CP/M

It was created in 1974.

It is a mass-market operating system. It stands for Control Program/Monitor. This helped many businesses.

Gary Kildall designed CP/M with his own PL/M

Programming language was designed to control 8-16 bit processors

Early versions of CP/M had 8-bit processor

Created for Intel 8080/85 based microcomputers

It was displaced by DOs after introduction of IBM PC

References

https://en.wikipedia.org/wiki/CP/M