Historical Context
Like Alan Turing, another mathematician, Alonzo Church, was very interested, during the 1930s, in the question “What is a computable function?”
He developed a formal system known as the pure lambda calculus, in order to describe programs in a simple and precise way.
Today the Lambda Calculus serves as a mathematical foundation for the study of functional programming languages, and especially for the study of “denotational semantics.”
Reference: http://en.wikipedia.org/wiki/Lambda_calculus