The first completely digital computer and an ancestor of most computers in use today: The Electronic Numerical Integrator and Calculator (ENIAC) was developed by Dr. John Mauchly and J. Presper Eckert during World War II at the Moore School of the University of Pennsylvania.

The massive ENIAC, which weighed 30 tons and filled an entire room, used some 18,000 vacuum tubes, 70,000 resistors, and 10,000 capacitors.

In December, 1945, it solved its first problem regarding the calculations for the hydrogen bomb. After its official unveiling in 1946, it was used to prepare artillery-shell trajectory tables and perform other military and scientific calculations.