Tony Hoare
Tony Hoare in 2011
Charles Antony Richard Hoare

(1934-01-11) 11 January 1934 (age 90)
Known for
SpouseJill Pym
Scientific career
FieldsComputer science
Doctoral students

Sir Charles Antony Richard Hoare FRS FREng,[3] also known as Tony Hoare or by his initials C. A. R. Hoare (/hɔːr/; born 11 January 1934) is a British computer scientist who has made foundational contributions to programming languages, algorithms, operating systems, formal verification, and concurrent computing.[4] His work earned him the Turing Award, usually regarded as the highest distinction in computer science, in 1980.

Hoare developed the sorting algorithm quicksort in 1959–1960.[5] He developed Hoare logic, an axiomatic basis for verifying program correctness. In the semantics of concurrency, he introduced the formal language communicating sequential processes (CSP) to specify the interactions of concurrent processes, and along with Edsger Dijkstra, formulated the dining philosophers problem.[6][7][8][9][10][11] Since 1977, he has held positions at the University of Oxford and Microsoft Research in Cambridge.

Education and early life

Tony Hoare was born in Colombo, Ceylon (now Sri Lanka) to British parents; his father was a colonial civil servant and his mother was the daughter of a tea planter. Hoare was educated in England at the Dragon School in Oxford and the King's School in Canterbury.[12] He then studied Classics and Philosophy ("Greats") at Merton College, Oxford.[13] On graduating in 1956 he did 18 months National Service in the Royal Navy,[13] where he learned Russian.[14] He returned to the University of Oxford in 1958 to study for a postgraduate certificate in statistics,[13] and it was here that he began computer programming, having been taught Autocode on the Ferranti Mercury by Leslie Fox.[15] He then went to Moscow State University as a British Council exchange student,[13] where he studied machine translation under Andrey Kolmogorov.[14]

Research and career

In 1960, Hoare left the Soviet Union and began working at Elliott Brothers Ltd,[13] a small computer manufacturing firm located in London. There, he implemented the language ALGOL 60 and began developing major algorithms.[16][17]

He was involved with developing international standards in programming and informatics, as a member of the International Federation for Information Processing (IFIP) Working Group 2.1 on Algorithmic Languages and Calculi,[18] which specified, maintains, and supports the languages ALGOL 60 and ALGOL 68.[19]

He became the Professor of Computing Science at the Queen's University of Belfast in 1968, and in 1977 returned to Oxford as the Professor of Computing to lead the Programming Research Group in the Oxford University Computing Laboratory (now Department of Computer Science, University of Oxford), following the death of Christopher Strachey. He became the first Christopher Strachey Professor of Computing on its establishment in 1988 until his retirement at Oxford in 2000.[20] He is now an Emeritus Professor there, and is also a principal researcher at Microsoft Research in Cambridge, England.[21][22][23]

Hoare's most significant work has been in the following areas: his sorting and selection algorithm (Quicksort and Quickselect), Hoare logic, the formal language communicating sequential processes (CSP) used to specify the interactions between concurrent processes (and implemented in various programming languages such as occam), structuring computer operating systems using the monitor concept, and the axiomatic specification of programming languages.[24][25]

Speaking at a software conference in 2009, Tony Hoare hyperbolically apologized for "inventing" the null reference:[26] [27]

I call it my billion-dollar mistake. It was the invention of the null reference in 1965. At that time, I was designing the first comprehensive type system for references in an object oriented language (ALGOL W). My goal was to ensure that all use of references should be absolutely safe, with checking performed automatically by the compiler. But I couldn't resist the temptation to put in a null reference, simply because it was so easy to implement. This has led to innumerable errors, vulnerabilities, and system crashes, which have probably caused a billion dollars of pain and damage in the last forty years.[28]

For many years under his leadership, Hoare's Oxford department worked on formal specification languages such as CSP and Z. These did not achieve the expected take-up by industry, and in 1995 Hoare was led to reflect upon the original assumptions:[29]

Ten years ago, researchers into formal methods (and I was the most mistaken among them) predicted that the programming world would embrace with gratitude every assistance promised by formalisation to solve the problems of reliability that arise when programs get large and more safety-critical. Programs have now got very large and very critical – well beyond the scale which can be comfortably tackled by formal methods. There have been many problems and failures, but these have nearly always been attributable to inadequate analysis of requirements or inadequate management control. It has turned out that the world just does not suffer significantly from the kind of problem that our research was originally intended to solve.

