Introduction to Computers

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

Introduction to Computers

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.

Introduction to Computers

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.

Introduction to Computers

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.

Introduction to Computers

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

Introduction to Computers

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.

Introduction to Computers

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.

Introduction to Computers

Touch Screen• A touch panel is transparent plate.• Input is registered when a finger or any other object

comes in contact with the plate.

Introduction to Computers

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.

Introduction to Computers

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.

Introduction to Computers

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.

Introduction to Computers

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.

Introduction to Computers

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.

Introduction to Computers

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.

Introduction to Computers

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).

Introduction to Computers

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.

Introduction to Computers

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.

Introduction to Computers

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

Introduction to Computers

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

Introduction to Computers

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

Introduction to Computers

Dot Matrix Printer• Print each character as a pattern of dots.• Relatively low in cost.

• Print at speed 50-500 character per second.

Introduction to Computers

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

Introduction to Computers

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

Introduction to Computers

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.

Introduction to Computers

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

Introduction to Computers

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

Introduction to Computers

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

Introduction to Computers

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

Introduction to Computers

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!

Introduction to Computers

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