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History, Plans, and Current Status of System
Initially an experimental time-sharing system was developed using the special three-Flexowriter subchannel designed and built under H. Teager's direction. The first public demonstrations of this system were in November 1961, and the work was reported at the Spring Joint Computer Conference in May, 1962. During the latter half of 1962, in addition to refinement of the initial system, studies were made of how to remove several limitations in the system, namely: 1) the limited number of typewriter console stations, 2) difficulties of installing and maintaining remote connections, 3) lack of compatibility of operation with other 7090 programming systems, and 4) problems of information retrieval and information security associated with a large on-line secondary memory.

These studies resulted in plans for the conversion of the experimental time-sharing system to a pilot system which would be capable of operating simultaneously with most of the work load already handled by the 7090 at the Center. These plans for the 7090 included: 1) the implementation of the interrupt clock, memory protection, and relocation features; 2) the addition of an IBM 7750 communications channel which allows up to 112 Teletype consoles to be attached via phone lines at remote locations; 3) the addition of a second bank of 32,768 words of core memory; 4) the installation of the IBM 1301 disk file; and 5) the design and programming of a master disk control subroutine (memo CC-196) and an associated disk editor program (memo CC-208) for flexibility in using the crucial secondary memory. As separate experiments, two smaller computers are being specially attached to the 7750 channel by telephone line links: the Electrical Engineering PDP-1 is to be used as an experimental display console, and the Civil Engineering IBM 1620 will be used to control remote analog input-output equipment such as a pen plotter. All of the above equipment and attachments should be installed by spring, 1963, and the necessary programming adaptation required for the 4