Chapter 3 input and out put devices

INPUT of system

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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.


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


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.


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.


That requires no wires

It is also called wireless keyboards.

It transmits data using wireless technology

like radio waves or light waves


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.


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


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.


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.


Movement of ball bearing is used to produce

electrical signal.

Small lights under the mouse are reflected

on the photoelectric cells.


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.


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


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.


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.


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


It can be used to digitize drawings with great

accuracy.

Reproducing drawings and designs

Producing layouts of printed circuit boards.

Digitizer Maps.


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


Is a video display screen that receives input

from the touch of finger

Examples

ATM

Petrol Pumps


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 cardsA phone Card Cash issue Terminals


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.


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


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.


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.


In department stores

To scan financial documents such as company


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


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



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.

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

Documents can still be read when folded,

written on

Disadvantages

Readers are very expansive

Only certain fonts are acceptable.


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.


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.


Stock is reordered without any writing or

typing the data.

Disadvantages:

They are small and are easily mislaid.


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.


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


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


Are the cash registers which act as the

terminals to a main computer system

Providing customers with itemised bills.

Give useful management information


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


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.


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


Digitiser pictures Can be printed in a

magazine or document

To make television adverts and to produce

pop videos.


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


Optical Scanner

Optical Reader


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


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 .


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


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


Advertising

Checking on children in nurseries

Checking on the weather on the other part of

the world


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)


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.


Size

Color

Resolution

Video Display Adapter


CRT

Flat Panel Monitors

Touch screen Monitors


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.


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.


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


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


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


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


Is a fast impact printer

It prints a entire line at a time

Its speed is measured in line per minute


Similar to typewriter

Uses print wheel

A motor rotates the wheel.

Its slower than Dot matrix but better in

quality


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


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 whiteThese 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


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


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


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


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


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


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


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.


An audio device translate audio information

from the computer into sounds that people

can understand

Speakers

Headsets


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)



A typical computer

controlled device

used in computer-

aided

manufacturing – a

robotic arm

Chapter 3 input and out put devices

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