see: * http://www-zeus.desy.de/~burow/cfortran/cfortran.html

You need cfortran.h.

Have a look at the examples. Compiling example easy with gcc:

$ gcc -ansi -Wall -O -c -Df2cFortran easy.cpp
$ g77 -ff2c -o easy easy.o easy_f.f
$ ./easy

Calling Fortran from C

#include "cfortran.h"

                PROTOCCALLSFSUB2(SUBNAME,subname,STRING,PINT)
#define SUBNAME(A,B) CCALLSFSUB2(SUBNAME,subname,STRING,PINT, A,B)

CCALLSFSUB is followed by number of arguments. In brackets comes the subname (in capital- and lower-case letters), then comes the Fortran-types of the arguments and finally the arguments them-self.