Editing Compatible Time-Sharing System (section)

===Experimental Time Sharing System===
By July, 1961<ref>{{cite report |url=https://archive.org/details/cooperating-colleges-progress-9 |title=Progress Report Number 9 of the Research and Educational Activities in Machine Computation by the Cooperating Colleges of New England |date=July 1961}}</ref> a few time sharing commands had become operational on the Computation Center's IBM 709, and in November 1961, [[Fernando J. Corbató]] demonstrated at MIT what was called the ''Experimental Time-Sharing System''. On May 3, 1962, F. J. Corbató, M. M. Daggett and R. C. Daley published a paper about that system at the [[Joint Computer Conference|Spring Joint Computer Conference]].<ref name="etss">{{cite web |url=http://larch-www.lcs.mit.edu:8001/~corbato/sjcc62/ |title=An Experimental Time-Sharing System |last1=Corbató |first1=Fernando J. |last2=Merwin Daggett |first2=Marjorie |last3=Daley |first3=Robert C. |date=May 3, 1962 |access-date=February 25, 2022 |archive-url=https://web.archive.org/web/20090906104446/http://larch-www.lcs.mit.edu:8001/~corbato/sjcc62/ |archive-date=September 6, 2009 |url-status=live}}</ref> "[M]ajor portions of [the CTSS system were largely prepared by]: Mrs. Marjorie M. Daggett, Mr. Robert Daley, Mr. Robert Creasy, Mrs. Jessica Hellwig, Mr. Richard Orenstein, and Professor F. J. Corbató".<ref name="CorbatVii">Corbató, p. vii</ref>

The system used an [[IBM 7090]], modified by [[Herbert M. Teager]], with added 3 [[Friden Flexowriter|Flexowriters]] for user consoles, and maybe a [[Programmable interval timer|timer]]. Each of the 3 users had two [[IBM 729|tape units]], one for the user's file directory, and one for dumping the core (program in memory). There was also one tape unit for the system commands, there were no disk drives. The [[Magnetic-core memory|memory]] was 27 k words (36-bit words) for users, and 5 k words for the supervisor (operating system). The input from the consoles was written to the buffers in the supervisor, by [[interrupt]]s, and when a [[Carriage return|return character]] was received, the control was given to the supervisor, which dumped the running code to the tape and decided what to run next. The console commands implemented at the time were ''login, logout, input, edit, fap, mad, madtrn, load, use, start, skippm, listf, printf, xdump'' and ''xundump''.{{citation needed |reason=CTSS command names are limited to six characters so how could xundump be a command? |date=February 2022}}

This became the initial version of the Compatible Time-Sharing System. This was apparently the first ever public demonstration of [[time-sharing]]; there are other claims, but they refer to special-purpose systems, or with no known papers published. The "compatibility" of CTSS was with background jobs run on the same computer, which generally used more of the compute resources than the time-sharing functions.