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three separate signals – red, green, and blue. All colour computer monitors are RGB monitors. An RGB monitor consists of a vacuum tube with three electron guns – one each for red , green, and blue at one end and the screen at the other end. The three electron
guns fire electrons at the screen, which contains a phosphorous coating.
When the electron beams excite the phosphors, they glow. Depending on which beam excites them, they glow red, green, or blue. Ideally, the three beams should converge for each point on the screen so that each pixel is a combination of the three colours. Colour and gray – scaling monitors are often classified by the number of bits they use to represent each pixel. For example, an 8- bit monitor each pixel with 8 bits. The more bits per pixel, the more colours and shades of gray the monitor can display.
CLASSIFICATION MONITORS – BASED ON SIGNALS: Another common way of classifying is in terms of the type of signal they accept; analog or digital. Digital Monitor A digital monitor accepts digital signals rather than analog signals. All monitors (except flat- panel displays) use CRT technology, which is essentially analog. The term digital, therefore, refers only to the type of input received from the video adapter. A digital monitor then translates the digital signals into analog signals that control the actual display. Although digital monitors are fast and produce clear images, they cannot display variable colours continuously. Consequently, only low-quality video standards such as MDA (Monochrome Display Adepter), CGA (Colour/Graphics Adapter), and EGA (Enhanced Graphics Adapter), specify digital signals. VGA (Video Graphics Array) and SVGA (Super VGA), on the other hand, require an analog monitor. Some monitors are capable of accepting either analog or digital signals. Analog Monitor This is the traditional type of colour display screen that has been used for years in televisions. In reality, all monitors based on CRT technology (that is, all monitors except flat- panel displays) are analog.
Some monitors, however, are called digital
monitors because they accept digital signals from the video adapter. EGA monitors, for example, must be digital because the EGA standard specifies digital signals. Digital
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