List of Environment variables used in DOS Navigator:
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 DN         - Directory name where DN system files are placed.
 OS2COMSPEC - Full pathname of OS/2 command interpreter (if you have
              OS/2 v2.10 or newer).
              For example (DOS session AUTOEXEC.BAT):
              SET OS2COMPSEC=C:\OS2\CMD.EXE
 DNOVR      - Directory name where DN.OVR (overlay file) is placed.
 DNSWP      - Temporary files of DN will be stored here
 DNDLG      - Directory name where DN.DLG & DN.LNG (resource files) are placed.
 DNLNG      - Reserved for future use (Multi-lingual support)
 DNIDLE     - Program name to start after 1 hour inactivity (only if
              screen saver is turned off)
 DNCFG      - String to be added to name of configuration file.
              For example:
                      you are using two different configurations in
                      DOS and OS/2. You can set DNCFG = OS2 in
                      DOS session Autoexec.BAT to store DN configuration
                      under OS/2 in file DNOS2.CFG.
              Note: if you want to use this variable, you can copy file DN.CFG
                    to file with name defined by you, after that you just
                    have to make necessary changes.
 DNDSK      - Same string for default desktop (DN.DSK) name.