History of CP/CMS - Early 60s: CTSS, Early Time-sharing, and Project MAC

Early 60s: CTSS, Early Time-sharing, and Project MAC

The seminal first-generation time-sharing system was CTSS, first demonstrated at MIT in 1961 and in production use from 1964–74. It paved the way for Multics, CP/CMS, and all other time-sharing environments. Time-sharing concepts were first articulated in the late 50s, particularly as a way to meet the needs of scientific computing. At the time, computers were primarily used for batch processing — where jobs were submitted on punch cards, and run in sequence. Time-sharing let users interact directly with a computer, so that calculation and simulation results could be seen immediately.

Scientific users quickly embraced the concept of time-sharing, and pressured computer vendors such as IBM for improved time-sharing capabilities. MIT researchers spearheaded this effort, launching Project MAC, which was intended to develop the next generation of time-sharing technology and which would ultimately build Multics, an extremely feature-rich time-sharing system that would later inspire the initial development of UNIX. This high-profile team of leading computer scientists formed very specific technical recommendations and requirements, seeking an appropriate hardware platform for their new system. The technical problems were awesome. Most early time-sharing systems sidestepped these problems by giving users new or modified languages, such as Dartmouth BASIC, which were accessed through interpreters or restricted execution contexts. But the Project MAC vision was for shared, unrestricted access to general-purpose computing.

Along with other vendors, IBM submitted a proposal to Project MAC. However, IBM's proposal was not well received: To IBM's surprise, MIT chose GE as the Multics system vendor. The fallout from this event led directly to CP/CMS.

Further information: IBM mainframe operating systems and CTSS