f2c is a Fortran-to-C converter.

This package includes libf2c, which must be linked to the resulting C
code.  Thus the general idea is

  f2c foo.f
  gcc foo.c -lf2c

Or use the fc script provided in the docs directory. Beware, fc is also
a bash builtin.

If combining with gfortran, you may want to use the gfortran -ff2c
option. See the gfortran man page.