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The circular and rectangular slide rule was invented by W. Oughtred.
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William Schickard (1592 - 1635) succeeded in designing and building the first mechanical calculating device.
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Blaise Pascal (1623 - 1662) invented one of the first calculator, called the Pascaline, to help his father with his work collecting taxes. An improvement on Schickard’s design.
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The Arithmometer or Arithmomètre was patented in France by Thomas de Colmar (1785-1870). It was the first digital mechanical calculator strong enough and reliable enough to be used daily in an office environment.
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George Barnard Grant (1849-1917) patented and manufactured several models calculating machines.
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William Seward Burroughs (1857 – 1898) filed his first patent for a calculating machine. However, his 1892 patent was for an improved calculating machine with an added printer.
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William Seward Burroughs (1857-1898) invented The Adding Machine as the first in a line of office calculating machines.
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The comptometer was the first commercially successful key-driven mechanical calculator, patented in the USA by Dorr E. Felt (1862-1930).
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A small, hand-cranked digital mechanical calculator introduced by Curt Herzstark (1902-1988).
