"It really was a proof of concept project to show that a general-purpose, high speed electronic machine could successfully be built," he says. "The fact that it could do 2,000 addition processes per second was a very big deal. Before that there had been computers built out of relays that could do only five adds per second."
ENIAC may have started the electronic computer revolution, but it was a very different machine physically from what we use today to run our IT infrastructures.
ENIAC itself was very large -- it filled a 30-by-50 foot room, weighed some 30 tons and incorporated about l8,000 vacuum tubes in its design and construction. It was built from 40 panels that were arranged in a U-shape.
"No one had ever built anything with this many tubes," Marcus says. "That level was beyond anything that people thought was possible."
Other key differences from computers of today were that ENIAC didn't include or run any stored programs and it also wasn't a binary machine using just zeroes and ones. Instead, it was run by entering normal arithmetic, Marcus says.
Yet it inspired so many improvements that we find in computers and other technologies today.
"The folks who designed it went on to design and do major work on the instructions sets of modern computers," Marcus says. "And the female programmers who ran ENIAC developed the use of subroutines that we still have today."
ENIAC even inspired the ways in which future computers would be programmed, according to Marcus. "The people who designed ENIAC were electrical engineers and designed it from an electrical perspective. But the women who programmed it dragged it away from that way of thinking and they invented the modern view of programming."
The programmers were all women because the men were away fighting in the war, according to Marcus. Those women were actually called "computors," which was the term given to anyone who worked with an adding machine in the early 1940s.
"The smartest of those women were recruited to be programmers for ENIAC," Marcus says. "The original idea was that scientists would program the machine and it turned out that the scientists found programming to be hard and that the women mastered it. The thing that ENIAC replaced was a room full of folks doing ballistics calculations, all women with undergraduate degrees in mathematics."
The importance of all of this can't be overstated, Marcus says. The roots of ENIAC are in today's servers, mobile devices, enterprise applications, PCs and laptops, the Internet and just about every IT process used in business and personal computing.