Alan Turing described an abstract machine that clarified what computation could mean. From wartime codebreaking and ENIAC's plugboards to the stored-program designs of EDVAC, ACE, and EDSAC, this episode traces how Turing, John von Neumann, and several engineering teams contributed to the architecture of modern computers.

In the 19th century, Charles Babbage designed pioneering mechanical computers, and Ada Lovelace's notes on the Analytical Engine included an early published computer program and described how a machine could repeat a sequence of operations.