Master Control Program was the name given to the operating system of three different architectures of machines
manufactured by Burroughs (now Unisys). I have a very limited recollection (so perhaps others who remain better informed
can fill in the details). The McpOs which ran on mainframes is, as far as I can tell, the oldest operating system
still in use and actively supported. It was written in Algol 60 and had an Algol-like job control language called WorkFlowLanguage?
(WFL). It had a screen editor called CANDE (Command and Edit) which required the user to input line numbers. -- DonaldFisk
It also was the name of the evil computer in TronMovieCategoryOperatingSystem