During World War II, the U. S. Navy had battleships with guns that could shoot 2700-pound projectiles 24 miles. At that range, a projectile spent almost 90 seconds in flight. In addition to the guns' elevation, angle of amplitude, and initial speed of propulsion, those trajectories were also affected by the motion of the ship, the weather conditions, and even the motion of the earth's rotation. Accurate calculations of those trajectories posed great problems.

To solve these computational problems, the U. S. Army contracted an engineering team at the University of Pennsylvania to build the Electronic Numerical Integrator and Computer (ENIAC), the first complete electronic programmable digital computer. Although not completed until after the war was over, it was a huge success.

It was also enormous, occupying a large room and requiring a staff of engineers and programmers to operate. The input and output data for the computer were recorded on Hollerith cards. These could be read automatically by other machines that could then print their contents.

ENIAC played an important role in the development of the hydrogen bomb. Instead of artillery tables, it was used to simulate the first test run for the project. That involved over a million cards.

Figure 5 ENIAC