The Primary Output device in a graphics system is a video Monitor. The display device in modern monitors is typically a thin film transistor liquid crystal display(TFT-LCD) thin panel, while older monitors used Cathode Ray Tube (CRT) about as deep as screen size.
In a Cathode Ray Monitor, beam of Electrons (Cathode rays) are emitted by an electron gun. These rays are then passes through focusing and deflection system that directs the beam on a phosphorus coated screen. When the beam hits the screen small spot of light is created, but this spot fades very quickly as it is necessary to quickly direct the electron beam over the same point to display that spot, this type of display is called refresh Cathode Ray tube.
