Herman Zuse’s Z3, completed in May 1941, was the first automatically controlled, programmable, electrical, binary machine. It was designed to do engineering problems rather than be a general-purpose machine. However, it was later shown that, in theory, it could have been used as a Turing-complete machine. Its major difference from modern computers was that it was electromechanical, dependent on clacking and slow relay switches, rather than electronic. Another shortcoming is that it never really went into full-scale service. It was destroyed by the Allied bombing of Berlin in 1943.

The computer designed by John Vincent Atanasoff, which was complete but not fully workable by the time Atanasoff abandoned it to serve in the Navy in September 1942, was the world’s first electronic digital computer, but it was only partly electronic. Its add-subtract mechanism used vacuum tubes, but its memory and data retrieval involved mechanical rotating drums. Its other main drawback, in terms of being considered the first modern computer, was that it was not programmable nor general purpose; instead it was hard-wired for the special task of solving linear equations. Also, Atanasoff never got it fully operational, and it disappeared into a basement at Iowa State.

Bletchley Park’s Colossus I, completed in December 1943 by Max Newman and Tommy Flowers (with input from Alan Turing), was the first digital computer that was fully electronic, programmable, and operational. It was not, however, a general-purpose or Turing-complete machine; it was geared to the specific purpose of breaking Germany’s wartime codes.

Howard Aiken’s Harvard Mark I, built with IBM and put into operation in May 1944, was programmable, as we will see in the following chapter, but it was electromechanical rather than electronic.

ENIAC, completed by Presper Eckert and John Mauchly in November 1945, was the first machine to incorporate the full set of traits of a modern computer. It was all-electronic, superfast, and could be programmed by plugging and unplugging the cables connecting its different units. It was capable of changing paths based on interim results, and it qualified as a general-purpose Turing-complete machine, meaning it could in theory tackle any task. Most important, it worked. “That’s a big thing with an invention,” Eckert later said, contrasting their machine with Atanasoff’s. “You have to have a whole system that works.”⁷⁵ Mauchly and Eckert got their machine to do some very powerful calculations, and it was in constant use for ten years. It became the basis for most subsequent computers.

That last attribute is important. When we ascribe credit for an invention, determining who should be most noted by history, one criterion is looking at whose contributions turned out to have the most influence. Invention implies contributing something to the flow of history and affecting how an innovation developed. Using historic impact as a standard, Eckert and Mauchly are the most noteworthy innovators. Almost all computers of the 1950s trace their roots to ENIAC. The influence of Flowers, Newman, and Turing is somewhat trickier to assess. Their work was kept top-secret, but all three men were involved in the British computers built after the war. Zuse, who was isolated and under bombardment in Berlin, had even less influence on the course of computer development elsewhere. As for Atanasoff, his main influence on the field, perhaps his only influence, came from providing a few inspirations to Mauchly when he visited.

The issue of what inspirations Mauchly gleaned during his four-day visit with Atanasoff in Iowa in June 1941 turned into a protracted legal dispute. That raised another criterion, more legalistic than historical, in assessing credit for invention: Who, if anyone, ended up with the patents? In the case of the first computers, nobody did. But that outcome was due to a controversial legal battle that resulted in the patents of Eckert and Mauchly being nullified.⁷⁶

The saga began in 1947, when Eckert and Mauchly, after leaving Penn, applied for a patent on their ENIAC work, which was finally granted (the patent system being rather slow) in 1964. By then the Eckert-Mauchly company and its patent rights had been sold to Remington Rand, which became Sperry Rand; it began pressuring other companies to pay it licensing fees. IBM and Bell Labs made deals, but Honeywell balked and started looking for a way to challenge the patents. It hired a young lawyer, Charles Call, who had an engineering degree and had worked at Bell Labs. His mission was to upend the Eckert-Mauchly patent by showing that their ideas weren’t original.

Pursuing a tip from a Honeywell lawyer who had gone to Iowa State and read about the computer that Atanasoff had built there, Call paid a visit to Atanasoff at his home in Maryland. Atanasoff was charmed by Call’s knowledge of his computer and somewhat resentful that he had never gotten much credit for it, so he handed over hundreds of letters and documents that showed how Mauchly had derived some ideas from his visit to Iowa. That evening Call drove to Washington to sit in the back of a lecture Mauchly was giving. In answer to a question about Atanasoff’s machine, Mauchly claimed he had barely examined it. Call realized that if he could get Mauchly to say this in a deposition, then he could discredit him at a trial by producing Atanasoff’s documents.

When Mauchly found out a few months later that Atanasoff might be helping Honeywell challenge his patents, he made his own visit to Atanasoff’s Maryland home, bringing with him a Sperry Rand lawyer. It was an awkward meeting. Mauchly claimed that during his visit to Iowa he hadn’t read Atanasoff’s paper carefully or examined his computer, and Atanasoff coldly pointed out that this was not true. Mauchly stayed for dinner and tried to ingratiate himself with Atanasoff, but to no avail.

The issue went to trial before a federal judge, Earl Larson, in Minneapolis in June 1971. Mauchly proved a problematic witness. Pleading poor memory, he sounded squirrely about what he had seen during his visit to Iowa, and he repeatedly backtracked from assertions he had made in his earlier deposition, including his claim that he had only seen Atanasoff’s computer partly covered and in dim light. Atanasoff, by contrast, was very effective. He described the machine he had built, demonstrated a model, and pointed out which of his ideas Mauchly had borrowed. In all, seventy-seven witnesses were called to testify, another eighty were deposed, and 32,600 exhibits were entered into the record. The trial lasted more than nine months, making it the longest federal trial to that point.

Judge Larson took another nineteen months to write his final decision, which was issued in October 1973. In it he ruled that the Eckert-Mauchly ENIAC patent was invalid: “Eckert and Mauchly did not themselves first invent the automatic electronic digital computer, but instead derived that subject matter from one Dr. John Vincent Atanasoff.”⁷⁷ Instead of appealing, Sperry settled with Honeywell.^IV

The judge’s opinion, at 248 pages, was thorough, but it disregarded some significant differences between the machines. Mauchly did not derive quite as much from Atanasoff as the judge seemed to think. For example, Atanasoff’s electronic circuit used binary logic, whereas Mauchly’s was a decimal counter. Had the Eckert-Mauchly patent claims been less sweeping, they probably would have survived.

The case did not determine, even legally, who should get what proportion of the credit for the invention of the modern computer, but it did have two important consequences: it resurrected Atanasoff from the basement of history, and it showed very clearly, though this was not the intent of the judge or either party, that great innovations are usually the result of ideas that flow from a large number of sources. An invention, especially one as complex as the computer, usually comes not from an individual brainstorm but from a collaboratively woven tapestry of creativity. Mauchly had visited and talked to many people. That perhaps made his invention harder to patent, but it did not lessen the impact he had.