IBM Series/1

The IBM Series/1 is a 16-bitminicomputer, introduced in 1976, that in many respects competed with other minicomputers of the time, such as the PDP-11 from Digital Equipment Corporation and similar offerings from Data General and HP. The Series/1 was typically used to control and operate external electro-mechanical components while also allowing for primitive data storage and handling.

Although the Series/1 uses EBCDIC character encoding internally and locally attached EBCDIC terminals, ASCII-based remote terminals and devices could be attached via an I/O card with a RS-232 interface to be more compatible with competing minicomputers. IBM's own 3101 and 3151 ASCII display terminals are examples of this. This was a departure from IBM mainframes that used 3270 terminals and coaxial attachment.

Series/1 computers were withdrawn from marketing in 1990. IBM intended the follow-up computer to be, depending on the user application, the IBM PC, AS/400, or RS/6000. The challenge faced by the users was how to migrate their applications to these new systems.

A US government asset report dated May 2016 revealed that an IBM Series/1 was still being used as part of the country's nuclear command and control systems.