When you touch the surface of such a screen, it detects exactly where you touched it. For example if you touched the screen 5cm down from the top and 3cm from the left, this data is used as input for the software currently running on its computer.

Usually there is some kind of graphics on display so that it appears you are 'touching' buttons and menu selections.

Uses:

• Dusty, dirty or wet environments where a keyboard would be damaged
  • Factory floors
• Hazardous environments where there must not be any chance of a spark
  • Petrol stations
  • Chemical plants
• Constricted areas where there is no room for another input device
  • Satellite Navigation system on a car dashboard.
• Hygenic environments where it must be simple to wipe clean
  • Restaurants
  • Surgical theatres
  • Hospitals

Advantage:

• Very easy to change what it is controlling by simply changing the software.
• No moving parts
• Can use any number of menu levels
• Can display large text to assist less-sighted people
• Can easily switch languages.

Disadvantages:

• Expensive compared to a standard keyboard or mouse.
• Has to have specific software to make sense of the input.
• Can be a problem seeing the screen in bright sunlight.