Editing Comptometer (section)

{{short description|Key-driven mechanical calculator}}
[[Image:Comptometer model ST Super Totalizer.png|thumb|upright=1.2|right|<div align="center">Model ST (1930s)</div>]]
[[Image:AnitaPrototype1.jpg|thumb|upright=1.2|right|<div align="center">Prototype of the first all-electronic desktop calculator marketed by {{nowrap|Sumlock Comptometer Ltd}} of the [[UK]]</div>]]

The '''Comptometer''' was the first commercially successful key-driven [[mechanical calculator]], patented in the United States by [[Dorr Felt]] in 1887.

A key-driven calculator is extremely fast because each key adds or subtracts its value to the accumulator as soon as it is pressed and a skilled operator can enter all of the digits of a number simultaneously, using as many fingers as required, making them sometimes faster to use than [[electronic calculator]]s. Consequently, in specialized applications, comptometers remained in use in limited numbers into the early 1990s, but with the exception of museum pieces, they have all now been superseded by electronic calculators and [[computer]]s.

Manufactured without interruption from 1887 to the mid-1970s, it was constantly improved. The mechanical versions were made faster and more reliable, then a line of electro-mechanical models was added in the 1930s. It was the first mechanical calculator to receive an all-electronic calculator engine in 1961, with the [[Sumlock ANITA calculator|ANITA Mark VII]] model released by Sumlock Comptometer. This created the link between the mechanical calculator industries and the electronic.

Although the comptometer was primarily an [[adding machine]], it could also do subtractions, multiplication and division. Its keyboard consisted of eight or more columns of nine keys each. Special comptometers with varying key arrays were produced for a variety of special purposes, including calculating [[currency exchanges]], times and [[Imperial weight]]s. The name comptometer was formerly in wide use as a [[generic trademark|generic name]] for this class of calculating machine.