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VM/CMS (Virtual Machine/Conversational Monitor System, originally called CP/CMS when it first appeared) is a bundled pair of operating systems used on IBM System/360, System/370, System/390, zSeries, and System z9 mainframes (and compatible systems). (Other operating systems for IBM mainframes include z/OS, z/TPF, z/VSE, Linux on zSeries, MVS, and MUSIC/SP.)
VM/CMS has two main components, VM and CMS, each an independent operating system. VM is a virtual machine operating system which provides each user with what seems to be their own personal mainframe. CMS is a relatively simple single-user operating system, designed to run principally in a virtual machine. Each VM/CMS user is given their own virtual machine in which to run CMS. When used with CMS, VM is an operating system which can support users, not just a hypervisor.
History
Development started on what was then called the "CP-40 Project," working with a modified System 360 Model 40, at IBM's Cambridge Scientific Center (CSC) in the autumn of 1964. CP-40 was a virtual machine operating system. A simple interactive computing single-user operating system, CMS, was designed to go along with it. Actual implementation started in 1965, and the complete system was first available to users in early 1966.
VM/CMS was not started as a formal IBM product, and for many years there was a great deal of political infighting within IBM over what resources should be available to the project as compared with competing IBM products. The basic "problem" was that VM/CMS arguably reduced customers' need for hardware, and IBM was, after all, in the business of selling computer systems.
After IBM announced the System/360 Model 67, the first system to feature early VM-oriented hardware, the software was converted to run on that. CP-40 was renamed CP-67 at that point. An early version of the system was installed at MIT's Lincoln Laboratory in 1967 because of Lincoln's dissatisfaction with the "standard" IBM time-sharing offering, TSS (Time Sharing System), which was at that time very slow and unreliable. Lincoln personnel co-operated with CSC in improving the system. Another influential IBM customer, Union Carbide, also decided to run VM/CMS and also contributed to its development.
By early 1968, word had spread, and most Model 67 sites were actually running VM/CMS, not the "official" IBM system for the machine, TSS. This popularity helped contribute to the demise of TSS in 1971.
Thereafter, the utility of the system — especially within IBM, where it was heavily used in developing MVS — prevented all attempts to kill it. IBM finally accepted the inevitable with relatively good grace, having learned through internal experience just how useful it was. That's fortunate, because today z/VM is all but mandatory to run Linux on zSeries.
IBM and third parties offer many applications for VM/CMS. Perhaps the most famous was OfficeVision, although today third parties offer HTTP servers, databases, etc.
VM/370 Welcome Screen
VM/370 ONLINE
VV VV MM MM
VV VV MMM MMM
VV VV MMMM MMMM
VV VV MM MM MM MM
3333333333 777777777777MMMM 00000000
333333333333 77777777777 MM 0000000000
33 VV33 77VV 77 00MM 00
V33 VV 77M 00MM 00
33 VV 77MM 00MM 00
3333VV VV 77 MM 00MM 00
3333 VVVV 77 MM 00MM 00
33 VV 77 MM 00MM 00
33 77 00 00
33 33 77 00 00
333333333333 77 0000000000
3333333333 77 00000000
RUNNING
Further reading
- Melinda Varian, VM and the VM Community: Past, Present, and Future (available online here) is an excellent detailed history, starting with CP-40 and its roots.
- Bob DuCharme, Operating Systems Handbook, Part 5: VM/CMS (available online here) is a fairly detailed user's guide to VM/CMS.
See also
- Linux on zSeries
- z/VM
- Hercules - a S/370, S/390, and zSeries emulator capable of running MVS
External links
"VM/CMS"