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A computer is a device that accepts information and manipulates it for some result based on a program or sequence of instructions on how the data is to be processed. Computer i.e a combination of two words ‘’compute’’ + ‘’er’’. Compute means calculation and er means device.

​In other word Computer is an electronic device. It can perform all type of mathematical and logical operation. It can accept data, store data, process data, retrieve data and print data.

Computer System

A computer system is a set of components that works together to accomplish one or more task.
Computers are available in different sizes, shapes and weights. Due to different size and shapes they perform different task from one another. They are classified into various category on the basis of physical size, function and processing and storing capacity.

On the basis of physical size, computers are divided into three parts:-

  1. Desktop:- A computer designed for home and personal use. You cannot carry this computer like Laptop. It is a personal computer (PC) i.e for regular use at a single location.
  2. Laptop:- A laptop computer is a portable computer and also known as Notebook. One can carry anywhere like briefcase. Another type of laptop is known as Net-book. Netbook is very popular among business man. One can use Net-book for small application like word-processing, accounting, presentation, internet accessing etc.
  3. Palmtop:- A small computer that fits on one’s palm. Palmtop is also called PDAs, hand help computers and pocket computers.

Classification of Computer, on the basis of function, Computers

Another classification of computer, on the basis of function, computers are divided into three parts:-
  1. Analog computer:- Analog Machine was introduced by Lord Kelvin. In Analog computers numerical data are represented by measurable physical variables, such as electrical voltage, pressure, temperature etc. A thermometer is a simple analog computer. As the temperature varies, the mercury moves correspondingly.
  2. Digital computer:- A computer that accepts and processes data in the form of number (0 - 9) and characters (A - Z) that has been converted into binary code. Most computers are digital.
  3. Hybrid computer:- The feature of analog and digital machines are combined to create a hybrid computers. You can see hybrid computers in hospitals, geological department etc.

Classification of computer on the basis of processing Speed and Storing Capacity, Computers

One more classification of computer on the basis of processing speed and storing capacity, computers are divided into four parts. It is also known as types of Digital computer:-
  1. Micro computers:- Micro computers known as Personal computers (PC). These are small, relatively inexpensive computers designed for personal use in home or office. It has lowest storing and processing speed. Users can use Micro Computers directly in Home, Office or Public places. Note that user uses micro computer that are digital and also can be laptop or Desktop.
  2. Mini computers:- Mini computers are powerful computer as compare to micro computers. It has higher memory, provide faster operating speeds and larger storage capacities than microcomputer and used as server. Minicomputer system known as small mainframe computer system. A mini computer is a multiprocessing system capable of supporting from 2 to 200 users simultaneously.
  3. Mainframes computers:- A mainframes computer is different from micro and mini. It has very high memory and processing speed and used as server (can support thousands of users). A mainframe is a high-performance computer used for large-scale computing purposes.
  4. Super Computers:- Super computer is a different type of computer and can be used for complex type of application. e.g: scientific research, weather forecasting, weapon designing etc. India’s first super computer PARAM-10000 developed by C-DAC, PUNE in 1998,. Another super computers are Padam-Param (Param series), EKA, SAGA-220 etc. India’s fastest Super Computer is EKA designed by TATA.

Computer of First Generation

  • ENIAC:- Electronic Numerical Integrator and Calculator
    • It was first general purpose computer.
    • Invented by John P. Eckret and John Mauchley in 1946
    • Vacuum tube was used as a storage device (18000 V.T)
    • Weight was around 70 tons
  • EDSAC:- Electronic Delay Storage Automatic Calculator
    • It was invented by Maurice wilkies in 1949
  • EDVAC:- Electronic Discrete Variable Automatic Computer (1950)
  • UNIVAC:- Universal Advance Computer
    • It was first commercial purpose computer.
    • Invented by John P. Eckret and John Mauchley in 1952
    • Vacuum tube was used as a storage device (around 28000 V.T)

Units uses in computers to store and process data

Bit:- The full form of Bit is "Binary Digit ” or “Binary Integer”. A bit is a single digit number in base-2 (‘0 or 1’) and is the smallest unit of computer data.
4 bit = 1 nibble
8 bit = 1 byte
1024 byte = 1 Kilo byte
1024 Kilo byte = 1 Mega byte
1024 Mega byte = 1 Giga byte
1024 Giga byte = 1 Tera byte
1024 Tera byte = 1 Peta byte
1024 Peta byte = 1 Exa byte
1024 Exa byte = 1 Zetta byte
1024 Zetta byte = 1 Yotta byte

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