The APE(X)C, or All Purpose Electronic (X) Computer series was designed by Andrew Donald Booth at Birkbeck College, London in the early 1950s. His work on the APE(X)C series was sponsored by the British Rayon Research Association. Although the naming conventions are slightly unclear, it seems the first model belonged to the BRRA. According to Booth, the X stood for X-company. One of the series was also known as the APE(X)C or All Purpose Electronic X-Ray Computer and was sited at Birkbeck. Background From 1943 on, Booth started working on the determination of crystal structures using X-ray diffraction data. The computations involved were extremely tedious and there was ample incentive for automating the process and he developed an analogue computer to compute the reciprocal spacings of the diffraction pattern. In 1947, along with his collaborator and future spouse Kathleen Britten, he spent a few months with von Neumann's team, which was the leading edge in computer research at the time. ARC and SEC Booth designed an electromechanical computer, the ARC (Automatic Relay Computer), in the late 1940s (1947-1948). Later on, they built an experimental electronic computer named SEC (Simple Electronic Computer, designed around 1948-1949) - and finally, the APE(X)C (All-Purpose Electronic Computer) series. The computers were programmed by Kathleen. The APE(X) C series The APE(X)C series included the following machines: APE(X)C: Birkbeck College, London, first time operated in May 1952, ready for use at the end of 1953 APE(N)C: Board of Mathematical Machines, Oslo ('N' likely stands for 'Norway'), also known as NUSSE APE(H)C: British Tabulating Machine Company (It is unclear what 'H' stands for - perhaps 'Hollerith' as the company sold Hollerith Unit record equipment APE(R)C: British Rayon Research Association ('R' stands for 'Rayon'), ready for use in June 1952 UCC: University College, London (circa January 1956) MAC or MAGIC (Magnetic Automatic Calculator): "built by Wharf Engineering Laboratories" (February 1955) The HEC (Hollerith Electronic Computer), built by the British Tabulating Machine Company (later to become International Computers and Tabulators (ICT), then International Computers Limited (ICL)), a commercial machine sold in several models and later known as the ICT200 series. There were likely the derivatives HEC 1, HEC 2, HEC 2M - M for 'marketable' denoting the machine's orientation toward commercial rather than scientific customers, and HEC 4 (before 1955) Only one of each of these machines was built, with the exception of HEC (and possibly MAC) which were commercial