Long before the invention of the electronic calculator or the computer, people counted and did calculations with a device called an abacus. Although its origins are ancient, the abacus is still used today. On this instrument, calculations are made with beads or counters instead of numerals.
The abacus was probably invented by an ancient group of people known as Sumerians in Mesopotamia. The earliest abacus likely was a board or slab on which the Sumerians spread sand so they could trace letters. The word abacus is of Greek origin, however. The Greeks and Romans used boards or patches of flat earth on which they moved pebbles or metal disks as counters. Later, the abacus took the form of a frame with counters or beads strung on wires stretched across it or on upright wooden rods.
In the early frame abacus, ten counters on one wire were equal to one on the wire next to it. Thus any number could be represented by counters placed on the various wires. Addition or subtraction sums could be done by simply moving counters from one wire to the next.
In addition to the Greeks and Romans, the ancient Egyptians, Hindus, and Chinese used the abacus. In about AD 700, the Hindus invented a numeral system that made adding with written numbers as easy as adding on an abacus. The Arabs soon adopted this system, and they introduced it into Europe more than 1,000 years ago. These so-called Arabic numerals allow numbers to be broken up into units, tens, hundreds, thousands, and so on (see arithmetic). The Hindu-Arabic system also included a separate numeral for zero. As written calculations became easier, the abacus passed out of use in Europe. But it continues to be used, especially in business, by people living in China, Japan, and the Middle East.
