Prof. Charles Antony Richard Hoare Tony Hoare

Born in Colombo (Sri Lanka) British parents

Oxford (England) University of Oxford: Hoare studied: Philosophy Latin and Greek Bacherol Degree in 1946 Extra year: Statistics

Moscow (Russia) Hoare studied: Russian (in the Royal Navy) Statistics a programming course

University State of Moscow - machine translation of languages - probability theory

Back to England (London) in 1960 Elliot Brothers (a small scientific computer manufacturer) First task: Elliot 803 Implementation of the method for internal sorting invented by Shell Hoare believed he had a faster method

Elliot 503 (the companie´s next computer) Goal: Design the language Course on the language Angol 60 (in Brighton - England ) First contact with recursive procedures Wrote the procedure of Quicksort New direction: Implementation of Algol 60 ( Hoare was invited to the group with responsibility for maintenance and development of Algol.)

Back to Elliot Brothers... Hoare was leading a team of 15 programmers ( task: Implementation of an operating system to the Elliot 503 computer) Promoted to Chief Engineer ( task: responsible for development and design of the company´s products)

Hoare left the industry what was the reason? -Hoare proposed once that a programming language definition should be formalized as a set of axioms instead of a just a functional notation. -But he did not see how actually to do it. Long Term research?

Research at Queen´s University (Belfast) ( ) -Theory of Programming and Languages

Hoare Logic

Instantiation axiom {p[t/y]} y:=t {p} For example: {y+5=10} y:=y+5 {y=10} {y+y<z} x:=y {x+y<z} {2*(y+5)>20} y:=2*(y+5) {y>20}

Composition rule {p} S1 {r} {r} S2 {q} ________________________________________________________________________ {p} S1;S2 {q} For example: if the antecedents are 1. {x+1 = y+2} x := x+1 {x=y+2} 2. {x = y+2} y := y+2 {x=y} Then the consequent is {x+1 = y+2} x := x+1; y := y+2 {x=y}

While rule {p/\e} S {p} ________________________________________________________________________ { p} while e do S od {p/\¬e}

Assertions example {x>=0 /\ y>=0} a:=0; b:=x; while b>=y do b:=b-y; a:=a+1 od. {x=a*y+b/\b>=0/\b<y}

Back to Oxford University (1977) Continuation of the research leads to: CSP (Communicating Sequential Processes)

1980 – Receives Turing Award For his fundamental contributions to the definition and design of programming languages

Back to Industry (1999) Senior researcher with Microsoft Research in Cambridge