The computer monitor was developed to give a high quality monochrome, and more recently colour output to modern computing systems. The green screen monochrome monitor is being superseded to a great extent by colour monitors mainly because of today's computer's multicoloured window user interfaces. There are many types of computer monitor catering for different display resolutions and video input types. The two most common input types are composite video and RGB (Red, Green, Blue). The composite monitor is used mainly on low cost display systems due to its relatively poor display quality. In the composite monitor the video signals are mixed together in the computer, fed along a single cable and unmixed by the monitor. This method leads to picture degradation and video noise from the mixing and un-mixing system. The RGB monitor keeps the Red, Green and Blue components of a video image separate at all times and therefore maintains maximum image quality by avoiding the noise found in composite video systems.
The monitor in many respects resembles a standard television set, the main differences being the monitor has a higher resolution display and no TV tuner decoding circuitry.
