APEXC

From 1943 on, the Booths 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. Andrew Booth developed an analogue computer to compute the reciprocal spacings of the diffraction pattern. ==ARC and SEC==

The Booths designed an electromechanical computer, the ARC (Automatic Relay Computer), in the late 1940s (1947-1948) under the sponsorship of the British Rayon Research Association. • Later on, they built an experimental electronic computer named SEC (Simple Electronic Computer, designed around 1948-1949). • Booth designs the All-Purpose Electronic Computer (APEC) in 1950. • Booth builds the first full-scale prototype in his father's barn 1950–1951. • Early 1951, BRRA commissions Booth for a version of the APEC, named APE(R)C. • BTM (free of IBM affiliation since 1949) sends engineers to visit the barn where the APE(R)C is being assembled, to copy the circuitry of the computer—which they then use to build the HEC 1. • and finally, the Booth team markets the APE(X)C (All-Purpose Electronic Computer) series. The computers were programmed by Kathleen Booth. ==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, • 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 machines produced in quite large numbers for the time, around 150. They were similar in design, with various small differences, mostly in I/O equipment. The APEHC was a punched card machine while the APEXC, APERC and APENC were teletypers (keyboard and printer, plus paper tape reader and puncher). Also, the UCC had 8k words of storage, instead of 1k word for other machines, and the MAC used germanium diodes in replacement of many valves. ==British Tabulating Machine Company machines==

In March 1951, the British Tabulating Machine Company (BTM) sent a team to Andrew Booth's workshop. They then used his design to create the Hollerith Electronic Computer 1 (HEC 1) before the end of 1951. The computer was a direct copy of Andrew Booth's circuits with extra Input/output interfaces. The HEC 2 was the HEC 1 with smarter metal casings and was built for the Business Efficiency Exhibition in 1953. A slightly modified version of the HEC 2 was then marketed as HEC2M and 8 were sold. The HEC2M was succeeded by the HEC4. Around 100 HEC4s were sold in the late 1950s. ==Further reading==