Drs. John Mauchly and Presper Eckert thought that a digital calculator could do the job. So, in April, 1943, through the Moore School of Engineering at Pennsylvania, they submitted a memo describing an electronic analyzer that would compute a trajectory and complete a table within 2 days.

The army bought the machine and had it constructed at an expenditure of some 200,000 man-hours. Truly an electronic machine, the ENIAC (an acronym for Electronic Numerical Integrator and Calculator) used vacuum tubes. It contained no moving parts except for input-output gear. It had 500,000 soldered joints, 18,000 vacuum tubes, 6,000 switches and 500 terminals. Counting was performed by electronic pulses. The machine operated on the decimal system. Output was on punched cards.