There had been different types of analog video and each differs on resolution and the maximum number of colors in its palette. Their evolution and types are discussed.
Monochrome – It is first video technology and was black-and-white video but, was sufficient for DOS operating system as DOS didn’t have any need for color. Images used only shades of grey called grayscale.
EGA and CGA – It was developed by IBM and was the first display device with color. Color Graphics Adapter (CGA) could display text, but it displayed graphics with a resolution of only 320 × 200 pixels with four colors and with resolution (640 × 200) using two colors—black and one other color. Enhanced Graphics Adapter (EGA) could display 16 colors out of a palette of 64 with a resolution of 320 × 200 or 640 × 350 pixels. Both were standard for color for long time.
VGA – Video Graphics Array (VGA) video technology had a 256KB of video memory on board and could display 16 colors at 640 × 480 pixels or 256 colors at 320 × 200 pixels. It became very popular. It’s an analog technology.
SuperVGA – The Video Electronics Standards Association (VESA) came out with a enhanced technology as a public standard called SuperVGA (SVGA) which could support 16 colors at a resolution of 800 × 600 (the VESA standard), but it expanded to support 1,024 × 768 pixels with 256 colors.
XGA – Extended Graphics Array (XGA) was introduced by IBM. It could support 256 colors at 1,024 × 768 pixels or 65,536 colors at 800 × 600 pixels. It was optimized for GUIs like Windows.
Other Analog Video – Other technologies are extensions of SVGA or XGA so, if it starts with letter W, it will have wider horizontal resolution to accommodate 16:9 or 16:10 wide-screen formats and if preceded with Q means horizontal and vertical resolutions were each doubled. So, if XGA with resolution of 1024 × 768, then QXGA resolution is 2048 × 1536and if SuperXGA (SXGA) has resolution of 1280 × 1024 then WSXGA have 1440 × 900.