Japanese abacus or soroban, c 1930.
© Science Museum / Science & Society Picture Library
The soroban is a derivation of the Chinese Suan Pan and is operated in the same way. This example shows the transition from the Chinese Suan Pan which has 2 beads above the bar and 5 below, to the modern Japanese version which has 1 bead above and 4 below. This type ws used from the late 19th century until the 1930s. The beads above the bar represent 5 units and those below, one unit. Numbers are set by moving beads up and down to touch the horizontal cros-bar. 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.