Turing, that unknown

In a month's time, the computing world will be celebrating the centenary of Alan Turing, who was born in London on 23 June 1912.

Much mystery still surrounds the life and work of this great Englishman, who can truly be considered as the founder of computer science. He designed a marvelous computing device that soon became known as the Turing Machine. It's so powerful and precise that it can perform any calculation whatsoever, no matter how complex, including those that are carried out today by the giant supercomputers used in space engineering, military calculations or meteorological predictions. My book Machina Sapiens, published in 1976, offered French readers (no doubt for the first time ever) a drawing of a Turing Machine, accompanied by demonstrations of how it worked.

But I don't have the impression that anybody went out and actually built such a machine... to handle his office accounting, say. In fact, although a simple Turing Machine can indeed perform any of the computations executed by a modern computer, I have to be truthful and point out that I wouldn't advise anybody to get involved in trying to use a Turing Machine to build a spreadsheet, say, or to carry out some word processing. And I'm even less certain that a Turing Machine would be an efficient tool for tweeting, or sending e-mails, or linking up to Facebook. The problem, you see, is that Turing Machines have to be programmed from scratch, and even the simplest tasks—such as the multiplication of two numbers—would represent a huge programming challenge. What's more, I'm not sure that anybody has ever bothered to actually build an operational Turing Machine. Like the model that illustrated my book, Turing Machines tend to remain on paper, on the pages of textbooks for computer science students.

So, why all the fuss about Alan Turing having invented a machine that is the grand-daddy of all computers, past, present and future? Well, it's a bit like Einstein's E = mC2. This simple equation was the key to understanding that matter can be transformed into energy. But, between understanding the equation and being able to obtain energy from a nuclear reactor, a lot of hard work needs to be carried out. You might say poetically that the Turing Machine defines the "soul" of any imaginable computer in the real world. But, to move from the abstract "soul" to a real "flesh and blood" computer, you have to envisage a huge amount of design, engineering and programming... of both a hardware and a software kind.

Funnily enough, although the Turing Machine can indeed carry out any imaginable task that might be performed by modern computers, it's greatest interest was that it enabled Turing and other logicians to discover that certain tasks could never be carried out by any imaginable computer whatsoever. For example, it is impossible for a computer to determine beforehand, when faced with certain algorithms, that it will indeed be able to reach the intended end of the algorithm and provide an answer. In this way, the Turing Machine appeared on the scene as a mechanical variant of the themes of incompleteness and undecidability elucidated mathematically by Kurt Gödel (seen in the following photo alongside Albert Einstein):

Gödel was still alive in the early '70s when I was visiting the USA in order to organize my future series of TV programs on the subject of men and machines (basically, artificial intelligence and brain research). I spoke on the phone with Gödel for 20 minutes or so, trying vainly to get him to agree to being interviewed for my TV project. But he insisted—no doubt sincerely—that he himself did not consider that his theorems had any significance whatsoever in modern society... that's to say, at the level of ordinary folk who watch TV. Maybe he was right.

Getting back to Turing, his most concrete claim to fame was surely the wizard-level code-breaking operations that he performed for the British government during World War II, at Bletchley Park.

He was a practicing homosexual at a time in the UK when relationships of this kind were branded as criminal. The poor man, suffering no doubt from a form of autism (Asperger Syndrome) that made him socially awkward, was obliged to undergo ignominious chemical castration. In June 1954, a fortnight before his 42nd birthday, Turing was found dead in his laboratory, poisoned by cyanide, and clutching a half-eaten apple.

A British journalist once asked Steve Jobs if the logo of Apple computer was intended as a tribute to Turing. "No, that's not the case," replied Jobs, "but God, we wish it were."