lan Mathison Turing was born in London, in Maida Vale, on June 23, 1912.

The family is affluent: the father serves as a civil servant of the English administration in India, and the mother comes from an excellent Anglo-Irish Protestant family.

Alan spends his childhood and adolescence in England at various boarding schools, or as a guest of a couple of Turing acquaintances, however far from his parents whom he rarely sees.

In 1926 he enters Sherbone high school where he will make friends and perhaps something more with Christopher Morcom, a classmate who died prematurely in 1930, deeply affecting Alan.

Already in these years Turing stands out for the propensity towards exact sciences and mathematics, so much so that at the age of 16 he wrote a short essay on Einstein's theory of general relativity.

In 1931 he was admitted to the King’s College, one of the most prestigious university institutions in the world, of which he became a fellow four years later. He studies mathematics and logic.

In the public 1936 On Computable Numbers with an Application to the Entscheidungsprobleme. It is in this essay that Turing invents the machines that bear his name and thanks to which he takes apart a piece of Hilbert's program - completing the work of Goedel- and demonstrates that there are no definite procedures for deciding the truth or falsity of all mathematical statements.

To learn more about this topic, see the article Turing machines published on 21 April this year.

From 1936 to 1938 he studied a Princeton, under the guidance of Alonzo Church, where he obtained the PHD. In 1939 he returned to Cambridge, attended the seminars held by Ludwig Wittgenstein on the foundations of mathematics and in September of the same year he was enrolled in the working group of Bletchley Park.


The purpose of Bletchley Park is to decipher the codes used by the Germans to communicate with the different units of the army and navy. In particular, the Turing group is concerned with trying to decipher the Enigma code used by the German navy. Enigma is a not particularly sophisticated but very effective encryption system. Its use allows the German navy to strike relatively undisturbed aid convoys arriving from the United States, causing enormous damage to British forces.

Enigma it consists of a machine with a keyboard and with letters that light up, thanks to a battery, depending on the key you press. Between the letter of the key that is pressed and the letter that lights up there are three rotors that rotate at different speeds at each beat. The rotors contain electrical wires that connect with those of the other rotors in a different way at each turn of the rotors causing the ignition of the letters. In addition, a dashboard equipped with several sockets allows you to connect cables for ten pairs of letters by inverting them. This complex mechanism then creates a code that depends on the starting position of the rotors and cable plugs. All complicated by the fact that the three rotors are chosen from a kit of five, according to the instructions. The possible positions are millions of millions, which makes the code almost unbreakable especially not having modern computers.

The German Navy provides its units with a ledger with the positions of rotors and pins for each day. When the message arrives the operators implement the setup of the day and enter the letters contained in the message one by one by typing them on the keyboard. Since Enigma is a reversible deterministic machine they get the original German message in this way.

Turing, head of hut 8 that deals with decrypting Enigma, immediately realizes that the work cannot be done with paper and pen, but must be automated with the help of a machine.

Thus he creates with his collaborators The Bombe, a machine capable of testing all or almost all the possible setups of the Enigma machine day by day and therefore of deciphering the messages of that specific day. In fact, let's remember that the Enigma setup was changed daily.

The great strength of Enigma is that the same letter in input when re-input gives rise to different letters in output, which makes it impossible to work on the frequencies of the occurrences of the different letters in German to decipher the message. But Enigma also has a serious handicap: a letter is never encrypted as itself, in other words if I type "a" I will never have "a" as an output.

Consequently, the Bombe with a heuristic approach (assuming for example that the first words of the message to be decrypted are "weather report" and the last "heil Hitler") begins to simulate all the Enigma setups, discarding all those where a letter in input match the same letter in output. This speeds up the work damnably, and in 1941, Bombe was able to decipher Enigma messages within half an hour, practically the same time it takes German operators to read them using the Enigma machine.

Thanks to Turing and his collaborators, the German navy is no longer able to intercept convoys from the USA.

It is estimated that the decryption of Enigma shortened the time of the war by about two years and saved the lives of two million Allied soldiers.


After the war, Turing will deal first of the ACE (Automatic Computing Engine) and then del Mark 1, both very advanced designs of universal (general purpose) and programmable computers.

In 1950 he published his famous article in Mind magazine Computing Machinery and Intelligence which among other things exposes for the first time the famous Turing test, still used today to distinguish men and machines (see CAPTCHA), and which is considered the foundation of studies on artificial intelligence.

On June 8, 1954, Alan's lifeless body is found by his servant. Cause of death is cyanide poisoning, most likely voluntarily taken to take his own life. The last two years of this giant of contemporary thought and war hero had been marred by a cruel trial for homosexuality at the end of which, to avoid jail, Turing had submitted to a chemical castration treatment that had deeply undermined his body. and in the soul.

Only in 2013 the British Crown will deign to "forgive" and rehabilitate Turing.