When GNUPLOT is run, it looks for an initialization file to load.
This file is called .gnuplot on Unix and AmigaDOS systems, and
GNUPLOT.INI on other systems. If this file is not found in the
current directory, the program will look for it in the home directory
(under AmigaDOS and MS-DOS, the environment variable GNUPLOT should
contain the name of this directory).
If this file is found, GNUPLOT executes the commands in this file.
This is most useful for setting the terminal type and defining any
functions or variables that are used often.