Conversation System Monitor

The conversational monitor or Conversation Monitor System (CMS) - initially Cambridge Monitor System - is a system of use since a terminal of a virtual computer. Conceived to function under the hypervisor of virtual machines VM (IBM), it could also function on a naked machine (it detected it besides and sent a message of reproaches to the user). This not very useful possibility disappeared in its most recent versions in order to allow other functions ( diagnosis ).

It had been developed in parallel by the universities of Cambridge and Grenoble - where was then an IBM research center.

Its characteristic, unusual for a use in Time-sharing, is to be mono-user! Indeed, hypervisor VM already simulating on a real machine an unspecified number of virtual machines, one could dedicate about it to each user who had the impression to be the only user about it. He saw the others however ( Q users ) and could communicate easily with them by the divisions of disc and the virtual units of transfer ( virtual reader , virtual punch ). The two last were usable with users located on other physical machines, even located at thousands of kilometers. The network IBM VNET , before even as does not exist UNIX, anarchically developed this way of the time of some impassioned pioneers. At the end of the Seventies, many universities étatsuniennes as some universities used the same structure under the name of Bitnet , connected besides to VNET.

CMS was of course charged in segment divided , in order to not have not to be duplicated as much in memory of time than there were virtual machines.

CMS had been developed at the beginning with a university aim, but was quickly claimed by the customers who used VM for migrations of the system to another more powerful. It often happened that these customers preserve VM/CMS once the finished migration because they had taken taste with his comfort.

The source codes of CMS being distributed free to any customer requiring it, the universities started to create their own versions improved of CMS, presenting them and exchanging them at meetings of users. It was soon necessary to create the expression vanilla CMS to indicate a CMS which did not have not been the subject of modifications!

Multiplicity of calls to the hot-line (then free) of IBM for defects not existing that in the modified versions resulted this company in adopting a strategy consisting in more not providing but the computer code and not the source code. This decision sounded, according to professor Melinda Varian (of Princeton), the death of CMS in the universities with the profit of an other system whose code remained accessible and modifiable for its part: UNIX.

External bonds

Site on the history of the systems
For the curious ones: guide use of CMS (French, pdf)

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