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Text File | 1993-08-16 | 11.6 KB | 197 lines

---------------------------------------------------------------- DISPLAY STANDARDS - WHY SOME PROGRAMS WON'T RUN! ---------------------------------------------------------------- All beginners must at some point learn the compatibilities of software, the monitor and the video display circuit cards attached to a computer. Your monitor is usually matched to a video circuit board within the computer. You can change the monitor and video circuit board to add color or upgrade to higher resolution color as you wish. The computer remains the same but the visual clarity changes! Many software packages allow several types of display in color or monochrome with varying degrees of resolution. These types of displays are listed below. Both the monitor and the video card within the computer determine the type of color and resolution which you see. Color quality and resolution can be changed by buying a different monitor and replaceable video circuit board. MONOCHROME DISPLAY ADAPTER or MDA refers to text (characters, letters and numbers) produced by a circuit card within the computer. A monochrome monitor is typically manufactured to produce green or amber letters on a dark field. A monochrome monitor is usually mated to a monochrome circuit board (card) inside the computer. MDA was the first IBM graphics display standard and supports older software packages but is not considered a modern standard. It is of utility for simple software needs - perhaps word processing and accounting use. Resolution or clarity of the image is fairly low with a structure of glowing dots or pixels making up the image. 720 dots accross the width of the screen by 350 vertically. Thus known as 720 x 350 resolution. HERCULES is a reference to a higher resolution monochrome standard. Hercules circuits usually drive or operate a monochrome monitor. By itself a Hercules circuit card CANNOT drive a monochrome monitor when you try to run a COLOR software package. Low priced computers frequently have Hercules display resolution and may have trouble displaying color games or graphics software on the monochrome Hercules circuit. Result: no display. Solution: obtain alternate software or purchase a true color monitor and color video circuit for the computer. Some models (Hercules Incolor card) offer up to 720 x 348 dot resolution. Hercules cards and monochrome monitors are a fair choice for office use where a color display is not necessary. Hercules display resolution is an affordable compromise for a low end PC for light office and home use where color is not required. Owners of older Hercules circuit boards who wish to use CGA or color software can try loading and running small software emulation programs which help a Hercules monochrome display card emulate CGA color mode. This is a "poor man's solution" which lets you display CGA color software on your monochrome monitor. You will only see shades of gray, but at least the software can display on the screen. Examples of these types of emulation programs for Hercules cards include the shareware program SIMCGA.COM and CGA.COM. Slight screen flicker may be apparent when using these CGA emulation programs. CGA (color graphics adapter) refers to the first IBM low resolution color display circuit. Color monitors and CGA circuit boards (cards) are usually mated together in this scheme. Alternatively, CGA color circuits can operate a monochrome monitor, but results can be unpredictable depending on the software program. Some color software programs produce faint or flickering images when a CGA color circuit operates a monochrome monitor. Of course, when a CGA circuit card operates a monochrome monitor, only black and white images can be seen. 640 x 200 dot resolution. Many games and good quality home and office software packages exist for CGA display and it is of fair quality for light office use. Some older CGA equipped computers have a monochrome monitor and can sometimes improve visual display by 1) slightly increasing screen brightness with the monitor light/dark control, but be careful! 2) using the DOS mode setting to switch the CGA circuit board to its black and white output (example: mode bw80). 3) Searching the software instructions for resetting the software package itself to display in other color shades which can be seen clearly on the monochrome monitor. EGA (enhanced graphics adapter) is high resolution color display circuit. The EGA card typically operates or drives a special high resolution EGA monitor. Most modern software packages support color EGA. Is is a popular, although not completely modern display standard. Up to 350 x 720 dot resolution. A reasonable compromise for cost conscious computing in a wide variety of home or office settings. Usually several software disks accompany the EGA circuit card to assist changing resolutions, colors and display fonts. Most EGA circuit cards can, under software control, "downshift" to run older CGA and monochrome resolution older software. A handy bonus. VGA has higher resolution and requires a