INPUT & OUTPUT DEVICES

Prepared by:

Mazhar Javed Awan

Input Devices

The data or instructions you type into the

computer are called input Input devices used to get data into a system. Get data into a system as accurately, least

amount of time. It’s a cheap device.

Examples of Input Devices

Keyboard Mouse Tracker ball Touch sensitive pad Joystick Light pen Touch screen Graphics tablets

Magnetic Strip Reader Bar Code reader Scanner MICR OMR Punched Card Microphone Digital cameras Web Camera

1.Keyboard

Keyboard is the oldest and most familiar of all input devices

Keyboard are intelligent devices and contain their own chips.

The microprocessor scans the keyboard hundreds of second to see if a key has been pressed .

The CPU translate that key and convert into ASCII code.

A standard keyboard called QWERTY keyboard.

Concept or Ergonomic Keyboard

New keyboards, called concept keyboards, have been developed for ergonomics

The goal of this keyboard is to provide comfort and safety.

The user who spends a lot of time in typing may experience repetitive injuries of wrist and hand.

Higher typing speeds can be achieved.

Disadvantages

It is easy to make mistakes when typing in data

If you can't touch type, it can be time consuming to enter data

Keyboards are not suitable for creating diagrams

Disabled people often find keyboards difficult to use

Excessive use can lead to R.S.I.

2.Mouse

That translate its movement on the desktop into digital information.

Moving the mouse produces movement of cursor or the pointer on the screen.

The mouse is also provided with buttons to press.

Technologies: Movement of ball bearing is used to

produce electrical signal. Small lights under the mouse are

reflected on the photoelectric cells.

uses

To select options from a menu or form a set of icons

To position the cursor when editing text or using a design package.

To draw shapes. It selects a position on the screen more

quickly than is possible with a keyboard.

3.Joysticks

Is similar to tracker ball. Is a device which enables the user to control

movement on the screen by a small lever. The lever can be moved in any direction. Some joysticks give more control on the screen.Uses Controlling objects in computer games Producing graphics Scanners in hospitals

4. Track point

Little joystick on the keyboard Move pointer by moving the joystick

4.Light Pen

Is a pen shaped device, held in the hand which can detect the presence or absence of light

It is connected by the cable to a recording device or to a computer or computer terminal.

Electrical signals are sent along the cable indicating whether or not light of sufficient intensity is being sensed.

Uses

To detect bar codes To indicate a point on the screen It removes the need to type or write. It is faster than typing.

Disadvantage: It can only record the presence or absence of

light. It only works with software written for it.

5.Graphics Tablet

Is also known as digitizing or digitizing pad.

The digitize data means to convert it from analog form to digital.

A design is put on the board and its shape is traced out with the stylus.

Electrical signals sent to the computer record the position of the stylus.

Encoding the picture into binary form

Uses

It can be used to digitize drawings with great accuracy.

Reproducing drawings and designs Producing layouts of printed circuit boards. Digitizer Maps.

6.Touch Pad /Track Pad

Is a small, flat surface over which the user moves his finger.

The movement of the finger moves the cursor on the screen.

A touch pad also has one or more buttons near it .

These buttons like mouse buttons. Touch pads are commonly used

with notebook computers

7. Touch screen

Is a video display screen that receives input from the touch of finger.

Examples Touch screens are used in a lot of

fast food chains and restaurants because they are easy to keep clean and re-program if changes need to be made to the menu.

ATM Petrol Pumps

8.Magnetic Strip Reader

Is a short length of magnetic tape stuck on the surface of a tag, card or document.

On plastic tags or cards the strip is sealed in. Tags with stripes identify the item they are attached

to.Examples: On credit card On bank cards A phone Card Cash issue Terminals

Advantages

It is simple to produce. It is not easily damaged. It stores a large no of characters.

Disadvantages The data can be changed or erased by

magnetic field.

