The Atanasoff-Berry Computer (ABC) occupies a special place in the history of computing in part for its technical accomplishments but also for being at the center of a landmark legal case. It was built by Iowa physics professor John Vincent Atanasoff and graduate student Clifford Berry.
Technically, the ABC was an electronic equation solver. It could find solutions to systems of simultaneous linear equations with up to 29 unknowns, a type of problem encountered in Atansasoff’s physics work. Construction of the ABC began in 1938 at Iowa State College (now University) in Ames, Iowa. It was about the size of a large desk, weighed 750 lbs, computed 0.06 operations per second (sustained) and had 0.37 KB of memory. It could also do 30 add/subtract operations per second. While not a computer in the modern sense (since it did not store its own program), it pioneered various techniques in digital computer design including binary arithmetic, parallel processing, and electronic (vacuum tube) switching elements. The device was completed in 1942 and worked, although its spark-gap printer mechanism needed further development.
The legal dimension to the ABC story involves a lawsuit between two computer makers, Honeywell and Sperry-Rand. In 1967, Honeywell sued Sperry over their ENIAC patents using the ABC as evidence of prior art. (ENIAC was an early digital electronic calculator completed in 1946). After years of proceedings, on October 19, 1973 the judge in the case, Earl R. Larson, agreed with Honeywell that some of the ideas in the ENIAC, which had been considered the ‘world’s first computer,’ in fact came from Atanasoff during a four-day visit ENIAC designer John Mauchly made to Atanasoff at Iowa State before ENIAC was designed. There was also months of correspondence between the two in which Mauchly expressed his desire to build a similar device. The net result of this judgment was that no one owned the patent on the computer: it was free to be developed by all. Gordon Bell has called this the ‘dis-invention of the computer.’
In 1993, Iowa State University began a historically-accurate reconstruction of the ABC, which it finished in 1997. The project cost $360,000 and involved about a dozen people in its realization. This film shows the ABC Reconstruction in operation, solving a simple algebra problem.