"SfR Fresh" - the SfR Freeware/Shareware Archive 
Member "gnuplot/bin/share/PostScript/README" of archive gp423win32.zip:
There are gnuplot postscript prologue files here.
On platforms where it is possible and easy to implement, the postscript
prologues files are installed as separate files and located at run-time.
On others (i.e. when the preprocessor variable GNUPLOT_PS_DIR is undefined),
they are included at compile-time. To do that, the *.ps files are processed by
the script ps_header.sh which creates char arrays suitable to inclusion in the
source code.