Alan Turing is pictured in a German museum exhibit in his honor.Bernd Thissen/European Pressphoto AgencyAlan Turing is pictured in a German museum exhibit in his honor.

Google honored him for the day with an online puzzle to commemorate his Turing Machine, which provided the basis of much of modern computing.LONDON — The centenary of the birth of Alan Turing, the World War II code-breaker and father of modern computing, was being marked on Saturday with memorials, exhibitions and academic gatherings in his native Britain and beyond.
“His essential insights into mathematics and the nature of computability dealt with the limits of what can be calculated by machines,” The New York Times wrote in an editorial recording his legacy.
The anniversary was also marked by renewed efforts to gain a pardon for the mathematical genius, who died by poison at the age of 41 after being hounded by an ungrateful establishment on account of his homosexuality.
He was brought to trial in 1952, at a time when homosexual acts were illegal in Britain, after police discovered his relationship with a young man in Manchester where he had settled to pursue research into the theory of growth and form in biology.
Turing avoided prison by accepting a course of hormones that amounted to chemical castration. He was found dead from cyanide poisoning at his home on June 8, 1954. The coroner ruled it as suicide “while the balance of his mind was disturbed.”
After his conviction, the man whose mathematical insights had helped developed the technology that contributed to the allied victory by cracking the Nazis’ wartime Enigma code, lost his security clearance and was placed under intense surveillance by authorities who regarded his sexuality as a security risk.
His scientific legacy was for decades obscured by the circumstances of his early death and the secrecy imposed until long after the war on those who had worked at Britain’s code-breaking center at Bletchley Park.
After a lengthy campaign that included leading scientists and academics, the British government in 2009 issued an unequivocal apology for what Gordon Brown, prime minister at the time, described as the “horrifying” and “utterly unfair” treatment that Turing had endured.
However, campaigners seeking a formal pardon were rebuffed earlier this year when the present government refused to overturn Turing’s 1952 conviction for the crime of gross indecency on the grounds he “would have known” that he was committing an offense under the law as it stood at the time.
Undeterred, some 35,000 people have since put their names to a formal petition to quash the conviction, in part as “an apology to many of the other gay men, not as well-known as Alan Turing, who were subjected to these laws.”
The widely accepted view, echoing that of the coroner’s, is that the mathematician took his own life in a moment of suffering and despair at his treatment.
Professor Jack Copeland, an authority on the mathematician’s life and work, has challenged that judgment.
Pointing to an inquest verdict that was “not supportable,” he told the BBC that Turing could as easily have died by accident as a result of a flawed scientific experiment.
At the time of his death, Professor Copeland said, Turing’s career was at an intellectual high, and he had borne his treatment “with good humor.” Turing had not sought to hide his sexual orientation.
“The exact circumstances of Turing’s death will probably always be unclear,” he said. “Perhaps we should just shrug our shoulders, and focus on Turing’s life and extraordinary work.”