**Alan Mathison Turing**, b. June 23, 1912, d. June 7, 1954. He played a significant rôle in cracking German codes during World War II, and proposed a test for machine intelligence. He went to King’s College, Cambridge in 1931 to read Mathematics. Alan Turing graduated in 1934, and was a fellow at Kings for two years, during which he wrote his now famous paper published in 1937, *On Computable Numbers, with an Application to the Entscheidungsproblem*. In it, he proposed a machine that could move from one state to another by following a rigorous set of rules. From this he was able to show the existence of uncomputable functions. For example, no program can determine if any arbitrary program will terminate. This led to a computing scheme that foreshadowed the logic of digital computers.

## 1912

Alan Mathison Turing born June 23 in Maida Vale, London, to Ethel Sara Turing (nee Stoney) and Julius Mathison Turing.

## 1918

Turing joins St Michael’s day school in Hastings, where he does not do very well.

His father was in the Indian Civil Service, and his parents returned to the UK for his birth, which took place in Maida Vale, London. When he was about one year old, his parents returned to India, leaving Alan and his older brother with a retired army couple, a Col. Ward, and his wife, who lived in St. Leonards in a large house, Baston Lodge, in Upper Maze Hill, with their own children and a nanny. The house is still there, and has a blue plaque commemorating his stay there. When he was six, he attended St. Michael’s day school at 20 Charles Road, until he was 10, when he went to Hazlehurst preparatory school. The building is still there, converted into flats. He and his brother weren’t very happy with the Wards,

and they stayed with a different family when he was at Hazlehurst. When he was 13 he joined his older brother at Sherborne School in Dorset, where he stayed until he went up to Cambridge. Their parents retired to France at about the time he went to Sherborne, and the brothers stayed with them during vacations. Turing doesn’t appear to have had any connection to St. Leonards after he left the Wards. –Leon Heller G1HSM

## 1922

Turing is sent to Hazelhurst Preparatory School where he does much better and learns to play chess.

## 1926-1931

He went on to Sherborne School, a well-known independent school in the market town of Sherborne in Dorset. His first day of term coincided with the 1926 General Strike. He was so determined not to miss his first day of school that he cycled the 97km from his home in Southampton. He is not interested in their traditional classical education as he really wants to study science and mathematics. His teachers were concerned that he leaned too heavily towards maths and science, at the expense of the classics. The headmaster wrote to his parents:

I hope he will not fall between two stools. If he is to stay at public school, he must aim at becoming educated. If he is to be solely a Scientific Specialist, he is wasting his time at a public school.

## 1928

Turing encountered Albert Einstein‘s work; not only did he grasp it, but he extrapolated Einstein’s questioning of Newton’s laws of motion from a text in which this was never made explicit. Turing enters 6th form at Sherborne and becomes great friends with Christopher Morcom, another talented boy who loves Maths and Science.

**1930**

Turing’s close school friend Christopher Morcom dies suddenly from bovine tuberculosis. Turing is devastated, renounces his religious faith and becomes an atheist.

## 1931-1934

Enters King’s College, Cambridge, as mathematics scholar. He gained first-class honours in Mathematics.

## 1935

Elected fellow of King’s College for his dissertation “Central Limit Theorem of Probability” Turing attended Max Newman‘s advanced course on the foundations of mathematics. This course studied Gödel’s incompleteness results and Hilbert‘s question on decidability: given a mathematical proposition could one find an algorithm which would decide if the proposition was true or false? He learnt that Hilbert’s *Entsceidungsproblem* (decision problem) was still open. Turing was motivated by Gödel’s work to seek an algorithmic method of determining whether any given propositions were undecidable, with the ultimate goal of eliminating them from mathematics.

## 1936

Submitted on 28 May 1936 and delivered 12 November to London Mathematical Society: *On Computable Numbers, with an Application to the Entscheidungsproblem* (decision problem) in which he outlines the Universal Machine, which later became known as the Turing Machine. This was an idealised computing device that is capable of performing any mathematical computation that can be represented as an algorithm. There cannot exist any universal method of decision and, hence, mathematics will always contain undecidable (as opposed to unknown) propositions. Turing invents programming in this paper (‘computer’ then was a human who computed):

It is always possible for the computer to break off from his work, to go away and forget all about it, and later to come back and go on with it. If he does this he must leave a note of instructions (written in some standard form) explaining how the work is to be continued … The note of instructions must enable him to carry out one step and write the next note. Thus the state of progress of the computation at any stage is completely determined by the note of instructions and the symbols on the tape.

## 1936-1938

In September Turing went to the Institute of Advanced Studies at Princeton, studying under Alonzo Church. There he started to study cryptology as well as mathematics.

