The ENIAC Turns 75

 I used to walk past the site of the ENIAC lab on the way to class at the U of Pa, and even got a tour of the space once.  Impressive, 

ENIAC Turns 75  By Samuel Greengard,   Commissioned by CACM Staff

Programming ENIAC, the Electronic Numerical Integrator and Calculator (it was not called a computer, because "computers" at that time were people).

The history of computing is filled with mythical figures, but often lost in the shuffle is the accomplishment of John Mauchly and J. Presper Eckert, Jr. On February 14, 1946, the pair publicly unveiled the world's first true computer: ENIAC (Electronic Numerical Integrator and Computer). From their lab at the University of Pennsylvania in Philadelphia, they launched a revolution that truly changed the world.

On its 75th anniversary, ENIAC is once again in the spotlight. "It was the big bang of the information age. It set in motion a paradigm that has become the underpinning of daily life, as well as of deepest science," observes Bill Mauchly, an inventor and software architect who, as the son of John Mauchly, has also become a historian for the computer.

"ENIAC was the first digital programmable computer. It demonstrated what was possible," adds Thomas Haigh, professor of history at the University of Wisconsin, Milwaukee, and co-author of ENIAC in Action: Making and Remaking the Modern Computer (MIT Press).

A Calculated Approach

ENIAC, built at a then-astounding cost of $487,000, used 10 position ring counters to store digits. Each digit required 28 vacuum tubes that counted pulses on the ring counters to perform arithmetic. "Because it was electronic, it was thousands of times faster than anything that came before it," Haigh explains. "The machine would complete its work in a flash and spend most of its time waiting for human intervention."

The computer supported 200 decimal digits of writeable electronic memory spread across 20 "accumulators." It was a then-revolutionary development. ENIAC added by transmitting ten-digit numbers directly between accumulators, incrementing the contents of the destination counters. An "add time" was 200 microseconds. The accumulators worked in parallel, allowing up to 50,000 additions per second. A 10-digit by 10-digit multiplication required 14 add times, or a total of approximately 2,800 microseconds. A division or square root problem required 143 add times, or 28,600 microseconds.

To be sure, ENIAC was notable for more than simply being the world's first fully electronic computer. It was incredibly consequential. From the day it was introduced to the public via a front-page story in The New York Times to its retirement nearly a decade later, it tackled an array of real-world tasks including ballistics trajectory research, Monte Carlo simulations, weather predictions, and early hydrogen bomb research conducted by John von Neumann and others.

"Although the architecture and programming style were very idiosyncratic and not copied by any later machine, the ENIAC project built a foundation for more advanced computing models," says Mark Priestley, a research fellow at the U.K.'s National Museum of Computing and co-author of ENIAC in Action. This included the EDVAC (Electronic Discrete Variable Automatic Computer) design that, among other advances, introduced binary rather than decimal computing, and modern programming techniques. ... "