Tony Hoare

Sir Charles Antony Richard Hoare (11 January 1934 – 5 March 2026), often called Tony Hoare or C. A. R. Hoare, was a British computer scientist. His work shaped programming languages, algorithms, operating systems, formal verification, and concurrent computing, earning him the 1980 ACM Turing Award, the field's highest honour. He created the quicksort sorting algorithm in 1959–1960, developed Hoare logic for proving program correctness, and introduced communicating sequential processes (CSP) to describe how concurrent processes interact. With Edsger Dijkstra, he also formulated the dining philosophers problem. From 1977 onward, he held roles at the University of Oxford and at Microsoft Research in Cambridge.

Hoare was born in Colombo, Ceylon (now Sri Lanka), to British parents—his father a colonial civil servant, his mother the daughter of a tea planter. He was privately educated in England at the Dragon School in Oxford and the King's School in Canterbury, then studied Classics and Philosophy at Merton College, Oxford. After graduating in 1956, he served 18 months in the Royal Navy, learning Russian. He returned to Oxford in 1958 for a postgraduate certificate in statistics, where Leslie Fox taught him Autocode on the Ferranti Mercury, starting his programming career. He then went to Moscow State University as a British Council exchange student, studying machine translation under Andrey Kolmogorov.

In 1960, Hoare left the Soviet Union to work at Elliott Brothers Ltd in London, a small computer manufacturer. There, he implemented a compiler for ALGOL 60 and began developing major algorithms. He served on the International Federation for Information Processing (IFIP) Working Group 2.1, which specified and maintained ALGOL 60 and ALGOL 68. In 1968, he became Professor of Computing Science at Queen's University of Belfast, then returned to Oxford in 1977 as Professor of Computing, leading the Programming Research Group after Christopher Strachey's death. He became the first Christopher Strachey Professor of Computing in 1988, retiring from Oxford in 2000, and remained an Emeritus Professor and principal researcher at Microsoft Research in Cambridge.

His key contributions include quicksort, quickselect, Hoare logic, CSP (implemented in languages like occam), the monitor concept for structuring operating systems, and axiomatic specification of programming languages. In 2009, he apologised for inventing the null reference in 1965 while designing ALGOL W, calling it his "billion-dollar mistake" for causing countless errors and crashes. Under his leadership, his Oxford department worked on formal specification languages like CSP and Z notation, but they saw limited industrial adoption. In 1995, he admitted that he and other formal methods researchers had overestimated how much industry would embrace formalisation to solve reliability problems; instead, most failures stemmed from poor requirements or management. A commemorative article marked his 90th birthday.

Hoare married Jill Pym, a member of his research team, in 1962; they had three children. He died on 5 March 2026 at age 92.