The Foundations of Computer Science

Computer science became a science in the 1930s and 1940s, when a small group of mathematicians and engineers worked out what computing actually is and how to build machines that do it. Their ideas still sit underneath every computer today.

Alan Turing came first. In 1936 he defined computation with an imaginary device now called the Turing machine and proved that a single machine could carry out any computation at all, which is the idea of the general-purpose computer. In the same decade Claude Shannon showed that Boolean logic could describe electrical switching circuits, giving engineers a way to build logic out of switches. That is the foundation of all digital hardware.

The war turned theory into machines. Codebreaking at Bletchley Park produced Colossus, and in the United States ENIAC showed that large electronic computers were possible. In 1945 John von Neumann set out the stored-program architecture, in which instructions and data share one memory, and it was first run on the Manchester Baby in 1948. By the early 1950s the computer, as we still understand it, existed.