In modern times the computer monitor is use to display information on a screen (you are reading this on a monitor right now).

Both information received from the computer (results of spreadsheet transactions, etc.), and the text or commands you type on the keyboard are displayed. A monitor can be adjusted for brightness and contrast, and many monitors have additional controls for moving the image left, right, or up and down.

• The computer monitor works very similar to the TV set in your home. The main difference is there is no sound provided by a monitor. The monitor uses a Cathode Ray Tube (CRT) to display text and images for your viewing just like your TV set. You could say the monitor is your window into what is happening inside of your computer.

How Monitors Work Monitors produce a display by dividing the screen into a pattern of tiny points of light called pixels. These pixels are organized in rows and columns across the screen area.

• The number of points possible determines the resolution of the monitor. CGA monitors would produce a grid of 320 X 200 pixels. In contrast, an XVGA monitor can produce a grid of 1024 x 768 pixels.

• Each point is either illuminated or not illuminated depending on the information or graphics to be displayed. As an example let us assume we are using a white screen background with black letters. When there are no letters on the screen, all the pixels are illuminated.

  Therefore, the smallest display area on a screen is a pixel.   A single character, or the space it takes to display a single character, can consist of dozens of pixels.   These pixels can be colored to display single colors, or a mix of colors to represent true colors.   The number of pixels a screen can contain is the "resolution" of a screen.

• As we type characters on the keyboard they are sent to the screen. As each character is placed on the screen a number of pixels are turned off in a pattern that we recognize as the character we just typed. - A little more on How they Work.

Dot Pitch is used with something called a "shadow mask". This is a thin film of metal which has tightly spaced holes in it. It determines how the color dots in a pixel are aligned. The lower the number for dot-pitch, the better resolution you will have. A "shadow mask" works something like this:

• The shadow mask is located inside the display tube, a short distance behind the phosphor coating of the screen.

• The mask and the phosphor coating are arranged so that the electron beam can only hit the phosphor dots of one color.

• The other two colors of the BGR group are in the "shadow" of the mask, and cannot be seen by the beam.

• The phosphor dots must be spaced at the same distance as the holes in the mask.

• The hole spacing of the mask determines the "dot-pitch" of the CRT.

Display Adapter (Video) Cards

• This adapter card is what controls the colors and resolution of computer monitors The term resolution refers to the sharpness and quality of text and graphics on your monitor screen.

• Monochrome - The first Personal Computers (PC's) could not display more than one or two colors at a time. These monitors were simple devices that did not require an additional adapter card. The majority of monochrome monitors displayed black text on a white background. A few manufacturer's did provide green or orange screens. These monitors were usually associated with PC's built in the early 1980's such as; The Radio Shack(Tandy) TRS-80; The Apple IIE; The Zenith H-89; The Commodore 64; etc.

• Color Graphic Adapter (CGA) - The CGA standard was the fist color standard,developed for personal computers. The display type used was usually 10 lines of 40 characters (Normally we have 20 lines of up to 80 characters).

  The original concept was a 640 x 200 pixel screen, and later evolved to 640 x 400 (double-Scanned CGA) pixel screen resolution. These figures (640 x 200) means that there are 640 columns and 200 rows of pixels on the screen, or about 128,000 pixels on a early CGA screen! That is a lots of little lights to turn on!.

  Text and graphics were usually very large. Color monitors were very expensive in those days. You not only had to pay a high price for the monitor, but you had to pay a very high price for a CGA graphics adapter card.

  The CGA standard had the ability to display 16 bright colors, assuming you understood that black, dark gray, light gray, and white were "bright" colors at 640 x 200 pixel resolution.

• Enhanced Graphics Adapter (EGA) - The next generation of adapter cards was the EGA card. This card produced by IBM, appeared on the market about 1985. EGA cards provided several major improvements over CGA. This card increase the number of pixels (dots of light ) on the screen which lead to smaller and sharper graphics pictures and text. The card could produce 256 colors but could only display 16 combinations at a time.

• Video Graphics Array - Developed iby IBM in 1987, the Video Graphics Array (VGA) was intended to improve the capabilities of the CGA or EGA standards by going to a 640 x 480 pixel resolution. It was backward compatible with all previously defined video standards.

  In text mode, you used 16 foreground colors and 8 background colors, make characters blink with 8 extra background colors. In text mode, each character was 9 x 16 dot boxes, so at 80 columns x 25 rows, the screen display was 720 x 400 pixels.

• SVGA - Super Video Graphics Array. SVGA is a term used by the Video Electronics Standards Association to refer to all modes and resolutions beyond the basic 640 x 480 graphics mode of VGA.

  VESA specifies standards for how your software to determine what the display adapter does. The VESA does not tell a manufacturer how to build a display adapter. It does tell how your programs connect to your display adapter, and how the rules for connecting your monitor.

  These VESA standards include resolution levels of

  1. 800 x 600
  2. 1024 x 768
  3. 1280 x 1024
  4. 1600 x 1200
  The VGA or Extended Video Graphics Array (XVGA) is standard used by the majority of personal computers manufactured today. Some of the most advanced cards can produce from 32,000 to 64,000 colors.

Note: There are many variations of the EGA/VGA standards which are too few to mention here. The type cards listed above are intended to give the reader a general overview of the standard cards on the market.

All new computers are using the SVGA standard video card or Video controllers built into the motherboard.

If you would like a little more detail on Video Display devices Click Here

Monitor sizes A monitor may range in size from a 13 inch diagonal to a 21 inch or larger diagonal measurement. The most common sizes in use today are:

• The15 inch Tube - One of the most common sizes found in monitors is the 15 inch tube. The 15 inch monitor is used for most business applications and offers 640 X 480 or 800 X 600 SVGA resolutions. Be aware that some bargain PCs offer 14 inch convex-tube monitors. It is better to upgrade to a Sony Trinitron tube. They have the best possible resolutions.

• The 17 Inch Tube - The 17 inch monitor is best suited when working with desktop publishing or spreadsheets. This particular monitor is the best all around monitor you can get for most desk tops. It offers a wider and larger viewing area that makes long sessions easier on the eyes. You will find that different brands are labeled with different sizes of display areas. Some may advertise only 15.9 while other will offer 16.0 inches diagonal. Be aware that all monitor sizes are measured diagonally across the viewing screen. We recommend this size tube for most home users.

• The 19 Inch Tube - While most people think bigger is better, this is not always the case here. Depending on your desktop layout, a 19 inch monitor can actually be harder on your eyes if it is too close. Not to mention the cost of these monitors is very high. This size monitor is usually reserved for Computer Aided Design (CAD) applications. Resolutions of1600 X 1200 are easily viewed on this size monitor.

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