A commemorative article was written in tribute to Hoare on his 90th birthday.[30]

Awards and honours

Personal life

In 1962, Hoare married Jill Pym, a member of his research team.[45]



  1. ^ a b Tony Hoare at the Mathematics Genealogy Project
  2. ^ Sampaio, Augusto (1993). An algebraic approach to compiler design. (DPhil thesis). University of Oxford. OCLC 854973008. EThOS[permanent dead link]
  3. ^ a b c "List of Fellows". Archived from the original on 8 June 2016. Retrieved 17 October 2014.
  4. ^ Jones, Cliff B.; Misra, Jayadev, eds. (2021). Theories of Programming: The Life and Works of Tony Hoare. ACM Books. Vol. 39. New York, NY: Association for Computing Machinery. doi:10.1145/3477355. ISBN 978-1-4503-8728-6. S2CID 238251696.
  5. ^ "Sir Antony Hoare". Computer History Museum. Archived from the original on 3 April 2015. Retrieved 22 April 2015.
  6. ^ Tony Hoare author profile page at the ACM Digital Library
  7. ^ C. A. R. Hoare at DBLP Bibliography Server Edit this at Wikidata
  8. ^ Tony Hoare publications indexed by Microsoft Academic
  9. ^ Shustek, L. (2009). "Interview: An interview with C.A.R. Hoare". Communications of the ACM. 52 (3): 38–41. doi:10.1145/1467247.1467261. S2CID 1868477.
  10. ^ Hoare, C. A. R. (1974). "Monitors: An operating system structuring concept". Communications of the ACM. 17 (10): 549–557. doi:10.1145/355620.361161. S2CID 1005769.
  11. ^ Bowen, Jonathan (8 September 2006). Oral History of Sir Antony Hoare. Hoare (Sir Antony, C.A.R.) Oral History, CHM Reference number: X3698.2007 (Report). Computer History Museum. Archived from the original on 3 July 2013. Retrieved 18 April 2014.((cite report)): CS1 maint: bot: original URL status unknown (link)
  12. ^ Lean, Thomas (2011). "Professor Sir Tony Hoare" (PDF). National Life Stories: An Oral History of British Science. UK: British Library. Archived (PDF) from the original on 15 September 2014. Retrieved 15 September 2014.
  13. ^ a b c d e Levens, R.G.C., ed. (1964). Merton College Register 1900-1964. Oxford: Basil Blackwell. p. 434.
  14. ^ a b Hoare, Tony (Autumn 2009). "My Early Days at Elliotts". Resurrection (48). ISSN 0958-7403. Retrieved 27 May 2014.
  15. ^ Roscoe, Bill; Jones, Cliff (2010). "1 Insight, inspiration and collaboration" (PDF). Reflections on the Work of C.A.R. Hoare. Springer. ISBN 978-1-84882-911-4. Archived (PDF) from the original on 9 October 2022.
  16. ^ a b Hoare, C.A.R. (February 1981). "The emperor's old clothes". Communications of the ACM. 24 (2): 5–83. doi:10.1145/358549.358561. ISSN 0001-0782.
  17. ^ Hoare, C. A. R. (1981). "The emperor's old clothes". Communications of the ACM. 24 (2): 75–83. doi:10.1145/358549.358561.
  18. ^ Jeuring, Johan; Meertens, Lambert; Guttmann, Walter (17 August 2016). "Profile of IFIP Working Group 2.1". Foswiki. Retrieved 7 October 2020.
  19. ^ Swierstra, Doaitse; Gibbons, Jeremy; Meertens, Lambert (2 March 2011). "ScopeEtc: IFIP21: Foswiki". Foswiki. Retrieved 7 October 2020.
  20. ^ "Christopher Strachey Professorship of Computing". Department of Computer Science, University of Oxford. 5 November 2021. Retrieved 18 January 2024.
  21. ^ Microsoft home page – short biography
  22. ^ Oral history interview with C. A. R. Hoare at Charles Babbage Institute, University of Minnesota, Minneapolis.
  23. ^ The classic article on monitors – The original article on monitors
