- This website is a Work In Progress dedicated to CP/M (Control Program for Microcomputers) which was (and is) an operating system similar to MS-DOS but which predated MS-DOS, and which is in fact the operating system that MS-DOS descended from. But CP/M is much more than simply an early version of MS-DOS and CP/M is very much alive in online communities of Enthusiasts and Others who still use CP/M in Old (and sometimes newer) Computers and Emulators.