Transcript Input and Output: The User Connection

Components of Computer
Output
• The data that has been processed into
useful information is called output.
• Types
–
–
–
–
Screen – soft copy
Printer – hard copy
Sound
Graphics
Output Devices
• Output devices are peripheral devices that enable
users to view or hear the computer’s processed data
• Visual output – Text, graphics, and video
• Audio output – Sounds, music, and synthesized
speech
3
Visual Display System
• A visual display system is composed of two parts:
– Video adapter – Responsible for video quality
– Monitor – Displays the video adapter’s output
4
Video Adapter
• A video adapter is also called display adapter, video card,
or graphics card
– It consists of circuit board which is attached to
motherboard
– It contains memory called video RAM (VRAM), VRAM
send screen full of data to the monitor.
– It is designed to work with digital or analog monitors
– It determines a monitor’s maximum resolution
(VGA/Super VGA)
– It determines a monitor’s refresh rate
• 3D graphics adapter – Enables 3-dimensional images
• Multi-display video adapter – Permits a connection of two
monitors at a time
5
Monitor
• Data that is entered appears on the screen
• Screen is part of the monitor
Monitor
1. Cathode Ray Tube (CRT)
2. Flat panel display
3. Liquid Crystal Display (LCD)
CRT
• Color vs. Monochrome
• Color
– Typical monitor sold today
– Display between 16 colors and 16 million
colors
• Monochrome
– Display output in single color
– Less expensive than color
– Used for text only displays
CRT Monitors
Flat-panel Screens
• Liquid Crystal Display
(LCD)
• Primarily on laptops
• Moving to desktop
• Skinny (depth)
regardless of size
Flat-Panel Screen
Disadvantages:
• Images can be difficult to see in bright
light.
• Limited viewing angle that is the angle
from which the display image can be
viewed clearly.
Comparing Monitors
• Size
• Resolution
• Refresh rate
• Dot pitch
Comparing Monitors
• Size
With a larger monitor, you can make the objects on
the screen appear bigger or you can fit more of them
on the screen.
• Resolution
It is determined by number of pixels on the screen
expressed as a matrix.
Comparing Monitors
• Refresh rate
1. Number of times per second that the electron gun scan every
pixel on the screen.
2. Screen appears to flicker if its not refresed often enough.
3. It is measured in Hertz ,cycles per second. 72 Hz or higher should
not cause eyestrain.
• Dot pitch
1. It is the distance between the phophors dots that make up a
single pixel.
2. In color monitor each pixel includes three dots, red, green and
blue.
3. If the dots are not close enough together, the images on the
screen will not be crisp
4. Dot pitch should be greater that 0.28mm
Printer
• Produces information
on paper
• Orientation
– Portrait
– Landscape
• Methods of printing
– Impact
– Nonimpact
Portrait
Landscape
Impact Printers
Line printer
Dot-matrix printer
One line at a time
One character
at a time
High volume
Low quality
Daisy Wheel Printer
One character at a time.
It uses wheel to print.
Dot Matrix Printers
• A dot matrix printer is an impact printer.
• It produces printed images when tiny pins on
a print head strike an inked ribbon.
• When the ribbon presses against the paper it
creates dots that form characters and
graphics.
• The print head on dot matrix printers can
contains nine to twenty-four pins.
Daisy Wheel Printer
• It is similar to typewriter. It
uses a print wheel . This print
wheel is called Daisy wheel.
• Each petal of daisy wheel
contains characters.
• Daisy wheel printer is slower
than dot matrix printers but
better in quality.
Line Printer
•
•
•
It is fastest impact printer. It prints an entire
line at a time. Its speed is measured in lines
per minute (lpm).
Many line printers can print 3000 lines per
minute.
There are two types of line printers.
. Band printers
. Chain printers
Nonimpact Printer
Laser Printer
Nonimpact Printer
Laser Printer
• Transfers images to paper using a light beam
• Laser in a laser printer aim at any point on
the drum, creating an electrical charge.
• Toner composed of oppositely charged ink
sticks to the drum in the places the laser has
charged.
• With pressure and heat the toner
transferred off the drum onto the paper.
is
Nonimpact Printer
Laser Printer
Prints one page at a time
• 600-1200 dpi – High quality
• Speed
– Personal laser printers: 8-10 ppm
– Network laser printers: 35-50 ppm
– High-volume laser printers: up to 1000 ppm
• Black and white / color
Nonimpact Printer
Ink-jet Printer
• Spray ink at paper
• Black and white / color
• Excellent graphics
• Good quality
• Slower than laser
Nonimpact Printer
Choose based upon:
• Speed
• Quality
• Black and white vs. color
• Price
Audio Output
• Audio output is the ability of the computer to output
sound
• Two components are needed:
– Sound card
recordings
–
Plays
contents
of
digitized
– Speakers – Attached to sound card
• Digital formats include WAV, MPEG, MP3, and MIDI
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Sound Card
• Complicated part of the system.
• A computers sound card is a circuit board that
converts sound from analog to digital and vice versa,
for recording or playback.
• The sound card accepts input in the form of analog
sound waves.
• You can think of analog signals as fluctuations in the
intensity of an electrical current.
• The sound card measures those signals and converts
them into a digital form.