  24. ^ "Preface to the ACM Turing Award lecture" (PDF). Archived from the original (PDF) on 19 April 2012.
  25. ^ "C. Antony (Tony) R. Hoare". Archived from the original on 1 July 2012.
  26. ^ Hoare, Tony (25 August 2009). "Null References: The Billion Dollar Mistake".
  27. ^ "Null: The Billion Dollar Mistake". 3 September 2020.
  28. ^ Hoare, Tony (2009). "Null References: The Billion Dollar Mistake" (Presentation abstract). QCon London. Archived from the original on 28 June 2009.
  29. ^ Hoare, C. A. R. (1996). "Unification of Theories: A Challenge for Computing Science". Selected papers from the 11th Workshop on Specification of Abstract Data Types Joint with the 8th COMPASS Workshop on Recent Trends in Data Type Specification. Springer-Verlag. pp. 49–57. ISBN 3-540-61629-2.
  30. ^ Jifeng, He; Jones, Cliff; Roscoe, Bill; Stoy, Joe; Sufrin, Bernard; Bowen, Jonathan (2 July 2024). Denvir, Tim (ed.). "Tony Hoare @ 90" (PDF). FACS FACTS (Magazine article). Formal Aspects of Computing Science (FACS) Specialist Group. pp. 5–42. ISSN 0950-1231. Archived (PDF) from the original on 10 July 2024. Retrieved 10 July 2024.
  31. ^ "ACM Programming Systems and Languages Paper Award". Association for Computing Machinery. 1973. Retrieved 7 July 2022.
  32. ^ Hoare, C.A.R. (1972). "Proof of correctness of data representations". Communications of the ACM. 1 (4): 271–281. doi:10.1007/BF00289507. S2CID 34414224.
  33. ^ Hoare, Charles Anthony Richard (27 October 1980). "The Emperor's Old Clothes: The 1980 ACM Turing Award Lecture" (PDF). Association for Computing Machinery. Archived from the original (PDF) on 19 April 2012.
  34. ^ Anon (1982). "Anthony Hoare FRS". London: Royal Society.
  35. ^ "Honorary Graduates 1989 to present". University of Bath. Archived from the original on 17 July 2010. Retrieved 18 February 2012.
  36. ^ "(Charles) Antony Richard (Tony) Hoare Biography". Archived from the original on 17 July 2014.
  37. ^ "Sir Antony Hoare: 2006 Fellow". Archived from the original on 3 April 2015. Retrieved 8 March 2020."Sir Antony Hoare | Computer History Museum". Archived from the original on 3 April 2015. Retrieved 22 April 2015.
  38. ^ "Annual Review 2007: Principal's Review". Archived from the original on 5 March 2016. Retrieved 29 March 2016.
  39. ^ "Preisverleihung auf der Festveranstaltung "40 Jahre Informatik in München": TU München vergibt Friedrich L. Bauer-Preis an Tony Hoare" (in German). Technical University of Munich. 26 October 2007. Archived from the original on 10 June 2016. Retrieved 14 May 2016.
  40. ^ "Programming Languages Achievement Award 2011". ACM. Retrieved 28 August 2012.
  41. ^ "IEEE John von Neumann Medal Recipients" (PDF). IEEE. Archived (PDF) from the original on 9 October 2022. Retrieved 26 February 2011.
  42. ^ Krzysztof, Diks (15 November 2012). "Profesor Hoare doktorem honoris causa Uniwersytetu Warszawskiego" (in Polish). University of Warsaw. Archived from the original on 26 August 2014. Retrieved 26 November 2012.
  43. ^ "Los informáticos Tony Hoare y Mateo Valero serán investidos hoy doctores honoris causa por la Complutense" (in Spanish). 10 May 2013. Retrieved 10 May 2013.
  44. ^ Royal Medal 2023
  45. ^ Jones, Cliff; Roscoe, A. W.; Wood, Kenneth R., eds. (2010). Reflections on the Work of C.A.R. Hoare. Springer Science. p. 3.

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