In April 1941, as IBM was constructing the Mark I to Aiken’s specifications at its lab in Endicott, New York, he left Harvard to serve in the U.S. Navy. For two years he was a teacher, with the rank of lieutenant commander, at the Naval Mine Warfare School in Virginia. One colleague described him as “armed to the teeth with room-length formulas and ivy-covered Harvard theories” and running “smack into a collection of Dixie dumbbells [none of whom] knew calculus from corn pone.”21 Much of his time was spent thinking about the Mark I, and he made occasional visits to Endicott wearing his full dress uniform.22
His tour of duty had one major payoff: at the beginning of 1944, as IBM was getting ready to ship the completed Mark I to Harvard, Aiken was able to convince the Navy to take over authority for the machine and assign him to be the officer in charge. That helped him circumnavigate the academic bureaucracy of Harvard, which was still balky about granting him tenure. The Harvard Computation Laboratory became, for the time being, a naval facility, and all of Aiken’s staffers were Navy personnel who wore uniforms to work. He called them his “crew,” they called him “commander,” and the Mark I was referred to as “she,” as if she were a ship.23
The Harvard Mark I borrowed a lot of Babbage’s ideas. It was digital, although not binary; its wheels had ten positions. Along its fifty-foot shaft were seventy-two counters that could store numbers of up to twenty-three digits, and the finished five-ton product was eighty feet long and fifty feet wide. The shaft and other moving parts were turned electrically. But it was slow. Instead of electromagnetic relays, it used mechanical ones that were opened and shut by electric motors. That meant it took about six seconds to do a multiplication problem, compared to one second for Stibitz’s machine. It did, however, have one impressive feature that would become a staple of modern computers: it was fully automatic. Programs and data were entered by paper tape, and it could run for days with no human intervention. That allowed Aiken to refer to it as “Babbage’s dream come true.”24
KONRAD ZUSE
Although they didn’t know it, all of these pioneers were being beaten in 1937 by a German engineer working in his parents’ apartment. Konrad Zuse was finishing the prototype for a calculator that was binary and could read instructions from a punched tape. However, at least in its first version, called the Z1, it was a mechanical, not an electrical or electronic, machine.
Like many pioneers in the digital age, Zuse grew up fascinated by both art and engineering. After graduating from a technical college, he got a job as a stress analyst for an aircraft company in Berlin, solving linear equations that incorporated all sorts of load and strength and elasticity factors. Even using mechanical calculators, it was almost impossible for a person to solve in less than a day more than six simultaneous linear equations with six unknowns. If there were twenty-five variables, it could take a year. So Zuse, like so many others, was driven by the desire to mechanize the tedious process of solving mathematical equations. He converted his parents’ living room, in an apartment near Berlin’s Tempelhof Airport, into a workshop.25
In Zuse’s first version, binary digits were stored by using thin metal plates with slots and pins, which he and his friends made using a jigsaw. At first he used punched paper tape to input data and programs, but he soon switched to discarded 35 mm movie film, which not only was sturdier but happened to be cheaper. His Z1 was completed in 1938, and it was able to clank through a few problems, though not very reliably. All the components had been made by hand, and they tended to jam. He was handicapped by not being at a place like Bell Labs or part of a collaboration like Harvard had with IBM, which would have allowed him to team up with engineers who could have supplemented his talents.
The Z1 did, however, show that the logical concept Zuse had designed would work in theory. A college friend who was helping him, Helmut Schreyer, urged that they make a version using electronic vacuum tubes rather than mechanical switches. Had they done so right away, they would have gone down in history as the first inventors of a working modern computer: binary, electronic, and programmable. But Zuse, as well as the experts he consulted at the technical school, balked at the expense of building a device with close to two thousand vacuum tubes.26
So for the Z2 they decided instead to use electromechanical relay switches, acquired secondhand from the phone company, which were tougher and cheaper, although a lot slower. The result was a computer that used relays for the arithmetic unit. However, the memory unit was mechanical, using movable pins in a metal sheet.
In 1939 Zuse began work on a third model, the Z3, that used electromechanical relays both for the arithmetic unit and for the memory and control units. When it was completed in 1941, it became the first fully working all-purpose, programmable digital computer. Even though it did not have a way to directly handle conditional jumps and branching in the programs, it could theoretically perform as a universal Turing machine. Its major difference from later computers was that it used clunky electromagnetic relays rather than electronic components such as vacuum tubes or transistors.
Zuse’s friend Schreyer went on to write a doctoral thesis, “The Tube Relay and the Techniques of Its Switching,” that advocated using vacuum tubes for a powerful and fast computer. But when he and Zuse proposed it to the German Army in 1942, the commanders said they were confident that they would win the war before the two years it would take to build such a machine.27 They were more interested in making weapons than computers. As a result, Zuse was pulled away from his computer work and sent back to engineering airplanes. In 1943 his computers and designs were destroyed in the Allied bombing of Berlin.
