At the end of the war Alan Turing resumed work on computers, this time for the National Laboratory in London. By March 1946 he completed a report proposing the design and implementation of an Automated Computing Engine (ACE) but it was regarded as impractical and hence not approved. He was way ahead of his time!

Turing spent 1947-1948 at Cambridge studying neurology and physiology but at the end of the year accepted a position at Manchester U (the university, not the soccer club, though he himself was an outstanding athlete). While there he published the paper “Computing machinery and intelligence,” in which he dealt with problems that are central to artificial intelligence today [**13**].

Sadly Turing’s life changed dramatically in 1952 when he reported an incident to police in which he mentioned his homosexuality. The end result was that he was charged with violating British homosexuality laws, yet the crime he reported was never pursued. At his trial he admitted his sexual preferences and stated that he saw nothing wrong with his actions. Found guilty, he chose estrogen injections instead of prison. After that he was labeled a security risk and his clearance withdrawn. Despondent, Alan Turing allegedly bit into a potassium-cyanide laced apple and died just weeks before his 42nd birthday.

Alan Mathison Turing (what an appropriate middle name!) was not the first person in history to conceive of a machine that could perform calculations automatically. The concept can be traced back to the 1670s, in fact, when the great cofounder of calculus, Gottfried Leibniz, built the so-called Leibniz wheel that could perform all four arithmetic operations. Some 150 years later Charles Babbage envisioned, but was unable to construct, an “analytical engine” capable of performing operations that arise in mathematical analysis and algebra. In the U.S. the father-and-son-and-daughter-in-law Lehmers, as well as Howard Aiken at Harvard, built electro-mechanical calculators. (The Lehmer team consisted of Derrick Norman Lehmer ("DNL"), Derrick Henry "Dick" Lehmer ("DHL"), and Emma Markovna Trotskaia Lehmer.)

But it was Alan Turing, in his seminal paper written in 1936, who realized that a computer could perform tasks far removed from mere numerical computations, a conception way ahead of today’s word processors, spreadsheets, graphics, music, and video. The main thesis of my account of Turing’s contributions above is that, as one biographer stated, “This generalized conception of the scope of computers is to be found in the vision of a computer as an engine of logic implicit in the abstract theory of computation developed by mathematical logicians” [**7**, p. 137].

We saw that Turing was involved in constructing a physical model of such a machine both before and after World War II. Indeed, in 1953, a year before his unfortunate demise, he published a paper that developed abstract properties related to the Riemann Hypothesis and used them on a Mark 1 computer at Manchester to give “a very picturesque account of the first calculations of zeros of \( \zeta(s) \) ever made by an electronic computer” [**9**, p. 28]. He harbored “an optimistic hope that a zero would be found off the critical line” \( \sigma = \frac12 \) [**14**, p. 99]. (See [**1**] for a description of the method and some recent developments setting this work in historical context.)

**Figure 7**. Turing statue in Sackville Park, Manchester, England, as photographed in 2004 (*Source:* Wikimedia Commons)

All along Turing was motivated to build a computer that would emulate, and possibly surpass, the human brain. As a result of his groundbreaking accomplishments the Association for Computing Machinery (ACM) named its annual prize established in 1966 in his honor; generally the Turing Award is regarded as the Nobel Prize in computer science. The photo in Figure 7 is of a statue of Turing seated on a bench with the putative ill-fated apple in his right hand. Dennis A. Hejhal described this 2001 memorial of Turing as “a poignant, life-like, life-size, bronze sculpture [that resides] in a small public park” [**9**, p. 29] located between the University of Manchester and the nearby “Gay Village” in that city.