Mechanical calculator
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A mechanical calculator, or calculating machine, is a mechanical device used to perform the basic operations of arithmetic automatically, or (historically) a simulation such as an analog computer or a slide rule. Most mechanical calculators were comparable in size to small desktop computers and have been rendered obsolete by the advent of the electronic calculator and the digital computer.
Four of Pascal's calculators and one machine built by Lépine in 1725, Musée des Arts et Métiers
Replica of Schickard´s calculator
Detail of a replica of an 18th-century calculating machine, designed and built by German Johann-Helfrich Müller.
A mechanical calculator from Anton Braun, dated 1727
Arithmetic
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Arithmetic is an elementary branch of mathematics that studies numerical operations like addition, subtraction, multiplication, and division. In a wider sense, it also includes exponentiation, extraction of roots, and taking logarithms.
Calculations in mental arithmetic are done exclusively in the mind without relying on external aids.
Abacuses are tools to perform arithmetic operations by moving beads.
Some historians interpret the Ishango bone as one of the earliest arithmetic artifacts.
Image: Vlčí radius