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Sir Charles Antony Richard Hoare (born 11 January 1934), commonly known as Tony Hoare or C.A.R. Hoare, is a Britishmarker computer scientist, probably best known for the development in 1960, at age 26, of Quicksort, one of the world's most widely used sorting algorithms. He also developed Hoare logic for verifying program correctness, and the formal language Communicating Sequential Processes (CSP) used to specify the interactions of concurrent process (including the Dining philosophers problem) and the inspiration for the occam programming language.


Born in Colombomarker (Ceylon, now Sri Lankamarker) to Britishmarker parents, he received his Bachelor's degree in Classics from the University of Oxfordmarker (Merton Collegemarker) in 1956. He remained an extra year at Oxford studying graduate-level statistics, and following his National Service in the Royal Navy (1956–1958). When he learned to speak Russian, he studied computer translation of human languages at Moscow State Universitymarker in the Soviet Unionmarker in the school of Kolmogorov.

In 1960, he left the Soviet Union and began working at Elliott Brothers, Ltd, a small computer manufacturing firm, where he implemented ALGOL 60 and began developing algorithms in earnest. He became a Professor of Computing Science at the Queen's University of Belfastmarker in 1968, and in 1977 moved back to Oxford as a Professor of Computing to lead the Programming Research Groupmarker in the Oxford University Computing Laboratorymarker, following the death of Christopher Strachey. He is now an Emeritus Professor there, and is also a senior researcher at Microsoft Research in Cambridgemarker, England.

His most significant work has been in the following areas: devising a widely-used sorting algorithm (Quicksort), Hoare logic, the formal language Communicating Sequential Processes (CSP) used to specify the interactions between concurrent processes, structuring computer operating systems using the monitor concept, and the axiomatic specification of programming languages.


The famous quote, "We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil", by Donald Knuth, has also been mistakenly attributed to him (by Knuth himself), although Hoare disclaims having coined the phrase.

Speaking at a conference in 2009, Hoare apologized for inventing the null reference, described by him as a "billion dollar mistake":




  1. preface to the ACM Turing Award lecture
  2. ACM Turing Award citation
  3. Knuth, Donald: Structured Programming with Goto Statements. Computing Surveys 6:4 (1974), 261–301.
  4. The Errors of Tex, in Software—Practice & Experience, Volume 19, Issue 7 (July 1989), pp. 607–685, reprinted in his book Literate Programming (p. 276)
  5. Tony Hoare, a 2004 email

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