there are many "variations" of DOS mode...depend what you mean ...

A Command.com session within Windows GUI (Graphic User Interface)?
DOS mode, as per "Use with current..."
DOS mode, as per "Specify a new..."?
DOS mode, as per F8 menu, "Command Prompt Only"?
DOS mode, as per F8 menu, "Safe Mode Command Prompt Only"?
DOS mode, via BootGUI=0, or as consequence of failure to start Windows?
Previous version of MS-DOS, as per F8 menu?
Anything that booted off a diskette or CD?
Windows in DOS Compatibility Mode, which is Windows really?
All of these fall into one of three categories; an emulated DOS environment within Windows, a true DOS mode using the DOS that is packaged with Windows, or a previous version of DOS (typically that over which Windows was installed).

description of the above...

http://users.iafrica.com/c/cq/cquirke/whatdos.htm