Often referred to as a monitor when packaged in a separate case, the display is the most-used output device on a computer. The display provides instant feedback by showing your text and graphic images as you work or play. Most desktop displays use a cathode ray tube (CRT), while portable computing devices such as laptops incorporate liquid crystal display (LCD), light-emitting diode (LED), gas plasma or other image projection technology. Because of their slimmer design and smaller energy consumption, monitors using LCD technologies are beginning to replace the venerable CRT on many desktops.
Displays have come a long way since the blinking green monitors in text-based computer systems of the 1970s. Just look at the advances made by IBM over the course of a decade: In 1981, IBM introduced the Color Graphics Adapter (CGA), which was capable of rendering four colors, and had a maximum resolution of 320 pixels horizontally by 200 pixels vertically. IBM introduced the Enhanced Graphics Adapter (EGA) display in 1984. EGA allowed up to 16 different colors and increased the resolution to 640x350 pixels, improving the appearance of the display and making it easier to read text. In 1987, IBM introduced the Video Graphics Array (VGA) display system. Most computers today support the VGA standard and many VGA monitors are still in use. IBM introduced the Extended Graphics Array (XGA) display in 1990, offering 800x600 pixel resolution in true color(16.8 million colors) and 1,024x768 resolution in 65,536 colors. Most displays sold today support the Ultra Extended Graphics Array (UXGA) standard. UXGA can support palette of up to 16.8 million colors and resolutions of up to 1600x1200 pixels, depending on the video memory of the graphics card in your computer. The maximum resolution normally depends on the number of colors displayed. For example, your card might require that you choose between 16.8 million colors at 800x600, or 65,536 colors at 1600x1200.
The combination of the display modes supported by your graphics adapter and the color capability of your monitor determine how many colors can be displayed. For example, a display that can operate in SuperVGA (SVGA) mode can display up to 16,777,216 (usually rounded to 16.8 million) colors because it can process a 24-bit-long description of a pixel. The number of bits used to describe a pixel is known as its bit depth. With a 24-bit bit depth, 8 bits are dedicated to each of the three additive primary colors -- red, green and blue. This bit depth is also called true color because it can produce the 10,000,000 colors discernible to the human eye, while a 16-bit display is only capable of produ cing 65,536 colors. Displays jumped from 16-bit color to 24-bit color because working in 8-bit increments makes things a whole lot easier for developers and programmers.
Briefly, the measure of how much space there is between a display's pixels. When considering dot pitch, remember that smaller is better. Packing the pixels closer together is fundamental to achieving higher resolutions. A display normally can support resolutions that match the physical dot (pixel) size as well as several lesser resolutions. For example, a display with a physical grid of 1280 rows by 1024 columns can obviously support a maximum resolution of 1280x1024 pixels. It usually also supports lower resolutions such as 1024x768, 800x600, and 640x480.
In monitors based on CRT technology, the refresh rate is the number of times that the image on the display is drawn each second. If your CRT monitor has a refresh rate of 72 Hertz (Hz), then it cycles through all the pixels from top to bottom 72 times a second. Refresh rates are very important because they control flicker, and you want the refresh rate as high as possible. Too few cycles per second and you will notice a flickering, which can lead to headaches and eye strain.
Video Adapter Timeline
Year: Model: By: Max Pixels: Colors: Palette: Type: Refresh
rate
1981 MDA Mono Display Adapter IBM 720x350 2 2 TTL 50 Hz
1981 CGA Color Graphics Adapter IBM 160x200 4 16 TTL 60 Hz
1981 RGBI Red Green Blue Intensity IBM 640x200 4 16 TTL 60 Hz
1982 HERC Hercules Display Adapter IBM 720x348 2 2 TTL 50 Hz
1984 PGA Professional Graphics Array IBM 640x480 Analog
1984 EGA Enhanced Graphics Adapter IBM 640x350 16 65536 TTL 60 Hz
1987 8514/A Video Standard for PCs IBM 1024x768 256 262,000 Analog 43.5 Hz
1987 MCGA MultiColor Graphics Array IBM 720x400 256 Analog 60Hz
1987 VGA
Video Graphics Array IBM 320x200 256 262144 Analog 70Hz
1988 VGA Video Graphics Array VESA 1600x1200 DDC 85Hz
1990 XGA eXtended Graphics Array IBM 1024x768 16 256 DDC 70 Hz
1990 SVGA Super VGA VESA 1600x1200 256 DDC Analog 60 Hz
1991 EVGA Extended VGA VESA 1024x768 256 DDC Analog 70 Hz
1997 AGP Accelerated Graphics Port Intel 2048x1536 16.7 million Digital 100 Hz
Never run your monitor out of spec. If your display is screwed up, there's
a good chance that the frequencies are out, so turn off the monitor!