9.Barcodes Readers Is set of parallel printed lines of differing thickness, which

represent a number. The number represented by the bars is also printed above

or below the bar code. When bar code are used on shop goods, the number coded

identifies the product and have following information 1. Country of region 2. Manufacturer 3. An item number for the product.Examples: Used in Barcodes Library System Warehouse stock

Advantages

Printed easily The type of item or its price does not have to

be repeatedly written down or typed.Disadvantages: bar codes cannot be changed and thus there

are unsuitable prices. Bar codes only be read by machine. Only numbers can be coded in this way.

10.Scanner

Read data or information from the source

Source could be written document, a price tag, a graphics image , or photograph

To scan text or images which manipulated in some way before being printed

There are two main types of scanner; hand-held and flat-bed.

11.Optical Card reader (OCR) Is a technology that reads typewritten , computer

printed or handwritten documents. It translate the image into a form that can be

recognized by computer. OCR devices read printed characters using OCR

font. An OCR device determines the shapes of

characters by detecting patterns of light and dark. Uses In department stores OCR is also used for the reading of typed

postcodes when mail is automatically sorted. Payment slips accompanying credit card payments are also read using OCR

To scan financial documents such as company

12.Optical Mark Recognition (OMR)

It is also called mark sensing device. It uses light to scan input data to convert it

into electrical/digital signal. The signals are then sent to the computer for

further processing. Examples Voting ballot Multiple choice answer sheet marking Enrollment forms

Mark sheet (OMR)

Advantages

In OMR there is typing involve so errors and takes time is less

Reduces the cost of inputting large amount of data The method is useful when results of the test are

needed very quickly Disadvantages Readers are very expansive Only certain fonts are acceptable. There is high rejection rate

13.Magnetic ink character reader (MICR)

Characters are printed using an ink containing iron oxide.

As the document passes into the reader the ink is magnetized, so that the character shapes can then be recognized electrically.

Use It is used by banks industry for check

processing. Each check contains MICR characters at the

lower left edge. These characters represent check

number ,bank number and account number

Branch codeCheque number

Account number

Advantages

Documents can still be read when folded, written on

Disadvantages Readers are very expansive Only certain fonts are acceptable.

14.Microphone

Is used for input device for a speech recognition system. The voice pattern of user is then converted into instructions to

the operating system or application software or text. Uses as voice mail messages A microphone is used to input sound into a computer system. Microphones are often used for voice recognition systems

which convert sounds made by a user into commands that the computer can carry out.

Systems like this are very useful for people who can’t use ordinary input devices such as the mouse and keyboard.

As computers become more powerful in the future, voice recognition will be a much more common input method for all computer users.

Advantage

Useful for handicapped people with limited movement

No typing or data preparation is necessary.

Disadvantage: Few words can be recognized and the error

rate is high. Not suitable in noisy places.

15.Punched cards

Contains holes in different positions which mean something when they are read by a reader.

Punched cards were the main method of entering data into computers.

Example: The clock card which is used to record the hours a

person works so that wages can be calculated.

16.Digital Camera

Is used to store, picture in digital form. Store images using different ways like floppy disk,

memory stick, mini CD ,PC Card and micro device. Can be connected to a computer easily through

USB port. Image resolution for digital camera measured by

megapixels. Higher resolution photo takes up more memory .

Advantages

No film is needed No expensive developing costs Pictures are in digital form so it can easily

sent over the internet You can adjust the size of image

17.Web camera ( Web Cams)

Is simply a digital camera that is used to capture still images and video images

These images can then be transmitted to a computer where they are stored in graphics format

Pictures can be used on the websites

Camera placed on top the screen such a system allow video conferencing

Uses

Advertising Checking on children in nurseries Checking on the weather on the other part of

the world

Output Device Output device provide results in a suitable form after data

processing. Output devices are used to get data out of a system. They should be able to do this as accurately and quickly as

possible, and with the minimum of human intervention. Visual devices (including Visual Display Units [VDUs],

screens, and monitors) Hard copy devices (including ink jet printer, laser

printers, dot-matrix printers, and plotters) Sound devices Computer controlled devices (including robots)

1.Monitor or VDU

Most common output deice It is known as display screen The output display by monitor is called soft

copy so it is ideal for showing the results from an enquire where no printed is needed.

