by admin on March 9, 2012
(1) Another term for display screen. The term monitor, however, usually refers to the entire box, whereas display screen can mean just the screen. In addition, the term monitor often implies graphics capabilities.
There are many ways to classify monitors. The most basic is in terms of color capabilities, which separates monitors into three classes:
monochrome : Monochrome monitors actually display two colors, one for the background and one for the foreground. The colors can be black and white, green and black, or amber and black.
gray-scale : A gray-scale monitor is a special type of monochrome monitor capable of displaying different shades of gray.
color: Color monitors can display anywhere from 16 to over 1 million different colors. Color monitors are sometimes called RGB monitors because they accept three separate signals — red, green, and blue.
After this classification, the most important aspect of a monitor is its screen size. Like televisions, screen sizes are measured in diagonal inches, the distance from one corner to the opposite corner diagonally. A typical size for small VGA monitors is 14 inches. Monitors that are 16 or more inches diagonally are often called full-page monitors. In addition to their size, monitors can be either portrait (height greater than width) or landscape (width greater than height). Larger landscape monitors can display two full pages, side by side. The screen size is sometimes misleading because there is always an area around the edge of the screen that can’t be used. Therefore, monitor manufacturers must now also state the viewable area — that is, the area of screen that is actually used.
The resolution of a monitor indicates how densely packed the pixels are. In general, the more pixels (often expressed in dots per inch), the sharper the image. Most modern monitors can display 1024 by 768 pixels, the SVGA standard. Some high-end models can display 1280 by 1024, or even 1600 by 1200.
Another common way of classifying monitors is in terms of the type of signal they accept: analog or digital. Nearly all modern monitors accept analog signals, which is required by the VGA, SVGA, 8514/A, and other high-resolution color standards.
A few monitors are fixed frequency, which means that they accept input at only one frequency. Most monitors, however, are multiscanning, which means that they automatically adjust themselves to the frequency of the signals being sent to it. This means that they can display images at different resolutions, depending on the data being sent to them by the video adapters.
Other factors that determine a monitor’s quality include the following:
bandwidth : The range of signal frequencies the monitor can handle. This determines how much data it can process and therefore how fast it can refresh at higher resolutions.
refresh rate: How many times per second the screen is refreshed (redrawn). To avoid flickering, the refresh rate should be at least 72 Hz.
interlaced or noninterlaced: Interlacing is a technique that enables a monitor to have more resolution, but it reduces the monitor’s reaction speed.
dot pitch : The amount of space between each pixel. The smaller the dot pitch, the sharper the image.
convergence : The clarity and sharpness of each pixel.
Also see Northern vs. Southern Hemisphere Monitors in the Did You Know . . . ? section of Webopedia.
(2) A program that observes a computer. For example, some monitor programs report how often another program accesses a disk drive or how much CPU time it uses.
by admin on March 9, 2012
Video technologies differ in many different ways. However, the major 2 differences are resolution and the number of colors it can produce at those resolutions.
Resolution
Resolution is the number of pixels that are used to draw an image on the screen. If you could count the pixels in one horizontal row across the top of the screen, and the number of pixels in one vertical column down the side, that would properly describe the resolution that the monitor is displaying. It’s given as two numbers. If there were 800 pixels across and 600 pixels down the side, then the resolution would be 800 X 600. Multiply 800 times 600 and you’ll get the number of pixels used to draw the image (480,000 pixels in this example). A monitor must be matched with the video card in the system. The monitor has to be capable of displaying the resolutions and colors that the adapter can produce. It works the other way around too. If your monitor is capable of displaying a resolution of 1,024 X 768 but your adapter can only produce 640 X 480, then that’s all you’re going to get.
When we talk about the different technologies, we’re talking about the video card and monitor that make up that display system. Also, standards describe the basic number of colors and resolutions for each technology, but individual manufacturers always take liberties, providing options and enhancements that are designed to make their product more appealing to the end user. This is, of course, how new standards come about.
Monochrome
Monochrome monitors are very basic displays that produce only one color. The basic text mode in DOS is 80 characters across and 25 down. When graphics were first introduced, they were fairly rough by todays standards, and you had to manually type in a command to change from text mode to graphics mode. A company called Hercules Graphics developed a video adapter that could do this for you. Not only could it change from text to graphics, but it could do it on the fly whenever the application required it. Today’s adapters still basically use the same methods.
CGA/EGA
The Color Graphics Adapter (CGA) introduced color to the personal computer. In APA mode it can produce a resolution of 320 X 200 and has a palette of 16 colors but can only display 4 at a time. With the introduction of the IBM Enhanced Graphics Adapter (EGA), the proper monitor was capable of a resolution of 640 X 350 pixels and could display 16 colors from a palette of 64.
VGA
Up until VGA, colors were produced digitally. Each electron beam could be either on or off. There were three electron guns, one for each color, red, green and blue (RGB). This combination could produce 8 colors. By cutting the intensity of the beam in half, you could get 8 more colors for a total of 16. IBM came up with the idea of developing an analog display system that could produce 64 different levels of intensity. Their new Video Graphics Array adapter was capable of a resolution of 640 X 480 pixels and could display up to 256 colors from a palette of over 260,000. This technology soon became the standard for almost every video card and monitor being developed.
SVGA
Once again, manufacturers began to develop video adapters that added features and enhancements to the VGA standard. Super-VGA is based on VGA standards and describes display systems with several different resolutions and a varied number 
of colors. When SVGA first came out it could be defined as having capabilities of 800 X 600 with 256 colors or 1024 X 768 with 16 colors. However, these cards and monitors are now capable of resolutions up to 1280 X 1024 with a palette of more than 16 million colors.
XGA
Extended Graphics Array was developed by IBM. It improved upon the VGA standard (also developed by IBM) but was a proprietary adapter for use in Micro Channel Architecture expansion slots. It had its own coprocessor and bus-mastering ability, which means that it had the ability to execute instructions independent of the CPU. It was also a 32-bit adapter capable of increased data transfer speeds. XGA allowed for better performance, could provide higher resolution and more colors than the VGA and SVGA cards at the time. However, it was only available for IBM machines. Many of these features were later incorporated by other video card manufacturers.
