Alan Turing was an English computer scientist and cryptanalysis, who was highly influential in the development of theoretical computer science, providing a formalisation of the concepts of algorithm and computation with the Turing machine, which can be considered a model of a general-purpose computer. 1
In 1936, Turing published his paper "On Computable Numbers, with an Application to the Entscheidungsproblem", known as Turing’s proof. A proof in which Turing redeveloped Kurt Gödel's 1931 findings on the constraints of proof and computation. 2 In which replaced Gödel's universal arithmetic-based formal language with the conventional and simple hypothetical devices that became known as Turing machines. 3
The Entscheidungsproblem was originally posed by German mathematician David Hilbert in 1928. The problem asks for an algorithm that considers, as input, a statement and answers "Yes" or "No" according to whether the statement is universally valid. Turing demonstrated that his "universal computing machine" would be able to perform any mathematical computation if it were representable as an algorithm. 4Avi Wigderson, an Israeli computer scientist, explains the importance of Turing’s demonstration. Wigderson recalls how Turing went on to demonstrate that there was no resolution to the decision problem by first demonstrating that the halting problem for Turing machines is undecidable. He discovered that is were not possible to determine algorithmically whether a Turing machine will ever stop. Wigderson noted that the paper is "easily the most influential math paper in history", creating the foundation for computer science and acknowledged that the concept of the modern computer was because of Turing's paper. 5
During the Second World War, Turing worked for the Government Code and Cypher School (GC&CS) at Bletchley Park, Britain's codebreaking centre that generated ULTRA intelligence. His role at Bletchley Park played a crucial role in codebreaking intercepted coded messages generated by the German Enigma machines, enabled the Allies to have a significant advantage and to defeat the Axis powers in many crucial engagements. 6
Thus, Turing’s work developing the first modern computers, decoding the encryption of German Enigma machines during the second world war, and detailing a procedure known as the Turing Test, forming the basis for artificial intelligence; he is extensively regarded as the father of theoretical computer science and artificial intelligence.7