Electronic Mail and Text Messaging in CTSS, 1965-1973

Applications from prior technologies are often reimplemented on new computing or communications platforms, and users sometimes don’t realize that the applications have been recycled. For example, text messaging was available between computer users for years before its implementation on cell phones, and email has precursors before its implementation on the Internet. My colleague Noel Morris and I implemented both an electronic mail command and a text messaging facility for the Massachusetts Institute of Technology’s Compatible Time-Sharing System (CTSS) in 1965. The MAIL command let a system user send a text message to another user’s ‘‘mail box’’ so the recipient could read the message later. The WRITE subcommand of the .SAVED command allowed a user to send a oneline message to another logged-in user’s terminal. Begun at the MIT Computation Center in 1961, CTSS was fairly operational the following year. By 1965, there were hundreds of registered users from MIT and other New England colleges, and the CTSS provided service to up to 30 simultaneous users every day on each of the two systems on which CTSS ran—the MIT Computation Center and Project MAC IBM 7094s. CTSS users logged into the 7094 from remote dial-up terminals and were able to store files on a disk online. This new ability encouraged users to share information in new ways.