A Abacus (Eastern) The abacus, which performs arithmetical calculttions, is used today mainly in East and Southeast Asia. It consists of a rectangular wooden frame, the two longer sides of which are joined by several equidistant parallel rods. These rods c re divided into two unequal parts by a trans-' erse bar and strung with beads. The abacus (Urrently in use in China (known as suanpan) bas five beads in the lower part and two in the upper part; the japanese abacus (known as wroban) has four beads in the lower part and one in the upper part. Other variants of the in-!trument have been used in the past.