migrating code from f77 to f90

[Tobias Schlüter]

Quoting Jack Howarth <howarth@bromo.msbb.uc.edu>:
>     Thanks I had seen convert.f90 already but wasn't sure if it was
> still the best freely available conversion program. I do have one
> other question. I know that xlf fortran claims to support linking
> together both Fortran 77 and Fortran 90 code in the same program.
> What is the situation in gfortran with that regard? Do we have to
> convert all the code at once and can it be mixed as long as we
> avoid F90 specific features?

You can, Fortran 77 is a subset of Fortran 90.  You should compile everything
with the same compiler, though, to avoid incompatibilities between compilers. 
You will also have trouble if you decide to move procedures or common variables
into modules, as you can't access modules from strictly F77 code.

These questions are more appropriate for comp.lang.fortran.

- Tobi