ANSI is the American National Standards Institute, but in the BBS world ANSI was the type of terminal emulation used by BBS programs, doors, games, that included screen codes (based on VT-100 emulation) with color, IBM PC font symbols and other things.
ANSI terminal emulation used the same codes as the ANSI.SYS or ANSI.COM program for MS-DOS used. Many MS-DOS users just had to load the ANSI program to see the special effects. Many terminal emulators like QMODEM, Procomm, Bitcom, etc used their own built in ANSI emulation. It allowed users to use split screen chats, full screen message ad email editing, doors and games that used special graphics to function and use the software, and the great ANSI Art that many BBSes had for login screens and status screens.
Programs used in ANSI Edit
There was a great DOS program called TheDraw that enabled people to draw ANSI screens and save them in *.ANS files for use in BBSes and Doors and Games. There were many other programs that did that, but TheDraw was one of the more popular ones.