Compatible Time-Sharing System

The Compatible Time-Sharing System, or CTSS, was the first general purpose time-sharing operating system, letting several users work on one computer at the same time while batch jobs ran alongside them. It was built at MIT's Computation Center and Project MAC under Fernando J. Corbato, with contributors including Marjorie Daggett, Robert Daley, Robert Creasy, Jessica Hellwig and Richard Orenstein, first demonstrated in November 1961 on a modified IBM 709 and moved to an IBM 7090 in 1962, with regular service running from summer 1963 until 1968. CTSS introduced innovations that became standard in later systems, including password protected login, early text editing tools called TYPSET and RUNOFF, electronic mail, instant messaging and the RUNCOM shell command concept, and it directly influenced Multics and Unix; Dennis Ritchie later described Unix as, in effect, a modern implementation of CTSS. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/