The APE(X)C, or All Purpose Electronic (X) Computer, was a series of stored-program electronic computers designed by Andrew Donald Booth and built with the close collaboration of his wife Kathleen Booth at Birkbeck College, University of London, in the early 1950s. Sponsored in part by the British Rayon Research Association (BRRA), the project produced several machines in the early to mid-1950s and provided the design basis for the commercially manufactured Hollerith Electronic Computer (HEC) series, an early British production-scale computer line that ran into the late 1950s and evolved into the ICT 1200 series. Booth maintained that the "X" in the name stood for "X-company", referring to an unnamed sponsor.
Background
From 1943 onwards, Andrew Booth worked at Birkbeck under the crystallographer J. D. Bernal on the determination of crystal structures by X-ray diffraction. The numerical calculations involved were prohibitively laborious to perform by hand, and provided a strong incentive to automate the process. Booth's first machine in this line was an analogue computer designed to compute the reciprocal spacings of diffraction patterns.
In 1947, the Booths visited John von Neumann at the Institute for Advanced Study in Princeton, where they learnt of the von Neumann architecture for stored-program computers. On returning to Birkbeck, Andrew Booth substantially redesigned the relay computer he had been working on (the Automatic Relay Computer, ARC) along stored-program lines, while Kathleen Booth co-authored with him the report General Considerations in the Design of an All Purpose Electronic Digital Computer (1947), which set out the design of what would become the APE(X)C. Between 1947 and 1948 the Booths built the electromechanical ARC under BRRA sponsorship, followed by an experimental valve machine known as the Simple Electronic Computer (SEC), developed around 1948-1949.
Construction
After a 1950 design of an All-Purpose Electronic Computer (APEC), Booth built the first full-scale prototype in his father's barn between 1950 and 1951. In March 1951, the British Tabulating Machine Company (BTM), which had ended its IBM affiliation in 1949, sent a team of engineers to visit the barn where the APE(R)C was being assembled and copied the circuitry of the machine for use in its own Hollerith Electronic Computer.
The APE(X)C proper, installed at Birkbeck College in London, was first operated in May 1952 and ready for routine use by the end of 1953.
Machines in the series
The APE(X)C series comprised the following machines, with the bracketed letter typically standing for the sponsoring or hosting organisation:
- APE(X)C, also known as the All Purpose Electronic X-Ray Computer, at Birkbeck College, London; first operated May 1952, in routine use from end of 1953.
The Booths set out the general programming methodology for the APE(X)C in their jointly-authored 1953 book Automatic Digital Calculators, which introduced the "Planning and Coding" style later widely adopted in British programming education.