ENIAC

The first general-purpose electronic computer, built at the University of Pennsylvania for the US Army's firing tables.

Core Principles & Analysis

• Completed in 1945: 17,468 vacuum tubes, 27 tonnes, 150 kilowatts.
• Reprogramming meant rewiring — the stored-program idea came next.
• The ENIAC programmers, six women including Kay McNulty, were long written out of the story.