The present-day computer has evolved through several stages. The roots of the evolution are spread evenly in the prehistoric periods when the ancient man started to settle down in dwelling centres. In this period he started cultivation and other productive engagements. He faced the need for counting his products at this stage. In the early stages, he used his fingers for counting purposes. This was the reason for the establishment of a counting system based on the number ten, which is considered to be the most ancient system.

__ABACUS__

The earliest counting machine, invented by man was a primitive one called ABACUS. It was developed by Chinese nearly 3000 years ago, the Abacus is known as 'Swan Pan' in China. This model is considered to be the best one among other Abacus models used in other countries.

Abacus consists of a rectangular wooden frame with horizontal rods. These rods carry round beads. These beads are made out of stones, pearls, wooden blocks. Counting is done by shifting the beads from one side of the Abacus to another. One bead on a particular wire has the value of 1; two together have the value of 2. A bead on the on next line has the value of 10, and the bead on the third line would have the value of 100. Therefore, three properly placed beads - two with values of 1 and one with the value of 10 - could signify 12, and the addition of a fourth bead with the value of 100 could signify 112. Thus, the Abacus works on the principle of a place-value notation. The Abacus can be cleared or set to zero by moving all beads away from the crossbar.

__JOHN NAPER__

John Napier was one of the earliest scientists who tried to invent some devices for calculations. He was A Scottish mathematician. Napier devised a set of rods for use in calculations involving multiplications. These rods were made from bones, and hence this device came to be known as NAPIER BONES. Napier introduced the use of notation to indicate a fractional position.

The invention of odometer which -is now known as speedometer initiated the development of mechanical adders and multipliers. It was John Napier who developed the method of logarithm in 1617. The tables used in the logarithm represent analogue computing techniques. In logarithm multiplications and divisions can be done by adding and subtracting not the numbers themselves but with the help of related numbers.

__BLAISE PASCAL__

The credit for the invention of the first mechanical calculating machine goes to Blaise Pascal. He was a French Mathematician and Physicist, born on June 19, 1623, at Clermont-Ferrand, Auvergne. From the very childhood, Pascal was very much interested in the study of mathematics. When he was only sixteen Pascal published a book on the geometry of the conic sections that for the first time carried the subject well beyond the point at which Apollonius has left it nearly nineteen centuries before.

In 1642, when Blaise Pascal was only nineteen, he invented the calculating machine called Pascaline, using cogged wheels, could add and subtract. It is considered as the ancestor of the mechanical devices that reached their culmination in the modern cash register.

Blaise Pascal invented the calculating machine only to assist his father in tax calculations. His father was appointed as the Tax Superintendent of Royen.

The calculating machine invented by Pascal consisted of gears, wheels and dials. Each wheel had ten segments, which can be compared to the wheel of a milometer. When one wheel completed 0 to 9 around their circumference, with this calculator addition and subtraction could be performed by dialling the series of wheels. He also invented the syringe, the hydraulic press, and Pascal's law of pressure. The basic principle of his calculator is still used today in water meters and modern-day odometers.

__GOTTFRIED WILHELM VON LEIBNIZ__

Leibniz was a German philosopher and mathematician, born on July 1, 1646, at Leipzig, Saxony. He devised a calculating machine superior to that of Pascal. Leibniz modified the mechanical calculator invented by Pascal and perfected it to a certain context. The modified machine could multiply and divide as well as add and subtract. Leibniz was the first to recognize the importance of the binary system of notation, making the use of 1 and 0 only. This is important in connection with modern computers.

__JOSEPH-MARIE JACQUARD__

He was a stonemason and later a weaver. He created the *Punched Card Loom *in 1801. This device was a new type of loom for weaving cloth—punched cards controlled its operation. Needles could pull threads through cards where there were holes and not where there were none. Thus patterns were stored on punched cards. It was adopted by Charles Babbage to control his Analytical Engine.

__CHARLES BABBAGE__

He was an English mathematician born on December 26, 1791. He conceived of a machine that could be directed to work using punched cards, that could store partial answers to be performed upon them later, and that could print the results. Babbage developed a machine which he called the 'DIFFERENCE ENGINE'. This machine worked on a mathematical technique which repeatedly added differences between numbers to perform various types of calculations. Charles Babbage made only a working model of the difference engine. He did not make a full-scale difference engine because the necessary technology needed for its completion was not available at that time.

Later on, he was able to develop another device called the 'ANALYTICAL ENGINE'. This was an automatic computing machine designed to make additions at the rate of sixty per minute. It had memory also. Babbage has introduced an input device also which was nothing but a collection of punched cards. He also introduced a control unit whose function would be to control the various operations of the engine. In short, the analytical engine was indeed a marvellous blueprint of a modern computer.

__GEORGE SCOUTS__

Two Swedish printers, George Scheutz and his son Edward attracted towards the difference engine, and they were successful in making the first difference engine which became very popular among scientists as well as common people. Subsequently, they build several different engines. They got a Gold Medal at the Paris Exhibition in 1855 as the makers of the difference engine.

__HERMAN HOLLERITH__

He built few difference engines in 1890 for use in the mathematical calculations of the census conducted there. These engines were proved to be highly efficient, and subsequently, several different engines were in use in the different parts of the world.

The success story of his machine encouraged Hollerith to start the 'Tabulation Machine Company' in 1896. Later in 1911, this company became the 'Computing Tabulating Recording Company' This company is now known as the 'International Business Machines' - IBM Company.