The abacus was invented on the basis that Chinese used the counting-rod for a long period. In ancient times, people used small rods to count. Later, with the development of productivity, the amount requiring calculation was greater, and calculation with counting-rods limited the calculation. Thus, people invented a more advanced counter -the abacus.
The abacus is rectangular with wooden frame on the four sides and small rods fixed inside strung with wooden beads; a girder across the middle separates the abacus into two parts: each rod has two beads on its upper part, each representing five, and five beads on the lower part, each representing one