A New Era of Calculation
In 1945, the University of Pennsylvania completed ENIAC (Electronic Numerical Integrator and Computer), the first programmable, electronic, general-purpose digital computer. Designed for the U.S. Army to calculate artillery firing tables, ENIAC’s speed and versatility far exceeded existing mechanical devices, earning it the nickname “Giant Brain.”
From Concept to Construction
The idea began in 1941 when physicist John Mauchly proposed an electronic solution to improve ballistic calculations. Partnering with engineer J. Presper Eckert, he secured U.S. Army funding, and construction started in 1943 under the secretive “Project PX.”
The massive machine was completed in May 1945 and began working by December. Its official dedication took place on February 15, 1946, attracting global attention.
Engineering Marvel
ENIAC was a colossal machine, weighing over 30 short tons (27 t) and containing 18,000 vacuum tubes, 7,200 crystal diodes, and 5 million hand-soldered joints. It measured about 100 ft (30 m) long, 8 ft (2.4 m) tall, and consumed 150 kW of power.
Capable of performing 5,000 additions or subtractions per second and 385 multiplications per second, it was roughly a thousand times faster than electro-mechanical machines of its time.
Programming the Future
Programming ENIAC was a complex, manual process involving plugboards and function tables, requiring weeks to set up. A team of six women—Kay McNulty, Betty Jennings, Betty Snyder, Marlyn Wescoff, Fran Bilas, and Ruth Lichterman—developed its first programs, including simulations for ballistic trajectories and early thermonuclear weapon research. In 1948, ENIAC was modified to allow stored programming, reducing setup times from days to hours.
Legacy and Retirement
In 1947, ENIAC was moved to the Aberdeen Proving Ground in Maryland, where it operated continuously until October 2, 1955.
Its success spurred the development of next-generation machines like EDVAC and UNIVAC and influenced computing worldwide. ENIAC’s debut marked the beginning of modern electronic computing and transformed scientific research, military planning, and technological innovation.
In 1945, ENIAC stunned the world as the first programmable, electronic, general-purpose digital computer.
Nicknamed the “Giant Brain,” it transformed computing with unprecedented speed and size, launching a new era of technology unlike anything seen before…🧵👇 pic.twitter.com/yu1iRFuJBz
— Fascinating True Stories (@FascinatingTrue) September 9, 2025