## 1938

He obtained his PhD from Princeton University; his Ph.D. thesis under the direction of the American mathematician Alonzo Church, *Systems of Logic Based on Ordinals*, introduced the concept of ordinal logic and the notion of relative computing, where Turin

g machines are augmented with so-called oracles, allowing a study of problems that cannot be solved by a Turing machine. He then returned to England and accepted a renewed fellowship at King’s College. From September 1938, Turing had been working part-time with the Government Code and Cypher School (GCCS), the British code breaking organisation. He concentrated on Cryptanalysis of the Enigma, with Dilly Knox, a senior GCCS codebreaker.

## 1939

Applied to the Royal Society for a grant of £40 for the engineering of a special machine to calculate approximate values for the Riemann zeta-function on its critical line. **September** – Turing is asked to join the Government Codes and Ciphers School and arrives at Bletchley Park the day after war is declared. There he works with Gordon Welchman to develop the Bombe, a device for decrypting the messages sent by Germans using their Enigma machines. The Bombe

built on a machine that the Polish had already made, called the Bomba Kryptlogiczna. Many of Germany’s secret messages could be deciphered and read with it. The periods when the Naval code could be broken saw dramatic reductions in the shipping losses from the Atlantic convoys so essential to the conduct of the Allied war effort.Turing used statistical techniques to optimise the trial of different possibilities in the code-breaking process using probability.

Conceptualises programmable computer; named Colossus, the first such machine is built 3 years later, based on his ideas. These machines were the predecessors to the first digital computers.

## 1940

First Turing Bombe is installed at Bletchley Park.

## 1941

Turing proposed marriage to Hut 8 co-worker Joan Clarke, a fellow mathematician and cryptanalyst, but their engagement was short-lived. After admitting his homosexuality to his fiancée, who was reportedly “unfazed” by the revelation, Turing decided that he could not go through with the marriage.

## 1942

Turing and his colleagues break the more complicated German Naval Enigma system. This is a tremendous help to the Allies in the Battle of the Atlantic as it could help them avoid the fearsome German U-boats, which had been responsible for sinking more than 700 Allied ships with 2.3 million tons of vital cargo. Turing travelled to the United States in November and worked with U.S. Navy cryptanalysts on Naval Enigma and bombe construction in Washington, visiting their Computing Machine Laboratory at Dayton, Ohio. He shared what he knew about Enigma in return for being allowed to inspect the speech encryption system being set up to allow conversations between Churchill and Roosevelt. Turing was somewhat dismissive of US cryptanalysis, believing the Americans to rely too heavily on machinery instead of thought.

## 1943

Turing is asked to work as a top level intelligence link with USA, which he visits to share information on cryptology (code-breaking). Works at Bell Laboratories on speech encypherment.

## 1944

Colossus, the world’s first large-scale electronic computer, is installed at Bletchley Park.

## 1945

Von Neumann‘s ‘First Draft of a Report on the EDVAC’ is circulated, setting out the design of the EDVAC (Electronic Discrete Variable Arithmetic Computer)

Begins designing a stored-program machine (MOSAIC), which will store data and programs in its electronic memory.

Turing’s ‘Proposed Electronic Calculator‘ is circulated, setting out the design of the ACE (Automatic Computing Engine). In it, he suggests that computers will ‘play very good chess‘

Published* “A Method for the Calculation of the Zeta-Function”,* which constitutes his first printed contribution to the subject.

Turing was awarded the OBE for his wartime services, but his work remained secret for many years.

**October:** Turing joined the National Physical Laboratory (NPL) where he worked on developing an electronic digital stored-program computing machine that would later become the ACE (Automatic Computing Engine). By 1946 he had a finished proposal for the computer, but NPL did not have the resources to turn it into reality.

ENIAC (Electronic Numerical Integrator and Computer) is the second large-scale electronic computer to operate

## 1946

**19 February**, published the first detailed design of a stored-program computer.

Turing and his group pioneer modern computer programming, writing a library of sophisticated programs for the unbuilt ACE.

Turing presents a course of lectures on Versions V, VI, and VII of the ACE design, at the Ministry of Supply in London (Dec. 1946 to Feb. 1947). Kilburn attends from Manchester University.

## 1947

He returned to Cambridge for a sabbatical year during which he produced a seminal work on *Intelligent Machinery* that was not published in his lifetime.

Turing lectures on the ACE at Burlington House in London, the first public lecture to mention computer intelligence.

The Pilot ACE was built in his absence and executed its first program on 10 May 1950.

Darwin, Director of the National Physical Laboratory, halts work on ACE Test Assembly, leaving the field to Manchester.

## 1948

Appointed Reader in the Mathematics Department at the University of Manchester.

He also invented the LU decomposition method in 1948, used today for solving matrix equations.

Manchester wins the race: the world’s first stored-program electronic computer comes to life on June 21 in Newman‘s Computing Machine Laboratory.

Turing, now at Manchester as Deputy Director of the Computing Machine Laboratory, writes ‘Intelligent Machinery‘, the first manifesto of Artificial Intelligence.

