Computer is an electronic device which is made up of different types of devices. These devices are made up of electronic circuits. These devices are input devices, output devices & storage devices. These devices are called Hardware. Hardware is nothing without Software. The set of instructions given to the devices to perform a particular task is called Software. Step by step instructions written to the computer system is called program. E.g. C, C++, JAVA, etc. are some of the programming languages. Now what comes next is the steps performed by the computer system. The steps include :-

  • Input
  • Storage
  • Processing
  • Output

Raw data given to the computer system is an input. This function is performed by an Input Devices. E.g. of input devices are keyboard, mouse, joystick, floppy disk, hard disk, CD-Rom, etc. Raw data are stored in the memory unit. There are two types of memory Primary Memory & Secondary Memory. Hence their storage ability differs. This is the most vital part of the system. E.g. of storage unit is RAM, ROM, etc. Processing is performed when the work of storage unit is done. But, the work of storage unit is performed even when the processing is done. The process by which raw data are converted into meaningfull information is called processing. E.g. of processing unit is CPU. Central Processing Unit(CPU) is the nervous system of the computer which consists of both the storage unit, memory unit & processing. Atlast the output unit works. The meaningfull information given by the computer system after processing raw data is called an output. Hence the device which gives us output is called an Output device. E.g. of output devices are Visual Display Unit(VDU) / moniter, printer, plotter, etc.

Here are some important terms to remember:-


Booting is the process of starting a computer system. There are two types of booting :-

  • Cold Booting
  • Hard Booting

Types of Booting

1. Cold Booting - When we simply switch on the computer for 1st time, it is called Cold Booting.

2. Hard Booting - While working on a computer, sometimes computer stops responding. It gets hanged. We either do the following without switching off the power & get started again :-

(a) we press RESTART key, or

(b) we press ALT+CTRL+DEL keys together

Computer starts working from the beginning.


Software can be classified as under :- 

  1. System Software
    1. Operating System
  2. Application Software
    1. User defined application
    2. Application Packages
  3. Utility software & packages
    1. Virus scanner & remover
    2. Disk Fragmentor

System Software

The instructions given by the manufacturers to control the internal affairs of the computer system is called System software.

Operating System

Operating system is the link between hardware and software. Operating system is the instructions which is given to the hardware to perform a task. Operating system is nothing but a program written in high level language. E.g. of operating system is DOS, Linux, Window OS, etc.

Application Software

The instructions given by the users to make the task easier is called Application software. Application software is the link between the user & the System software. E.g. of application software are the software packages made for business purpose, etc.

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