1.1          Introduction

computer is an electronic device that manipulates information or  a programmable machine designed to perform arithmetic and logical operations automatically and sequentially on the input given by the user and gives the desired output after processing. Computer is defined in the Oxford dictionary as “An automatic electronic apparatus for making calculations or controlling operations that are expressible in numerical or logical terms”.

The definition clearly categorizes computer as an electronic apparatus although the initial computers were mechanical and electromechanical, definition is also pointing towards the two major areas of computer application viz. data processing and computer assisted control/operations. Another important confluence of the definition is the fact that the computer can perform only those operations/calculations which can be expressed in Logical or Numerical terms.

The term computer is derived from the Latin word ‘computare’, which means to calculate. Charles Babbage is called the “Father” of the computer. Babbage was designed the First mechanical computer called Analytical Engine.

Computer components are divided into two major categories viz. – hardware and software. Hardware is the machine and its connected devices such as monitor, keyboard, mouse etc. Software the set of programs that make use of hardware for performing various functions. Computer takes raw data as input from the user and processes them with the help of set of instructions (called program) and gives the result (output) and saves output for the future use. It can process both numerical and non-numerical (arithmetic and logical) calculations.

A computer has four functions:

  1. accepts data                                                 Input
  2. processes data                                              Processing
  3. produces output                                           Output

D.stores results                                                Storage

Input (Data):

Input is the raw information entered into a computer from the input devices. It is the collection of letters, numbers, images etc.

Example : Keyboard, mouse, flash drive, scanner, speech recognition system OCR (optical character recognition), OMR (Optical mark recognition) MICR (Magnetic Ink Character recognition), touch pad, digital camera Bar code reader etc.


Process is the operation of data as per given instruction. It is totally internal process of the computer system. The main unit inside the computer is the CPU. This unit is responsible for all inside the computer. It controls all internal and external devices, performs arithmetic and logic operations. The CPU (Central Processing Unit) is the device that interprets and executes instructions.


Output is the processed data given by computer after data processing. Output is also called as Result. We can save these results in the storage devices for the future use.

Example : Monitor printer, speakers, voice response system, projectors, headphones and headsets etc.



A computer can transfer data quickly from storage to memory, process it, and then store it again for future use. Many computers store enormous amounts of data and make this data available for processing anytime it is needed. t describes into 2 ways

1.Primary memory

2.Secondary memory

  1. Examples for primary memory :
  2. A.RAM(Random Access Memory / Read-Write Memory)
  3. ROM(Read-only-memory) they are also called volatile because it erases data if system shutdown or switch off
  4. Examples for Secondary primary:
  5. Hard Disk(Local Disk)
  6. Optical Disks: CD-R, CD-RW, DVD-R, DVD-RW
  7. External Hard Disk etc. it is non volatile


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