Chapter 3 input and out put devices

INPUT & OUTPUT of INPUT & OUTPUT of system system

INPUT & OUTPUT of INPUT & OUTPUT of system system

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• Digital cameras• Web Cameras

• OCR • MICR• OMR• Punched Card• Kimball tag• Voice recognition • Microphone• EPOS• EFTPOS• Video digitiser• Scanner• Touch Phone Telephone

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.

Cordless keyboard• That requires no wires• It is also called wireless

keyboards.• It transmits data using wireless

technology like radio waves or light waves

Special keyboards• These keyboards make it easy for

blind users to input data into a computer

• There are also keyboards with large coloured keys that are easier to see.

• Each key is about one inch square.

Advantages

• Most computers come with a keyboard supplied

• People are used to using keyboards to enter data, they need very little training

• A skilled typist can enter data very quickly

• Specialist keyboards are available e.g. ergonomic, gaming keyboards

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.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

Touch screen • Is a video display screen that

receives input from the touch of finger

• Examples• ATM • Petrol Pumps

Magnetic Strip • 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.

7.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.

8.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 • To scan financial documents such

as company

9.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

10.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.

11.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.

12.Kimball tag • Kimball tags are the small cards

with holes punched in them that you see attached to clothing in certain shops.

• When you buy the goods, one of the tags is removed and sent for processing to a computer centre.

Advantage • Stock is reordered without any

writing or typing the data.• Disadvantages:• They are small and are easily

mislaid.

Voice Recognition • Using a microphone human speech is

coded into a sequence of electrical signals.

• The computer searches a set of stored patterns for the sound which has been input

• It is now popular for inputting data into word processing or database packages.

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.

13.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

14.Electronic point of sale Terminal (EPOS)

• Are the cash registers which act as the terminals to a main computer system

• Providing customers with item used in bills.

• Give useful management information

15.Electronic Fund transfer at point of sale

(EFTPOS)• Similar to EPOS terminal but some

additional features.• They are able to transfer funds from

your bank account directly to a store’s switch card called a debit card.

• Example:• Switch card

Advantage• You can use it instead of a cheque.• Faster method of payment • Money is instantly transferred into its

account.• You can also get cash back using your

debit card.Disadvantage:• They may be stolen and they are said to

encourage people to spend more money.

16.Video Digitizer• Is the combination of hardware and Software that

converts an analogue video signal into a digital signal in computer’s memory

• Is used to convert a frame from a video sequence into a picture

• Each frame from the video is converted using video digitiser.

• It may be played back in any required sequence.• Is also called image grabbing or frame grabbing• Take up a lot of main memory and when stored use a

large amount of disk space

Uses• Digitiser pictures Can be printed

in a magazine or document • To make television adverts and to

produce pop videos.

17.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

Types of Scanner • Optical Scanner • Optical Reader

Optical Scanner • It is a light sending input device.• The scanner image depend upon resolution• Image will be sharper if the scanner provides

high resolution • it provide OCR Software • Different types of Optical Scanner are • Flatbed Scanner • Sheetfed Scanner • Handheld Scanner

18.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

19.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

20.Touch tone Telephones

• Having a different tone of each number when pressed key

• Using these different tones that the numbers dialed are recognized and routed to correct telephone

• Can be used as a data entry device • Home banking system use touch

tone telephone

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.

Output Device – 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)

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.

Features of Monitor • Size • Color • Resolution• Video Display Adapter

Types of Monitor • CRT • Flat Panel Monitors • Touch screen 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.

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.• The molecules this substances line up in

such a way that the light behind the screens and creates an image.

• Use in banks and Multinational companies

Graphical Display unit ( GDU)

• Larger than VDU and have greater resolutions

• lines on the screen don’t look as through they are made up of lots of tiny dots.

• Are often used in conjunction with light pens

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 where • It generates lot of noise ,its print quality is not

good

2.Line printer• Is a fast impact printer • It prints a entire line at a time • Its speed is measured in line 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

Electrical Signals• Sometimes the output from one computer system can

simply be a series of electrical signal• In this case one computer is being used as a terminal

and work that is done sent as electrical signals • Electrical signals can be output and used to control all

kinds of devices such as • Heating system • Alarms • Robots • Actuators • Computer aided manufacturing (CAM)• Computerised numerical control (CNC)

Computer controlled devices - Robots

A typical computer controlled device used in computer-aided manufacturing – a robotic arm