The GA's

CGA   VGA/SVGA   XGA   SXGA   UXGA   WXGA   WSXGA   

QXGA   QSXGA   QUXGA

NOTE:  all resolutions listed below are given as WxH (Width x Height).  So the second number always refers to the number of horizontal scan lines stacked vertically.

In the early days of monitors and video adapters - the lack of a widely accepted standard for VGA pixel addressabilities was a problem for manufacturers, system builders, programmers and end users alike. 

This was solved with the emergence of VESA ( Video Electronics Standards Association ).  VESA ia a consortium of video adapter and monitor manufacturers whose goal is to standardize video protocols - who developed a family of video standards that were backward compatible with VGA but offered greater resolution and more colors. For a while - prior to the emergence of the "XGA" family of definitions - VESA's VGA BIOS Extensions (collectively known as Super VGA) were the closest thing to a standard.

Here are the usual screen sizes, in pixels, for each of these specifications:

The settings above all have an aspect ratio of 4:3. There are also a few other funky settings, with either a 5:4 or 16:9 ratio:

 

Resolution is a term often used interchangeably with addressability, but it more properly refers to the sharpness, or detail, of the visual image. It is primarily a function of the monitor and is determined by the beam size and dot pitch (sometimes referred to as "line pitch"). An image is created when a beam of electrons strikes phosphors which coat the base of the monitor's "screen. A group comprising one red, one green and one blue phosphor is known as a pixel. A pixel represents the smallest piece of the screen that can be controlled individually, and each pixel can be set to a different color and intensity. A complete screen image is composed of thousands of pixels and the screen's resolution - specified in terms of a row by column figure - is the maximum number of displayable pixels. The higher the resolution, the more pixels that can be displayed and therefore the more information the screen can display at any given time. Resolutions generally fall into predefined sets and the table below shows the series of video standards since CGA, the first to support color/graphics capability:
 

Date Standard Description

Typical Resolution

Number of Colors
1981 CGA Color Graphics
Adapter
640x200
160x200
2
16
1984 EGA Enhanced Graphics
Adapter

640x350

16 from 64
1987 VGA Video Graphics
Array
640x480
320x200
16 from 262,144
256
  SVGA Super Video Graphics
Array
800x600 256 to 16.7 million
  8514/A IBM interlaced standard 1024x768 16 from 262,144
1990 XGA Extended Graphics Array 1024x768 16.7 million
  SXGA Super Extended Graphics Array 1280x1024 16.7 million
  UXGA Ultra XGA 1600x1200 16.7 million
  WXGA Wide XGA 1366x768 16.7 million


 

XGA  4:3 Ratio   WXGA  16:9 or 16:10 Ratio


CGA (Color Graphics Adapter) - Introduced in 1981 by IBM, CGA was the first color graphics system for IBM PCs. Designed primarily for computer games, CGA does not produce sharp enough characters for extended editing sessions. CGA's highest-resolution mode is 2 colors at a resolution of 640 by 200

EGA (Enhanced Graphics Adapter) - 

VGA (Super Video Graphics Array) - developed by IBM. VGA has become one of the de facto standards for PCs. In text mode, VGA systems provide a resolution of 720 by 400 pixels. In graphics mode, the resolution is either 640 by 480 (with 16 colors) or 320 by 200 (with 256 colors). The total palette of colors is 262,144. 

Unlike earlier graphics standards for PCs -- MDA, CGA, and EGA -- VGA uses analog signals rather than digital signals. Consequently, a monitor designed for one of the older standards will not be able to use VGA.  All computer/monitor systems today support and are backwards compatible with VGA !!!

SVGA (Super Video Graphics Array) - a set of graphics standards designed to offer greater resolution than VGA. SVGA supports 800 x 600 resolution, or 480,000 pixels.  In general, the larger the diagonal screen measure of an SVGA monitor, the more pixels it can display horizontally and vertically. Small SVGA monitors (14in diagonal) usually use a resolution of 800x600 and the largest (20in+ diagonal) can display 1280x1024, or even 1600x1200, pixels..  Supports the display of 16 million colors, but the number of colors that can be displayed simultaneously is limited by the amount of video memory installed in a system. The greater number of colors, or the higher the resolution or, the more video memory will be required. However, since it is a shared resource reducing one will allow an increase in the other.  

