APEXC

APEXC

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.

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. Booth designed an electromechanical computer, the ARC, in the late 1940s. Later on, they built an experimental electronic computer named SEC (Simple Electronic Computer), and finally the APE(X)C (All-Purpose Electronic Computer) series.

The APE(X)C series included the following machines:

• APE(X)C: Birkbeck College, London (before 1955)
• APE(N)C: Board of Mathematical Machines, Oslo ('N' likely stands for 'Norway')
• APE(H)C: British Tabulating Machine Company (It is unclear what 'H' stands for)
• APE(R)C: British Rayon Research Association ('R' stands for 'Rayon')
• 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 BTM1200 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 APEXC, and APEHC were punched card machines while the 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 tubes. The HEC used standard punched cards; the HEC 4 had a printer, too, and it featured several instructions (such as divide) and registers not found on the APEXC.