Showing posts with label Output Devices. Show all posts
Showing posts with label Output Devices. Show all posts


Different Types of Printers

            Many different types of printers are in use today. Two primary technologies used for printing are impact printing and non-impact printing. Impact Printers use a print head containing a number of metal pins which strike an inked ribbon placed between the print head and the paper. The non-impact printers are much quieter than impact printers as their printing heads do not strike the paper.

The Most Common Printer Types Are:
  • Dot matrix printers,
  • Ink-jet printers,
  • Laser printers. 

Dot Matrix Printers

              These printers work by firing a matrix of tiny pins (which are located in the print head), through a ribbon similar to that found on a typewriter. As the head moves across the paper the correct pins are fired out to hit an inked ribbon and form the shape of the character required. The greater the number of pins, the higher the quality of the print. Dot matrix printers are impact printers and are used to print multipart stationery. So print several copies of a document at the same time you will need to use a dot matrix printer. Such printers are cheap and have the lowest running cost compared to any other type of printer.

Laser Printers

            These non-impact printers offer high-speed printing and an excellent quality of text and graphics. A laser beam is used to from an image on a rotating, charged metal drum. This then picks up toner from the toner cartridge and transfers it onto paper. Very soon after wards heat and pressure are applied so the toner sticks to the paper. Since they are page printers they are very fast. Colour laser printers are now available and are mainly used for desktop publishing. Although they are expensive, they are likely eventually to come into widespread use.

Inkjet Printers

             Inkjet printers can produce high quality text and graphics. They are quieter than dot matrix printers. The technology involves ink flowing through the appropriate nozzles (usually in an array of 64) where it is then heated and a bubble is formed. This expands to release a tiny droplet of ink onto the paper.


Different Types of Display Screens

CRT Monitor

                  A cathode-ray tube and associated electronics connected to the video output of a computer. These have higher resolution than TVs. Lager monitors with high resolution are used for specialized application such as desktop publishing and CAD.

LCD (Liquid Crystal Display) Monitor

               LCDs are screens made from two glass/plastic plates with liquid in between. LCDs are commonly used for calculators and laptop computers, as they are far flatter than is possible with cathode ray screens used in TVs and Standard computer monitors.

Main difference of LCDs as compared with CRT monitors are:
  • Takes very little space.
  • Small energy consumption.
  • Sharp pictures.
  • Fairly expensive.
  • Limited viewing angle.
  • Slower response time.

Different Types of Output Devices

             Output devices translate information processed by the computer into a form that either humans or other machines can understand. There are a variety of output devices, which can be connected to a computer. Some of the common output devices are explained in the following sections.


            The most common form of output is the computer screen. It is more correctly called 'monitor' and sometimes referred to as the visual display or VDU.
             The quality of a computer monitor is based on the following properties:
  • Resolution: Resolution is the number of pixels, which the screen can display. A 'pixel' is the 'picture element' and refers to the smallest area of the screen that the computer can change.
  • The number of colours: it can display (dependent on the computer as well)
  • Radiation output. 


                                                               More About Printers..

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