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Christopher Strachey (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 promiment in government, arts, administration and academia.

Strachey was educated at Gresham's School, Holt and King's College, Cambridge, where he took a First in Mathematics and Physics.

After Cambridge, he worked as a research physicist at laboratories of Standard Telephone & Cables Ltd, where he designed electron tubes for centimetric radar.

Immediately after the Second World War, he became a schoolmaster at St Edmund's School, Canterbury, moving from there to 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 Turing’s Automatic Computing Engine (ACE) the concept of which dated from 1945: the Pilot ACE. In May 1950 the first computations were performed on this machine. After the meeting with Woodger, in his spare time Strachey developed a programme for the game of draughts, which he finished in February 1951. The game completely exhausted the Pilot ACE’s memory. The draughts programme ran for the first time on 30 July 1951 at NPL. When Strachey heard about the Manchester Mark I, which had a much bigger memory, he asked his former fellow-student Alan Turing for the manual and transcribed his programme into the operation codes of that machine by around October 1951. The program could "play a complete game of draughts at a reasonable speed". A second program he wrote in that time printed loveletters on the teleprinter. He collaborated with Dana Scott and Peter Landin in the 1960s and went on to work in Cambridge and Oxford universities, becoming the director of the Programming Research Group at the latter.

He developed the Combined Programming Language (CPL) and, as seen in the C programming language, he formalized the distinction between L- and R- values. 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. An interesting quote in that regard is "Optimum programming is to be avoided because it tends to become a time-wasting intellectual hobby of the programmers" (slightly paraphrased)^{[citation needed]}.

The macro language M4_(computer_language) derives much from GPM which is described in C. Stratchey: "A General Purpose Macro generator", Computer Journal 8,3 (1965), pp. 225 ff. GPM is one of the earliest macro expansion languages (General_Purpose_Macro_Processor).

• Pegasus computer
• Lytton Strachey, the writer and critic
• John St Loe Strachey, writer and member of Parliament

• Copeland, B.J. (June 2000). "A Brief History of Computing" at AlanTuring.net
• Campbell-Kelly, M. Christopher Strachey, 1916–1975 — A Biographical Note, IEEE Annals of the History of Computing, Vol.7, No.1, pp.19–42, 1985.

• Christopher Strachey (1916–1975) at the Virtual Museum of Computing
• A simulator of the Manchester Mark I, executing Christopher Strachey's Love letter algorithm from 1952