Zuse and Stibitz, working independently, had both come up with employing relay switches to make circuits that could handle binary computations. How did they develop this idea at the same time when war kept their two teams isolated? The answer is partly that advances in technology and theory made the moment ripe. Along with many other innovators, Zuse and Stibitz were familiar with the use of relays in phone circuits, and it made sense to tie that to binary operations of math and logic. Likewise, Shannon, who was also very familiar with phone circuits, made the related theoretical leap that electronic circuits would be able to perform the logical tasks of Boolean algebra. The idea that digital circuits would be the key to computing was quickly becoming clear to researchers almost everywhere, even in isolated places like central Iowa.
JOHN VINCENT ATANASOFF
Far from both Zuse and Stibitz, another inventor was also experimenting with digital circuits in 1937. Toiling in a basement in Iowa, he would make the next historic innovation: building a calculating device that, at least in part, used vacuum tubes. In some ways his machine was less advanced than the others. It wasn’t programmable and multipurpose; instead of being totally electronic, he included some slow mechanical moving elements; and even though he built a model that was able to work in theory, he couldn’t actually get the thing reliably operational. Nevertheless, John Vincent Atanasoff, known to his wife and friends as Vincent, deserves the distinction of being the pioneer who conceived the first partly electronic digital computer, and he did so after he was struck by inspiration during a long impetuous drive one night in December 1937.28
Atanasoff was born in 1903, the eldest of seven children of a Bulgarian immigrant and a woman descended from one of New England’s oldest families. His father worked as an engineer in a New Jersey electric plant run by Thomas Edison, then moved the family to a town in rural Florida south of Tampa. At nine, Vincent helped his father wire their Florida house for electricity, and his father gave him a Dietzgen slide rule. “That slide rule was my meat,” he recalled.29 At an early age, he dove into the study of logarithms with an enthusiasm that seems a bit wacky even as he recounted it in earnest tones: “Can you imagine how a boy of nine, with baseball on his mind, could be transformed by this knowledge? Baseball was reduced to near zero as a stern study was made of logarithms.” Over the summer, he calculated the logarithm of 5 to the base e, then, with his mother�
��s help (she had once been a math teacher), he learned calculus while still in middle school. His father took him to the phosphate plant where he was an electrical engineer, showing him how the generators worked. Diffident, creative, and brilliant, young Vincent finished high school in two years, getting all A’s in his double load of classes.
At the University of Florida he studied electrical engineering and displayed a practical inclination, spending time in the university’s machine shop and foundry. He also remained fascinated by math and as a freshman studied a proof involving binary arithmetic. Creative and self-confident, he graduated with the highest grade point average of his time. He accepted a fellowship to pursue master’s work in math and physics at Iowa State and, even though he later was admitted to Harvard, stuck with his decision to head up to the corn belt town of Ames.
Atanasoff went on to pursue a doctorate in physics at the University of Wisconsin, where he had the same experience as the other computer pioneers, beginning with Babbage. His work, which was on how helium can be polarized by an electric field, involved tedious calculations. As he struggled to solve the math using a desktop adding machine, he dreamed of ways to invent a calculator that could do more of the work. After returning to Iowa State in 1930 as an assistant professor, he decided that his degrees in electrical engineering, math, and physics had equipped him for the task.
There was a consequence to his decision not to stay at Wisconsin or to go to Harvard or a similar large research university. At Iowa State, where no one else was working on ways to build new calculators, Atanasoff was on his own. He could come up with fresh ideas, but he did not have around him people to serve as sounding boards or to help him overcome theoretical or engineering challenges. Unlike most innovators of the digital age, he was a lone inventor, drawing his inspiration during solo car trips and in discussions with one graduate student assistant. In the end, that would prove to be a drawback.
Atanasoff initially considered building an analog device; his love of slide rules led him to try to devise a supersize version using long strips of film. But he realized that the film would have to be hundreds of yards long in order to solve linear algebraic equations accurately enough to suit his needs. He also built a contraption that could shape a mound of paraffin so that it could calculate a partial differential equation. The limitations of these analog devices caused him to focus instead on creating a digital version.
The first problem he tackled was how to store numbers in a machine. He used the term memory to describe this feature: “At the time, I had only a cursory knowledge of the work of Babbage and so did not know he called the same concept ‘store.’ . . . I like his word, and perhaps if I had known, I would have adopted it; I like ‘memory,’ too, with its analogy to the brain.”30
Atanasoff went through a list of possible memory devices: mechanical pins, electromagnetic relays, a small piece of magnetic material that could be polarized by an electric charge, vacuum tubes, and a small electrical condenser. The fastest would be vacuum tubes, but they were expensive. So he opted instead to use what he called condensers—what we now call capacitors—which are small and inexpensive components that can store, at least briefly, an electrical charge. It was an understandable decision, but it meant that the machine would be sluggish and clunky. Even if the adding and subtracting could be done at electronic speeds, the process of taking numbers in and out of the memory unit would slow things down to the speed of the rotating drum.
