Computer Components

THE INPUT UNIT • Used to accept data and Instructions from the User. • This work is done with the help of Input Devices.

KEYBOARD • It is used to write letters, digits and commands. • Each key when pressed sends a digital code to the computer. • The keys on computer keyboards are often classified as follows: alphanumeric keys -- letters and numbers punctuation keys -- comma, period, semicolon, and so on. special keys -- function keys, control keys, arrow keys, Caps Lock key, and so on.

MOUSE

• It is a pointing device with a roller on its base. • It controls the movement of POINTER on the screen. • It contains two or three buttons and it may or may not have a wheel.

• It is used to play computer games. • Used to Input directional data but unlike mouse it works only in left, right, up and down directions.

Joystick

Scanner • It creates the Electronic form of a printed image by shining light on to the image and sensing the intensity of reflection at every point. • There are 3 types of Scanners: Hand-Held, Flatbed and Drum scanners.

Hand-held scanner • These are small and can be held in a hand. • Multiple passes are required to scan an image.

• They have a flat surface, on which the printed image to be scanned, is placed. • They can scan a page in a single pass.

Flatbed Scanner

Drum Scanners • The sheet is fed through the scanners so that the drum rolls over the entire sheet to be scanned. • Medium sized.

Magnetic Ink Character Reader

MICR is used to read the characters printed using Magnetic ink (ink containing Iron oxide) by magnetizing the ink and examining the characters.

MICR

Light Pen • It is a pointing device. • It consists of a photocell mounted in a pen shaped tube. • Clicking is performed by pressing the pen on screen.

Bar Code Readers • It emits a beam of light which reflects off the bar code image. • A light sensitive detector in the bar code reader then identifies the bar code image.

MICROPHONE • It is used to send sound input . • It converts the sound received into computer’s format called digital sound. • It needs a special hardware called SOUND CARD.

• The light passing through the lens of the camera is digitized by special servers that are sensitive to light. • The image is stored in camera’s storage memory.

DIGITAL CAMERA

PROCESSING UNIT • Central Processing unit (CPU) is responsible for carrying out the processing job. • CPU is the brain of computer. • It does all the processing work. • CPU has two components: 1. Arithmetic Logic Unit (ALU) 2. Control Unit (CU)

Arithmetic Logic Unit (ALU) • Arithmetic operations include : +, -, *, /. • The result of Arithmetic operations is a number. • Logic Operations include : >, <, >=, <=, =, <>. • The result of Logic Operations is either TRUE or FALSE.

CONTROL UNIT • The entire processing is monitored and controlled by CU. • Whenever an input reaches into memory, the CU determines what type of instruction it is and accordingly instructs the ALU or I/O devices.

Working Of CU • Read value A (Input) • Read value B (Input) • If A > B then (ALU) – (If result is true) Set C = A – B Print C (Output) • Otherwise (ALU) – (If result is false) Set C = A + B Print C (Output) • End

3 Factors that determine your computer’s efficiency:• CPU Speed – How many instructions are executed per second. A normal CPU runs at 3 GHz per second i.e. 3 billion instructions are executed in a sec. • Memory Size – i.e. the size of RAM. You can increase the size of RAM. • No. of applications – Limit the amount of applications that are running at one time.

OUTPUT UNIT • The function of an Output device is to present processed data to the user. • MONITOR – The computer sends the output to the monitor if the user needs to see it. • PRINTER – The output is send to printer if it is needed in printed form • SPEAKERS – The sound output is send to the speakers. • PLOTTERS – Graphic output is send to plotters.

MONITOR • The picture on a monitor is made up pf thousands of tiny colored dots called pixels. • There are two types of monitors:Cathode Ray Tube (CRT) Liquid Crystal Display (LCD)

CATHODE RAY TUBE (CRT)

LIQUID CRYSTAL DISPLAY (LCD)

PRINTERS There are 2 categories of Printers: • Impact Printer – There is mechanical contact between the Print head and paper. • Non-Impact Printer – There is no mechanical contact between the print head and the paper.

DOT MATRIX (IMPACT) PRINTER • The printing head contains the vertical array of pins. • As the head moves, selected pins fire against the ribbon to form a pattern of dots.

INKJET (NON-IMPACT) PRINTER • The print head of Ink jet printer contains tiny nozzles which fire extremely small droplets of ink onto paper,

LASER (NON-IMPACT) PRINTER is • The powered ink transferred to paper to form a text/image pattern. • It is then fixed by heat and pressure. • Similar to a photocopier.

PLOTTERS – Flat bed and Drum

SPEAKERS • Speakers receive sound in form of electric current from the sound card and then convert it to sound format.

STORAGE DEVICES • Magnetic Media: Floppy Disks Hard Disks • Optical Media: CD ROMs DVDs

FLOPPY DISKS Tracks Sector • It is made of a flexible substance called Mylar. • They have a magnetic surface which allows the recording of data. • All disks must be formatted which means marking and dividing the disk into TRACKS and SECTORS.

Hard Disks

Compact Disks (Working)