CP/CMS
| Developer | IBM Cambridge Scientific Center |
|---|---|
| Written in | Assembler (F) |
| OS family | VM |
| Working state | Historic |
| Source model | Source code (see text for details) |
| Initial release | May 1968 |
| Latest release | 3.2 / 1972 |
| Available in | English |
| Platforms | IBM System/360-67; also System/370 with virtual memory hardware (not present in original S/370 models); also used on experimental hardware |
| Default user interface | Command-line interface |
| License | IBM Type-III Library (free in source code form at no charge to IBM customers, without support) |
CP/CMS (Control Program/Cambridge Monitor System) is a discontinued time-sharing operating system of the late 1960s and early 1970s. It is known for its excellent performance and advanced features. Among its three versions, CP-40/CMS was an important 'one-off' research system that established the CP/CMS virtual machine architecture. It was followed by CP-67/CMS, a reimplementation of CP-40/CMS for the IBM System/360-67, and the primary focus of this article. Finally, CP-370/CMS was a reimplementation of CP-67/CMS for the System/370. While it was never released as such, it became the foundation of IBM's VM/370 operating system, announced in 1972.
Each implementation was a substantial redesign of its predecessor and an evolutionary step forward. CP-67/CMS was the first widely available virtual machine architecture. IBM pioneered this idea with its research systems M44/44X (which used partial virtualization) and CP-40 (which used full virtualization).
In addition to its role as the predecessor of the VM family, CP/CMS played an important role in the development of operating system (OS) theory, the design of IBM's System/370, the time-sharing industry, and the creation of a self-supporting user community that anticipated today's free software movement.