HISTORICAL BACKGROUND OF COMPUTER

Throughout history man has constantly looked for ways of making calculations easier. In the ancient world the abacus, or counting frame, was commonly used. Beads or stones were threaded onto a number of rods held in a frame. The first rod represented units, the second tens, the third hundreds and so on. Calculations were done by moving the beads along with the wires.
An important development in the history of computers was the invention of the Slide rule in the early part of the 17th century. Numbers were represented on a special scale, known as a logarithmic scale, on two rulers, and results of multiplications and division could be read by sliding the rules next to each other.
In 1642 a Frenchman called Blasé Pascal invented the first mechanical calculator. Numbers were represented as teeth on a set of gear wheels. Numbers could be added or subtracted by simply turning the wheels.
In 1821 Charles Babbage, an English mathematician began to build the Difference Engine to calculate mathematical tables. Alas, the machine was never successfully completed because at the time it was just not possible to build it accurately enough, despite this he went on to set-out his ideas for what he called an Analytical Engine. This was also never built, but his ideas are important because he had designed the first automatic computer. It would have been possible to enter numbers and instructions and do complicated arithmetic storing the results at each stage.

Early Computers
This next major advancement was made by Herman Hollerith, an American statistician who worked in the bureau of the Census. It became apparent that the job of counting and sorting the return from the 1890 census wouldn't be finished by 1900 when the next census was due! He saw that the answer lay in some measure of mechanization using punched card. He realized that answers such as "yes" or "no" could be represented by the presence or absence of a hole punched in the card and more complex information could be coded by using a group of holes.
A machine was developed which could read punched cards using electricity – a hole would allow electricity to pass through and the absence of a hole would stop it. In this way the cards were read, counted and sorted.
In the 1940s work began on the first electronic computers. In 1946 ENIAC (Electronic Numerical Integrator And Calculator) was built at the University of Pennsylvania. It was designed to work out the target distances of artillery used in World War II.


COMPUTER ARCHITECTURE
Input – Central Processing <>Memory>> – Output

Computer is a group of integrated parts that have common purpose of performing the operations, called the program, which being executed qualifies it to be called a system. Computer is basically made of (1) Input unit, by which data can be given to the computer, (2) Central processing unit, which does all arithmetic and logic operations and (3) Output unit, which display the result of these processing operations and (4) Memory.



Input unit
The input unit is like the 'eyes' and 'ears' of the computer. Information is put into the computer from the outside world using the keyboard, joystick or other input equipment. There are numerous input devices, but floppy disk, hard disk and keyboard are the main elements of input device. The input unit turns the information into a series of electronic pulses, which the computer can understand and passes it on to the Central processing unit.

Central Processing Unit (CPU)
It is here that the actual work is done. The CPU is like the 'brain' of the computer. it takes information from the input unit and memory and uses or processes it according to the instructions the computer has been given. It may put information into the memory or give results to the output unit.

Output unit
The computer uses the output unit to give its results to the outside world. The electronic pulses passed from the CPU may be turned into something we can hear or even something that will control other machines for us. The common output devices are monitor and printer.
Memory
The computer memory stores instructions and information that the computer is currently working on or that will be needed at a later time. The data and instructions are understood by the main memory of the computer where its processing takes place and the processing results are displayed on the screen, or printed by a printer.
Elements of Computer
There are two elements, which work together to mark up a computer system, namely Hardware and Software.

"The physical components of a computer system such as electronic, magnetic and mechanical devices is called Hardware."

"Hardware is the name given to all the equipments and electronics circuits that make up the computer- the keyboard, screen, tape recorder , disk drive and printer."
Hardware is the name given to all the equipments and electronic circuits that make up the computer- the keyboard, screen, tape-recorder, disk drive and printer. However, the hardware can be nothing without the software.

Software is the name given to the information that the computer needs to work on. The information can be instructions, which tell the computer what to do, or data, which is information that is used by the instructions. For. Example, you can instructions that perform a task is known as a program.