VM/CMS Trademark, Acronym for virtual machine, conversational monitor system. An operating system originally produced in Cambridge, Mass. (On its first introduction the C stood for Cambridge.) The original system ran on a specially modified IBM 360/44, and was the first to make formal use of the concept of a virtual machine, as distinct from a virtual memory. The basis of the system is a supervisory level that creates a number of virtual machines (VMs); in each of these VMs a user can run his or her own program, using a terminal to control the VM and also to provide the route by which the user passes input to, or receives output from, this VM. Most users run a copy of CMS, the monitor system, which in turn actually controls the running of the jobs.

VM/CMS Computing, trademark virtual machine, conversational monitor system