Types of Monitor

CRT Flat Panel Monitors

Cathode Ray Tube (CRT) Creates the image on the

screen through electronic beam This is same type that is use in

Television It consists of one or more guns These guns generate

red ,green and blue (RGB) colors.

Disadvantages of CRT Monitors

CRT monitors are big, take up desktop place and can be difficult to move. Standard CRT monitor weighs around 30 pounds.

Require lot of power to operate (run), hence not practical for notebooks.

Liquid Crystal Display (LCD) LCD screens are most often seen on portable or

laptop computers These are used in these applications because they

are small and light. Also used where space is at the premium. Create image with special liquid crystal, which is

transparent normally and becomes opaque when charged electronically.

Use in banks and Multinational companies Disadvantages Image can be difficult to see in bright light Limited viewing angle

Printers

It prints character ,symbols and graphics on paper.

Print resolution is commonly measured in dots per inch (dpi)

Different types of printer are Impact Printer Non Impact Printer

Impact Printer

Its act like a typewriter It prints characters or images by striking a

print hammer or wheel against an inked ribbon

Dot matrix printer Line printer Daisy wheel Printer

1.Dot Matrix printer It produces printed images when tiny

pins on a print head strike an inked ribbon

When ribbon pressed against the paper, it creates dots that they form characters and graphics

Which can transfer print through layers of paper.

Able to print multi-part sheet. It generates lot of noise ,its print quality

is not good

2.Line printer

Special type of impact printer Works like Dot Matrix printer but uses a

special wide print head that can print entire line of text at a time

Don’t offer high resolution Incredibly fast Fastest line printer – 3000 lines per minute

3.Daisy wheel printer

Similar to typewriter Uses print wheel A motor rotates the wheel. Its slower than Dot matrix but better in quality

2. Non Impact Printer

Prints characters and graphics on a piece of paper without striking the paper.

These printers are faster than impact printers Inkjet printer Laser printer Thermal printer

1.Inkjet printer It prints characters and graphics by spraying tiny

drops of liquid ink on paper The print head of an inkjet printer consists of

nozzles It has two cartridges black and white These printers can produce quality text and graphics

in both black and white color slower than laser printer but faster than dot matrix

printer They can print 1 to 6 pages per minute Cheaper in price Satisfactory in color

2.Laser Printer

Creates image on the paper by the laser beam

Also called page printer because they print complete page at a time

It contain toner Throws magnetic powder on paper in the

form of microscopic dots

Advantages

Print a page at a time so it is fast and it print pages 10ppm

They produce high quality of text and graphics

They are quiet in operation compared with dot matrix

Equipped with paper trays for both the input and the output papers

Disadvantages

Are more expensive than dot matrix or ink-jet printer

They are quite large and can take up lot of disk space

Quite complex so the repair bills can be high Multi part stationary cannot be used

Thermal printer

Is a printer that uses heat process to transfer colored dyes or inks to the paper

Is the best color printers currently available but it is very expensive

Plotters

Is an output device that is used to produce image quality graphics in variety of colors

Used to create maps, architecture drawings, graphs and charts

A plotter works by drawing lines on paper using pens held in a mechanical arm

It may be in form of Flatbed Plotter Drum plotter

Plotters

Is an output device that is used to produce image quality graphics in variety of colors

Used to create maps, architecture drawings, graphs and charts

A plotter works by drawing lines on paper using pens held in a mechanical arm

It may be in form of Flatbed Plotter Drum plotter

Flatbed Plotter

Used to plot or draw images. It contains pens for drawing images. The paper is placed on table like surface Software instructs the pens to move down on

the paper

Drum Plotter

Uses a rotating drum or cylinder

The drawing pens are mounted on the drum

The pens move to the left and right as the drum rotates

Advantage of drum plotter is that the length of the plot is almost unlimited

Voice Output

Visually people find the spoken word from the computer

Special software is used for this process In a word processor each letter is typed and it

can hear with headphone.

Audio Output

An audio device translate audio information from the computer into sounds that people can understand

Speakers Headsets