Conversational Monitor System

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Conversational Monitor System (CMS)

Developer	IBM
Initial release	1967; 57 years ago (1967)
Platforms	IBM CP-40
Influenced by	Compatible Time-Sharing System

The Conversational Monitor System (CMS, originally Cambridge Monitor System)^[1] is a simple interactive single-user operating system. CMS was originally developed as part of IBM's CP/CMS operating system, which went into production use in 1967. CMS is part of IBM's VM family, which runs on IBM mainframe computers. VM was first announced in 1972, and is still in use today as z/VM.

CMS runs as a "guest" operating system in a private virtual machine created by the VM control program. The control program plus CMS together create a multi-user time-sharing operating system.