Transcript Output Devices

Output devices
Prof. K Regis
Types of output devices
• Monitor
• Printer
• Speaker
• Plotter
Monitors
• It’s the most important output device
• 2 common types
– CRT
– LCD
• Featured by:
– Refresh rate
– Resolution
– Visible screen size
– Response time
CRT monitors
• This acronym stands
for Cathode Ray Tube
• Very widespread
• Cheap
• Good performance
Working method of CRT monitor
• The back of the tube has a negatively
charged cathode, so called electron gun.
The electron gun shoots electrons down
the tube and onto a positively charged
screen. The screen is coated with a
pattern of red, green and blue phosphor
dots that will glow when struck by the
electron stream. The three dots together
make up a pixel.
LCD screens
• LCD means Liquid
Crystal display
• Good quality
• Environment friendly
(no lead in the glass)
How it works?
• There is a thin liquid cristal layer between a
horizontal and a vertical filter. Thanks to an
appropriate voltage liquid cristals get arranged
and light can pass the filters. This light will
appear on the screen.
• In color LCDs each individual pixel is divided
into three cells, or subpixels, which are colored
red, green, and blue. Each subpixel can be
controlled independently to yield thousands or
millions of possible colors for each pixel.
Printers
• A computer printer, or more commonly just a
printer, is a device that produces a hard copy of
documents stored in electronic form, usually on
physical print media such as paper.
• In addition, many modern printers can directly
interface to electronic media such as memory
sticks or memory cards, or to image capture
devices such as digital cameras, scanners;
some printers are combined with a scanners
and/or fax machines in a single unit.
Main types of printers
• Dot matrix
• Inkjet
• Laser
• Thermal
Dot matrix printer
• A dot matrix printer or
impact matrix printer
refers to a type of
computer printer with a
print head that runs back
and forth on the page and
prints by impact, striking
an ink-soaked cloth
ribbon against the paper,
much like a typewriter.
Unlike a typewriter,
graphics can be
produced.
Inkjet printers
• Inkjet printers are a type
of computer printer that
operates by propelling
tiny droplets of liquid ink
onto paper. They are the
most common type of
computer printer for the
general consumer due to
their low cost, high quality
of output, capability of
printing in vivid color, and
ease of use.
Laser Printers
Laser printers are printer that
uses laser technology to print
images on the paper. These
work in a manner similar to a
photocopier.
The
laser
recreates the image on a
negatively drum. A roller is
charged with electricity, then a
laser is used to remove the
charge from portions of the
roller. Powdered ink (toner)
sticks to the parts of the roller
that were hit by the laser, and
this toner is transferred from
the roller to the paper. Then
the ink is baked into the paper
using a heater.
Speaker
• Speakers allows the
computer to display
sound.
• There are built-in ones,
but you can choose
external types too. It’s
better, because it
provides a better quality
even can perform
surround sounding which
is the best choice for
games and videos.
Plotter
• A plotter is a vector graphics printing
device that connects to a computer.
• Plotters print their output by moving a
pen across the surface of a piece of
paper. This means that plotters are
restricted to line art, including text, but
do so very slowly because of the
mechanical movement of the pens.
Plotters are used primarily in technical
drawing where they have the advantage
of working on very large paper sizes
while maintaining high resolution.
Happy end