ll not have
any compiler errors, and will likely crash at runtime.  So, greater
care is needed.  Also, technically interfacing older Fortran versions
to C is nonstandard, but in practice we have found that the techniques
used in this chapter have worked with all known Fortran compilers for
many years.

   <p>The legacy Fortran interface differs from the C interface only in the
prefix (&lsquo;<samp><span class="samp">dfftw_</span></samp>&rsquo; instead of &lsquo;<samp><span class="samp">fftw_</span></samp>&r