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CTSS -- The Compatible Time-Sharing System: Excerpts from "An Experimental Time-Sharing System"14

IP.com Disclosure Number: IPCOM000129710D
Original Publication Date: 1992-Mar-31
Included in the Prior Art Database: 2005-Oct-06
Document File: 2 page(s) / 17K

Publishing Venue

Software Patent Institute

Related People

Fernando J. Corbato: AUTHOR [+4]

Abstract

Before proceeding further, it is best to give a more precise interpretation to time-sharing. One can mean using different parts of the hardware at the same time for different tasks, or one can mean several persons making use of the computer at the same time. The first meaning, often called multiprogramming, is oriented towards hardware efficiency in the sense of attempting to attain complete utilization of all components. The second meaning of time-sharing, which is meant here, is primarily concerned with the efficiency of persons trying to use a computer. Computer efficiency should still be considered but only in the perspective of the total system utility. An experimental time-sharing system has been developed. This system was originally written for the IBM 709 but has been converted for use with the 7090 computer. The 7090 of the MIT Computation Center has, in addition to three channels with 19 tape units, a fourth channel with the standard Direct Data Connection. Attached to the Direct Data Connection is a real-time equipment buffer and control rack designed and built under the direction of H. Teager and his group. This rack has a variety of devices attached but the only ones required by the present systems are three Flexowriter typewriters. Also installed on the 7090 are two special modifications (i.e., RPQ's): a standard 60cycle accounting and interrupt clock, and a special mode which allows memory protection, dynamic relocation and trapping of all user attempts to initiate input-output instructions.

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THIS DOCUMENT IS AN APPROXIMATE REPRESENTATION OF THE ORIGINAL.

Copyright ©; 1992 by the American Federation of Information Processing Societies, Inc. Used with permission.

CTSS -- The Compatible Time-Sharing System: Excerpts from "An Experimental Time-Sharing System"14

Immediately after -- if not before -- the presentation of Lithe Long Range Computation Study Group report to Albert Hill, Fernando Corbato began to develop an experimental system that would show the feasibility of a timeshared system such as that envisaged by several members of the group. Within a very short time, he was able to demonstrate the first steps in this direction, as shown in the following excerpts from a 1962 paper he coauthored with Marjorie Merwin-Daggett and Robert C. Daley. The selection from the paper, which reported work completed in late 1961, is reprinted from prom Spring Joint Computer Conf., Vol. 21 (O 1962 AFIPS).

Fernando J. Corbato

Marjorie Merwin-Daggett

Robert C. Daley

Before proceeding further, it is best to give a more precise interpretation to time-sharing. One can mean using different parts of the hardware at the same time for different tasks, or one can mean several persons making use of the computer at the same time. The first meaning, often called multiprogramming, is oriented towards hardware efficiency in the sense of attempting to attain complete utilization of all components. The second meaning of time-sharing, which is meant here, is primarily concerned with the efficiency of persons trying to use a computer. Computer efficiency should still be considered but only in the perspective of the total system utility.

An experimental time-sharing system has been developed. This system was originally written for the IBM 709 but has been converted for use with the 7090 computer.

The 7090 of the MIT Computation Center has, in addition to three channels with 19 tape units, a fourth channel with the standard Direct Data Connection. Attached to the Direct Data Connection is a real-time equipment buffer and control rack designed and built under the direction of H. Teager and his group. This rack has a variety of devices attached but the only ones required by the present systems are three Flexowriter typewriters. Also installed on the 7090 are two special modifications (i.e., RPQ's): a standard 60cycle accounting and interrupt clock, and a special mode which allows memory protection, dynamic relocation and trapping of all user attempts to initiate input-output instructions.

In the present system, the time-sharing occurs between four users, three of whom are on-line each at a typewriter in a foreground system, and a fourth passive user of the background FAP- MAD-MADTRAN-BSS Monitor System (FMS) used by most of the Center programmers and by many other 7090 installations.

Significant design features of the foreground system [for the user] are [that he can]:

1. Develop programs in languages compatible with the background system, 2. Develop a pri...