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Input & Output Devices
An input device captures data and sends it to a computer system.
Input devices convert physical movement, such as key pressing, or environmental data, such as temperature, sound or light into electrical signals.
Input Devices
There are two types of input device: manual andautomatic.
Manual Input Devices
A manual input device requires a human hand tocontrol it…
Mouse
Scanner
Camera
Keyboard
Computer Hardware Servicing
Function Keys
Alphanumeric key
Numeric Key Pad
Arrow Keys
Back
Internal External
Back Next
Back
Types of Keyboard
Types of Scanners
Back
Manual Input Devices
Tracker ball
Joystick Graphics tablet
A manual input device requires a human hand tocontrol it…
Manual Input Devices
Keyboard
The most common input device
You press keys to input data into the computer
The most common type of keyboard is the QWERTY keyboard
People are familiar with keyboards, so they don’t need to be trained
Skilled typists can work very quickly
A lot of different keyboards are available, e.g. ergonomic
They are very reliable and cheap
Incorrect use or over-use can cause RSI
Many people cannot type and look at the screen at the same time, so typing can be time consuming
Uses Advantages DisadvantagesDevice
Manual Input Devices
GraphicsTablet
A graphics tablet consists of a pad and a special pen
The image is instantly converted to digital data
User can get much more control, similar to the natural way of drawing
The user can zoom in to an area of the drawing for higher accuracy
Large models are very expensive
Need a large desk area
Holding a pen for a long time is more tiring than holding a mouse
Uses Advantages DisadvantagesDevice
Manual Input Devices
Mouse
Most common pointing device
Used to point and click on icons or menus
Combines well with a keyboard
Fast and accurate
Most people are skilled at using a mouse, so no training is needed
Prolonged use can lead to RSI
Need a flat surface to use them
For an optical mouse, the laser does not work wellon all surfaces
Tracker ball
A tracker ball is basically an upside down ball mouse.
The user runs their thumb over the ball to control the on-screen pointer
User can get great pointing accuracy, without moving the hand
Useful where desk space is limited
Some people find that the thumb gets painful with prolonged use
Ball can get greasy and dirty
Uses Advantages DisadvantagesDevice
Manual Input DevicesUses Advantages DisadvantagesDevice
Scanner
Used to convert printed images or text into a file of digital data
There are two types: handheld and flatbed
Even cheap scanners produce quality images
Any printed image can be inserted into a document
Images can be edited before use
The quality of the final image is dependent on the original image
Joystick Originally designed forpilots to control aeroplanes
Used to control wheelchairs and for playing games
They give a more realistic gaming experience when playing games such as flight simulators
Many different types available
Some people find them difficult to operate,
Manual Input Devices
Digital Camera
Used for taking still images which can be uploaded to a computer for permanent storage
You can preview the image before pressing the shutter button
No film needed or
Unwanted images can be deleted
When the drive is full, images need to be uploaded to a computer or deleted
Touchpador
Fingerpad
A pointing device, built into a laptop for convenience
Portable - built into the laptop
Don’t need to carry extra equipment around
Small movements needed to move the cursor
Takes practice to master
Some people find them very fiddly
Fingers need to be clean and free of grease
Uses Advantages DisadvantagesDevice
Automatic Input Devices
An automatic input device inputs data without the need for human intervention (once the device has been set up), e.g. MICR, OMR, barcode reader, webcam, microphone, sensor.
Microphone
Webcam
Barcode reader
Automatic Input Devices
MICR
MagneticInk
Character Recognition
Banks print important data on the bottom of cheques using magnetic ink
This ink is then read by a computer
Very quick and accurate processing of data – very low error rate. Humans could not achieve the same accuracy
Very secure as any attempt to change the numbers on a cheque will be ignored as the reader only recognises magnetic ink in the same font
Banks are the main user – very few other applications
Uses Advantages DisadvantagesDevice
Automatic Input Devices
OMROpticalMark
Recognition
Used when youmark the numbers with a pencil ona lottery ticket
Very fast method of reading data, which reduces queuing time for lottery tickets
More accurate than humandata entry
Sometimes incomplete marks are not read correctly
Uses Advantages DisadvantagesDevice
OCR Optical
CharacterRecognition
Uses a scanner to scan text, then software converts the text into a word processor file
Quicker than typing in the text
Reduces the cost of posting a letter
Sometimes it is not very accurate
Automatic Input Devices
Barcode Readers
Used to identify products in shops
The code is read by a barcode scanner which identifies the product name, manufacturer and country of origin
Very quick and accurate way to enter data – suits busy shops
All barcodes need to be programmed into the computer in advance
The reader maynot be able to readthe barcode on wrinkled packaging
Uses Advantages DisadvantagesDevice
Magnetic Stripe
Reader
Found on the back of bank cards and store loyalty cards
The stripe holds information, suchas the account number and the PIN
Simple, cheap and effective
The data on the card can be altered if needed
Magnetic stripe can get scratched Not much data can be storedThieves can read data on cards then use the cards themselves
Uses Advantages DisadvantagesDevice
Microphone
Used to input sound into the computer
Very cheap piece of equipment
Helpful for people with additional needs or for busy people who need very quick letters
Computer can misread voice instructions due to natural variations in people’s voices
Generally, the sound quality from a PC microphone is poor
Automatic Input Devices
Webcam Used to input moving images into the computer for use in online communication
Very cheap piece of equipment
Enables people to see each other whilst they chat
The image quality from most webcams is poor
The moving picture tends to flicker due to current limitations in data transfer
Output Devices
Output Devices
An output device is used to display or use information that comes out of a computer system.
Output devices convert electrical signals from a computer system into…
Sound (speakers or headphones) Images & Text (screen or printer) Movement (actuator, electric motor)
Output Devices
Monitor Speakers
Plotter
Headphones
Printer
Output Devices
TFT Monitor
Thin Film Transistor monitors are more commonly known as flat screens or LCD screens
Take up very little space
Run very quietly and produce little heat
Use about a third of the energy ofa CRT monitor
Easy to damage
Colour contrast on cheaper models is not as good as CRT monitors
Uses Advantages DisadvantagesDevice
CRT Monitor
Cathode Ray Tube is very old technology.Almost completely replaced by flat screen monitors
Robust and difficult to damage
Reliable
Last for a very long time
Large, bulky
Can be heavy
Produce a lot of heat
Old technology
Output Devices
Speakers&
Headphones
When connected to a computer through a sound card, music can be played
Can help blind people use the computer
A presentation can be more powerful with sound
Games are a lot more involving and realisticwith sound
Speakers are not useful in a network room, as everyone would disturb each other
Headphones can be uncomfortable with extended use
Uses Advantages DisadvantagesDevice
Plotter These are specialist printers that can produce high quality printoutson large piecesof paper
Very high quality printouts
Almost any size paper can be used
Slower than normal printers
Expensive to purchase and run
Printers
There are 3 main types of printer…
Dot Matrix
Laser
Inkjet
Uses Advantages DisadvantagesDeviceGeneral purposeuse for family orhome office
Cheap to buy
Latest modelscan be very fast
Ink cartridges can be very expensive
Print quality not always very good
Business use for letters,stationery and images
Quality printing
Good for large areas of colour
Quiet & Quick
More expensive to buy than inkjets
Toner cartridges are expensive
Business usefor duplicatedocuments
Can make a carbon copyCan print on continuousrolls of paper
Noisy and rather old-fashioned technology
Poor quality and only prints in black ink
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Input & Output Devices
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