Extension file edit...
 This  command  is  used to create and maintain the extension
 file, which associates programs with  file  extensions. This
 feature  allows you to point-and-shoot (move the cursor to a
 file and press Enter, or double-click) on  a  file  to  load
 that file into the application that created it.

 Lines in the file consists of an extension, and the commands
 to run on files with that extension:

        +---- Extension
        |            +---- Insert file name and extension
        .            .
       doc: word /c !.!
            @ cls
            +---------+
              Commands

 tells the Commander to run  Microsoft Word  when  you  press
 Enter on a file that ends  in .doc (such as "somename.doc"),
 and then to clear the screen.

           +--------------     Enter
 So for:   |    Name    |      ----.   "word /c somename.doc"
           |somename doc|              "cls"

 A comment line must contain symbol ' in first column.

 You can type symbol @  before  any  DOS  command  to  cancel
 output of the prompt and the command line.

 Here are all the ! arguments that you can use in commands:

   Argument     What                             Example
   --------     ---------------------------      ------------
   !.!          File name with the extension     filename.ext
   !            File name, without extension     filename
   !:           The current drive letter         A:
   !\           The current page                 \PATH
   !!           Insert the `!' character         !

   Notes:
     .  You  can  use  ":"  to  match  any  file  without  an
        extension.

     .  You can use DOS wildcard characters. So, for example,
        "*:" will match any extension.

     .  There  are  two  types  of  extension  file: Main and
        Local. The main extension file is stored in the  same
        directory as the Commander (or the directory given by
        the  VC environment  variable). The  local  extension
        file is an extension file in the  current  directory.
        This  allows  you to have a number of extension files
        in different directories.