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The abacus is a digital calculator of ancient origin and the first computing device to provide fixed decimal orders. It is manually operated and has no automatic features. In the fully developed version, counting beads are strung on a series of wires or rods. Computation is performed by moving the beads back and forth according to a set of rules. The position of the beads in relation to the ends of the frame denotes their numerical value. The abacus is still in use in many parts of the world.
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