ram that draws text needs to read a font file at run time; if it cannot find the file, no text will be drawn, and a warning message will be issued. Usually the font file is called <code>grfont.dat</code> and is placed in the same directory as the PGPLOT library. If you use routine <a href="subroutines.html#PGSCRN">PGSCRN</a>, the program also needs to read file <code>rgb.txt</code>. You tell PGPLOT where to find both files by defining an environment variable giving the name of the directory containing the f