The history of computing: Creation story Turing's Cathedral: The Origins of the Digital Universe. By George Dyson. Pantheon; 401 pages; $29.95. Allen Lane; £25. "I AM thinking about something much more important than bombs," John von Neumann remarked in 1946. I am thinking about computers. The Hungarian-born mathematical genius knew that weapons and computers were closely intertwined. During the second world war computers had been built to crack codes (Colossus, in Britain) and calculate artillery firing tables (ENIAC, in America). But these were dedicated machines built to perform specific tasks. Von Neumann dreamed of building a far more flexible and powerful general-purpose computer, the theoretical capabilities of which had been determined in the 1930s by Alan Turing, a British mathematician. As the cold war began, along came the perfect opportunity: the hydrogen bomb, whose construction would require detailed mathematical modelling. Von Neumann did a deal with his American military paymasters. They got their bomb, and the scientists got their computer, a key ancestor of all modern machines. The subsequent explosion of computing changed the world. As George Dyson explains in "Turing's Cathedral," von Neumann was just as excited by the other possibilities opened up by computers, from artificial life to weather forecasting. But the hydrogen-bomb project offered him the freedom and the money to build a new type of computer: a "stored-program" machine that could be reconfigured quickly to perform different tasks by changing its software, rather than rewiring its hardware. The project took shape in the unlikely surroundings of the Institute for Advanced Study (IAS) at Princeton University, an academic Utopia where some of the world's finest minds, including von Neumann, Albert Einstein and Mr Dyson's father, Freeman Dyson, were given extraordinary freedom to pursue theoretical research. Von Neumann and the band of engineers he assembled to build his computer were looked down upon by other members of the IAS faculty, who preferred to grapple with esoteric theories rather than cathode-ray tubes, thermionic valves and soldering irons - let alone thermonuclear weapons. But von Neumann got his way, and by 1953 his machine was simulating nuclear explosions by day and modelling the evolution of artificial life forms, the creations of Nils Barricelli, by night. The computer let humans play God, creating life in the digital realm while devising new ways to destroy it in the real world. That same year James Watson and Francis Crick revealed the digital nature of life itself, with the discovery of the structure of DNA. Mr Dyson, who relishes such ironies, observes that the digital ecosystem of the internet has now assumed biological complexity. Yet despite establishing the blueprint for all subsequent computers, which are known to this day as Neumann machines, the IAS machine is less well known, even among computer-history buffs, than ENIAC or Colossus. Admittedly, it was not the first stored-program machine; during its construction, von Neumann and others modified ENIAC to a stored-program design, and other stored-program machines were also built in Britain. But the IAS machine's design was distributed and widely copied; one of its many offspring was the IBM 701, the first commercially successful computer. Mr Dyson's book, the product of ten years in the IAS archives, is an effort to remedy this blind-spot in computing history. It seems to have arisen, in part, because the IAS was embarrassed by the practical nature of von Neumann's project, making it reluctant to highlight its role in the genesis of modern computing. This is a technical, philosophical and sometimes personal account: as a boy Mr Dyson encountered many of the protagonists of his story while visiting his father at the IAS. The chronology of "Turing's Cathedral" is confusing at times, and Mr Dyson sometimes gets sidetracked by minor details: Kurt Gödel's visa problems, for example, or the construction and layout of IAS buildings. But there are fascinating detours into the histories of science and mathematics, the origins of weather forecasting, the development of nuclear weapons and the earliest work on artificial life. This wide-ranging and lyrical work is an important addition to the literature of the history of computing.