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Introduction to Computer System and its History

The word ‘Computer’ comes from the word ‘compute’, which means to calculate. In the past, the computer was used only as calculating device used to perform arithmetic operations. But today, computer is used in every field and aspects of our daily life to solve problems of various types. In the detailed form, a computer is an electronic device that uses data for information and manipulates it for result. A computer is like the human physiology which has capability to store data and information. A computer is programmable i.e. the computer depends totally on the program, which the computer is using. A program is the list of instructions, telling the computer ‘what to do’. Computers hardware is designed to be as flexible as possible. By using computer program, called software, one transforms this flexible hardware into tools for specific purpose. No matter which program a computer is using, the machine itself performs only four basic operations, as shown in figure. The most widely accepted definitions of computer include the following operations.
  • Input
    A computer accepts data that is provided by means of an input device, such as mouse, keyboard, scanner and so on.
  • Processing
    A computer performs operations in the form of data to transform it into information in some way.
  • Output
    A computer produces output through output devices, such as printer, monitor, that show the results of processing operations.
  • Storage
    A computer stores the results of processing operations on storage devices for future use.


  • A computer is an electronic device that uses data or information in the form of digitalized data and manipulates it for result based on a program of instructions on how the data is to be processed.
  • A computer is an input-output device which processes raw data in the form of information and stores it in storage devices for future purposes.

A computer is being used for many purposes as making supermarket bill, ATM machines by bank, also used by writers, television broadcasting, producers, musicians, professors, poet, graphic illustrators, scholars and so on other personnels for their various purpose. A computer has different application on following fields as Business, Medicine, Education, Engineering, Military, Government, Music, Film etc

Characteristics of Computers
Computer is an intelligent machine that performs the operations in an accurate, faster and efficient way, it creates extra leisure time which can be used in matters involving creativity & judgment. Some of the common characteristics possessed by computers are as follows:
  • Automatic Machine
  • High processing speed
  • High accuracy
  • High storage capacity
  • Repetitiveness
  • Versatility
  • Diligence
  • Consistency
  • Arithmetical and logical operations
  • Communications

Though the computer has become the most powerful tool, it works on the principle of ‘Garbage In Garbage Out’. It depends totally on our instructions for the way it operates. It is not capable of doing anything if we don’t instruct how to do it.

Computation began with computing, initially stones, knots in thread; sticks etc were used in calculating the number of cows, sheep, goats, horses a man had. There is the development of calculation process with the change of time by various calculating devices. Today finally the modern computers have developed.

ABACUS (3000 BC)
An abacus is a computing device consisting of a rectangular frame with number of rods or wires and disk. A central bar divides each of these rods into two unequal portions. The rods and disk can be moved up and down on a series of sticks or strings usually within wooden frame for calculation. The abacus doesn't compute itself; it's simply a device or machines for helping human being to calculate large numbers by remembering what has been counted.

Pascal’s Calculator (16th century)
A French scientist Blaise Pascal in 1642 developed Pascal’s calculator or Pascaline considered as first mechanical calculator. This mechanical calculator only adds and subtracts the digits. Pascal used wheel with ten gears, one wheel for a digit, were mounted close to each other. It was especially successful in the design of its carry mechanism, which adds 1 to 9 on one gear, and when it changes from 9 to 0, carries 1 to the next gear. His contribution on this made each digit independent of the state of the others, which enabled multiple carriers to rapidly flow from one digit to another regardless of the machine's capacity.

Babbage’s Analytical Engine and Differential Engine (1833 and 1812)
The father of computer, Charles Babbage, an English Mathematician invented the Differential Engine. It is based on the difference table of the squares of numbers. He wants to calculate polynomial functions using the method of differences but such machine was to have hundreds of gears, shafts, and counters. He continued working on his difference engine for full ten years, but in 1833, he lost his interest because of better idea. His new idea was the construction of a general purposefully programmable mechanical counting computer. Babbage called his machine an “Analytical Engine”.
An idea of Analytical Engine was considered as a great step in the history of development of modern computer. By this idea, the dream of modern computer comes true in our eye. This machine was capable of working on some form of charge and calculating up to twenty decimal at about 60 additions per minute, could store information, make decisions, and carry out instructions based on its decisions.
The analytical engine was designed only but never built by Babbage because of the technology of manufacturing exact technical parts were not developed. In his lifetime the dream could not become true. However, he was honored as the father of computer as result of his contributions . 



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