My code is written in Fortran 77/90/95. Do I need to learn Fortran 2003 to use ForTrilinos?
No. The only requirement is to pass in compatible argument types. You can either pass the Fortran types you currently use (in which case an implicit conversion to a C type occurs) or you can explicitly convert the arguments you’re passing to C types. Only the latter approach requires you to learn any Fortran 2003. Even then, the new features will feel very natural as Fortran 2003 specifies a set of KIND parameters that provide direct access to standard C types within Fortran code.
