Penn Library Exhibitions

John W. Mauchly and the Development of the ENIAC Computer


The ENIAC was a large-scale, general purpose digital electronic computer. Built out of some 17,468 electronic vacuum tubes, ENIAC was in its time the largest single electronic apparatus in the world. There were two fundamental technical innovations in the ENIAC. The first had to do with combining very diverse technical components and design ideas into a single system that could perform 5,000 additions and 300 multiplications per second. Although slow by today's standards--current microprocessors perform 100 million additions per second--this was two to three orders of magnitude (100 to 1,000 times) faster than existing mechanical computers or calculators. The sheer speed of the machine and its limited, but sufficiently versatile, programming mechanisms allowed the ENIAC to demonstrate that electronic computing could be applied to some of the nation's most pressing problems, such as the development of the hydrogen bomb. The significance of electronic computing to national security was an important factor in the birth of the modern computing industry.

The initiating and cycling units of ENIAC, 1946. The picture on the oscilloscope shows one of the fundamental electrical signals transmitted to all units of the machine. The bulk of the neons above the scope correspond to the twenty different parts of an addition. Each of the parts represent 1/100,000 of a second. (click to expand to 165k)

Article on ENIAC, "Answers by Eny," Newsweek, 18 February 1946. (click to expand to 303k)
The second, and equally impressive, technical achievement was the machine's reliability. Many others working on large-scale precision machinery, such as electronic fire control systems and differential analyzers, considered the possibility of electronic computation before either Mauchly or Atanasoff. These scientists, however, rejected digital electronic computing, because they felt that a system large enough to do useful computations would require too many vacuum tubes to provide reliable operation. As the main project engineer for the ENIAC, J. Presper Eckert proved to be an outstanding engineer who overcame the most difficult technical challenges in building the ENIAC. The rigorous vacuum tube reliability studies that he oversaw and the cautious reliability design methods adopted by the entire ENIAC project team made it possible to operate the ENIAC, with all of its vacuum tubes, within a comfortable margin of reliability.

The ENIAC was officially unveiled to the public on Valentine's Day, 14 February 1946. Press releases from the War Department and articles that appeared in popular magazines, such as Newsweek, attest to the widespread attention that ENIAC received upon its public dedication.

* Some pertinent web resources:

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