Monitor

The monitor is primarily an output device. It converts electronic signals from the computer into a visual display that is the result of processing information. It can be thought of as a high resolution TV set. The monitor can also determine if the display will be color, black and white, or include graphical objects (pictures).

The monitor displays text and images (pictures) converted to output from the video adapter. The video adapter is an expansion card that plugs into the motherboard. The adapter changes the instructions from the central processing unit (CPU) into a way that the monitor can understand it.

Characteristics of a monitor are as follows:

• Size : The most important aspect of a monitor is its screen size. Screen sizes are measured in diagonal inches. Atypical size for small VGA monitors is 14 inches. Monitors that are 16 or more inches diagonally are often called as full-page monitors. Monitors are either portrait or landscape.
• Resolution : Resolution refers to the number of dots on the screen or pixels. . It is expressed as a pair of numbers that give the number of dots on a line (horizontal) and the number of lines (vertical).  The smaller the pixels, the clearer and sharper the picture appears on the monitor. The number of bits used to represent each pixel determines how many colours or shades of gray can be displayed.
• Color Depth : Memory on the video adapter limits the number of colors that can be display at each resolution. High quality photography needs at least 1MB of memory. Multimedia applications with high resolution graphics need at least 2 MB of memory.
• Refresh Rate : The Refresh Rate determines the speed that the display uses to paint the dots on the screen. Simply speaking, refresh rate relates to the number of times a screen is redrawn. The refresh rate for a monitor is measured in hertz (Hz) and is also called as vertical frequency or vertical refresh rate.
• Graphics Accelerator : With the invention of the graphics accelerator chip on the video card, the display adapter can draw lines and boxes, scroll text, rotate graphics, make background fills, and also use and manage a mouse pointer, and other pointing devices. Application programs can now send requests and with the help of a Windows Driver routine, the adapter can calculate the bits without the help of the CPU, making the procedure faster.
• Dot-pitch : A measurement that indicates the vertical distance between end pixel and a display screen. Measured in millimeters, the dot-pitch is one of the principal characteristics that determine the quality of display monitor.
• Convergence : Convergence refers to how sharply an individual colour pixel on a monitor appears. If the dots are badly misconverged, the pixel will appear blurly.

Different types of monitors include:

• LCD Monitor : A flat panel display usually uses an LCD (Liquid Crystal Display) screen to display output from the computer. The LCD consists of several thin layers that polarize the light passing through them. The polarization of one layer, containing long thin molecules called liquid crystals, can be controlled electronically at each pixel, blocking varying amounts of the light to make a pixel lighter or darker. Other types of flat panel technology exist (such as plasma displays) but LCDs are most commonly used in computers, especially laptops. Flat panel displays are much lighter and less bulky than CRT monitors, and they consume much less power. They have been more expensive than CRTs in the past, but the price gap is narrowing.
• CRT Monitor : The traditional output device of a person computer has been the CRT (Cathode Ray Tube) monitor. Just like a television set  the CRT monitor contains a large cathode ray tube that uses an electron beam of varying strength to “paint” a picture onto the color phosphorescent dots on the inside of the screen. CRT monitors are heavy and use more electrical power than flat panel displays, but they are preferred by some graphic artists for their accurate color rendition, and preferred by some gamers for faster response to rapidly changing graphics.
• Monochrome Monitors : They actually display two colours, one on the background and the other on the foreground. The colours can be black and white, green and black or amber and black.
• Gray-scale Monitors : It is a special type of monochrome monitor capable of displaying different shades of gray.
• Colour Monitors : They can display anywhere from 16 to over 1 million different colours. They are sometimes called RGB monitors because they accept3 separate signals – Red, Green and Blue.
• Digital Monitors : A monitor that accepts digital 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 continuously variable colors. Consequently, only low-quality video standards, such as MDA , CGA, and EGA, specify digital signals. VGA and SVGA, on the other hand, require an analog monitor. Some monitors are capable of accepting either analog or digital signals.
• Analog Monitors : The traditional type of color 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 monitors must nevertheless translate the signals into an analog form before displaying images. Some monitors can accept both digital and analog signals. Some analog monitors are also called digital because they support digital controls for adjusting the display.  Most analog monitors are multifrequency monitors, which means that they are designed to accept signals at two or more preset frequency levels.