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A mechanical counting device consisting of a frame holding a series of parallel rods on each of which beads are strung. Each bead represents a counting unit, and each rod a place value. The primary purpose of the abacus is not to perform actual computations, but to provide a quick means of storing numbers during a calculation. Abaci were used by the Japanese and Chinese, as well as the Romans.
See also Roman Numeral, Slide Rule
References
Boyer, C. B. and Merzbach, U. C. ``The Abacus and Decimal Fractions.'' A History of Mathematics, 2nd ed.
New York: Wiley, pp. 199-201, 1991.
Fernandes, L. ``The Abacus: The Art of Calculating with Beads.''
http://www.ee.ryerson.ca:8080/~elf/abacus/.
Gardner, M. ``The Abacus.'' Ch. 18 in
Mathematical Circus: More Puzzles, Games, Paradoxes and Other Mathematical Entertainments from Scientific American.
New York: Knopf, pp. 232-241, 1979.
Pappas, T. ``The Abacus.'' The Joy of Mathematics. San Carlos, CA: Wide World Publ./Tetra, p. 209, 1989.
Smith, D. E. ``Mechanical Aids to Calculation: The Abacus.'' Ch. 3 §1 in History of Mathematics, Vol. 2.
New York: Dover, pp. 156-196, 1958.