Dr. Dobb's Journal October 1998
Assertions of paternity in computer technology being as contentious as they are, I'll start this out with an invitation to be corrected. But I believe that John McCarthy deserves sole credit for the invention of timesharing. Here's the history as I understand it:
On January 1, 1959, McCarthy, a professor at MIT, laid out the concept of general-purpose timesharing in a memo he wrote to Phillip Morse, head of the MIT Computation Center.
Two projects were inspired by this memo: One at MIT, under the direction of Fernando Corbato and involving Marjorie Daggett and Bob Daley, apparently became the first working timesharing system. It ran on an IBM 709 in November 1961, and evolved into CTSS (Compatible Time-Sharing System) when the IBM 7090 hardware became available the following year.
The other project was run at BBN under McCarthy and Ed Fredkin. McCarthy was consulting at BBN, and shared his ideas with Fredkin and J.R. Licklide. Fredkin judged the concept achievable on the PDP-1, which was Digital's first machine and of which BBN happened to have the prototype. According to McCarthy, "Fredkin designed the architecture of an interrupt system and designed a control system for the drum to permit it to be used in a very efficient swapping mode." Digital's chief engineer, Ben Gurley, built the equipment. Sheldon Boilen did the programming. After Fredkin left, McCarthy supervised Boilen. This system was operational a few months after Corbato's.
Both systems were basically demonstrations and were not used for much serious computation. In late 1962, at Stanford, McCarthy created the first serious display-oriented timesharing system around a DEC PDP-1 with eight Philco random-access displays, and it was used for years afterward.
So McCarthy first clearly articulated the concept, was deeply involved in one of the first two demonstrations, and was responsible for the first serious implementation of timesharing. He is the father of timesharing.
Supporters of BBN, Strachey, Licklider, Wiener, or other claimants can send alternate histories to mswaine@ swaine.com.
-- M.S.