<application>X11
</application> can use either the
<filename>.pfa
</filename> or the
<filename>.pfb
</filename> format fonts. The
<application>X11
</application> fonts are located in various subdirectories under
<filename>/usr/X11R6/lib/X11/fonts
</filename>. Each font file is cross referenced to its
<application>X11
</application> name by the contents of
<filename>fonts.dir
</filename> in each directory.