Abacus is an ancient device used in China and othercountries to perform arithmetic problems. It can be used to add, subtract, multiply, and divide, and to calculate square roots and cube roots.
The abacus consists of a frame containing columns of beads. The beads, which represent numbers, are strung on wires or narrow wooden rods attached to the frame.
The abacus was used by the ancient Greeks and Romans. The Chinese abacus is called suanpan, which means counting, or reckoning, board. 
A typical Chinese abacus has columns of beads separated by a crossbar. Each column has two beads above the crossbar and five below it. Each upper bead represents five units, and each lower bead equals one unit. The first column on the right is the ones column. The second column is the tens column. The third column is the hundreds, and so on. The ones column represents numbers from one to nine. Each bead below the crossbar has a value of one or 1, and each bead above the crossbar has a value of 5 ones or 5. The tens column represents numbers from 10 to 90. Each lower bead in the tens column represents 1 ten or 10, and each upper bead represents 5 tens or 50. A number is represented on the abacus by moving the appropriate beads to the crossbar.