Mark I

A programmable, electromechanical calculator designed by professor Howard Aiken. Built by IBM and installed at Harvard in 1944, it strung 78 adding machines together to perform three calculations per second. It was 51 feet long, weighed five tons and used paper tape for input and typewriters for output. Made of 765,000 parts, it sounded like a thousand knitting needles according to Rear Admiral Grace Hopper. The Mark I worked in decimal arithmetic, not binary, but it could go for hours without intervention. At its dedication ceremony, Aiken asserted that the Mark I was the modern embodiment of Babbage's Analytical Engine, although it did not have a conditional statement in its programming repertoire. The experience helped IBM develop its own computers a few years later. See Analytical Engine.

The Mark I

Five tons of mechanical calculator and 51 feet long, the Mark I could perform three calculations a second in 1944. (Image courtesy of The Computer History Museum, www.computerhistory.org)