What Is A Visual Display Unit?

           A user would normally like to see the output on the screen of a visual display unit or monitor. If results are found satisfactory then output may be taken on the screen. The contents of the screen are saved by a special program called screen dump. Any text or graphical display on the screen is stored in the special video ram in the binary form while it is being displayed. One common way of storing the contents of screen is to store each pixel on the screen separately. Pixel is an acronym for picture element.

           On a monochrome screen, one pixel needs one bit for storage. If the screen has 4 colours then 2 bits would be required for storing each pixel and 4 bits would be required if there are 16 colours. In fact it is like 4 bits that accommodate 16 different binary numbers. An 8-bit pixel can store 256 colours. Screens are used for graphical displays have  high resolution over 1280x1024 pixels screens are quite common.  There are LCDs are used as display systems where output consists of a small set of characters. The display unit consists of two thin glass sheets with liquid crystal between them.

A visual display unit is a temporary output device. A monitor is also called visual display unit. Any devices which can show the data in visual form is called visual display unit.

Every Visual Display Unit is connected with computer through a video controller. Video controller is responsible to provide data. A Visual Display Unit can have a Cathode Ray Tube (CRT). The most basic element of a Visual Display Unit is pixel. Pixel is also called a dot. The higher the pixel in a Visual Display Unit, the higher the quality will be. Pixel are measured in DPI (Dot Per Inch) or PPI (Pixel Per Inch).

The earlier Visual Display Units were able to show only two colors but now a days, Visual Display Unit are capable of showing millions of colors. In a Visual Display Unit the screen is refreshed after a specific time. The refresh rate is used to measure the number of time a screen is refreshed in a second. The high refresh rate provide better picture quality.

CGA, EGA, VGA, XGA and XVGA the types of video controllers. The XVGA is the latest type. Now a days LCD and Plasma Visual Display Unit are also use. In these Visual Display Units the CRT is not used. They use the more advanced technology.

Video Display unit is the most commonly used output device on most personal computers. Visual display unit is another name for monitor of a computer .There are two basic types of VDUs. First is the typical monitor that you see on a desktop computer which looks like a television screen. This type of monitor uses a large vacuum tube called cathode ray tube. The second type, known as the flat panel display is used primarily with portable computers .There are several types of flat panel monitors but the most common is Liquid crystal display monitor .LCD monitors creates images with a special kind of liquid crystal that is normally transparent but becomes opaque when charged with electricity.

Visual Display units can be compared by the following factors:-
Size
Refresh rate
Resolution
Dot Pitch

The physical size of a monitor's display area has an obvious bearing on how well you can see images. The resolution of a visual display unit can be classified by the number of pixels on the screen, expressed as a matrix e.g 640 x 480.The refresh rate is the number of times per second that the electron gun scan every pixel on the screen and is measured in Hertz . Dot Pitch is the distance between the phosphor dots that make up a single pixel.