An Irishman's Diary

IT WAS WHILE I was correcting exam scripts recently that an enterprising student made me aware of the Irish family connections of Alan Turing, one of the founding fathers of computer science.

His maternal grandparents hailed from counties Tipperary and Longford. His mother, Ethel Stoney, spent her childhood years in Co Clare, with the family later moving to Dublin in 1891. She was educated in Alexandra College in Milltown and married Julius Turing, a member of the Indian Civil Service, in St Bartholomew’s church in Ballsbridge in October 1907.

Five years later found them in London, where their son Alan Turing was born, 100 years ago today.

At that time, while there would have been telephones, cars, films, music players, electric lighting and airplanes, there were no computers. The work of Turing, among others, made the computing revolution possible. It was his independent and innovative thinking which led him to analyse and dissect the nature of knowledge, a quest which would eventually change the world.

After being elected a fellow at Cambridge at the age of 22, the young Turing set his mind to solving one of the great problems of mathematics known as the Entscheidungsproblem. The question was whether the work of mathematicians might feasibly be replaced by a machine, which could grind out any mathematical proof by simply applying logical rules repetitively until a solution eventually popped out.

Turing found that for any general-purpose computing machine, there would always be some problems that it cannot solve. One of the major impacts of this work was that Turing formally defined for the first time the notion of an algorithm, that is, a step by step procedure for solving a problem.

Previously it had been assumed that different tasks would require different machines. For example, machines existed to process the data from census returns, or to calculate astronomical data, but each was built for just that specific purpose. But Turing defined the abstract concept of a Universal Machine, an idea which demonstrates that, by first loading and then running a program, one computer can complete the same tasks as any special-purpose machine. Today this forms the basis of the flexible general purpose computer, which can run your desktop, laptop, mobile phone or microwave.

During the second World War, Turing played a key role in cracking the secret codes used by the German military to encrypt their communications. The day after the United Kingdom declared war on Germany, Turing reported to Bletchley Park, where a group of leading scientists, engineers and mathematicians was assembled with the task of decrypting enemy traffic. Turing played a key role in the building of electromechanical machines for speeding up the statistical analysis of encrypted messages. By 1945, these could often be decoded in less than a day, shortening the war by up to two years and potentially saving millions of lives.