<p>How do I declare a private function in Fortran?</p>

I've never written a line of FORTRAN, but
this thread about "Private module procedures"
seems to be topical, at least I hope so. Seems to contain answers, at least.
jaredor
summary:
The public/private attribute exists within modules in Fortran 90 and later. Fortran 77 and earlier--you're out of luck.