still higher performance monitor and is considered a modern standard. VGA color monitors are somewhat expensive, but buyers can opt for a VGA monochrome monitor screen which is quite affordable if high resolution is desired, but color is not necessary. VGA cards can also "downshift" and run older software packages, including older CGA, EGA and monochrome software. Usually a software disk accompanies a VGA circuit card to assist changing resolutions, colors and display fonts. VGA features either 320 x 200 pixel resolution with 256 colors or 640 x 480 pixel resolution with 16 colors. SUPER VGA or SVGA. This is a rapidly evolving display circuit which is NOT yet widely standardized. A wide variety of manufacturers sell SVGA circuit cards which move to still higher resolution but are NOT widely standardized among themselves. Resolutions of 800 x 600 and 1024 x 768 pixels are available. The key here is to consult with the manufacturer of your software to see if it will run with that SVGA display resolution. Typically a call to your software dealer will provide information if a special software "driver" utility is available for that SVGA circuit card which will operate with your software. Standard VGA cards with older "8 bit interfaces" will run on original 8088 processor-equipped IBM PC's, although you may need to supply a special software driver, replace a BIOS circuit chip within the PC or both. Newer "16 bit" VGA cards are available - and generally preferred - due to faster screen display times. Generally it makes sense to install a VGA card, expecially the 16 bit versions, on computers having 80286 or 80386 processor chips since the faster processor and wider 16 bit data bus can better support the overhead of moving those extra pixels around the screen. Occasionally compatability problems have been reported with a few VGA circuit cards running on computers operating at 12.5 MHz or above. Ask your vendor to guarantee refund or replacement if compatability with your PC or software fails. XGA is a newly emerging video display standard for IBM compatible computers. The majority of software packages do not, as yet, completely support this high fidelity color resolution. Likewise a newly emerging 8514 display standard is under development by IBM. Do not overlook the role of the monitor. While the display circuit card within the computer moves data around, it is the monitor that will affect your eyes most directly. For the budget conscious, monochrome "gray scale" VGA monitors are available. The buyer may wish to investiage various color "multisync" or "multiscan" monitors which automatically adjust to a wide assortment of VGA, EGA or CGA color circuit cards. Watch out though, since some "multiscan" monitors synchronize only to VGA, yet when emulating EGA will display a small picture in the middle of a large blank screen. Not entirely favorable. Try a variety of software packages you might use at a variety of display resolutions to make sure that BOTH the circuit card and monitor work together as a team. Most display schemes are "downward compatible". This means that a high end VGA card can, through software command, be switched downwards into EGA, CGA or Hercules modes. Many utilities are available to help you set the color spectrum and output quality of EGA and VGA display circuits. The trick is to determine what display circuit standard you have (VGA, for example) and use software which will work with that display resolution. Of course you can always upgrade to a higher standard by swapping both the monitor and display card. Older users or those with eye difficulties may actually prefer lower resolution, larger text images. Thus if you have a VGA card, you may actually NEED to switch to low resolution (larger typface) CGA mode! For the most part monochrome is satisfactory for light office use, Hercules is adequate if you need to do graphing and text work, CGA is useful for games and other types of color graphing. Some owners find that their computer contains an EGA card, for example but they only have a simple monochrome monitor. The upgrade path here is simply to replace the monitor and retain the existing video circuit card. Final thought for the bewildered beginner: find out from your instruction book or computer salesperson which video circuit card (CGA, Hercules, etc) is contained inside your computer. Determine which type of monitor you have. Finally check software purchases to be sure the software package will display properly with that equipment combination. Consider purchase of an alternate display circuit card if the software you need does not display with your computer. If you use the machine mostly for office use, monochrome or Hercules text mode is fine. For more sophisticated design, graphics or intensive office use VGA color adds clarity. Tutorial finished. Have you registered PC-Learn to receive your bonus disks? Registration is encouraged. Shareware works on the honor system! Send $25 to Seattle Scientific Photography, Department PCL6, PO Box 1506, Mercer Island, WA 98040. Latest version of PC-Learn and two bonus disks shipped promptly!