Originally a 'calculator' actually meant a real person who did calculations. Nowadays it means an electronic device used to do arithmetical sums automatically. The very first non-human calculators were mechanical machines. They consisted of lots of cogs and dials with levers to press and handles to turn. One of the earliest was invented by the scientist Blaise Pascal in 1642. Later the famous mathematician Leibniz invented a more sophisticated mechanical calculator. All sorts of different mechanical calculators were made in the 18th, 19th and the first half of the 20th century.

Mechanical calculators only went out of date when electronic calculators were invented n the late 1960s. One of the first pocket electronic calculators was made by the electronics company Hewlett Packard.