If GNUTERM is defined, it is used as the name of the terminal type to be used. This overrides any terminal type sensed by GNUPLOT on start up, but is itself overridden by the .gnuplot (or equivalent) start-up file (see start-up), and of course by later explicit changes.
On Unix, AmigaDOS, and MS-DOS, GNUHELP may be defined to be the pathname of the HELP file (gnuplot.gih).
On VMS, the symbol GNUPLOT$HELP should be defined as the name of the help library for GNUPLOT.
On Unix, HOME is used as the name of a directory to search for a .gnuplot file if none is found in the current directory. On AmigaDOS and MS-DOS, GNUPLOT is used. On VMS, SYS$LOGIN: is used. See help start-up.
On Unix, PAGER is used as an output filter for help messages.
On Unix and AmigaDOS, SHELL is used for the shell command. On MS-DOS, COMSPEC is used for the shell command.
On AmigaDOS, GNUFONT is used for the screen font. For example: ``setenv GNUFONT sapphire/14''.
On MS-DOS, if the BGI interface is used, the variable BGI is used to point to the full path to the BGI drivers directory. Furthermore SVGA is used to name the Super VGA BGI driver in 800x600 res., and its mode of operation as 'Name.Mode'. For example, if the Super VGA driver is C: \TC \BGI \SVGADRV.BGI and mode 3 is used for 800x600 res., then: 'set BGI=C: \TC \BGI' and 'set SVGA=SVGADRV.3'.