You can use several approaches to sharing data between mixed-language routines, which can be used within the individual languages as well.
Generally, if you have a large number of parameters to work with or you have a large variety of parameter types, you should consider using modules or external data declarations. This is true when using any given language, and to an even greater extent when using mixed languages.
See also Using Modules in Fortran/C Mixed-Language Programming.
See these topics:
Passing Arguments in Mixed-Language Programming
Using Common External Data in Mixed-Language Programming