In Pictures: ENIAC, world's first digital computer...
ENIAC was developed under a 1943 contract with the US Army to speed ballistics calculations. It was built under total secrecy and completed only after WWII, however. At 30 feet by 60 feet, weighing 30 tons and using 19,000 vacuum tubes, ENIAC was the epitome of a large system.
In Pictures: ENIAC, world's first digital computer, turns 66