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Output Medium for Digital
Graphics
Selection and use of output
medium
Stages
• The three stages of computing are input,
processing and output.
• A computer works through these stages
by‘running’ a program.
• A program is a set of step-by-step instructions
which tells the computer exactly what to do with
input in order to produce the required output.
Input
• This stage of computing is concerned with
getting the data needed by the program into the
computer.
• Input devices are used to do this.
• The most commonly used input devices are the
mouse and the keyboard.
Processing
The instructions about what to do with the input
are contained in a program.
During the processing stage the computer follows
these instructions using the data which has just
been input.
What the computer produces at the end of this
stage is called output.
Output
This stage of computing is concerned with
producing the processed data as information in
a form that is useful to the user.
Output devices are used to do this.
The most commonly used output devices are
the screen, which is also called a monitor or
visual display unit (VDU) and the printer.
Manual Input Devices
Manual input devices are used by people to
enter data by hand.
• Keyboard
• Pointing devices
• Joystick
• Digital camera
• Touch screen
• Scanner
• Concept keyboard
• Graphics tablet
• Microphone
• Light pen
Output Methods
Before any output can be produced by a computer
it must have an output device connected to it.
The output devices that you are probably most
used to will be the screen, or monitor, and the
printer.
Another sort of output that you will have
experienced when using a computer is sound,
which is output through a speaker.
VDUs
A monitor or screen is an output
device that can display graphics and
text and video.
The picture on a monitor is made up
of thousands of tiny coloured dots
called pixels.
The quality of the output on a monitor depends on its
resolution.
The resolution of a monitor depends on the number of
pixels that it can display.
Printers
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Types of printer:
Dot Matrix
Inkjet
Laser
3D
• When choosing a printer, you need to
consider what it will be used for.
Dot Matrix Printers
A dot matrix printer forms characters and graphics on the
paper by producing patterns of dots. If you look closely
at a print-out from a dot matrix printer you will see the tiny
dots which make up the printout.
The part of the printer which forms the patterns of dots is
called the print head. The print head is made up from
pins which are pushed out in different arrangements to
form the various patterns of dots needed.
Inkjet Printers
Inkjet printers work like dot matrix printers because
the printouts that they produce are made up of
patterns of very small dots but the print head has a set
of tiny holes rather than pins. As the print head moves
across the paper ink is forced out through the holes to
form the image.
Inkjet printers are very quiet to
operate and can produce good
quality printouts of both
graphics and text. Relatively
cheap colour graphics can be
printed using a colour inkjet.
Laser Printers
Laser printers give very high-quality printed output of
both text and graphics very quickly and quietly.
They are generally more
expensive to buy than
inkjet printers and the
toner cartridges are more
expensive.
They are very suitable for
large volume printouts
because of their speed.
3D Printers
The 3D printing process turns
a whole object into thousands
of tiny little slices, then makes
it from the bottom-up, slice by
slice. Those tiny layers stick
together to form a solid
object. Each layer can be very
complex, meaning 3D printers
can create moving parts like
hinges and wheels as part of
the same object
Plotters
The main difference between a plotter and a printer is
that a plotter uses a pen to draw the computer output
onto the paper.
Some plotters use a set of
coloured pens to produce
colour output. Plotters produce
very accurate drawings and
are often used in computer
aided design or CAD.
Data Projectors
• Very common on business demonstrations
• Project from a PC or laptop onto a big
screen
• Quality is improving so that some can be
used in natural light.
• Often used in classrooms.
• Development of 3D Projectors
Case Study
• The checkout at the supermarket has a
large number of output devices:
• As products are scanned, a screen
displays details of the purchase
• A speaker makes a beeping sound to
indicate item has been scanned
• Can you think of any other output devices
they use?
Choosing an output device
• What kind of image needs to be
viewed?
• Where is it going to be viewed?
• Who is going to view the images?
• How many documents?
• What kind of media?