User:Spinality/TRHsandbox

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CP/CMS was a remarkable time-sharing operating system of the late 60s and early 70s, known for its excellent performance and advanced features. It was the first practical implementation of a virtual machine architecture – instead of dividing up memory and other resources among users (the traditional approach), CP/CMS provided each user a simulated stand-alone computer. By isolating users from each other, system reliability and security were greatly improved.

CP/CMS was built by IBM's Cambridge Scientific Center (CSC), an R&D lab with very close ties to MIT. The system's goals, development process, release, and legacy – and of course its breakthrough technology – all set this system apart from other operating systems of its day, and from other large IBM projects. In particular, CP/CMS was an open-source system: It was made available in source form to all IBM customers at no charge.

CP/CMS, and its VM successors at IBM, were always viewed as "the other operating system" – a poor cousin to IBM's recommended operating systems. But CP/CMS rose above limited resources and company politics to create an enduring and important technical legacy, a fiercely loyal user base, major derivative systems in the time-sharing industry, and, ultimately, a heritage as the grandparent of 21st-century products from IBM.

Overview

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During the 60s and 70s, CP/CMS had four important legacies:

1. Within IBM, CP/CMS helped establish the viability of virtual memory technology – which was proven by CP/CMS on the 360/67, but not added to the succeeding S/370 product line for several years
2. Within IBM, the core CP/CMS concepts (and some code) were carried forward into the VM/370 operating system and its successors.
3. Within the IBM user community, numerous organizations adopted CP/CMS, particularly academic sites; many of them implemented exstensive customizations, and some played an active role in the further development of the shared code base.
4. Independent time-sharing vendors customized CP/CMS to sell remote computer services, ultimately creating a sizable industry; one in particular (National CSS) created what was essentially a new operating system (VP/CSS) using CP/CMS as a starting point.

References

Secondary sources

R.J. Adair, R.U. Bayles, L.W. Comeau, and R.J. Creasy, "A Virtual Machine System for the 360/40," IBM Cambridge Scientific Center Report 320-2007, Cambridge, MA, May, 1966