Dartmouth Time-sharing System

Sun, Jun 15, 2025

DTSS, the Dartmouth Time-sharing System, was developed at the eponymous New England college in 1963/4. Running on a pair of GE computers, it achieved campus-wide access to computing and was the origin of the BASIC language.

Captures from "Educating the Computer", a 1969 video by GE. Source: Youtube.

Dartmouth had experimented with several smaller computers from the late 1950s but wanted to extend this to all students and faculty. This had two immediate issues - batch processing was not viable for a large number of inexperienced users, and existing high level languages like Fortran or Algol were too complex.

Professors John Kemeny and Thomas Kurtz decided to solve the first problem by building a time-sharing system (famously after Kurtz had talked to John McCarthy at MIT, who suggested "why don't you guys do time-sharing?"). They got funds from the NSF and evaluated several computers, eventually settling on a large GE-225 computer together with a GE DATANET-30 communication controller. Their plan was to build a real time user facing operating system on the D-30 that would talk to user teletype terminals, and would then send work to the GE-225 for compilation and execution. Disks drives were shared between both computers. This combination of systems looked to the end user like a single time-sharing system.

To solve the language issue, they invented the BASIC programming language specifically for people new to programming: with a small number of keywords it was ideal for developing programs of 10-100 lines. Over time, the system would also run other languages but BASIC was the most popular.

All the software for both computers had to be written in house - they enlisted several undergraduates to help, writing code on paper before the machine arrived. The system went into service for the fall term of 1964. The GE-225 was soon replaced with a more powerful GE-235.

It met their goals, with the system being able to serve tens and later hundreds of users at the same time. Terminals were installed throughout the college and the surrounding area, including many high schools. A library of programs developed by people in different faculties was built up, including many games.

A second version of DTSS came along in 1969 that extended its capacity and added more features; copies were was installed at at least 10 external sites, and became the basis of several commercial time-sharing services. BASIC went on to be used on many mini- and micro-computer systems, and still has users today in products like Visual BASIC.

The Wikipedia article and its references are a good way to find out more on the history of DTSS.