1. What are output devices?
    • The devices which are used to display information are called output devices.
  2. Explain Audio-Visual output devices?
    • CRT(Cathode Ray Tube) monitor:
      • A monitor displays text and images.  CRT monitors are large and boxy.  They are heavy and take a lot of desk space.  They have largely been replaced by flat screen monitors.  However, some are still used in the design industry since the colour, accuracy and brightness of CRT monitors is excellent and designers need to see true to life colours.  CRT montiors are cheaper than flat screen monitors.
      • Advantages
        • They are cheap to buy.
        • Brightness and colour quality is excellent than flat screen monitors.
      • Disadvantages
        • They are heavy and need lot of desk space.
    • Flat Screen (TFT and LCD) monitors:
      • Thin Film Transistor or TFT and Liquid Crystal Display or LCD are two of the technologies used in flat screen monitors.  Flat screen displays have replaced the CRT monitors.  They are light in weight and take up very little desk space.  Modern flat screen monitors have a picture quality as good as CRT monitors.  Another technology that may replace these is OLED (Organic Light Emitting Diodes).
      • Advantages (TFT, LCD and OLED)
        • They are light in weight.
        • They need very little space.
        • Picture quality as good as CRT monitors.
      • Disadvantages
        • They are costlier than CRT monitors.
        • They are not useful for designers as they need true colours.
    • Digital/Multimedia Projectors:
      • Digital projectors are used in situations when a very large area is required for viewers.  For example, during presentations for advertising or in your home for watching movies.
      • A projector connects through a computer, a DVD/CD player or satellite receivers just like an ordinary monitor.  The usage is produced inside the device and then projected through a large lens using a powerful light source.
      • Advantages
        • Many people can view what is being presented.
        • Can show video to a large audience who may be seated some distance from the screen.
      • Disadvantages
        • Image quality may not be as high as when seen on a computer screen at normal size.
        • The cooling fan on the projector creates noise which can be distracting.
        • The image needs a darkened room otherwise it will appear dim.
    • Speakers
      • Speakers are essential for applications such as music editing, video conferencing, watching movies, etc.  Speakers convert electrical signals into sound waves.  If you want to hear music from your computer, you will have to attach speakers to it.
  3. What is a printer and what are the types of printers?
    • If you want a hard copy of some data on a paper, you will need a device which is called Printer.  The different types of printers are:
      • Dot Matrix Printer
      • Inkjet Printer
      • Laser Printer
      • Dot Matrix Printer
        • A dot matrix printer is named after the pattern (a grid or matrix) of dots used when creating the paper print out.  These dots are formed by tiny pins in the printer’s print head that hit an ink ribbon against the paper leaving marks.  As the print head moves along, it leaves a pattern of dots behind it which can form letters, images, etc.  A dot matrix printer is often used in continuous stationery (long, continuous strips of paper) rather than separate sheets of A4 size paper.  After the printing, the printout is torn off from the long strip.  These printers are used in offices and factories where multiple print outs re needed and noise is not an issue.
        • Advantages
          • Can be used to print continuous stationery – this is useful when the print out needs to be sent to different places.
          • Can be used with continuous stationery.
          • Cheaper to run than inkjet printer.
        • Disadvantages
          • Very noisy – the pins make a lot of noise when they strike the inked ribbon.
          • Low quality printouts.  The text can look dotty.
          • Unsuitable for printing graphics.
          • More expensive to buy than Inkjet printers.
        • Uses
          • Since the pins usually hit the paper, several carbon copies can be printed in one go.  For example, Invoices which have several duplicate pages, all printed in one go.
          • The print mechanism is very cheap and the ink ribbon lasts for a long time.  So where cheap and low quality printouts are required, Dot matrix printers are used.  For example, Shop receipts.
      • Inkjet Printer:
        • These printers have a similar print head mechanism to a dot matrix printer.  The print head passes left and right across the paper.  However, instead of using pins to hit, ink marks onto the paper.  The inkjet printer uses tiny droplets of ink on the surface of the paper.  Coloured ink can be used to produce colour print-outs.

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