In 1919, long before the invention of electronic computers, a pair of British physicists invented the circuit that would become their key building block. William Eccles (1875-1966), who had pioneered the development of radio communication and assisted Guglielrno Marconi, together with Frank Jordan worked with the leading-edge electronic technology of the time—vacuum tubes, the predecessor of the transistor.
Eccles was a radio pioneer, and his interest in vacuum tubes stemmed from their use in radio. In particular, the vacuum-tube diode was used to detect radio signals (the term "diode" was coined by Eccles).
Experimenting with vacuum tubes, Eccles and Jordan found a circuit with an interesting property—it had a memory. Unlike other circuits whose output would change depending on what their inputs were doing, this "trigger" circuit would cling on to the last state it had been put in. The circuit had two stable states: a brief pulse applied to one input would "flip" the circuit into one state, and it would stay there— until a pulse was applied to the other input, which would "flop" the circuit back into the other state.
With the "flip" and "flop" standing for 0 and 1, the fundamental element of an electronic digital memory had been created. With no moving parts, this vacuum tube memory was much faster than its mechanical predecessors.
Vacuum tube flip-flops were first pressed into service as computer memories in the build-up to World War II, enabling a new electronic generation of computers to be prepared for battle. Flip-flop circuits, now transistorized and crammed onto silicon chips, still flip and flop in their millions in the hearts of modern computers.
