Sir Tony Hoare FRS FREng

We are saddened to hear of the death of Emeritus Professor Sir Tony Hoare. 

Tony Hoare was one of the most influential figures in the history of Computer Science and a defining presence in the department. He joined Oxford in 1977, appointed to what is now the Christopher Strachey chair, and went on to build up the Programming Research Group founded by Strachey, helping to establish Oxford as an international centre for research in formal methods and programming language theory. 

His scientific contributions transformed the discipline. In 1961 he published Quicksort, a sorting algorithm he had discovered while a graduate student in Moscow during his work on machine translation. That work reflected an early and enduring interest in languages and formal structure, and the need to process them efficiently. Quicksort remains one of the most widely used sorting methods in computing. In 1969 he proposed what is now known as Hoare logic, providing an axiomatic basis for verifying program correctness. This work laid the foundations for modern formal verification and continues to underpin research and practice in software reliability. 

He later developed Communicating Sequential Processes (CSP), a mathematical framework for modelling and reasoning about concurrent systems. CSP profoundly influenced both theory and practice, inspiring programming languages such as occam and informing industrial verification tools. In his later Oxford years, he worked with Professor He Jifeng on Unifying Theories of Programming, an ambitious framework that sought to place diverse programming paradigms on a common mathematical foundation. 

Tony Hoare was one of the very most significant researchers in all of Computer Science. He pioneered so many areas of Computer Science including the logical foundations of computer science, the study of concurrent processes, programming language specification, and the discovery of Quicksort. His leadership and wisdom contributed massively, both to our department, and to Computer Science internationally. Professor Leslie Goldberg

Tony Hoare’s achievements were recognised with the highest international honours in computing. In 1980 he received the ACM Turing Award, often described as the Nobel Prize of computing, for his fundamental contributions to the definition and design of programming languages. He retired from Oxford in 1999, becoming a principal researcher at Microsoft. He was knighted in 2000 for his contributions to Computer Science. 

During his time at the department he supervised many doctoral students, including Professor Bill Roscoe and Emeritus Fellow Geraint Jones. Those students have in turn supervised subsequent generations of researchers, including members of the department such as Professors Sadie Creese and Joël Ouaknine. He will be remembered with great respect by colleagues, students and collaborators across the department and the wider research community. He is survived by Jill, his wife of 63 years, a computer scientist who helped look after many members of the department whilst Tony was in Oxford. 

Tony became my mentor in 1978 and my friend for life. He immediately taught me the need to look for simplicity in my work and that I should follow the philosophy that he shared with Strachey: that theory and practice are inextricably bound together in Computer Science. Professor Bill Roscoe