History of Computer

Abacus is the first calculating device.Mathematical concepts and their offspring, arithmetical operations, were considered for thousands of years a pure intellectual exercise which could not be duplicated or performed by a man-made artifact. Even the Abacus which appeared in Asia Minor 2500 years ago and is still in use today, is only a memory-helping device rather than a real calculating machine.

The Abacus is an ingenious counting device based on the relative positions of two sets of beads moving on parallel strings. The first set contains five beads on each string and allows counting from 1 to 5, while the second set has only two beads per string representing the numbers 5 and 10. The Abacus system seems to be based on a radix of five. Using a radix of five makes sense since humans started counting objects on their fingers.

he normal method of calculation in ancient Rome, as in Greece, was by moving counters on a smooth table. Originally pebbles, calculi, were used. Later, and in medieval Europe, jetons were manufactured. Marked lines indicated units, fives, tens etc. as in the Roman numeral system. This system of 'counter casting' continued into the late Roman empire and in medieval Europe, and persisted in limited use into the nineteenth century.^[12]

Writing in the 1st century BC, Horace refers to the wax abacus, a board covered with a thin layer of black wax on which columns and figures were inscribed using a stylus.^[13]

One example of archaeological evidence of the Roman abacus, shown here in reconstruction, dates to the 1st century AD. It has eight long grooves containing up to five beads in each and eight shorter grooves having either one or no beads in each. The groove marked I indicates units, X tens, and so on up to millions. The beads in the shorter grooves denote fives – five units, five tens etc., essentially in a bi-quinary coded decimal system, obviously related to theRoman numerals. The short grooves on the right may have been used for marking Roman