Turing joined Max Newman’s Computing Laboratory at Manchester University, where he wrote programs for the Manchester Automatic Digital Machine (MADAM), the computer with the largest memory capacity in the world at that time.

Turing, working with his former undergraduate colleague, D. G. Champernowne, began writing a chess program for a computer that did not yet exist. Lacking a computer powerful enough to execute the program, Turing played a game in which he simulated the computer, taking about half an hour per move. ‘Turochamp’ plays its first game of chess.

ENIAC is set up to run in (read-only) stored-program mode

## 1949

He became Deputy Director of the Computing Laboratory, working on software for one of the earliest stored-program computers—the Manchester Mark 1.

Four more electronic stored-program computers become operational:EDSAC (Electronic Delay Storage Automatic Calculator) at the University of Cambridge, followed by BINAC (Binary Automatic Computer) in the U.S., the CSIR Mark I (Council for Scientific and Industrial Research Mark I Computer) in Australia, and Whirlwind I in the U.S.

Turing’s paper ‘Checking a Large Routine’ inaugurates the area now known as ‘program verification’.

## 1950

Pilot Model ACE is operational, preceded in the U.S. by SEAC (National Bureau of Standards Eastern Automatic Computer) and followed by SWAC (National Bureau of Standards Western Automatic Computer).

Publishes Computing Machinery and Intelligence, introducing a test of intelligence, that he said would prove a machine could think. This test later became known as the Turing Test. Turing was convinced that if a computer could do all mathematical operations, it could also do anything a person can do, a still highly controversial opinion. (Mind, October 1950), Turing addressed the problem of artificial intelligence, and proposed an experiment which became known as the Turing test, an attempt to define a standard for a machine to be called “intelligent”. The Turing Test has a computer and a person with the interrogator trying to distinguish which is the computer. The interrorgator asks questions via teletype so no visual identification can be made. The test is repeated with a range of people in the human position and if the number of times that repeated identification is less than pure guesswork then the machine has passed.

Used the prototype Manchester University Electronic Computer to do some calculations concerned with the distribution of the zeros of the Riemann zeta-function, specifically whether there are any zeros not on the critical line in certain intervals.

## 1951

Turing is elected Fellow of the Royal Society FRS and also gives a talk about Artificial Intelligence on the BBC radio’s Third Programme.

The Ferranti Mark I is the first commercially-available electronic stored-program computer. The first off the production line is installed at Manchester University.

Turing begins using the Ferranti Mark I to study biological growth.

UNIVAC is the first commercially-available electronic stored-program computer in the U.S.

von Neumann’s computer at the Princeton Institute for Advanced Study is operational.

Oettinger at Cambridge University writes the first program capable of learning.

## 1952

EDVAC is operational in the US.

Strachey‘s draughts (checkers) program plays its first game on the Manchester computer.

Turing worked from 1952 until his death in 1954 on mathematical biology, specifically morphogenesis. He worked on what would now be called Artificial Life, using the Ferranti Mark I computer to model aspects of biological growth, in particular a chemical mechanism by which the genes of a zygote could determine the anatomical structure of the resulting animal or plant. He published one paper on the subject called *The Chemical Basis of Morphogenesis* in 1952, putting forth the Turing hypothesis of pattern formation.

During the final years of his life Turing was working on what would now be called Artificial Life or A-Life. He used the Ferranti Mark I computer belonging to the Manchester University Computing Machine Laboratory to simulate a chemical mechanism by which the genes of a zygote may determine the anatomical structure of the resulting animal or plant. He described these studies as ‘not altogether unconnected’ to his work on neural networks, as ‘brain structure has to be … achieved by the genetical embryological mechanism, and this theory that I am now working on may make clearer what restrictions this really implies’. During this period Turing achieved the distinction of being the first to engage in the computer-assisted exploration of non-linear dynamical systems (his theory used non-linear differential equations to express the chemistry of growth). He died while in the middle of this groundbreaking work, leaving a large pile of handwritten notes and some programs. This material is still not fully understood. –Jack Copeland

Turing is arrested for gross indecency and loses his security clearance. Turing’s homosexuality resulted in a criminal prosecution in 1952, when homosexual acts were still illegal in the United Kingdom. He is offered chemical treatment as an alternative to imprisonment. The hormone treatment has a very detrimental effect on him.

## 1953

Turing publishes his classic paper on computer chess.

## 1954

Dies of cyanide poisoning June 7 in Wilmslow, Cheshire, England. June 8th – Turing’s body is found in his home in Wilmslow, Cheshire. The post-mortem finds that his death had been caused by cyanide poisoning. His body is cremated at Woking crematorium.

## Sources & Further Reading

- Wikipedia entry
- Alan Turing – Timeline
- Alan Turing, Father of the Modern Computer
- Biography of Turing By Jack Copeland
*On Computable Numbers, with an Application to the Entscheidungsproblem*- A history of the Pilot ACE and ACE computers, the computing machines developed at NPL as a result of Turing’s work, and of those involved