of computers. The series of calculating and computing machines whose designs were started between 1940 (approximately) and 1955. These machines are characterized by electronic tube (valve) circuitry, and delay line, rotating, or electrostatic (Williams tube) memory. The majority of them embodied the stored program concept. For the most part, first-generation machines used as input/output punched paper tape, punched card, magnetic wire, magnetic tape, and printers. Despite these seeming handicaps, impressive computations in weather forecasting, atomic energy calculations, and similar scientific applications were routinely performed on them.

Important first-generation development machines include the Manchester Mark I, EDSAC, EDVAC, SEAC, Whirlwind, IAS, and ENIAC while the earliest commercially available computers include the Ferranti Mark I, UNIVAC I, and LEO I.