CP/M
In 1975 Gary Kildall introduced the CP/M operating system. In 1976 he founded Digital Research, Inc. Digital Research marketed and supported CP/M and other CP/M based operationg systems. CP/M was originally written for the Intel 8080 microprocessor based computers, although later processors, like the Intel 8085 and the Zilog Z80 also support CP/M.
At one time CP/M was the dominant operating system for personal computers. Many machines used it. The Kaypro II, Osborne 1, Morrow Decision, and other computers all used this system.
If you would like to learn more about CP/M there were many good books on the subject. Here are some titles to check out:
cp/m bible The
Authoritive Reference Guide to CP/M
By Mitchell Waite and John Angermeyer
Published by Howard W. Sams & Co. Inc.
CP/M and the Personal Computer
By Thomas A. Dwyer and Margaret Critchfield
Published by Addison-Wesley Publishing Company