Dartmouth Time Sharing System

The Dartmouth Time-Sharing System, or DTSS for short, was the first large-scale time-sharing system to be implemented successfully. DTSS was inspired by a PDP-1-based time-sharing system at Bolt, Beranek and Newman. In 1962, John Kemeny and Thomas Kurtz at Dartmouth College submitted a grant for the development of a new time-sharing system to NSF (funded in 1964).^[1] Its implementation began in 1963 by a student team ^[2] under the direction of Kemeny and Kurtz with the aim of providing easy access to computing facilities for all members of the college.^[3] On May 1, 1964, at 4:00 a.m., the system began operations. It remained in operation until the end of 1999.^[4][5] DTSS was originally implemented to run on a GE-200 series computer with a GE DATANET-30 as a terminal processor that also managed the 235. Later, DTSS was reimplemented on the GE 635,^[1] still using the DATANET-30 for terminal control. The 635 version provided interactive time-sharing to up to nearly 300 simultaneous users in the 1970s, a very large number at the time.

Because of the educational aims, ease of use was a priority in DTSS design.

DTSS implemented the world's first Integrated Design Environment: a command-based system implementing the following commands.

• CATALOGUE — to list previously named programs in storage
• LIST — to display the current program in memory
• NEW — to name and begin writing a program in memory
• OLD — to copy a previously named program from storage to memory
• RENAME — to change the name of the program in memory
• RUN — to execute the current program in memory
• SAVE — to copy the current program from memory to storage
• SCRATCH — to clear the content of the current program from memory
• UNSAVE — to remove the current program from storage

These commands were often believed to be part of the Dartmouth BASIC language by users but in fact they were part of the time sharing system and were also used when preparing ALGOL^[6] or FORTRAN programs via the DTSS terminals.

Any line typed in by the user, and beginning with a line number, was added to the program, replacing any previously stored line with the same number; anything else was immediately compiled and executed. Lines which consisted solely of a line number weren't stored but did remove any previously stored line with the same number. This method of editing provided a simple and easy to use service that allowed large numbers of teleprinters as the terminal units for the Dartmouth Timesharing system.

By 1968 and into the mid-1970s, the nascent network included users at other schools and institutions around the East Coast (including Goddard College, Phillips Andover, the U.S. Naval Academy, and the United States Merchant Marine Academy), connected with Teletype Model 33 machines and modems. The system allowed email-type messages to be passed between users and real-time chat via a precursor to the Unix talk program.

In 2000 a project to recreate the DTSS system on a simulator was undertaken and as a result DTSS is now available for Microsoft Windows systems and for the Apple Macintosh computer.^[7]

See also

• Dartmouth BASIC
• Timeline of operating systems

References