MP/M

MP/M, short for Multi-Programming Monitor Control Program, was a multi-user operating system that Digital Research developer Tom Rolander created in 1979 as a multi-user extension of the company's single-user CP/M. It let several users connect to one computer at once, each from a separate terminal, and let each user run and switch between several of their own programs at the same time, using a priority-scheduled multitasking kernel with memory protection, concurrent input and output through XIOS, and support for print spooling and queueing. Digital Research built versions of MP/M for both 8 bit processors, the 8080 and Z80, and 16 bit processors, the Intel 8086 and 80286, each under its own version name. Originally proprietary, MP/M was later open sourced, with Caldera and then Lineo permitting redistribution and modification of Digital Research's source code starting in 1997. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/