Abacus
A manual computing device used in ancient China, the abacus (suan pan, or "counting plate") was probably invented there in ancient times. The word "abacus" has its roots in the Phoenician term for a flat surface, and its Greek and Roman forms used flat surfaces with grooves for beads.
The Chinese abacus has a frame of thirteen wires holding seven beads on each wire; a horizontal divider separates the top two beads from the bottom five, sometimes referred to as the "heaven" and the "earth" beads, respectively. Chinese sources show wide use of the device by 190 CE, popularization during the Song dynasty (960–1279), and printed instructions appearing in the 1300s during the Yuan (1279–1368). By the Ming dynasty (1368–1644), the Chinese abacus had taken on its modern form and had become an integral part of business and financial accounting. This basic counting machine spread by the 1600s to Japan and then to eastern Russia, with small modifications in the number of beads above and below the divider.
In China, the abacus replaced paper-and-pencil mathematical calculations; the beads served as markers representing quantity, and the beads' position on the vertical wires represented value. A skilled user of an abacus performed addition, subtraction, multiplication, and division quickly and easily, with the additional advantage of requiring no electricity to produce a readout that cannot be lost or erased without being manually changed. Because of the traditional Chinese use of 16 as an important standard weight, the Chinese abacus is particularly useful for calculations using a base number system of 2 and 16.
Among storekeepers and small businesses in China, an abacus remained a standard piece of office equipment until the 1980s. Even today, shopkeepers in Russia sometimes use abaci to calculate customers' purchases. A good-quality abacus is generally about two feet wide by one foot tall and made of sturdy brass with hardwood beads.
Further Reading
Dilson, Jesse. (1968) The Abacus: A Pocket Computer. New York: St. Martin's Press.
Menninger, Karl. (1992) Number Words and Number Symbols: A Cultural History of Numbers. Trans. by Paul Broneer. New York: Dover.
Pullan, J. M. (1968) The History of the Abacus. London: Hutchinson and Company.
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