Computer Components

Components of Computer System

A computer system has three components i.e.,
1)Computer Hardware
2)Computer Software
3)Computer  Users

Hardware: Computers are made up of many electronic and electromechanical devices. The devices together are referred to as computer hardware.

 Hardware is the physical components of the computer which are tangible and visible to the user.
 Hardware is mainly categorized into following three parts.
1) Input devices,
2) Output devices,
3) Peripherals


1) Input devices help to capture data into the computer. They also help the user the communicate with the computer. Few input devices are as follows:

a) Keyboard:  It is the most common input device used with a computer system
It include:

i) Characters with a standard arrangement, mostly in the QWERTY arrangement, named for the six characters at the beginning row of the top left corner of the keyboard.
ii) Numeric keypad for easy numbers entry.
iii) Special keys for cursor movement
iv) Function Keys

b) Mouse: A mouse is a push button control device that eliminates to type computer commands. Instruction are given by the user to the computer  by pointing an arrow on the screen  to a picture or word and then pushing the button on the mouse. The user moves the arrow on the screen by sliding the mouse across the desktop.

c) Joy Stick: A joy stick is typically used for game playing but can also be enter user request. This device enables the user to interact with screen image by moving the stick in multi-direction. It is commonly used to play computer games.

 d) Light Pen and Touch Sensitive Screen : Some CRT allow input via a light pen or a touch sensitive screen. The light pen is a device that allows the operator to identify a particular point or character displayed on the screen, and can be used alone or in conjunction with a keyboard to add, rearrange or delete information displayed on the screen.

e) Optical Character Reader: An information processing technology that converts human readable data into another medium for computer input. Light reflected from character is recognized by optical character recognition equipment.

f) Optical  Mark Reader: An optical mark reader, sometimes called a mark sense reader, detects the presence of pencil marks on pre-determined grids. The method involves directing thin beams of light onto the paper surface which are reflected onto a light detector, unless the beam is absorbed by dark pencil mark, i.e., a mark is recognized by reduction in the intensity of the reflected light .

g) Magnetic Ink Character Reader: This device is capable of reading magnetic ink character  on MICR document, and either passing the data directly to a computer or storing it offline. Document are passed through a strong field causing the iron oxide in the ink encoded character to magnetise. Document are then passed under a read head, where current flows at a strength according to the size of the magnetized area.

H) Bar Code System: Bar encoding is a special type of point of sale recording. Although several different bar codes exist, the most easily recognizable is the Universal Product Code (UPC). The bar code reader has a scanning device that translates black and white bars of different widths into electrical impulses.

i) Voice Data Entry: In the Foreseeable future VDE system will allow you to talk to your computer. It is unlikely to be employed for the input of a large amount of data as this can be handled by faster and more cost effective methods.

2) Output Devices: output devices help the computer to communicate the results of the processing to the user. Few output devices are as follows: 

a) Printer: A printer is a device that can record information permanently on paper in the form of printed copies.
Computer printers fall into three main categories :

i) Line printers             ii) Serial printer                    iii) page printers.

 Line Printer are further divided into :-      Page Printers are further divided into :-
i) Drum                                                              i) Laser
ii) Chain                                                   ii) Electrostatic Photo-graphic
iii) Electrostatic                                                     iii) Electrosatatic
iv) Band                       

Serial Printers are further divide into :-
i) Impact                                                              ii) Non-Impact
Impact-Wire Matrix, Daisy wheel, Golfball
Non-Impact-Electrothermal, Inkjet

2) Monitor/VDU: Monitor is a device to interact with the computer. The messages from computer are displayed on the screen of the monitor. It is the most common output device which uses a Cathode Ray Tube(CRT) to produce images. Images are formed by collection of spots, each known as pixel.
Monitor can be classified based as:

A) Resolution: The number of pixels that make up the screen:
  i) CGA (Colour Graphic Adapter)
  ii) EGA (Enhanced Graphic Adapter)
  iii) VGA (Video Graphic Array)
  iv) SVGA(Super Video Graphic Array Adapter)
CGA having the least resolution and SVGA the highest resolution.

B) Colour Facilities
i) Monochrome: Single colour display on a black background.
ii) Colour Monitors: Which can display multicolour output by combining red, green and blue in vary intensities.

iii) Plotter:  Plotter is an output device that is used to produce graphical outputs on paper.It uses pens, either of single colour or multi-colour to draw pictures. Engineering designs can be printed with good precision by making use of plotters. There are two types of plotters:

i) Drum plotters                                      ii) Flat bed plotter
Applications of Plotters:
I) Computer Aided Design( CAD)
ii) Map Drawing,
iii) Architectural Drafting
iv) General Business Applications

3) Peripherals
All the other electronic and electromechanical devices are considered as computer peripherals. It includes C.P.U. storage devices.

System unit: It is a box like case that houses the electronic components of computer that are used to process data. The system unit is made of metal or plastic and is designed to protect the electronic components from damage. The Electronic components and most storage devices reside inside the system unit.

a) Mother Board: It is the main printed circuit board in an electronic device, which contains sockets that accept additional board. In a personal computer, the mother board contains the bus, C.P.U., memory sockets, keyboard controller and supporting chips.

b)Central Processing Unit: It is the brain of as it is responsible for  almost all the activities in a system. The  Parts of CPU are connected by an electronic component referred to as a bus, which acts as an electronic highway between them in order to store data and instructions temporarily. It has three parts:

i) C.U (control unit): 
It controls the movement of data program instructions into and out of the CPU and to control the operations of A.L.U. C.U. fetches the  instructions from the main memory into registers , decodes it and sends control signals to other components of the computer so that the appropriate actions are carried out. This is known as fetch executes cycle.

ii) ALU (Arithmetic Logic Unit): The ALU performs all the arithmetic and logical functions, that is , it adds subtracts, multiplication, divided and does comparison. It also performs logical operations (AND, OR and NOT).  These operations provide the facility of decision making through the computer. The result of a logical operation is either TRUE or FALSE

iii) Registers: A registers is a special temporary locations within the CPU. Registers very quickly accept, store and transfer data and instruction that are being used immediately. To execute an instruction, the control unit of the CPU retrieves it from main memory and places it into a register.