed IBM when they wanted to negotiate a good deal for their upcoming Intel 8088 personal computer.

The "not-readiness" was what lead Tim Paterson to write a reduced clone of CP/M under the name of QDOS to make a development board with 8086 hardware work.

MS-DOS (PC-DOS) 1.0 felt a lot more like CP/M than what we know under that name now. Interestingly MS-DOS 2 seems to have been a nearly complete rewrite modeled more after Unix (Xenix) the sourcecode and rights for microcomputers of which MS's Paul Allan had licensed in '79 or so and which, running on Motorola based hardware, was the most important OS inside MS through the 80ies. MS-DOS 2 supported hard disks and hierarchical directories. It seems though that for a number of reasons MS didn't go or get very far in the process of cloning Unix.

CP/M however had been modeled by Kildall after a DEC OS for PDPs, probably TOPS-10 or -20. When CP/M 86 was ready to ship it was a lot more expensive than DOS and although it might have been better than DOS in some ways, the whole SW cycle was just starting anew with software like Lotus 123 that was tightly knitted to hardware, the IBM basic input and output system and MSDOS functions calls. Lotus outperformed every other spreadsheet in its day. And spreadsheets, lest we forget, was what carried personal computers to its first wide spread successes.

Still it can be said that in terms of OS paradigm development it was PC-DOS that made the Unix paradigm win out over all other proposals in the world of small computers, namely the DEC TOPS and VMS models. plink, nix,    praise or blame!