STORED PROGRAMS
From the beginning, Mauchly and Eckert understood that there were ways to make ENIAC easier to reprogram. But they didn’t try to do so because building in that capability would have required them to make the hardware more complicated, and it wasn’t necessary for the tasks they originally envisioned. “No attempt has been made to make provision for setting up a problem automatically,” they wrote in their year-end 1943 ENIAC progress report. “This is for the sake of simplicity and because it is anticipated that the ENIAC will be used primarily for problems of a type in which one setup will be used many times before another problem is placed on the machine.”37
But more than a year before ENIAC was finished, indeed as early as the beginning of 1944, Mauchly and Eckert realized that there was a good way to make computers easily reprogrammable: store the programs inside the computer’s memory rather than load them in every time. That, they sensed, would be the next great advance in computer development. This “stored-program” architecture would mean that a computer’s tasks could be changed almost instantly, without manually reconfiguring cables and switches.38
To store a program inside of the machine, they would need to create a large memory capacity. Eckert considered many methods for doing that. “This programming may be of the temporary type set up on alloy discs or of the permanent type on etched discs,” he wrote in a January 1944 memo.39 Because such disks were not yet affordable, he proposed using instead, on the next version of ENIAC, a cheaper storage method, which was called an acoustic delay line. It had been pioneered at Bell Labs by an engineer named William Shockley (about whom there will be a lot more later) and developed at MIT. The acoustic delay line worked by storing data as pulses in a long tube filled with a thick and sluggish liquid, such as mercury. At one end of the tube, an electrical signal carrying a stream of data would be converted by a quartz plug into pulses that would ripple back and forth the length of the tube for a while. The ripples could be refreshed electrically for as long as necessary. When it came time to retrieve the data, the quartz plug would convert it back into an electrical signal. Each tube could handle approximately a thousand bits of data at one-hundredth the cost of using a circuit of vacuum tubes. The next-generation ENIAC successor, Eckert and Mauchly wrote in a memo in the summer of 1944, should have racks of these mercury delay line tubes to store both data and rudimentary programming information in digital form.
JOHN VON NEUMANN
At this point, one of the most interesting characters in the history of computing reenters the tale: John von Neumann, the Hungarian-born mathematician who was a mentor to Turing in Princeton and offered him a job as an assistant. An enthusiastic polymath and urbane intellectual, he made major contributions to statistics, set theory, geometry, quantum mechanics, nuclear weapons design, fluid dynamics, game theory, and computer architecture. He would end up significantly improving upon, getting his name attached to, and reaping most of the credit for the stored-program architecture that Eckert, Mauchly, and their colleagues had begun to consider.40
Von Neumann was born to a prosperous Jewish family in Budapest in 1903, during a glittering period after the Austro-Hungarian Empire abolished the restrictive laws against Jews. Emperor Franz Joseph awarded a hereditary title in 1913 to the banker Max Neumann for “meritorious service in the financial field,” thus allowing the family to be called margittai Neumann or, in German, von Neumann. János (known as Jancsi and later, in America, as John or Johnny) was the eldest of three brothers, who all converted to Catholicism (“for convenience sake,” one admitted) after their father’s death.41
Von Neumann was another innovator who stood at the intersection of the humanities and sciences. “Father was an amateur poet and he believed that poetry could convey not only emotions but also philosophical ideas,” John’s brother Nicholas recalled. “He regarded poetry as a language within a language, an idea that might be traced to John’s future speculations on the languages of the computer and the brain.” Of his mother he wrote, “She believed that music, art, and related aesthetic pleasures had an important place in our lives, that elegance was a quality to be revered.”42
There is a wealth of stories about young von Neumann’s prodigal genius, some of them probably true. At age six, it was later said, he would joke with his father in classical Greek, and he could divide two eight-digit numbers in his head. As a party trick, he would memorize a page of the phone book and recite back the names and numbers, and he could recall verbatim pages from novels or articles he had read, in any of five languages. “If a mentally superhuman race ever develops,” the hydrogen bomb developer Edward Teller once said, “its members will resemble Johnny von Neumann.”43
In addition to school, he had private tutors in math and languages, and by age fifteen he had completely mastered advanced calculus. When the communist Béla Kun briefly took over Hungary in 1919, von Neumann’s tutelage was moved to Vienna and a resort on the Adriatic, and he developed a lifelong aversion to communism. He studied chemistry at the Swiss Federal Institute of Technology in Zurich (where Einstein had gone) and mathematics at both Berlin and Budapest, earning his doctorate in 1926. In 1930, he went to Princeton University to teach quantum physics, and he stayed on after being appointed (along with Einstein and Gödel) among the founding faculty of the Institute for Advanced Study.44
Von Neumann and Turing, who met in Princeton, would become paired as the grand theorists of the general-purpose computer, but in personality and temperament they were binary opposites. Turing led a spartan existence, lived in boardinghouses and hostels, and generally kept to himself; von Neumann was an elegant bon vivant who hosted sparkling parties with his wife once or twice a week at their huge house in Princeton. Turing was a long-distance runner; there were very few thoughts that could be said never to have crossed von Neumann’s mind, but running long distances (or even short distances) was among them. “In dress and habits he tended to be slovenly,” Turing’s mother once said of her son. Von Neumann, by contrast, wore a three-piece suit at almost all times, including on a donkey ride down the Grand Canyon; even as a student he was so well dressed that, upon first meeting him, the mathematician David Hilbert reportedly had but one question: Who is his tailor?45
Von Neumann loved telling jokes and reciting risqué limericks in various languages at his parties, and he ate so heartily that his wife once said he could count anything except calories. He drove cars with an abandon that was reckless but not always wreckless, and he was fond of flashy new Cadillacs. “He bought a new one at least once a year, whether he had wrecked the previous one or not,” wrote the science historian George Dyson.46
While at the Institute in the late 1930s, von Neumann developed an interest in ways to mathematically model explosive shock waves. This led him to become, in 1943, a member of the Manhattan Project, making frequent trips to the secret facilities in Los Alamos, New Mexico, where atomic weapons were being developed. Because there was not enough uranium-235 to build more than one bomb, the scientists at Los Alamos were also trying to design a device that would use plutonium-239. Von Neumann focused on ways to construct an explosive lens that would compress the plutonium core of the bomb to reach critical mass.III