George Stibitz (1904–95) circa 1945.
Konrad Zuse (1910–95) with the Z4 computer in 1944.
John Atanasoff (1903–95) at Iowa State, circa 1940.
Reconstruction of Atanasoff’s computer.
Once he had settled on the memory unit, Atanasoff turned his attention to how to construct the arithmetic and logic unit, which he called the “computing mechanism.” He decided it should be fully electronic; that meant using vacuum tubes, even though they were expensive. The tubes would act as on-off switches to perform the function of logic gates in a circuit that could add, subtract, and perform any Boolean function.
That raised a theoretical math issue of the type he had loved since he was a boy: Should his digital system be decimal or binary or rely on some other numerical base? A true enthusiast for number systems, Atanasoff explored many options. “For a short time the base one-hundred was thought to have some promise,” he wrote in an unpublished paper. “This same calculation showed that the base that theoretically gives the highest speed of calculation is e, the natural base.”31 But, balancing theory with practicality, he finally settled on base-2, the binary system. By late 1937, these and other ideas were jangling around in his head, a “hodgepodge” of concepts that wouldn’t “jell.”
Atanasoff loved cars; he liked to buy, if he could, a new one each year, and in December 1937, he had a new Ford with a powerful V8 engine. To relax his mind, he took it for a late-night spin for what would become a noteworthy moment in the history of computing:
One night in the winter of 1937 my whole body was in torment from trying to solve the problems of the machine. I got in my car and drove at high speeds for a long while so I could control my emotions. It was my habit to do this for a few miles: I could gain control of myself by concentrating on driving. But that night I was excessively tormented, and I kept on going until I had crossed the Mississippi River into Illinois and was 189 miles from where I started.32
He turned off the highway and pulled into a roadhouse tavern. At least in Illinois, unlike in Iowa, he could buy a drink, and he ordered himself a bourbon and soda, then another. “I realized that I was no longer so nervous and my thoughts turned again to computing machines,” he recalled. “I don’t know why my mind worked then when it had not worked previously, but things seemed to be good and cool and quiet.” The waitress was inattentive, so Atanasoff got to process his problem undisturbed.33
He sketched out his ideas on a paper napkin, then began to sort through some practical questions. The most important was how to replenish the charges in the condensers, which would otherwise drain after a minute or two. He came up with the idea of putting them on rotating cylinder drums, about the size of 46-ounce cans of V8 juice, so they would come into contact once a second with brushlike wires and have their charges refreshed. “During this evening in the tavern, I generated within my mind the possibility of the regenerative memory,” he declared. “I called it ‘jogging’ at that time.” With each turn of the rotating cylinder, the wires would jog the memory of the condensers and, when necessary, retrieve data from the condensers and store new data. He also came up with an architecture that would take numbers from two different cylinders of condensers, then use the vacuum-tube circuit to add or subtract them and put the result into memory. After a few hours of figuring everything out, he recalled, “I got in my car and drove home at a slower rate.”34
* * *
By May 1939, Atanasoff was ready to begin construction of a prototype. He needed an assistant, preferably a graduate student with engineering experience. “I have your man,” a friend on the faculty told him one day. Thus he struck up a partnership with another son of a self-taught electrical engineer, Clifford Berry.35
The machine was designed and hard-wired with a single purpose: solving simultaneous linear equations. It could handle up to twenty-nine variables. With each step, Atanasoff’s machine would process two equations and eliminate one of the variables, then print the resulting equations on 8 x 11 binary punch cards. This set of cards with the simpler equation would then be fed back into the machine for the process to begin anew, eliminating yet another variable. The process required a bit of time. The machine would (if they could get it to work properly) take almost a week to complete a set of twenty-nine equations. Still, humans doing the same process on desk calculators would require at least ten weeks.
Atanasoff demonstrated a prototype at the end of 1939 and, hoping to get funding to build a full-scale machine, typed up a thirty-five-page proposal, using carbon paper to
make a few copies. “It is the main purpose of this paper to present a description and exposition of a computing machine which has been designed principally for the solution of large systems of linear algebraic equations,” he began. As if to fend off criticism that this was a limited purpose for a big machine, Atanasoff specified a long list of problems that required solving such equations: “curve fitting . . . vibrational problems . . . electrical circuit analysis . . . elastic structures.” He concluded with a detailed list of proposed expenditures, which added up to the grand sum of $5,330, which he ended up getting from a private foundation.36 Then he sent one of the carbon copies of his proposal to a Chicago patent lawyer retained by Iowa State, who, in a dereliction of duty that would spawn decades of historical and legal controversy, never got around to filing for any patents.
* * *
By September 1942 Atanasoff’s full-scale model was almost finished. It was the size of a desk and contained close to three hundred vacuum tubes. There was, however, a problem: the mechanism for using sparks to burn holes in the punch cards never worked properly, and there were no teams of machinists and engineers at Iowa State he could turn to for help.
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