ABC - Atanasoff-Berry Computer
Friday, 11 September 2009
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ABC - Atanasoff-Berry Computer
Berry builds the prototype ABC
Disputed patent

Disputed patent

In 1954 an IBM patent lawyer contacted Atanasoff with an offer to break the Mauchly-Eckert patent. The patent was owned by IBM's rivals and so destroying it would be to IBM's advantage. Atanasoff refused at first and then agreed, beliving that they had a good chance of proving that he and Berry built a real computer before the ENIAC. But the pace of legal proceedings concerning patents is very slow and unfortunately Clifford Berry committed suicide in 1963 (Atanasoff has hinted several times that it might have been murder) and this lost them a key witness to the fact that the ABC had been built when Atanasoff claimed it had.

The case finally came to court in 1970 and Atanasoff demonstrated a reconstruction of the machine to the judge. It clearly made a big enough impression for the decision to be made in his favour. The judgement described Atanasoff as the inventor of the electronic computer and maintained that Eckert and Mauchly had built a machine that derived from the ABC. The patent was also overturned because ENIAC had been used on the H bomb calculations at least a year before the patent was filed.

The decision was announced on October 19th 1973 and had the bad luck to be up against the Watergate scandal for the attention of the national press. As a result, what might have been a big story, went virtually unreported. Atanasoff remained bitter that he didn't get the credit he deserved. He did get honours of a sort - Bulgaria gave him the Order of Saint Cyril and Saint Methodius, its highest scientific award. The rest of the scientific community has never been quite so sure.

It is clear that the ABC was an early attempt at a digital computer but some claim that it was not the first such machine because it was never finished and working. Atanasoff claims that this is irrelevant because it was enough to demonstrate that his ideas were workable. However this just puts him in the position of having reinvented Babbage's ideas rather than actually building the first machine. The best evaluation of the ABC is that it was a collection of digital components rather than a complete system.

The key question is whether or not ENIAC was derived from the ABC, as the legal ruling states. The confusing factor here is whether or not Mauchly told Atanasoff of his work on digital computers at the time of their first meeting on 14 June 1941. Mauchly certainly wrote a letter in 1940, i.e. before the trip to see the ABC, about a digital design he was working on, but Atanasoff claims that Mauchly did not mention any such project.

Atanasoff and Mauchly were also at odds about what happened at the meeting. Atanasoff claimed that Mauchly "expressed joy" at seeing parts of the ABC work out some simple arithmetic. Mauchly stated,

"I found that although he used valves and did do it relatively cheaply he lost most of the advantage because he wasn't doing it fast."

Mauchly also claimed that Atanasoff couldn't make flip flops work reliably and the flip flop was the main component in the ENIAC.

The difference in viewpoint over the visit is striking. Atanasoff said Mauchly was fascinated. Mauchly said it was a waste of time. Whatever the truth it is likely that both Atanasoff and Mauchly had good cause to regret the short visit for many years.

Working Replica


Replica ABC

The original ABC was eventually dismantled when the University converted the basement it occupied to classrooms, and the only item to be salvaged was a single memory drum. However in 1997 researchers from Ames Laboratory (located on the Iowa State campus) constructed a working replica at a cost of $350,000.






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