VM (operating System)

VM (operating System)

VM (often: VM/CMS) refers to a family of IBM virtual machine operating systems used on IBM mainframes System/370, System/390, zSeries, System z and compatible systems, including the Hercules emulator for personal computers. The first version, released in 1972, was VM/370, or officially Virtual Machine Facility/370. This was a System/370 reimplementation of earlier CP/CMS operating system. Milestone versions included VM/SP. The current version is z/VM, and is still widely used as one of the main full virtualization solutions for the mainframe market.

VM's differences with other IBM mainframe operating systems are primarily due to the unique circumstances in which CP/CMS was built and distributed.