Monika

INPUT AND OUTPUT DEVICES Introduction to Computers

Introduction
Devices which are a means of communication between the computer and the outside world are called PERIPHERAL DEVICES
The processors which are required to convert the input data into machine readable form and to convert the output generated by the computer into human readable form are known as INPUT/OUTPUT (I/O) interfaces.
Introduction to Computers

Input Devices
Those peripheral devices which supply information i.e. data and program from the outside world to the computer are called INPUT DEVICES.
Punched Cards
Keyboard
Mouse
Light Pen
Joystick
Track Ball
Touch Screen
Digitizer
Scanners
Voice Recognition Systems

Punched Cards
Data is recorded on punched cards or tapes.
It uses standard codes, like HALLERITH code.
Cheap and reliable.
Cannot be reused.
Special care has to be taken.
If a single card is misplaced then it is very difficult to rearrange and detect the problem.
Require large storage space & cannot be folded.

Keyboard
Similar to typewriter keyboard.
Keys on keyboard consist up of letters, numbers, symbols and function keys.
Special keys like Tab, Del, Ctrl, PgUp, PgDn,etc.
Easy to use and offers number of facilities.
Can edit the input data very easily.
Relatively inexpensive.

Mouse
A pointing device.
Control and manipulate cursor movement on monitor.
Has three or four buttons on it and roller ball which signals the movements on a flat surface.
Move fast from one part of the screen to the other.

Light Pen
A picking device.
Contains a photocell placed in a small tube.
Photocell detect the presence of light on the CRT (monitor).
Tip of pen is moved on the surface of the screen to write or sketch data.
Specially useful in Computer Aided Design (CAD) application

Joystick
Widely used in computer or video games.
The direction and speed with which the joystick is moved is converted into digital signal and sent to the computer system.
This in turn controls the movement of the cursor on the screen.

Track Ball
Also known as roller ball.
Uses a hard sphere to control cursor movement.
Ball can be rotated in any direction by hand.
This digital signal in translated to control the cursor movement on the screen.

Touch Screen
A touch panel is transparent plate.
Input is registered when a finger or any other object comes in contact with the plate.

Digitizer
It converts a graphical or pictorial data into digital form which can be directly entered and stored in a computer.
It is also called a graphical tablet.

Flat Bed Digitizer
The drawing to be digitized is fixed over a flat bed table and a stylus or a pen is moved over the surface of the drawing.
This scans the drawing and produces the output related to X and Y coordinate.

Image scan digitizer
The entire image is scanned and reproduced automatically.
It is more powerful as compared to flat bed digitizers.
It is mainly used in simple drawings, graphs etc. whereas image scan digitizers are used for photographs and pictures.

Scanner
It is able to directly enter text and images into the computer memory.
Eliminated the duplication work of entering data .
This result into increase in speed of data entry and accuracy.

Optical Mark Reader
Capable of reading pre-specified marks made by pencils or pen with the help of light.
Used where data is preprinted for application.
Used for the answer papers of the objective tests where the answers are marked with pencils or preprinted forms.

Optical Character Reader
It can read alphabets, characters and numbers printed on paper.
Character can either handwritten or typed.
It reads each character as a collection of pixels
Mainly used in processing where the data volumes are large .

Bar Code Reader
It reads bar coded data.
Laser beam scanner is used to read the bar code.
Most commonly used bar code is the Universal Product Code (UPC).

MAGNETIC INK CHARACTER RECOGNITION (MICR).
Mainly finds application in banking areas.
It is used to encode the character to be read.
It speed up data entry, and even roughly handled cheques can be processed relatively easily.
Only a limited number of digits and character are available for encoding.

Voice Recognition System
Uses microphone or telephone, a sound card an special software.
Voice recognition system are highly operator dependent.
Reduces the cost of data entry.
Can move freely while talking into the computer.

Output Devices
The output devices allow computer to communicate with the outside world by accepting data from the computer & transforming I into user readable form.
Printers
Plotters
Monitor
Video Display Terminal
Computer Output Microfilm

Printer
It produces the output from the computer on the paper.
Produces a hard copy i.e. permanent copy of the result which can be stored and read later.
Impact Printers
Non-Impact Printers

Impact Printer
Similar to typewriter.
Use hammer to strike a character against an ink ribbon.
Noisy in operation.
Its functioning is relatively easily.
It can produced multiple copy at the same time.
Subject to wear and tear of mechanical parts

Dot Matrix Printer
Print each character as a pattern of dots.
Relatively low in cost.
Print at speed 50-500 character per second.

Daisy Wheel Printer
Also called as letter quality printers
Letter quality of these printer is much superior as compared to the dot matrix printer
They are slow and typically print in the range of 10-50 characters per second

Line Printer
Very fast printer and print at speed of 200-2500 lines per second.
It normally have 132 print positions per lines.
It is normally used in application where large volumes of data are to be printed

Ink Jet Printer
Prints character by spraying ink from tiny nozzles onto the paper.
Output is of a superior quality.
Possible to obtain coloured output.
Number of character styles and sizes are available.

Laser Printers
Produced a very superior quality output.
Have a buffer memory to store entire pages and hence their speed is very fast.
No mechanical movement is involved.
Noiseless in operation.
Comparatively expensive

Plotter
A plotter is a an output device used in applications where printouts of graphs and drawings are required
Plotters are of two types
Flat Bed Plotter
Drum Plotters

Flat Bed Plotters Introduction to Computers

Drum Plotters Introduction to Computers

Monitors
Monitor is a device like television screen which is used to display information
The resolution of monitors is the number of picture elements
Monitors are of two types
Cathode Ray Tube Monitor (CRT)
Flat Panel Display

Cathode Ray Tube Monitor Introduction to Computers

Flat Panel Display Introduction to Computers

Video Display Terminal
The most popular output device in direct access processing is the Video Display Terminal
The Monitor & Keyboard together are called a Terminal
3 types of terminals
Dumb
Smart
Intelligent

Computer Microfilm Output (COM)
This technology is used to record computer output as a microscopic film images.
Information is recorded on a roll of film.
COM devices are used applications where there are large volumes of data.
They are much more faster than normal printers
Sophisticated & Expensive

Enjoy Frnzz!

Thank You!! Introduction to Computers

Monika

by Monika Rawat on Nov 22, 2011

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