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The Eckert Tapes: Computer Pioneer Says ENIAC Team Couldn't Afford to Fail -- and Didn't

The all-electronic system made its debut 60 years ago. In interviews taped in 1989, co-inventor J. Presper Eckert discusses the technology behind ENIAC and debunks some myths.

By Alexander Randall V
February 20, 2006 12:00 PM ET

Computerworld - There are two epochs in computer history: before ENIAC and after ENIAC. While there are controversies about who invented what, there's universal agreement that the Electronic Numerical Integrator and Computer was the watershed project that showed all-electronic digital computing was practical. ENIAC was unveiled Feb. 14, 1946, after nearly three years of development at the University of Pennsylvania's Moore School of Electronics. The two men most responsible for its success were J. Presper Eckert and John W. Mauchly, who together went on to build commercial systems such as Univac and also founded one of the companies that merged to form Unisys Corp.
Eckert died in 1995. I recorded two days of interviews with "Pres" in 1989, when he was 70 years old. My father was Eckert's best friend -- as a child, I played with his children, and I visited him regularly as an adult. I sat on the interview tapes for many years but decided to transcribe them for ENIAC's 60th anniversary and release the text publicly. Excerpts from the interviews follow:

Eckert was chief engineer on the ENIAC project.
Eckert was chief engineer on the ENIAC project.
How did calculating machines work before ENIAC? Well, a person with a paper and pencil can add two 10-digit numbers in about 10 seconds. With a hand calculator, the time is down to 4 seconds. The Harvard Mark 1, an electromechanical computer, could add two 10-digit numbers in 0.3 seconds, about 30 times faster than paper and pencil. The ENIAC was the first electronic digital computer and could add those two 10-digit numbers in 0.0002 seconds -- that's 50,000 times faster than a human, 20,000 times faster than a calculator and 1,500 times faster than the Mark 1. For specialized scientific calculations, it was even faster.

So it's a myth that ENIAC could only add, subtract, multiply and divide. That's a calculator. ENIAC could do three-dimensional, second-order differential equations. We were calculating [artillery] trajectory tables for the war effort. The trajectory tables were calculated by hundreds of people operating desk calculators -- people who were called "computers." So the machine that does that work was called a computer.

There's a story that ENIAC dimmed the lights in Philadelphia when it was in use. That story is total fiction, dreamed up by some journalist.

Did the military guys working on ENIAC salute the machine? Another ENIAC myth.

How many tubes did ENIAC use? ENIAC had 18,000 vacuum tubes. The tubes were off-the-shelf; we got whatever the distributor could supply in lots of 1,000. We used 10 tube types but could have done it with four; we just


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