Method of complements
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In mathematics and computing, the method of complements is a technique to encode a symmetric range of positive and negative integers in a way that they can use the same algorithm for addition througho
Complement numbers on an adding machine c. 1910. The smaller numbers, for use when subtracting, are the nines' complement of the larger numbers, which are used when adding.
Comptometer from the 1920s, with nines' complements marked on each key
Pascaline
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The Pascaline is a mechanical calculator invented by Blaise Pascal in 1642. Pascal was led to develop a calculator by the laborious arithmetical calculations required by his father's work as the super
A Pascaline signed by Pascal in 1652
Top view and overview of the entire mechanism. This version of Pascaline was for accounting.
Four Pascalines and a clone from Lépine on display at the CNAM museum in Paris
Detail of the carry mechanism and of the sautoir