All you need to know about computers
There are three types of computer displays:
- The CRT monitor. These are heavy, use a lot of desk space and electricity. It is the oldest technology used by monitors and is based on the cathode ray tube technology that was developed for television. Monitors are made with better parts which give a much higher display resolution and picture sharpness than a television. This type of monitor is no longer popular.
- The LCD monitor. Often called a Flat panel display. It is a newer technology than CRT. LCD monitors use much less desk space, are lightweight and use less electricity than CRT. This type of screen has been used for many years in the screens of laptop and notebook computers. It is also used for screens in every mobile phone, and many handheld technologies. It can produce a very high quality and stable display of graphics and text.
- In the early 21st century the price of video projectors has fallen and they are now used in many places to produce very large images. These use a range of different technologies to make the image including LCD - Liquid crystal display and DLP - digital light processing which uses very small mirrors to direct the light.
A type of display screen that has a touch-sensitive transparent panel covering the screen. Instead of using a pointing device such as a mouse or light pen, you can use your finger to point directly to objects on the screen.
Although touch screens provide a natural interface for computer novices, they are unsatisfactory for most applications because the finger is such a relatively large object. It is impossible to point accurately to small areas of the screen. There are three types of touch screen technology:
- Resistive: A resistive touch screen panel is coated with a thin metallic electrically conductive and resistive layer that causes a change in the electrical current which is registered as a touch event and sent to the controller for processing. Resistive touch screen panels are generally more affordable but offer only 75% clarity and the layer can be damaged by sharp objects. Resistive touch screen panels are not affected by outside elements such as dust or water.
- Surface wave: Surface wave technology uses ultrasonic waves that pass over the touch screen panel. When the panel is touched, a portion of the wave is absorbed. This change in the ultrasonic waves registers the position of the touch event and sends this information to the controller for processing. Surface wave touch screen panels are the most advanced of the three types, but they can be damaged by outside elements.
- Capacitive:: A capacitive touch screen panel is coated with a material that stores electrical charges. When the panel is touched, a small amount of charge is drawn to the point of contact. Circuits located at each corner of the panel measure the charge and send the information to the controller for processing. Capacitive touch screen panels must be touched with a finger unlike resistive and surface wave panels that can use fingers and stylus. Capacitive touch screens are not affected by outside elements and have high clarity.