EVOLUTION OF A COMPUTER:

Although 'computer', as we understand it today, is relatively of recent innovation, its development rests on centuries' of research. This section presents some of the landmarks that -led to its present state of development. Though machines such as abacus have been used as aids in day-to-day numerical calculation for many hundreds of years, it was not until the middle of the nineteenth century that Charles Babbage first devised the idea of a general purpose computing machine. He realised that it should be possible to design a machine which could carry out an infinite number of possible sequences of operations, the actual operations required for any particular purpose being specified by the programming of the machine. This concept of stored program control provides the basis for all modem computers, while Babbage also introduced many other modern concepts, such as the idea of separate storage and arithmetic units in a computer, and the input of programs and data on punched cards. 

The engineering technology of Babbage's time did not allow him to implement his designs successfully. Thus, his analytical engine could not become popular. The next landmark in this direction was the effort of Herman Hollerith, who first developed electromechanical calculating machines in 1890. These machines used punched card input arid performed simple arithmetic calculations and card sorting operations. They were controlled by hand wired control panels. 

In 1920s and early 1930s significant advances in punched card equipment resulted in machines that could not only perform addition and substraction, but also multiplication. These machines have been further improved with capabilities to interpret alphabetic data apart from being able to perform arithmetic operations. With these enhanced capabilities these machines were used for record keeping and accounting functions. That was the reason why such machines were referred to as 'accounting machines'. 

Another significant step towards the development of computer was made in the year 1944 by Froward Aiken of Harvard University in the form of designing an automatic calculator, which was known as Mark 1. It was an electronic computer but utilised electromagnetic relays and mechanical counters. Instructions were fed to Mark 1 by means of holes in a punched paper tape and the result (output) was obtained in the form of holes punched in the card.Maik 1 was an electromechanical device rather than an electronic one; It was used for the computation of tables of mathematical functions. The substitution of vacuum tubes for electromechanical relays set the stage for development of electronic digital computer. A model electronic digital computer was built by John Atanasoff and his assistant Clifford Berry at Iowa University between the years 1939-1942. In fact, there has been a difference of opinion as to who should be credited with this invention - whether it is J.P. Eckert and John Mauchly or Vincent Atanasoff and Clifford Berry. In 1974, the Federal Court of America declared John Vincent Atanasoff to be the real inventor along with his assistant Clifford Berry.

In competition with Atanasoff and Berry for the honour of developing the first electronic computer were J.P. Eckert and J.W. Mauchly of the University of Pennsylvania. Their project was completed' in 1946. The machine they designed was called the -ENIAC (Electronic Numerical Integrator and Calculator). The ENIAC could perform a multiplication in three thousandths of a second (1/3000 of a second). It was a huge machine with 18,000 vacuum tubes and occupied a space of 10 ft high, 10 ft wide and 100 ft long. Since this machine had no internal memory, instructions had to be fed into it by the use of combination of switches. On the other hand; the computer built by Atanasoff and Berry combined a vacuum tube computation unit with a rotating electrostatic memory drum. For reasons of simplicity, Atanasoff chose binary over decimal arithmetic for computation.