Japanese abacus from the Japanese Chamber of Commerce and Industry, 1996.
© Science Museum / Science & Society Picture Library
The abacus was still in regular use in China and Japan at the end of the 20th century. This is a Japanese soroban abacus. The soroban was developed from the Chinese Suan Pan abacus which has two beads above the bar and five below. The modern Japanese version has one bead above and four below. The beads above the bar represent five units and those below, one unit. Numbers are set by moving beads up and down to touch the horizontal crossbar. Taking any particular rod as the unit rod, the rods to the left represent tens, hundreds, thousands, and so on; those to the right being tenths, hundredths, and so on. Made by Sanko Soroban, Japan.