Information Technology Center

Softcopy Output Devices

Softcopy devices produce temporary output. Computer monitors are the most common softcopy output devices.

Three Types

  1. Visual output devices
  2. Sound output devices
  3. Modems

Computer monitors output information on a screen in a form a human can read and understand. This type of output is said to be human readable. Monitors are sometimes called visual display unit (VDU) or simply screens.

CRT Monitors

Cathode ray tube monitors are large and heavy. They are now mostly obsolete. No details are listed on this site about them but you can follow the link at the bottom of this page if you want to know more about them.

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Flat panel display monitors

There are three types :

  1. Liquid crystal display
  2. Plasma display
  3. LED display

Liquid crystal display

LCD monitors are lite and have no moving parts so they consume less energy than CRT displays. They are used extensively on laptop computers.

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Plasma display

Light is created by a plasma discharge when it passes between two flat panels of glass. This technology was used mainly for televisions before the now popular LCD displays.

Light emitting diodes

LED technology is used now because it uses less power than traditional LCDs. These displays use an array of light-emitting diodes to produce light.

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Multimedia projectors

These softcopy output devices are used to deliver dynamic presentations that include sound and video.

More about monitors

The resolution of a monitor determines the clarity and sharpness of an image displayed on screen. The more pixels on a screen the greater the level of detail that is shown on the monitor. A pixel is a picture element. It is the smallest unit on a screen. Pixels are turned on and off constantly to generate output. Another factor to consider when purchasing a monitor is the refresh rate.This is the number of times an image is repainted on the screen per second. Images displayed on screen are not still. The image must be repainted or refreshed constantly. If the refresh rate is slow the screen appears to flicker. Finally, image aspect ratio is the width to height ratio of an image on the screen. Most monitors have a 4:3 width to height ratio.

The following will affect monitor output quality :

  1. Monitor size
  2. resolution
  3. refresh rate
  4. image aspect ratio
  5. graphics/video card
The graphics card is most important because it determines the display resolution, the number of colours available and the refresh rate of the monitor. Gamers spend alot of money upgrading this component often to ensure the best gaming experience.

Modems

The word "modem" is a contraction of the words modulator-demodulator. A modem is used to send digital data over an analog phone line. The sending modem modulates the digital data into a signal that is compatible with the analog phone line, and the receiving modem demodulates the signal back into digital data. Wireless modems convert digital data into radio signals and back.


DSL modem
A DSL modem uses regular telephone lines for high-speed internet connections. A digital subscriber line (DSL) connection is a very high-speed connection that uses the same wires as a regular telephone line.

Links

Learn More Youtube - how monitors work (7 mins)

Browse How stuff works - monitors for even more details.

Test Yourself

Choose the correct answer
Questions Options Verify
 1)  The smallest unit on a computer screen is a pixel True
False
 2)  Softcopy output is permanent. True
False
 3)  Images on screen appear still but are refresed many times each second. True
False
 4)   CRT monitors are very popular today. True
False
 5)  Refresh rate is measured in Hertz (cycles per second). True
False