Computer :

Computer is an electronic device which operates under the control of instructions stored in its own memory. A computer can take data from the user through input devices (Input), process the user given data (Processing), produces the result to the user through output devices (Output)and stores data (Information) for future use.

Computer can be defined as follows...

Computer  Systems :

It is made up of 2 major components

They are :

1) Hardware

2) Software

Computer Hardware :

• These are the physical components of a computer
• It consists of 5 Parts
  1. Input Devices           
  2. Output Devices            
  3. CPU
  4. Primary Storage
  5. Secondary Storage

Block diagram of a Computer :

Input Devices :

• These are used to enter data and program into the computer
• These are for man to machine communication

      Example : Keyboard, mouse, scanner, touch screen, audio input.

Output Devices :

• These are used to get the desired output from the computer
• These are for machine to man communication
• If the output is shown on monitor then it is called “Soft copy”
• If the output is printed on a paper using printer then it is called “hard copy”

      Example : Printer, Monitor, Speakers

CPU (Central Processing Unit) :

• It is responsible for processing the instructions
• It consists of 3 parts
  • ALU – Arithmetic and Logic Unit
    • ALU performs arithmetic and logical operations like comparisons among data
  • CU- Control Unit
    • CU is responsible for movement of data inside the system
  • Memory
    • Memory is used for storage of data and programs. It is divided into
      • 1) Primary Memory / Main Memory
      • Secondary Memory / Auxiliary Memory

1) Primary Memory :

• It is also called main memory
• Data is stored temporarily i.e. data gets erased when computer is turned off

       Example : RAM

2) Secondary Memory :

• It is also called as auxiliary memory
• Data is stored permanently so that user can reuse the data whenever he wants.

      Example : Hard disk, CD, DVD, Floppy etc.

Computer Software :

• The software is used to make the hardware of the computer to function
• Software is collection of programs (or) instructions
• Computer software is divided into 2 categories
  • System Software
  • Application Software
•  They constitute set of programs that manage the hardware resources of a computer

1.System Software :

• It is divided into 3 classes

Operating System :

• It acts as an interface between the user and the hardware
• It makes the system to operate in an efficient manner

      Example : MS DOS, Windows, UNIX, LINUX, etc.

System Support :

• They provide some utilities and other operating services

     Example : Sort utilities, disk formatting utilities, Security monitors

System Development :

• It includes
  1. Language translators – Used for converting programs into machine language
  2. Debuggers – for error free programs
  3. CASE tools – Computer Assisted Software Engineering Tools

2.Application Software :

• It contains programs for performing tasks
• It is divided into 2 classes

General purpose software :

• These are purchased from software developers
• They can be used for more than one application

       Example : Word processors, DBMS etc…

Application Specific Software :

• It can be used only for intended purpose i.e. for which they were designed

      Example : Accounting system, Hospital management system, Banking system. Etc.