ABSTRACT
Introduced into Japan in about the sixteenth century from China, this arithmetic tool can be used for both simple and complex calculations. There is a cross bar with twenty-three or twenty- seven rows of two beads above the bar and the same number of rows of five beads below the bar. Calculations are made by moving beads up to and down from the cross bar. Each vertical row is a digit row with five units of one below the bar and two units of five above the bar. An experienced abacus user can easily outpace a calculator on addition, subtraction, multiplication and division.
