The CP/M operating system was an early single-user operating system produced by Digital Research, Inc. (DRI). The acronym CP/M stands for Control Program for Microcomputers. The CP/M operating system was based primarily on Intel microprocessors. The first DRI operating system, the CP/M-80, was the most popular operating system for Intel 8080 and Zilog Z80 microprocessor-based microcomputers. DRI also developed CP/M-86 for Intel 8086/8088-based computers, CP/M-Z8000 for Zilog Z8000-based computers, and CP/M-68K for Motorola 68000-based computers. At its height DRI was selling over a quarter-million copies annually of the CP/M operating system to run on 3,000 different types of microcomputers.

American computer scientist Gary Kildall (1946-1998) wrote the original CP/M software in 1974 while working on a project that he had contracted with Intel Corporation several years earlier. Kildall's product was the first true operating...