Basics of Computer, Input Devices, Output Devices, Software, Computer Languages (For CBSE, ICSE, IAS, NET, NRA 2022)

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Basics of Computer

  • Computer is a device that transforms data into meaningful information. Computer can also be defined in terms of functions it can perform.
  • The major characteristics of a computer are high speed, accuracy, diligence, versatility and storage.
  • The computer basically performs five units:
    • Input: This is the process of entering data and programs into the computer system.
    • Control Unit (CU) : The process of input, output, processing and storage is performed under the supervision of a unit called ‘Control Unit’ . It takes care of step-by-step processing of all operations inside the computer.
    • Memory Unit: Computer is used to store data and instructions.
    • Arithmetic Logic Unit (ALU) : The major operations performed by the ALU are addition, subtraction, multiplication, division, logic and comparison.
    • Output: This is the process of producing results from the data for getting useful information.
Block Diagram of a Digital Computer

Peripheral devices are connected to the computer externally such as:

Input Devices

Input devices accept data and instructions from the user. Some input devices are:

  • A keyboard is the most common input device. Several kinds of keyboards are available. The keyboard in most common use is the QWERTY board.
  • A mouse is an electro-mechanical, hand-held device. It is used as a pointer and it can perform various functions.
  • Light Pen is an input device that utilizes a light-sensitive detector to select objects on a display screen.
  • Optical Scanner devices are used for automatic data collection. The devices of this category completely eliminate manual input of data.
  • Touch Screen - Touch panel displays and pads are now being offered as alternatives to keyboard.
  • Microphone takes voice as input. It is more prone to error than keyboard typing.
  • Trackball, a pointing device, is a mouse lying on its back. To move the pointer, you rotate the ball with your thumb, your fingers, or the palm of your hand.

Output Devices

Output devices return processed data that is information, back to the user. They are:

  • Out of all the output devices, monitor is perhaps the most important output device because people interact with this device most intensively than others.
  • Two basic types of monitors are:
    • Cathode Ray Tube (CRT) : CRT or Cathode Ray Tube Monitor is the typical monitor that you see on a desktop computer.
    • Liquid Crystal Displays (LCD) : This type of monitors is also known as flat panel monitor. These days LCD monitor are very popular.
  • After a document is created on the computer, it can be sent to a printer for a hard copy (printout) . Some of the most commonly used printers are:
    • Laser Printer: A laser printer produces high quality print that one normally finds in publishing. It is extremely fast and quiet.
    • Ink-Jet Printer: An ink-jet printer creates an image directly on paper by spraying ink through as many as 64 tiny nozzles.
    • Dot Matrix Printer: The dot matrix printer was very popular at one point of time. It is a very versatile and inexpensive output device. Although it is less expensive, it is louder, slower and produces lower print quality.
    • Line Printer: A line printer is generally used with large computer systems to produce text-based data processing reports.
  • A plotter is a special kind of output device that, like a printer, produces images on paper, but does so in a different way. Plotters are designed to produce large drawings or images.
  • Speakers are another type of output device, which allow you to listen to voice like music, and conversation with people.


In order to perform any task, you have to give a set of instructions in a particular sequence to the computer. These sets of instructions are called Programs. Software refers to a set of programs that makes the hardware perform a particular set of tasks in particular order. Software can be classified as below:

System Software

  • When you switch on the computer the programs stored in ROM are executed which activates different units of your computer and makes it ready for you to work on it.
  • This set of programs can be called system software.

Application Software

Application software is a set of programs, which are written to perform specific tasks. Application software can be broadly classified into two types:

  • Generalized Packages: which is user friendly software written to cater to user՚s very general needs that provide general purpose tools to solve specific problems. E. g. : Word Processing Software, Spreadsheets, Presentations, Database Management System and Graphics Tools.
  • Customized Packages: which are the applications that are customized (or developed) to meet the specific requirements of an organization/institution. These packages are developed using high-level computer language.

Computer Languages

Computer languages are broadly classified as:

Low Level Language

The term low level means closeness to the way in which machine understand. The low-level languages are:

Machine Language

This is the language (in the form of 0՚s and 1՚s, called binary numbers) understood directly by the computer. It is machine dependent. It is difficult to learn and even more difficult to write programs.

Assembly Language

This is the language where the machine codes comprising of 0՚s and 1՚s are substituted by symbolic codes (called mnemonics) to improve their understanding. It is the first step to improve programming structure.

High Level Language

You know that low level language requires extensive knowledge of the hardware since it is machine dependent. Higher level languages are computer independent and programming becomes quite easy and simple. Various high-level languages are BASIC, COBOL, FORTRAN, C and

Compiler and Assembler

  • Compiler and Assembler are required to convert the instructions into machine language.
  • The software that reads a program written in high level language and translates it into an equivalent program in machine language is called as Compiler.
  • The program written by the programmer in high level language is called source program and the program generated by the compiler after translation is called as object program.
  • The software that reads a program written in assembly language and translates it into an equivalent program in machine language is called as Assembler.

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