Overview Of a Computer System

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What is Computer

                A computer is an electro-mechanical device, which takes the input from the user and after processing it, gives the required output to the user.
                The first general-purpose electronic computer is Electronic Numerical Integrator And Computer (ENIAC).

Generation

          1. First Generation

    • Vacuum Tubes were used as major components.
    • For input information, punched cards were used.
    • Example: Eniac, IBM 650

          2. Second Generation
    • Using Transistor in place of vacuum tubes.
    • Example: IBM 7000, Honey Well 200.
         3. Third Generation
    • Integrated Circuit (IC) in place of transistors.
    • Example: IBM 360, ICL 1900
         4. Fourth Generation
    • Large Scale Integrated Circuit (LSIC) and Very Large Scale Integrated Circuit (VLSIC) made dramatic changes both hardware and software.
    • Example: IBM 370, HP 3000.
         5. Fifth Generation
    • This generation computer is yet to be developed. It is felt that Artificial Intelligence (AI) will be added to the computers so that these will have that capacity of thinking and reasoning.


Classification

         Classification According to Logic Used

             1. Analog - It process or represents data by measurable quantities or physical nature such as Voltage, temperature, pressure etc.

             2. Digital - It process data in the form of binary representation or two state form, namely 0 and 1.

             3. Hybrid - It is a computer system consisting of a combination of analog and digital computer system having both types of components is called a Hybrid Computer.


Basic Organization


Central Processing Unit (CPU)

  • CPU is the brain of any computer system.
  • All major calculation, manipulation and comparisons are made by the CPU.

The major parts of a CPU are:
  • Control Unit (CU)
  • Arithmetic Logic Unit (ALU)

Storage or Memory Units

It is that part of the computer which stores data temporarily or permanently for future use.

Memory units can be classified as:
  • Primary Memory
    • Primary Memory is a small and relatively first storage unit which stores data, instruction and program which are being currently used by the CPU. 
    • It is also known as Main Memory.

         Primary memories are two types:



  • Secondary Memory
    • Secondary Memory or Secondary Storage Devices are permanent storage units used for storing programs and data.
    • Examples: Hard Disk Drive (HDD), CD, DVD, etc.

Applications
  • In Data Processing
  • In Office Automation
  • In Drawing, Design and Manufacturing Field
  • In Publishing Work
  • In Information and Communication System
  • In Weather Forecasting
Components
  • Hardware
    • That type of device which we can see and touch and which is physically present is called Hardware. 
    • Example: Mouse, Keyboard, Monitor etc.
  • Software
    • The program that runs on the computer is called Software.
    • A software is an untouchable component of a computer.
    • Example: MS Office, VLC Media player, Photoshop etc.
Input Devices / Units
            The input unit accepts input from the user using an input device and converts it into the machine understandable form.

 Some Input Devices are as Follows:
  • Keyboard: A keyboard is a used mainly for typing text into the computer.
  • Mouse: A mouse is a small pointing device used to point to and select items on the computer screen. It is held in one hand and moves across a flat surface.
  • Joystick: It is also a pointing device, used for playing games.
  • Scanner: A scanner is a hardware device used to scan text or images into the computer.
  • Web Camera: A web camera allows a computer to accept input just by focusing on the input object to take a picture of the object.
Output Devices / Units
                Output devices are those devices of the computer that supplies information or results either in the form of hardcopy (Printer) or softcopy (Monitor).
Some of the Output Devices are as Follows:
  • Monitor: A monitor displays information in visual form, using text and graphics.
             There are two basic types of monitors:
      • LCD (Liquid Crystal Display) Monitor
      • CRT (Cathode Ray Tube) Monitor
  • Printer: A printer transfers data from a computer to on a paper.
  • Speaker: Speakers are used to plays sound.
Secondary Storage Devices
  • Magnetic Device
    • Floppy Disk: It is called a floppy disk because the round film inside the disk's plastic shell is flexible (floppy).
    • Hard Disk Drive (HDD): A hard disk is a device used for mass storage of data. a PC normally uses 80gb or more capacity of HDD.
  • Optical Device
    • An optical disk is a personal computer storage device that stores data optically, rather than magnetically.
    • Example: 
      • Compact Disk (CD)
      • Digital Video Disk (DVD) 
  • Pen Drive
    • USB flash drive or pen drives are typically small, lightweight, and rewritable.
    • It is a flash memory card that plugs into the computer's USB port.

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