The EGA is generally upwardly-compatible with the CGA  and the MDA , but
it has loads of additional features.  It was introduced in 1985 and has
been popular since about 1986.  It is mostly replaced by VGA and SVGA
systems.  TECH Help! covers the following EGA and general video topics:

Video Modes ........... includes EGA modes
Video Services ........ INT 10H video services

Video Memory Layouts .. accessing EGA video memory

EGA Data Areas ........ BIOS data variables specific to EGA
BIOS Data Area ........ includes video-specific variables in low memory
Screen Attributes ..... codes determine colors for text mode
Color Table ........... exhaustive listing of screen attributes

EGA I/O Ports ......... I/O port addresses; video controller registers
EGA Switch Settings ... those pesky switches at the rear of the adaptor
EGA Pin Outs .......... connectors on EGA cards

Font Definition Data .. layout of binary data that defines a font
.CPI Font Files ....... the DOS interface for EGA font definition

The EGA supports 25- and 43-line text modes and graphics modes up to
640x350 with 16 colors.  You can redefine fonts and remap the color
palette.  It is upwardly-compatible with CGA.  VGA, and SuperVGA are all
upwardly-compatible with EGA, supporting all of its modes, I/O ports, and
BIOS variables.

In text modes, video memory begins at b800:0.  In graphics modes 0dH-10H,
video memory is at a000:0 (see Video Memory Layouts).

  Testing for an EGA  
To see if you are running on an EGA, use INT 10H 12H BL=10H.  If on
return,  BL>4 then the EGA BIOS is not present, so you must be running
on a CGA or MDA.

See Also: CGA
- -

Enhanced Graphics Adapter (EGA)