CRT - Cathode Ray Tube

CRT stands for 'Cathode Ray Tube' and it is the most commonly used output device of modern digital computer. It has an electron gun located at the back of a tube which produces the electron beams. The screen has a layer of phosphor which emits light when it is struck by electron beam.

The monitor is composed of a number of dots arranged in rows and columns. Each dot is called a picture element (pixel for short). A picture is displayed on the screen by brightening or darkening the selected pixels. The resolution of the screen means the number of pixels per unit of the screen – for example the number of pixels per square cm or inch. The higher resolution has more pixels per square cm and the higher the resolution, the greater the details which can be displayed. The CRT screen can be classified into 2 types in terms of color capabilities.

i) Monochrome:- The monitor which displays output only in 2 colors i.e. one for background and the other for foreground.
ii) Color:- The screen which can display output in more colors by combining red, green and blue electron bean is the color screen. It is also called RGB monitor.