Computer users today often take it for granted that they can easily send data from one device to another, but computer networks are actually relatively recent inventions.

Predecessors of modern computers included devices such as the Atanasoff–Berry computer (completed in 1942) and ENIAC (completed in 1946), which were designed to be stand-alone devices that people had to program locally to complete assigned tasks. They could not receive data directly from another computer or send data to another computer.