A Primitive Calculator 

Meanwhile in Asia, the Chinese were becoming very involved in commerce with the Japanese, Indians, and Koreans. Businessmen needed a way to tally accounts and bills. Somehow, out of this need, the abacus was born. The abacus is the first true precursor to the adding machines and computers which would follow. It worked somewhat like this:
The value assigned to each pebble (or bead, shell, or stick) is determined not by its shape but by its position: one pebble on a particular line or one bead on a particular wire has the value of 1; two together have the value of 2. A pebble on the next line, however, might have the value of 10, and a pebble on the third line would have the value of 100. Therefore, three properly placed pebblestwo with values of 1 and one with the value of 10could signify 12, and the addition of a fourth pebble with the value of 100 could signify 112, using a placevalue notational system with multiples of 10.Thus, the abacus works on the principle of placevalue notation: the location of the bead determines its value. In this way, relatively few beads are required to depict large numbers. The beads are counted, or given numerical values, by shifting them in one direction. The values are erased (freeing the counters for reuse) by shifting the beads in the other direction. An abacus is really a memory aid for the user making mental calculations, as opposed to the true mechanical calculating machines which were still to come.
Computers: From the Past to the Present
Abacus: A Primitive Calculator:
Last modified July 30, 2006
©19942006 by Michelle A. Hoyle