(VM/CMS) An IBMtime-sharing and personal comPUting environment executing under {Virtual Machine} (VM) in a virtual machine environment. VM/CMS is designed to support large numbers of interactive users. It relies on numerous APIs into the Control Program (CP) to provide very efficient single-user processing VM/CMS was only adopted some time after the original design of Virtual Machine as a more efficient personal comPUting environment than MVS/TSO. (1999-01-19)