One of the big names in ComputerScience.
It was he who discovered QuickSort in 1960, which is perhaps the single most widely used Algorithm ever.
He also described the formal logic system now known as Hoare logic or Hoare calculus in his 1969 paper An axiomatic basis for computer programming. This system defines axioms which can be used to reason about computer programs in order to do such things as formally proving their correctness.
He now works at the Microsoft Research Labs.
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