Public unveiling of the ENIAC computer

ENIAC (; Electronic Numerical Integrator and Computer) was the first programmable, electronic, general-purpose digital computer, completed in 1945. Other computers had some of these features, but ENIAC was the first to have them all. ENIAC was Turing-complete and able to solve "a large class of numerical problems" through reprogramming.

ENIAC was designed by Ursinus College physics professor John Mauchly and J. Presper Eckert of the University of Pennsylvania to calculate artillery firing tables for the United States Army's Ballistic Research Laboratory (which later became a part of the Army Research Laboratory). However, its first program was a study of the feasibility of the thermonuclear weapon.

ENIAC was completed in 1945 and first put to work for practical purposes on December 10, 1945.

ENIAC was formally dedicated at the University of Pennsylvania on February 15, 1946, having cost $487,000 (equivalent to $7,000,000 in 2024), and called a "Giant Brain" by the press. It had a speed on the order of one thousand times faster than that of electro-mechanical machines.

ENIAC was formally accepted by the U.S. Army Ordnance Corps in July 1946. It was transferred to Aberdeen Proving Ground in Aberdeen, Maryland, in 1947, where it was in continuous operation until 1955.