CP/M. A Microcomputer Operating system devised by Dr Gary Kildall in 1975. CP/M was the dominant Operating System for 8 bit CPUs in the late 1970s. It was one of the three optional OSes available with the IBM PC. MSDOS -- which was similar and less expensive became the dominant OS in the early 1980s.

CP/M was influenced by minicomputer Operating systems -- primarily DEC's TOPS-10 OS used on their low end DEC-10 mainframe. CP/M separated the Basic Input Output system BIOS from the rest of the OS, and arrangement that has become standard in the IBM PC world at least. This innovation allowed the majority of the OS to be somewhat independent of the underlying hardware. The BIOS took care of the translation of services to the format of an idealized machine. This, in turn allowed CP/M to be used on a variety of platforms with minimal difficulty. CP/M also separated the Disk handling (BDOS) from the command processing (CCP) -- a concept carried over into MSDOS.

CP/M was known for it's small size and substantial capability. It was also noted for it's extreme user unfriendliness. Basic user applications such as spread sheets and word processors were available for CP/M

For most of it's life, CP/M was available from a company called Digital Research. Versions were available for a number of 8 bit CPUs including both Intel and Motorola products. Digital Research was eventually acquired by Caldera. CP/M is currently available as a commercial product (free for non-commercial use). The source code (that which hasn't been lost) is available free to non-commercial users.

http://www.mathcs.emory.edu/~cfs/cpm/ (Can not connect 20081225. Remove link if still dead in March)

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