Glossary
Analog The traditional method of modulating radio signals so that they can carry information. Amplitude modulation (AM) and frequency modulation (FM) are the two most common methods of analog modulation. Today, most U.S. cellular systems carry phone conversations using analog; the transition to digital transmissions is happening slowly.
DDC Display Data Channel, a VESA standard for communication between a monitor and a video adapter. Using DDC, a monitor can inform the video card about its properties, such as maximum resolution and color depth. The video card can then use this information to ensure that the user is presented with valid options for configuring the display.
dpi dots per inch, which indicates the resolution of images. The more dots per inch, the higher the resolution. A common resolution for laser printers is 600 dots per inch. This means 600 dots across and 600 dots down, so there are 360,000 dots per square inch.
ISA Industry Standard Architecture, is the bus design that has been used in most PCs since IBM released the PC/AT more than a decade ago. It's a limited 8-bit and 16-bit bus, but it's so widely compatible that it has outlasted technologically superior and much faster bus standards like PCI.
PCI Peripheral Component Interconnect, a self-configuring PC local bus called PCI. Designed by Intel, PCI has gained wide acceptance (even by Apple, in its PowerPC series). It beats out the VESA Local Bus spec from a technical standpoint and will presumably win out in the long run. The bottom line: if you have a Pentium, make sure any add-in board you buy is a PCI device.
Pixel A pixel on a monitor is a number of red, green, and blue phosphor dots. These dots are "excited" to varying degrees by the monitor's three electron guns, and the results mix additively to generate a specific color. By manipulating large numbers of pixels in precise ways, patterns emerge to make up an identifiable picture.
Refresh rate The image on your computer monitor doesn't just appear fully formed on the screen's phosphors: it's drawn line by line with beams fired from three electron guns at the back of the CRT. (The three guns are for different colors--red, green, and blue. The colors blend to build all the colors you see.) The frequency at which they redraw the image is called the refresh rate, and it's an important measure of how steady the image will appear.
Resolution A monitor's resolution refers to the number of pixels in the whole image, because the number of dots per inch varies depending on the screen's dimensions. For example, a resolution of 1,280 by 1,024 means that 1,024 lines are drawn from the top to the bottom of the screen, and each of these lines is made up of 1,280 separate pixels--and in turn, each dot may have any number of combinations of red, green, and blue intensities.
RGB RGB refers to the so-called scientific hues--the additive primary colors red, green, and blue--that, when mixed together in equal amounts, create white light. Television sets and computer monitors display their pixels based on values of red, green, and blue.
TTL Transistor-Transistor Logic, a common type of digital circuit in which the output is derived from two transistors. The first semiconductors using TTL were developed by Texas Instruments in 1965. The term is commonly used to describe any system based on digital circuitry, as in TTL monitor.
Video Adapter A board that plugs into a personal computer to give it display capabilities. The display capabilities of a computer, however, depend on both the logical circuitry (provided in the video adapter) and the display monitor. A monochrome monitor, for example, cannot display colors no matter how powerful the video adapter.
VESA This industry organization formed to create various personal computer standards, including those for Super VGA video displays and the VLB bus standard.
VLB VESA Local Bus, This 32-bit, far speedier improvement over the IBM PC's 8-bit and 16-bit ISA bus architecture gained popularity with the advent of Intel's 80486 processor. However, VLB has been superceded recently with the introduction of the Pentium and Intel's superior PCI bus.
Standard Color Depth
32 bit 16,777,216 (True Colors + Alpha Channel)
24 bit 16,777,216 (True Colors, SVGA)
16 bit 65,536 (High Color, XGA)
8 bit 256 colors (VGA)
4 bit 16 colors (EGA)
2 bit 4 colors (CGA)
1 bit 2 colors (monochrome)
Source http://bugclub.org/beginners/history/MonitorsHistory.html
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