In accordance with methods and systems consistent with the present invention, a system that automatically generates Fortran 90 interfaces to Fortran 77 code is provided. These interfaces provide for the use of optional parameters and, because they are written in Fortran 90, also allow for parameter checking. These interfaces are automatically generated to allow a programmer to reap the benefits of Fortran 90 calling without having to rewrite the Fortran 77 underlying code. When generating the interfaces, the method performs an optimization that saves a significant amount of processing time as well as a significant amount of memory. This optimization involves generating the interfaces in such a way as to prevent the compiler from performing a gather and a scatter.