8514/A - A high-resolution video standard for PCs developed by IBM in 1987. It is designed to extend the capabilities of VGA. The 8514/A standard provides a resolution of 1,024 by 768 pixels, which gives it about 2.5 times the pixels of VGA (640 by 480). Like VGA, 8514/A provides a palette of 262,000 colors, of which 256 can be displayed at one time. On monochrome displays, 8514/A provides 64 shades of gray. In its original version, 8514/A relies on interlacing, a technique that makes it possible to provide resolution at low cost. Interlacing, however, carries a performance penalty, so many manufacturers produce noninterlaced 8514/A clones.

XGA (Extended Graphics Array) - XGA replaced 8514/A and was non-interlaced, developed by IBM and was originally used to describe proprietary graphics adapters designed for use in Micro Channel Architecture expansion slots. It has subsequently become the standard used to describe cards and displays capable of displaying resolutions up to 1024x768 pixels.  It has 768 horizontal scan lines.

SXGA (Super Extended Graphics Array) - this standard is used to describe the next screen size up - 1280x1024. SXGA is notable in that its standard ratio is 5:4, while VGA, SVGA, XGA and UXGA are all the traditional 4:3 aspect ratio found on the majority of computer monitors.

Pixels are smaller at higher resolutions and prior to Windows 95 - and the introduction of scaleable screen objects - Windows icons and title bars were always the same number of pixels in size whatever the resolution. Consequently, the higher the screen resolution, the smaller these objects appeared - with the result that higher resolutions worked much better on physically larger monitors where the pixels are correspondingly larger. These days the ability to scale Windows objects - coupled with the option to use smaller or larger fonts - affords the use far greater flexibility, making it perfectly possible to use many 15in monitors at screen resolutions of up to 1024x768 pixels and 17in monitors at resolutions up to 1600x1200.

WXGA (Wide Extended Graphics Array) resolution can vary depending on the size of the screen. WXGA basically means wide screen, the aspect ratio is 16:9 or 16:10 versus the more box like 4:3 aspect ratio of a standard laptop. If you're a movie fanatic who wishes you could watch that great DVD collection while on the road/plane/lunch break then you may want to take a look at laptop computers with this type of screen. There are variations on this such as WSXGA or WUXGA which are wide screen versions of the higher resolution modes.

WSXGA (Wide Super XGA) - a resolution that supports 1600 by 900 pixels or 1600 by 1024 pixels.

UXGA (Ultra Extended Graphics Array) - a display specification that is capable of displaying 1600 x 1200 resolution, or approximately 1.9 million pixels.  It has 1200 horizontal scan lines.

UXGA (Ultra Extended Graphics Array) - resolution of 1600x1200. This is featured on mainly high end laptops which have medium to large screens (15.4 inch or greater). Like SXGA+ this resolution is great for when you need to see more of the screen at once such as with spreadsheets or editing large photos, etc.

QXGA (Quad Extended Graphics Array)* - a display specification that is capable of supporting 2048 x 1536 resolution, or approximately 3.2 million pixels. (2048 by 1536 pixels; 1.33:1 aspect ratio)

QSXGA (Quad Super XGA)* - a Display Standard referring to a video adapter capable of a resolution of up to 2560 by 2048 pixels. (2560 by 2048 pixels; 1.25:1 aspect ratio)

QUXGA (Quad Ultra XGA)* - 3200 by 2400 pixels; 1.33:1 aspect ratio

* these high-resolution screens are made possible by a new screen technology called TFT

TFT (Thin Film Transistor) - also referred to as active matrix or even used at the same time such as “TFT Active Matrix LCD!”. You would be hard pressed to find a modern laptop that doesn't use this type of screen, it has become the standard for bright and colorful screens, although “bright” and “colorful” may vary from each manufacturer.

LCD (Liquid Crystal Display) - LCD's are found in countless gadgets that require a small or flat screens such as cell phones, handheld game systems, computer monitors, etc.