Abacus

           An instrument used for learning place value.Also it is the earliest and simplest calculating device.Its first version consisted of a set of grooves in sand or dust filed in a board in which pebbles were used to represent units,tens, hundreds according to their position in the groove.
          This device was extensively used by the Egyptians,Greeks and Romans. The use of Abacus later spread throughout the civilized worid in modified forms.But the Roman Abacus become very popular.It consisted of grooves in metal surface in which pebbles were used for mathematical operations.The Chinese Abacus is known as Suan Pan and the Japanese Abacus is divided into two parts with sets of two and five beads .
          The upper part was called 'heaven' and the lower part 'earth'.The Japanese Abacus consisted of row of beads strung on wire and mounted in a frame.