On MS-DOS, the name of the command interpreter to use. This is used to make a default value for the SHELL environment variable.

On MS-DOS, this variable defaults to the value of the USER variable.

On MS-DOS, these specify the name of the directory for storing temporary files in.

On MS-DOS, this specifies a file to use to log the operation of the internal terminal emulator. This feature is useful for submitting bug reports.

Used on MS-DOS systems to set screen colors early, so that the screen won't momentarily flash the default colors when Emacs starts up. The value of this variable should be two-character encoding of the foreground (the first character) and the background (the second character) colors of the default face. Each character should be the hexadecimal code for the desired color on a standard PC text-mode display.

The PC display usually supports only eight background colors. However, Emacs switches the DOS display to a mode where all 16 colors can be used for the background, so all four bits of the background color are actually used.

Used when initializing the Sun windows system.