Editing Michigan Terminal System (section)

==Origins==
In the mid-1960s, the University of Michigan was providing [[batch processing]] services on [[IBM 7090]] hardware under the control of the [[University of Michigan Executive System]] (UMES), but was interested in offering interactive services using [[time-sharing]].<ref name=Topol30Years>[https://babel.hathitrust.org/cgi/pt?id=mdp.39015040313788;view=1up;seq=97 "A History of MTS&mdash;30 Years of Computing Service"], Susan Topol, ''Information Technology Digest'', Volume 5, No. 5 (May 13, 1996), University of Michigan</ref> At that time the work that computers could perform was limited by their small [[computer memory|real memory]] capacity. When IBM introduced its [[System/360]] family of computers in the mid-1960s, it did not provide a solution for this limitation and within IBM there were conflicting views about the importance of and need to support time-sharing.

A paper titled ''Program and Addressing Structure in a Time-Sharing Environment'' by [[Bruce Arden]], [[Bernard Galler]], [[Franklin H. Westervelt|Frank Westervelt]] (all associate directors at UM's academic Computing Center), and Tom O'Brian building upon some basic ideas developed at the Massachusetts Institute of Technology (MIT) was published in January 1966.<ref>[https://dl.acm.org/citation.cfm?doid=321312.321313 "Program and Addressing Structure in a Time-Sharing Environment"], B. W. Arden, B. A. Galler, T. C. O'Brien, F. H. Westervelt, ''Journal of the ACM'', v.13 n.1, p.1-16, Jan. 1966</ref> The paper outlined a [[virtual memory]] architecture using dynamic address translation (DAT) that could be used to implement time-sharing.

After a year of negotiations and design studies, IBM agreed to make a one-of-a-kind version of its S/360-65 mainframe computer with dynamic address translation (DAT) features that would support [[virtual memory]] and accommodate UM's desire to support time-sharing. The computer was dubbed the Model S/360-65M.<ref name=Topol30Years/> The "M" stood for Michigan. But IBM initially decided not to supply a time-sharing operating system for the machine. Meanwhile, a number of other institutions heard about the project, including [[General Motors]], the [[Massachusetts Institute of Technology]]'s (MIT) [[Lincoln Laboratory]], [[Princeton University]], and Carnegie Institute of Technology (later [[Carnegie Mellon University]]). They were all intrigued by the time-sharing idea and expressed interest in ordering the modified IBM S/360 series machines. With this demonstrated interest IBM changed the computer's model number to [[IBM System/360 Model 67|S/360-67]] and made it a supported product.<ref name=Galler-LifeAndWork-IEEE/> With requests for over 100 new model S/360-67s IBM realized there was a market for time-sharing, and agreed to develop a new time-sharing operating system called [[TSS/360]] (TSS stood for Time-sharing System) for delivery at roughly the same time as the first model S/360-67.

While waiting for the Model 65M to arrive, U of M Computing Center personnel were able to perform early time-sharing experiments using an [[IBM System/360 Model 50]] that was funded by the [[Defense Advanced Research Projects Agency|ARPA]] CONCOMP (Conversational Use of Computers) Project.<ref>[https://deepblue.lib.umich.edu/handle/2027.42/8249 ''CONCOMP: Research in Conversational Use of Computers: Final Report''], Westervelt, F. H., University of Michigan Computing Center, 1970</ref> The time-sharing experiment began as a "half-page of code written out on a kitchen table" combined with a small multi-programming system, LLMPS from MIT's [[Lincoln Laboratory]],<ref name=Galler-LifeAndWork-IEEE/> which was modified and became the U of M Multi-Programming Supervisor (UMMPS) which in turn ran the MTS job program. This earliest incarnation of MTS was intended as a throw-away system used to gain experience with the new IBM S/360 hardware and which would be discarded when IBM's [[TSS/360]] operating system became available.

Development of TSS took longer than anticipated, its delivery date was delayed, and it was not yet available when the S/360-67 (serial number 2) arrived at the Computing Center in January 1967.<ref>[https://www.multicians.org/thvv/360-67.html ''The IBM 360/67 and CP/CMS''], Tom Van Vleck</ref> At this time UM had to decide whether to return the Model 67 and select another mainframe or to develop MTS as an interim system for use until TSS was ready. The decision was to continue development of MTS and the staff moved their initial development work from the Model 50 to the Model 67. TSS development was eventually canceled by IBM, then reinstated, and then canceled again. But by this time UM liked the system they had developed, it was no longer considered interim, and MTS would be used at U of M and other sites for 33 years.