CP/CMS

CP/CMS

(Control Program/Conversational Monitor System) An early operating system from IBM that provided a virtual machine environment. Introduced in the late 1960s, it was the predecessor to IBM's VM operating system, which came out in 1972. CP provided the virtual machine function, while CMS was a lightweight operating system that ran in its own virtual machine for each user.

A Separate Research Group
The virtual machine timesharing concepts in CP/CMS were not part of IBM's mainstream development, because the System/360 line, a huge undertaking for the company, was geared toward batch processing. These developments were undertaken by IBM's Cambridge Scientific Center (CSC), founded in 1964 (CMS originally stood for Cambridge Monitor System). Due to academic pressure, IBM announced the System/360 timesharing Model 67, which featured virtual memory hardware. Before it could obtain the new model, CSC customized a Model 40 and developed CP-40/CMS, launched in 1967. It was followed by CP-67/CMS for the Model 67 and CP-370/CMS, renamed VM/370 in 1972 for the System/370 and subsequent IBM mainframe lines. See VM and System/360.