 A monitor or display is an electronic visual display for computers.  The monitor consists of : o the display device o circuitry o enclosure The display device in modern monitors is a Thin film transistor - liquid crystal display (TFT-LCD). Older monitors use a cathode ray tube (CRT).

 The size of a rectangular display is usually given as the distance between two opposite screen corners, that is, the diagonal of the rectangle.  The diagonal measurement of the rectangle is equal to the diameter of the tube's face.  This method continued even when cathode ray tubes {CRT} were manufactured as rounded rectangles.

An example to show how the screen size can be calculated

The performance of a monitor is measured by the following : 1.Luminance is measured in candelas per square meter. 2.Viewable image size is measured diagonally. For CRTs, the viewable size is 1 in (25 mm) smaller than the tube itself. 3.Aspect ratios is the ratio of the horizontal length to the vertical length. 4:3 is the standard aspect ratio 4.Display resolution is the number of distinct pixels in each dimension that can be displayed. 5.Dot pitch is the distance between subpixels of the same color in millimeters.

6.Refresh rate is the number of times in a second that a display is illuminated. 7.Response time is the time a pixel in a monitor takes to go from active (black) to inactive (white) and back to active (black) again. 8.Contrast ratio is the ratio of the luminosity of the brightest color (white) to that of the darkest color (black) that the monitor produced. 9.Power consumption is measured in watts. 10.Viewing angle is the maximum angle at which images on the monitor can be viewed, without distortion.

Adv. High dynamic range, excellent color, low black level. No input lag Sub-millisecond response times Near zero color, saturation, contrast or brightness distortion. Excellent viewing angle. Usually much cheaper than LCD or Plasma screens. Disadv. Large size and weight High power consumption Geometric distortion Older CRTs are prone to screen burn-in Produces flickers at low refresh rates

Adv. Very compact and light Low power consumption No geometric distortion Rugged Little or no flicker Disadv. Limited viewing angle, causing color, saturation, contrast and brightness to vary, causing some distortion Slow response times Input lag Dead pixels may occur during manufacturing or through use.

Adv. Compact and light. High contrast ratios excellent color, low black level. High speed response. Near zero color, saturation, contrast or brightness distortion No geometric distortion. Highly scalable, with less weight gain per increase in size Disadv. Large pixel pitch, meaning large screen. Flickers when viewed at close range High operating temperature and power consumption Fixed bit depth Input lag Older ones may burn-in Dead pixels are possible during manufacturing

o Phosphor burn-in In older screens the phosphor layer of a CRT screen where it has displayed a static bright image for many years. This results in a faint permanent image 3:4 on the screen, even when turned off. o Plasma burn-in Burn-in is existing with early plasma displays, which are more week to this than CRTs. Screen savers with moving images may be used with these to minimize burn.

o Glare Glare is a problem caused by the relationship between lighting and screen, or by using monitors in bright sunlight o Color mis-registration Most LCD screens, have mis-registration of the color channels, that is, the centers of the red, green, and blue dots do not line up perfectly. o Incomplete spectrum RGB [registered] displays produce most of the visible color spectrum, but not all. This can be a problem.

o Multiple monitors More than one monitor can be attached to the same device. To show the same image or each monitor can display a different image. o Multiple video sources Multiple devices can be connected to the same monitor using a video switch. It is designed to switch all of the user interface devices for a workstation between different computers at once. o Virtual displays Much software and video hardware supports the ability to create additional, virtual pieces of desktop, commonly known as workspaces.

o Power saving Most modern monitors will switch to a power-saving mode. This allows modern operating systems to turn off a monitor after a specified period o Integrated accessories Many monitors have other accessories integrated. So no need for another separate, camera, microphone, and speakers. o Glossy screen Some displays replace the traditional anti-glare matte finish with a glossy one. The image is better. o Directional screen Narrow viewing angle screens are used in some security applications.

o Auto polyscopic screen A directional screen which generates 3D images. o Touch screen These monitors use touching of the screen as an input method. Items can be selected or moved with a finger. o Tablet screens A combination of a monitor with a graphics tablet. Such devices are typically unresponsive to touch without the use of one or more special tools' pressure.