The first electronic general-purpose computer, completed in 1945, was ENIAC, short for Electronic Numerical Integrator and Computer. It was built at the University of Pennsylvania’s Moore School for the U.S. Army to calculate artillery firing tables.
John Mauchly and J. Presper Eckert designed ENIAC, while construction began under the wartime Project PX. The machine used roughly 18,000 vacuum tubes and occupied a large room, yet it could perform calculations far faster than contemporary electromechanical machines.
ENIAC was completed and tested in 1945, then publicly unveiled and formally dedicated in February 1946. It was reprogrammable, but operators changed programs mainly by setting switches and reconnecting cables rather than loading instructions from stored memory.
The wording matters because earlier machines had some, but not all, of ENIAC’s characteristics. Z3 was programmable but electromechanical, Colossus was electronic but specialized for codebreaking, and UNIVAC was a later commercial computer.