Christopher Strachey

Christopher Strachey
Born	(1916-11-16)16 November 1916 Hampstead, England
Died	Oxford, England
Residence	UK
Citizenship	UK
Fields	Computer Science
Institutions	University of Cambridge, University of Oxford
Alma mater	King's College, Cambridge
Doctoral students	Peter Mosses
Known for	CPL, denotational semantics, Fundamental Concepts in Programming Languages

Christopher S. Strachey (/ˈstreɪtʃi/; 1916–1975) was a British computer scientist. He was one of the founders of denotational semantics, and a pioneer in programming language design. He was a member of the Strachey family, prominent in government, arts, administration, and academia.

Life

Christopher Strachey was born on 16 November 1916 to Oliver Strachey and Rachel (Ray) Costelloe in Hampstead, England. Oliver Strachey was the son of Richard Strachey and the great grandson of Sir Henry Strachey, 1st Baronet. In 1919 the family moved to 51 Gordon Square. The Stracheys belonged to the Bloomsbury Group whose members included Virginia Woolf, John Maynard Keynes and Christopher's uncle Lytton Strachey. At 13, Christopher went to Gresham's School, Holt where he showed signs of brilliance but in general performed poorly. He was admitted to King's College, Cambridge (the same college as Alan Turing) in 1935 where he continued to neglect his studies. Strachey studied mathematics and then transferred to physics. At the end of his third year at Cambridge, Strachey suffered a nervous breakdown, possibly related to coming to terms with his homosexuality. He returned to Cambridge but managed only a "lower second" in the Natural Sciences Tripos.

Unable to continue his education, Christopher joined Standard Telephones and Cables (STC) as a research physicist. His first job was providing mathematical analysis for the design of electron tubes used in radar. The complexity of the calculations required the use of a differential analyser. This initial experience with a computing machine sparked Strachey's interest and he began to research the topic. An application for a research degree at the University of Cambridge was rejected and Strachey continued to work at STC throughout the Second World War. After the war he fulfilled a long-standing ambition by becoming a schoolmaster at St Edmund's School, Canterbury, teaching mathematics and physics. Three years later he was able to move to the more prestigious Harrow School in 1949, where he stayed for three years.

In January 1951, a friend introduced him to Mike Woodger of the National Physical Laboratory (NPL). The lab had successfully built a reduced version of Alan Turing’s Automatic Computing Engine (ACE) the concept of which dated from 1945: the Pilot ACE. In his spare time Strachey developed a program for the game of English draughts (known by Americans as "checkers"), which he finished in February 1951. The game completely exhausted the Pilot ACE’s memory. The draughts program ran for the first time on 30 July 1951 at NPL. When Strachey heard about the Manchester Mark 1, which had a much bigger memory, he asked his former fellow-student Alan Turing for the manual and transcribed his program into the operation codes of that machine by around October 1951. The program could "play a complete game of Draughts at a reasonable speed". He also wrote one of the first computer music programs, which played Baa Baa Black Sheep on the Ferranti Mark 1 at Manchester.

Strachey worked for the National Research Development Corporation (NRDC) from 1952 to 1959. While working on the St. Lawrence Seaway project, he was able to visit several computer centres in the United States and catalogue their instruction sets. Later, he worked on programming both the Elliott 401 computer and the Ferranti Pegasus computer. He also worked on the analysis of vibration in aircraft, working briefly with Roger Penrose, and developed the concept of time-sharing.

In 1959, Strachey left NRDC to become a computer consultant working for NRDC, EMI, Ferranti and other organisations on a number of wide-ranging projects. This work included logical design for computers, providing autocode and later the design of high-level programming languages. For a contract to produce the autocode for the Ferranti Orion computer, Strachey hired Peter Landin who became his one assistant for the duration of Strachey's consulting period.

In 1962, while remaining a consultant, he accepted a position at Cambridge University.

In 1965, Strachey accepted a position at Oxford University as the first director of the Programming Research Group and later the University's first Professor of Computer Science and fellow of Wolfson College, Oxford. He collaborated with Dana Scott.

In 1973, Strachey (along with R. E. Milne) began to write an essay submitted to the Adams Prize competition, after which they continued work to revising it into book form. Strachey contracted an illness diagnosed as jaundice which, after a period of seeming recovery, returned and he died of infectious hepatitis on May 18, 1975.

Work

He developed the Combined Programming Language (CPL). His influential set of lecture notes Fundamental Concepts in Programming Languages formalised the distinction between L- and R- values (as seen in the C programming language). Strachey also coined the term currying, although he did not invent the underlying concept.

He was instrumental in the design of the Ferranti PEGASUS computer.

The macro language m4 derives much from Strachey's GPM (General Purpose Macrogenerator), one of the earliest macro expansion languages.

See also

• Pegasus computer

Further reading

• Copeland, B.J. A Brief History of Computing, AlanTuring.net, June 2000.
• Lavington, S. The Pegasus Story, Science Museum, 2000. ISBN 1-900747-40-5.
• C. Strachey, An impossible program, The Computer Journal, 7(4):313, January 1965.

External links

• Christopher Strachey's publications indexed by the DBLP Bibliography Server at the University of Trier
• Christopher Strachey (1916–1975) at the Wayback Machine (archived September 26, 2007) at the Virtual Museum of Computing
• A simulator of the Manchester Mark 1, executing Christopher Strachey's Love letter algorithm from 1952
• A web based version of Christopher Strachey's Love letter algorithm showing word lists
• Higher-Order and Symbolic Computation Volume 13, Issue 1/2 (April 2000) Special Issue in memory of Christopher Strachey
• "Pioneer Profiles - Christopher Strachey" in RESURRECTION. The Bulletin of the Computer Conservation Society. Number 43. Summer 2008. ISSN 0958-7403.