Transcript Slide 1

Chapter 2: Input and output devices
Revision
2.1 Input devices and their uses
Keyboards
Alphanumeric keyboard – used for entering
Alphanumeric
keyboard – used for and
text and numbers
numbers
Numeric
Numeric keypad
keypad –– small
small keyboard
keyboard
that just has number used at ATM’s
PIN Pad – used for entering PIN when paying for
items using credit card
Also found on electronic security doors to unlock
them
2.1 Input devices and their uses
Pointing Devices
Mouse – used with most GUI devices
• Touch Pad – mainly found on most laptops
because take less space than a mouse
• Trackball/Tracker ball – not moved like a
mouse but has a large ball that spins to
control curser
– Suitable for very young or elderly with
limited movement
2.1 Input devices and their uses
Pointing Devices
Touch screen user selects item on screen by
touching it on the surface
• Graphics Tablet – pointing device often
used by artists and designers to input
graphics – allows hand drawn sketches
• Joy stick – mainly used for playing games
but small ones can also be found on mobile
phones
• Light Pen – used a pointing device to ‘write’
on the screen of a computer
2.1 Input devices and their uses
Input – audio/visual devices
Scanner – device that ‘scans’ images, book pages
etc.
Digital Camera – device that captures photos and
can be stored on a memory card
• Video Camera – device that captures moving
images or video
• Web Cam – basic video camera used for live
feeds but has poorer quality
• Microphone – converts sound into a signal that
can be fed into a computer
2.1 Input devices and their uses
Sensors
• A computer or microprocessor has no
way of knowing what is happening in
the real world
• As humans or animals we use our
eyes, ears , mouths, skin and noses to
sense thing around us – our senses
• A normal PC has no senses but we can
give it some.
A sensor is a device that converts a real
world property into data that a
computer can process
2.1 Input devices and their uses
Sensors
Examples
2.1 Input devices and their uses
Typical Exam Question
Why does a computer not
understand physical variables (real
world) read from sensors?
2.1 Input devices and their uses
Answer
Real world measurements are
collected as an analogue signal
from the sensor
A computer only understands
digital signals
An ADC (Analogue-to-digital
converter) is needed to convert
the signal so a computer
understands the signal
2.2 Direct Data entry and associated devices
Input – Card Readers
Magnetic Strip Reader – data can be stored in the form of magnetised
dots
• Data can be entered faster and more accurately
• Data stored on the card include:
– Credit card number
– Expiry date
– Customer name
Smart Card/’chip’ Reader – used in modern credit cards
• Smart and satellite TV decoder cards can store much more data
that magnet strip cards
– Credit card number
– Expiry date
– Customer number
• Even an image of customer
2.2 Direct Data entry and associated devices
Magnetic Ink Character Reader
• Allows details from bank cheques to be
read from bank cheques quickly and
accurately because it’s a automatic
method
MICR
• Cheque number and bank account
number are print at the bottom of each
cheque is a special magnetic ink using a
special font
• These numbers can be detected using
the MICR Reader
Faster method of data entry and more
accurate than a keyboard (manual input)
2.2 Direct Data entry and associated devices
Optical Mark Reader
• Allows data from ‘multiple choice’ type
forms to be read quickly and accurately into
a computer
OMR
• Special OMR Forms are used which have
spaces that can be coloured using a pencil
• These marks are then detected by the OMR
Scanner
• Used in multiple choice exam answers and
lottery tickets
Faster method of data entry and more
accurate than a keyboard (manual input)
2.2 Direct Data entry and associated devices
Optical Character Reader
• Converts images or text from hard copies
into computer files which can be edited in
word processors
OCR
• Typically used to scan pages from a book
• OCR software analysis letter shapes and
generates matching electronic files
• Some advanced OCR software also
recognises handwriting
Faster method of data entry and more
accurate than a keyboard (manual input)
2.2 Direct Data entry and associated devices
Optical Character Reader
Self-registration Immigration System:
OCR
• A device that can automatically enter information on
foreign visitor’s entry:
• Facilitate foreign visitors with filling out entry- exit
registration information
• Reduce manual entry workload of immigration
registration cards
• Improve data accuracy of immigration information
collection
Faster method of data entry and more
accurate than a keyboard (manual input)
2.2 Direct Data entry and associated devices
Barcode Reader
• A Barcode is simply a numeric code
represented as a series of lines
Barcode
Reader
• These lines can be read by a barcode reader
or scanner
• Barcode readers are typically used at pointof-sale (POS) in shops
• Far quicker and more accurate than typing in
code using a keypad
Faster method of data entry and more
accurate than a keyboard (manual input)
2.2 Direct Data entry and associated devices
Radio Frequency Identification
• An RFID tag is a very small and thin silicon chip
that can be placed on a sticker
RFID
• RFID tags are used in some passports and by
companies who track the movement of products
• An RFID reader can read objects from a distance
and can be written to and read from
• Can be used to store and read information
including biometric readings and photos
• Far quicker and more accurate than typing in
code using a keyboard
Faster method of data entry and more
accurate than a keyboard (manual input)
2.2 Direct Data entry and associated devices
Radio Frequency Identification
The RFID tag can be affixed to an object and
used to track and manage inventory, assets,
people etc
RFID
Seaports – To track daily arriving containers.
