By the Second World War, the development of computers a fast flight. In the United Kingdom was the Colossus used to crack German secret codes, including those of the Enigma cipher. The Colossus was the first electronic computer, using vacuum tubes. The first computer was the ENIAC in the U.S., which took some classrooms. The first computer in the Netherlands was at the Mathematical Centre ARRA. The first computer in a commercial environment, the Miracle, a Ferranti Mark I to the Shell laboratory in Amsterdam. During the period when the permanent memory (hard disk) is not generally existed, entering data or programs in a computer quite difficult. This was done initially with switches and paper tape, punch cards a little later, and still later a magnetic tape.
Woman using her computer for work (1983)
The computers in the years 1950-1980 were mainly mainframes: very large machines, where hundreds to thousands of simultaneous users could work on. Mainly banks and insurance companies using such large-scale mainframes. The mainframe was connected to the user through a simple application on a desktop computer (once called by a so-called dumb terminal). The mainframe with the advent of small computers is not extinct and is still used by professional institutions. The most famous builder of IBM's mainframes.