The English mathematician, logician and codebreaker Alan Turing was a computer pioneer. Often remembered for his contributions to the fields of artificial intelligence and modern computer science (before either even existed), Turing is probably best known for what is now dubbed the "Turing Test". It is a process of testing a machine´s ability to "think".

The basic premise of the Turing Test is that a person would be placed in isolation and have two conversations with a computer and one with another person - but they would not be told which one was which. If the computer could fool them into thinking they were speaking to another person, then the computer would have passed the Turing Test. At the time of writing this, no computer has ever succeeded in doing so. Less is known however, about Turing´s intelligence work during World War Two when he used his mathematical and codebreaking skills to help break one of the most difficult of German ciphers, ENIGMA.

Though often used interchangeably, the terms codes and ciphers are very different. A code changes the meaning of a word or phrase by replacing it with a different word or phrase to make amessage secret. A cipher, on the other hand, makes a word of phrase secret by changing or rearranging the individual letters in a message Together, codes and ciphers are called encryption. 

ENIGMA was a cipher machine - each keystroke replaced a character in the message with another character determined by the machine´s rotor settings and wiring arragements that were previously established between the sender and the receiver. For extra security, the German military services usually double-encrypted their messages by changing the original text with code words and then enciphering the encoded text.

In the early years of World War Two, Turing worked at Britain´s code breaking headquarters in Bletchley Park. In addition to mathematicians, Bletchey Park also recruited linguists and chess champions, and attracted talent by approaching winners of a complex crossword competition held by The British newspaper, The Daily Telegraph.

Turing´s mathematical and logic skills made him a natural cryptanalyst. Whereas cryptographers write encryption systems, and cryptologists study them, cryptanalysts like Turing break them. In 1939, Turing created a method called "the bombe", an electromechanical device that could detect the settings for ENIGMA, allowing the Allied powers to decipher German encryptions.

Turing and his colleagues were also able to break the more complicated Naval ENIGMA system, which from 1941 to 1943 helped the Allies avoid German U-boats during the Battle of the Atlantic. Turing´s work at Bletchley Park played a vital part in ending the Second World War, and he helped save thousands of British and American lives. 

Nevertheless, Turing would spend most of his career focused on what would eventually become modern day computing. He was posted to serve with the US Navy´s Cryptanalytic Section for several months in 1943, where he met and discussed mathematical models of communication and computation with Claude Shannon (the father of information theory). To this day, our communications networks are built on top of Shannon´s ideas, while our computer devices, processors and chips are built upon Turing´s ideas. Turing´s contribution to modern computing was so significant that the prestigious A.M. Turing Award, sometimes known as the "Nobel Prize" of computer science, is named after him. 

Alan Turing died tragically in 1954 from cyanide poisoning, at the age of 41. His death was officially declared a suicide, although some people believe he died accidentally. It wasn´t until the 1970s that the story of ENIGMA could be told and Turing could be recognized for his significant contributions to modern computer science, the world of cryptography, and the defeat of Germany and its allies in World War Two.