People Tracking – The United Nations uses RFID technology to track
the movements of its personnel.
Airlines – Airlines uses RFID tags to track passenger
bags to reduce the number of lost bags and make it
easier to route bags if customers change their flight
plans.
Retail - In the retail section, taking inventory of
stock on the shelf is dramatically faster.
Paying for goods using debit/credit cards
2.2 Direct Data entry and associated devices
Typical Exam Question
Compare and contrast a OCR,
OMR, MICR and a keyboard as a
method of data entry?
2.2 Direct Data entry and associated devices
Device
OMR
Use
Benefit
Drawback
Used to mark
multiple choice
exam papers
Automatically corrects exam
papers more quickly and
accurately than a teacher
marking
OCR
Used to scan
hardcopies of
books into a
computer for
later editing
Very fast and fairly accurate
Can be slower in
of transferring hardcopies
comparison to
into computers files rather
OMR and MICR
than typing using a keyboard.
MICR
Used to read
special
characters on
cheques
Fast and accurate method of
data entry – less errors than
typing on number pad
Used to
manually input
alphanumeric
data
Useful for typing
alphanumeric and can easily
edit.
Keyboard
Boxes must be
filled out properly
using a pencil
otherwise wont
read
Slowest method
compared with
others and more
likely to make
mistakes
2.3 Output devices and their uses
Output Devices: Audio Visual
CRT Monitor stand for cathode-ray tube and have
been around for a long time – cheaper and
sometimes used by designers because can offer true
colour
Flat Screen (CRT or LCD) Monitor – replaced CRT
monitors, are light and take up little desk space
Load speaker converts electrical signals into sound
waves and essential for movies, video conferencing
and sound waves.
Digital/multimedia projector used when very large
viewing is required.
2.3 Output devices and their uses
Dot-Matrix Printer
• A dot-matrix printer is named after the
pattern (a grid or ‘matrix’) of dots used when
creating the paper printout.
• A tiny pin impacts against an ink ribbon which
leaves a pattern of tiny dots. Since the PIN
hits the paper several carbon copies can be
made in one go.
• Dot-matrix printer is a continuous stationary –
uses long continuous strips of paper.
• So, where cheap, low-quality printouts are
required, dot-matrix printers are used. An
example is shop receipts.
Not affected by hot/cold or dusty environments
2.3 Output devices and their uses
Inkjet Printer
• Inkjet Printer offers cheap high quality
printing
• Squirts tiny droplets of ink onto paper –
linking drops can produce full colour photos
• Small dots allow for high quality images
• Very quiet to use as they don’t have many
moving parts
• Cheap to buy however the ink for the printer
can be expensive.
2.3 Output devices and their uses
Laser Printer
• Very complex printers and expensive to buy
• The laser and toner system allows for very fast
printing compared to other printers (just a few
seconds per page).
• Cheap because they use a toner – uses fine
dust on the paper
– Can produce 5000 – 10000 pages on a
single toner
Laser printers commonly used in offices since
they print very quickly , quite cheap to use and
can work quietly
2.3 Output devices and their uses
3D printer
• 3D printer is a new generation of
printer that can produce 3D objects (in
different materials)
• 3D Printer works by adding tiny layers
on top of each other to produce the
object
• Can be used to produce objects from
3D models on the computer prototype models
• Expensive to buy 3D printers and
associated printing materials
2.3 Output devices and their uses
Actuator
An actuator is a device that can be used to
affect or control the real world
2.3 Output devices and their uses
Actuators
Motor: Provides movement – washing machine door etc.
Pump: motor attached to a device that can pump water
Buzzer: Provides noise – microwave buzzer – sirens or
electric bells (in schools)
Light Bulbs and LED’s: Motor attached to a device that
can pump water – car dashboard is car has problems