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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