**Q4. Write a note on evolution of computers.**

**Ans. **The concept of a computer did not materialize overnight. Just as the growth and development of mature biological species normally took place in fits and started over the ages, the computer also took thousands of years to mature.

Ancient people used stones for counting or made scratches on a wall or tied knots in a rope to record information. But all these were manual computing techniques. Attempts had been going on for developing faster computing devices and the first achievement was the abacus, the pioneer computing device used by man; Let us take a look at the development of the computer through various stages.

**Abacus**

Around 3000 years before the birth of Jesus Christ, the Mesopotamians quite unknowingly laid the foundation of the computer era. They discovered the earliest form of a dead-and-wire counting machine, which subsequently came to be known as abacus. The Chinese improved upon the abacus so that they could count and calculate fast.

An abacus consists of deads divided into two parts which are movable on the rods of the two parts. Addition and multiplication etc. of numbers is done by using the place value of the digits of the numbers and position of beads in the abacus.

**Napier ‘Logs’ and ‘Bones’**

John Napier (1550-1617) developed the idea of Logarithm. He used ‘logs’ to transform multiplication problem to addition problem. Napier’s logs later became the basis for a well known invention – the computing machine known as ‘slide rule’ (invented in 1661). Napier also devised set of numbering rods known as Napier’s Bones. He could perform both multiplication and division with these ‘Bones’.

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The ideas of logarithm, developed in 1614, notably reduced the tedium of repetitive calculations.

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**Pascal’s Adding Machine**

Blaise Pascal, a French mathematician, invented a machine in 1642 made up of gears which was used for adding numbers quickly. This machine was named as Adding Machine (also known as Pascaline) and was capable of addition and subtraction. It worked on clockwork mechanism principle. The adding machine consisted of numbered toothed wheels having unique position values. The rotation of wheels controlled the addition and subtraction operations. This machine was capable of carry-transfer automatically.

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**Leibnitz’s Calculator**

Gotfried Leibnitz, a German mathematician, improved an adding machine and constructed a new machine in 1671 that was able to perform multiplication and division as well. This machine performed multiplication through repeated addition of numbers. Leibnitz’s machine used stepped cylinder each with nine teeth of varying lengths instead of wheels as was used by Pascal.

**Jacquard’s Loom**

Joseph Jacquard manufactured punched cards at the end of American Revolution and used them to control looms in 1801. Thus the entire control weaving process was automatic. The entire operation was under a program’s control. With the historic invention of punched cards, the era of storing and retrieving information started that greatly influenced the later inventions and a advancements.

**Babbage’s Difference Engine**

Charles Babbage, a professor of mathematics, developed a machine called Difference Engine in the year 1822. This machine was expected to calculate logarithmic tables to a high degree of precision. The difference engine was made to calculate various mathematical functions. The machine was capable of polynomial evaluation by finite difference and its operation was automatic multiston operation.

**Figure: Babbage’s Difference Engine**

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**Babbage’s Analytical Engine**

In 1833, Charles Babbage started designing an Analytical Engine which was to become a real ancestor of the modern day computer. With the methodical design of his Analytical Engine, Babbage meticulously established the basic principles on which today’s computers work. The Analytical Engine was capable of performing ll four arithmetic operations as well as comparison. It had a number of features startlingly similar to those in today’s electronic computers. He included the concept of central processor, storage area, memory and input-output devices in his design. The two revolutionary innovations incorporated in Analytical Engine were comparisons and modification of stored information. The first innovation enabled the machine to compare quantities and then decide which of the instruction sequences to follow. The second permitted the results of a calculation to change numbers and instructions already stored in the machine. Owing to the lack of technology of the time, the Analytical Engine was never built. Its design remained conceptual.

**Figure: Babbage’s Analytical Engine**

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His great inventions of difference engine and analytical engine earned Charles Babbage the title ‘Father of Modern Computers’ – a fitting tribute to him.

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**Hollerith’s Machine**

In 1887, an American named Herman Hollerith (1869-1929) fabricated what was dreamt of by Charles Babbage. He fabricated the first electromechanical punched-cared tabulator that used punched cards for input, output and instructions. This machine was used by American Department of Census to compile their 1880 census data and was able to complete compilation in 3 years which earlier used to take around 10 years.

**Figure: Hollerith’s Machine**

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**Mark-I**

Prof. Howard Aiken (1900-1973) in U.S.A. constructed in 1943 an electromechanical computer named Mark-I which could multiply two 10-digit numbers in 5 seconds – a record at that time. Mark-I was the first machine which could perform according to pre programmed instructions automatically without any manual interference. This was the first operational general purpose computer.

**Figure: Mark-I Computer**