The monitor is the piece of computer hardware that displays graphic information generated by the computer through the video card. It is classified as an output device. Monitors often resemble televisions. The main difference between a monitor and a television is that a monitor does not have a television tuner to change channels. Monitors often have a higher screen resolution than televisions.
The most common type of screen is the one we see in desktop computers and in terminals, the CRT screen, apart from other technologies such as liquid crystal, implanted in portable computers, that are becoming more and more widespread.
The primary function of a computer monitor is to display video and graphic information generated by the computer’s graphics adapter, allowing the user to interact with the computer. The monitor is an essential part of the overall computer system. It is sometimes known as a video screen or video display unit.
Monitors come in three main types: CRT, LCD, and LED. CRT monitors look a lot like old-fashioned televisions and are very large in size. LCD monitors are much thinner, consume less power, and provide better graphics quality. LED display is a flat screen, flat panel computer monitor or television. It has a very short depth and is light in terms of weight. The real difference between an LED and LCD is the backlight. Early LCD monitors used CCFLs instead of LEDs to illuminate the screen.
The screens are classified, according to the ability or not to display colors, in:
- Monochrome monitor: The usual colors on a monochrome monitor are black and white, amber, or green.
- Color monitor: The color of each point is obtained by mixing the colors red, green and blue, being able to program the intensity of each basic color.
According to their representation capacity they can be classified into:
- Character screens: They only accept characters.
- Graphic screens: They allow the drawing of continuous lines and curves.
In character screens, the image memory (which is a part of RAM memory) stores the information corresponding to each cell (character codes and their attributes). Patterns of characters represented as a dot matrix are stored in ROM. This read-only memory is called a character generator.
In the graphic screens, the user has access to the image point, being able to represent in them configured images not only with the forms of characters included in the ROM. In this case, the image memory contains the information corresponding to each image point (intensity, color and other possible attributes), instead of that corresponding to each cell. The drawings, despite being made up of image points, have the appearance of continuous lines. The quality of the graphic display depends on the density of image points.
The main parameters that characterize a screen are:
- Size: It is given based on the size of the main diagonal, and there is a bad habit of giving it in inches. The most common are the 14″ (356 mm), although in many countries the 381 mm are being used.
- Number of cells or characters: The usual is a representation of 24 rows * 80 columns of characters.
- Resolution: It is the number of image points on the screen. This number does not depend on the size of the screen.
Basically three types of resolution are usually considered:
- CGA 640 * 200 points
- VGA 640*480 dots
- SVGA 1024*768 dots
Currently there are higher resolutions, but little used.