A list of file extensions and what they are used for and what they mean.
Written by Allan, Jan 2004
Revised April 2006
.CUI
XML based menu file new for AutoCAD 2006, superseeds older menu files.
.MNU
Template menu file. (This is where we code from)
.MNC
Compiled menu file. This binary file contains the command strings and menu syntax that defines the functionality and appearance of the menu.
.MNR
Menu resource file. This binary file contains the bitmaps used by the menu.
.MNS
Source menu file (generated by AutoCAD).
.MNT
Menu resource file. This file is generated when the MNR file is unavailable, for example, read-only.
.MNL
Menu LISP file. This file contains AutoLISP expressions that are used by the menu file and are loaded into memory when a menu file with the same file name is loaded.
.BMP
Standard bitmap icons used on the toolbars. (16×15 pixels for the small size and 24×22 pixels for the big size. Most of us use the 16×15 size.
ACADBTN.DLL
A Windows resource file containing the standard AutoCAD toolbar bitmaps, all bundled into a single file. This is a standard AutoCAD support file, and it lives in the AutoCAD program directory.