Editing IBM System/4 Pi (section)

{{Short description|Family of avionics computers}}
{{More footnotes|date=May 2018}}
[[File:Space Shuttle General Purpose Computer.jpg|thumb|The IBM AP-101B CPU and I/O processor (right) and AP-101S (left)]]
The [[IBM]] '''System/4 Pi''' is a family of [[avionics]] [[computer]]s used, in various versions, on the [[F-15 Eagle]] fighter, [[E-3 Sentry]] AWACS, [[Harpoon (missile)|Harpoon Missile]], [[NASA]]'s [[Skylab]], [[Manned Orbital Laboratory|MOL]], and the [[Space Shuttle program|Space Shuttle]], as well as other aircraft. Development began in 1965, deliveries in 1967.{{sfn|IBM|1967|p=1-3 (9)}} They were developed by the [[IBM Federal Systems Division]] and produced by the Electronics Systems Center  in Owego, NY.{{sfn|IBM|1967|p=iv}}

It descends from the approach used in the [[System/360]] [[IBM mainframe|mainframe]] family of computers, in which the members of the family were intended for use in many varied user applications. (This is expressed in the name: there are 4[[Pi|π]] [[steradians]] in a sphere, just as there are 360 [[Degree (angle)|degrees]] in a circle.{{sfn|IBM|1967|loc=Foreword, p. iii/iv (6)}})  Previously, custom computers had been designed for each aerospace application, which was extremely costly.