John Mauchly and John Presper Eckert , trying to more quickly ascertain artillery shell trajectories for the United States War Department, demonstrated ENIAC (Electronic Integrator & Calculator) at the Ballistic Research Laboratory at the Aberdeen Proving Grounds in Maryland. It is the first electronic computer. It used punched cards for input and output. It was 100 feet long, consumed over 100 kilowatts of power in 18,000 electronic valves. Its speed made made possible calculations which were so tedious and time-consuming that they could not have been undertaken previously.