Computer display standard
Various computer display standards or display modes have been used in the history of the personal computer. They are often a combination of display resolution (specified as the width and height in pixels), colour depth (measured in bits), and refresh rate (expressed in hertz). Associated with the screen resolution and refresh rate is a display adapter. Earlier display adapters were simple frame-buffers, but later display standards also specified a more extensive set of display functions and software controlled interface.
Until recently, most computer monitors had a 4:3 aspect ratio and some had 5:4. Recently, monitors with 16:9 and 16:10 aspect ratios have become available, leading to new widescreen formats. Productive uses for such monitors, i.e. besides widescreen movie viewing and computer game play, are the wordprocessor display of two standard letter pages side by side, as well as CAD displays of large-size drawings and CAD application menus at the same time. The VESA industry organization has defined several standards related to power management and device identification. Ergonomy standards are set by the TCO.
Standards
A number of common resolutions have been used with computers descended from the original IBM PC. Some of these are now supported by other families of personal computers. These are de-facto standards,usually originated by one manufacturer and reverse-engineered by others, though the VESA group has co-ordinated the efforts of several leading video display adapter manufacturers. Video standards associated with IBM-PC-descended personal computers include:
- UXGA
Ultra XGA, a de facto standard with a resolution of 1600 × 1200 with 32 bit pixels, true colour. - SXGA
Super XGA, a de facto standard with a resolution of 1280 × 1024 with 32 bit pixels, true colour. This is an unusual resolution because the numbers work out for a 5:4 display rather than a 4:3 one, so many images appear wider on SXGA displays than most other resolutions. The resolution probably should have been 1280 × 960 (a popular standard resolution for Unix workstations). - XGA
Extended Graphics Array is an IBM display standard introduced in 1990. XGA supports a resolution of 1024×768 pixels with a palette of 256 colours (8 bits per pixel), or 640×480 with high colour (16 bits per pixel). XGA-2 added 1024 × 768 support for high colour and higher refresh rates, improved performance, and supports 1360 × 1024 in 16 colours (4 bits per pixel).- Some manufacturers, noting that the de facto industry standard was VGA (Video Graphics Array), termed this the Extended Graphics Array or XVGA.
- 8514
Precursor to XGA and released about the same time as VGA. 8514/A cards had a maximum resolution of 1024 × 768 with 256 colours (8 bits per pixel), interlaced at 43.5 Hz.
- SVGA
Super VGA, a video display standard created by VESA for IBM PC compatible personal computers. The resolution is 800 × 600 4-bit pixels. Each pixel can therefore be one of 16 colours. - VGA
Video Graphics Array is actually a set of different resolutions, but is most commonly used today to refer to 640 × 480 pixel displays with 16 colours (4 bits per pixel) and a 4:3 aspect ratio. Other display modes are also defined as VGA, such as 320 × 200 at 256 colors (8 bits per pixel) and a text mode with 720 × 400 pixels. VGA displays and adapters are generally capable of Mode X graphics.- MCGA
Multicolor Graphics Array. Introduced on selected PS/2models in 1987, with reduced cost compared to VGA, MCGA had a 256 color (from a 262,144 color palette) mode, and a 640x480 monochrome resolution mode. However, whereas VGA had 256k of video memory, MCGA only had 64k, which limited it to black and white at 640x480 and 256 colors in 320x200 mode.
- MCGA
- QVGA
Quarter VGA (320x240) - Professional Graphics Controller with on-board 2D and 3D acceleration introduced in 1984 for the 8-bit PC-bus, intended for CAD applications,a triple-board display adapter with built-in processor, up to 640× 480 at 256 colors and 60 Hz frame rate.
- EGA
Enhanced Graphics Adapter, with a resolution of 640 × 350 pixels of 16 different colours (4 bits per pixel) selectable from a 64-colour palette (2 bits per each of red-green-blue). - CGA
Color Graphics Adapter, developed in 1981, IBM's first color graphics card for IBM PCs. CGA can display 80 × 25 or 40 × 25 text in 16 colours (4 bits per pixel), 640 × 200 pixels graphics in 2 colours (1 bit per pixel) or 320 × 200 in 4 colors (2 bits per pixel) (IBM PC video modes 0-6). The original card came with a composite video output connector, designed for connection with an NTSC capable television/video monitor, which is the origin of the aspect ratio for this resolution. - Hercules
a monochrome display with a resolution of 720 × 348, capable of sharp text and graphics. Very popular with the Lotus 1-2-3 spreadsheet, which was the PC's first killer app. - MDA
Monochrome Display Adapter, the original standard on IBM PCs and IBM PC XTs. Supports text mode only at 720 × 350 pixels.
See also
External links
- This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.