Chapter 2 input and output devices

Input and Output Devices
Chapter 2

Alphanumeric Keyboard
• Very common, general purpose, input device
that allows text (abc…), numbers (123…) and
symbols (%$@...) to be entered into a
computer.

Numeric Keypad
• A small keyboard that only has numbers.

PIN Pad
• This is a device with a numeric keypad used to
enter a person’s Personal Identity Number
(PIN) e.g. when paying with a credit card.

Input - Pointing Devices
• These devices are used to move an on-screen
pointer or cursor (usually an arrow). They are
commonly used with graphical user interfaces
(GUIs)

Mouse
• A pointing device found on most PCs. Sensors
on the bottom of the mouse detect when the
mouse is moved

Touchpad / Trackpad
• A pointing device found on most laptops.
Used instead of a mouse since it takes up less
space.

Trackball / Tracker Ball
• This pointing device is not moved about like a
mouse, instead it has a large ball that the user
spins.
• Used by people with limited
movement (disabled, very young)

Touch Screen
• With a touch screen the user selects items on
the screen by touching the surface.
– Because they are so intuitive to use, and now they are
getting cheaper to manufacture, touch screens will
probably become the most common hardware interface for
our electronic gadgets.

Graphics Tablet
• A pointing device often used by designers and
artists to allow natural hand movements to be
input to graphics applications.

Joystick / Joypad
• Used mainly for playing games.

Light Pen
• A light pen is a device used as a pointing
device or to ‘write’ on the screen of a
computer.

Scanner
• A device that ‘scans’ images, book pages, etc.

Digital Camera
• A device that captures digital photographs
– The camera’s computer runs a very simple
operating system (stored on ROM) and usually
provides a menu-based GUI for the user.

Video Camera
• A device that captures moving images,
or video.

Web Cam
• This is a very basic video camera used to
feed live video into a computer.

Microphone
• An input device that converts sound into a
signal that can be fed into a computer.
• An Analogue-to-Digital Convertor (ADC) is
used for this (usually built into the computer’s
sound card)

Magnetic Strip Reader
• Usually the data stored on this strip in the
same data shown on the front of the card
(e.g. the credit card number, expiry date and
customer name).
• A magnetic strip/stripe reader is used to read
the data from the stripe.

Smart Card / 'Chip' Reader
• Data can be stored in this memory and read
back using a ‘chip’ reader.

Input - Reading Text / Codes
• All data could be input to a computer using
a keyboard, but this would often be
a slow process, and mistakes would be made.
• Sometimes speed and accuracy is required...

MICR Reader
• Magnetic Ink Character Recognition (MICR) is
a technology that allows details from bank
cheques to be read into a computer quickly
and accurately.

OMR Scanner
• Optical Mark Recognition (OMR) is a
technology that allows the data from
a multiple-choice type form to be
read quickly and accurately into a computer.

OCR Scanner
• Optical Character Recognition (OCR) is a
software technology that can convert images
of text into an actual text file that can then be
edited

Barcode Reader / Scanner
• A barcode is simply a numeric
code represented as a series of lines.

Input - Sensors
• A sensor is a device that converts a real-world
property (e.g. temperature) into data that a
computer can process.
Sensor What it Detects
Temperature Temperature
Light Light / dark
Pressure Pressure (e.g. someone standing on it)
Moisture Dampness / dryness
Water-level How full / empty a container is
Movement Movement nearby
Proximity How close / far something is
Switch or button If something is touching / pressing it

Input - Sensors
• A sensor measures a specific property data
and sends a signal to the computer.
– analogue signal
– Converted into digital
– Analogue-to-Digital Converter (ADC).
• Sensors are used extensively

Input - Remote Control
• They send data signals each time a button is
pressed using infrared light or radio signals.
• The signals can control a computer from some
distance.

CRT Monitor
• A cathode-ray tube (CRT) monitor is the type
that has been around for years and
is large and boxy.
• The color accuracy and brightness of CRT
monitors is excellent, and designers need to
see true-to-life colors.

Flat-Screen Monitor
(TFT or LCD)
• TFT and LCD are two of the technologies used in flat-
screen monitors: TFT is Thin-Film-Transistor,
and LCD is Liquid-Crystal Display.
• Another technology that may replace these is OLED,
or Organic Light-Emitting Diodes.

Digital / Multimedia Projector
• Used in situations when a very large viewing area is
required.
• A projector connects to a computer, a DVD player or
a satellite receiver just like a ordinary monitor.
• The image is produced inside the device and then
projected out through a large lens, using a powerful
light source.

Loudspeaker
• If you want to hear music or sounds from your
computer, you will have to attach
loudspeakers. They convert electrical signals
into sound waves.

Output - Printing / Plotting
• If you want a physical copy of some data
on paper (a ‘hardcopy’) you will need a device
that can make marks on paper - a printer or a
plotter

Dot Matrix Printer
• A dot-matrix printer is named after the
pattern (a grid or ‘matrix’) of dots used when
creating the paper printout.
• These dots are formed by tiny pins in the
printer’s print head that hit an inked ribbon
against the paper leaving marks (dots).

Dot Matrix Printer
• Dot matrix printers often use continuous
stationary: long, continuous strips of paper
(rather than separate sheets of A4 like ink-jet
and laser printers use).

Dot Matrix Printer
• Dot-matrix print quality is poor, the printers
are noisy
– Since the pins actually hit the paper, several
‘carbon-copies’ can be printed in one go.
– The print mechanism is very cheap, and the inked
ribbons last for a long time.

InkJet Printer
• Cheap, high-quality, full-colour printing became
available during the 1980s due to the
development of ink-jet printers.
• It squirts tiny droplets of ink onto the surface of
the paper. The droplets of ink come from tiny
holes (the jets)
– Perfect for photographs.
– Very quiet in use
– Cheap to purchase and manufacture
– Ink is very expensive to buy

InkJet Printer
• This is a close-up of the tiny ink dots on a
page. The dots combine to form light and dark
areas.

Laser Printer
• Very complex devices
• Expensive to buy
• Very cheap to use
• A single toner cartridge will often last for 5,000-
10,000 pages of printing.
• Very fast printing

Plotter
• Draw on the paper using a pen
• More accurately
• More quickly

Plotter
• Plotters are only suitable for producing line
drawings.
• Plotters have been largely superseded by
large-format ink jet printers that can produce
more detailed printouts and in full-color

Output - Control Actuators
• An actuator is a device, controlled by a
computer, that can affect the real-world
Actuator What it Can Do
Light bulb or LED Creates light
Heater Increases temperature
Cooling Unit Decreases temperature
Motor Spins things around
Pump
Pushes water / air through
pipes
Buzzer / Bell / Siren Creates noise

Motor
• Motors can provide movement

Pumps
• A pump is basically a motor attached to a
device that can push water or air along pipes.

Buzzer
• For example, the buzzer in a microwave
oven can be switched on by the controlling
computer when the food is cooked.

Lights
• Lightbulbs and LEDs can by used to
provide light, or to indicate something.

Heaters / Coolers
• Heaters can provide heat, and coolers
can cool things down.

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Chapter 2 input and output devices