Pascal's calculator

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Blaise Pascal invented the second mechanical calculator, called alternatively the Pascalina or the Arithmetique, in 1645, the first being that of Wilhelm Schickard in 1623.

Pascal began work on his calculator in 1642, when he was only 19 years old. He had been assisting his father, who worked as a tax commissioner, and sought to produce a device which could reduce some of his workload. By 1652 Pascal had produced fifty prototypes and sold just over a dozen machines, but the cost and complexity of the Pascaline – combined with the fact that it could only add and subtract, and the latter with difficulty – was a barrier to further sales, and production ceased in that year. By that time Pascal had moved on to other pursuits, initially the study of atmospheric pressure, and later philosophy.

The Pascaline was a decimal machine. This proved to be a liability, however, as the contemporary French currency system was not decimal. It was instead similar to the Imperial pounds ("livres"), shillings ("sols") and pence ("deniers") in use in Britain until the 1970s, and necessitated that the user perform further calculations if the Pascaline was to be used for its intended purposes, as a currency calculator.

In 1799 France changed to a metric system, by which time Pascal's basic design had inspired other craftsmen, although with a similar lack of commercial success. Child prodigy Gottfried Wilhelm von Leibniz produced a competing design, the Stepped Reckoner, in 1672 which could perform addition, subtraction, multiplication and division, but calculating machines did not become commercially viable until the early 19th century, when Charles Xavier Thomas de Colmar's Arithmometer, itself based on Von Leibniz's design, was commercially successful [1].

The initial prototype of the Pascaline had only a few dials, whilst later production variants had eight dials, the latter being able to deal with numbers up to 9,999,999.

The calculator had metal wheel dials that were turned to the appropriate numbers; the answers appeared in boxes in the top of the calculator. Since the gears of the calculator only rotated in one direction, negative numbers could not be directly summed. To subtract one number from another, the method of nines' complements was used. To help the user, when a number was entered its nines' complement appeared in a box above the box containing the original value entered.