Components from the Harvard Mark I computer, 1937-1944.
© Science Museum / Science & Society Picture Library
Electromagnetic counters from the IBM Automatic Sequence Control Calculator (ASCC), more commonly known as the Harvard Mark I. This was the first digital computer and was designed and constructed in the United States by the IBM Corporation between 1937 and 1944. It was based on a proposal by H H Aiken of Harvard University, Masachusetts. Counters were used to store decimal numbers and relays for control and switching. The computer was composed of a series of calculators which each worked on different parts of a problem, supervised by a central control unit. The machine was made up of over 750,000 components and weighed 5 tons. It was mainly used for making scientific calculations in the fields of ballistics and ship design.