Migration Planning

This section describes how you should go about planning a Fortran migration. In particular, this section provides information about how to scope a Fortran migration to Win32 and provides a brief look at other migration strategies.

Scoping the Fortran Migration

At first glance, an ANSI Fortran application migration can have most (if not all) of the same migration combinations as a C or a C++ migration. A Fortran application can:

• Be multi- user .

• Have a GUI for user interaction.

• Use platform specific features.

However, most Fortran applications perform specialized functions where the Fortran language is particularly suitable. For example, Fortran is particularly suited as a language for computationally intensive mathematical operations. Other languages, such as C and C++ provide more widely used features and libraries for such things as process and thread support, and GUI features. For this reason, Fortran source code often performs only the computationally intensive functions in an application, leaving the process management and user interaction to C and C++.

Using Fortran in this manner removes most of the platform-specific issues from an ANSI Fortran migration. This means that in most cases, you can port the Fortran code of an application from UNIX to Win32 with minimal changes. The C/C++ code usually requires the majority of the migration effort.

Porting Fortran to Interix

Before rewriting a Fortran application for Win32, you should consider other migration strategies. Porting to Interix represents another possible strategy.

For porting UNIX style source to Interix, the GNU Fortran 77 compiler is provided. Since the level is Fortran 77, applications that need Fortran 90 support, such as Module support, cannot be ported to Interix. Additionally, since POSIX subsystem libraries cannot be mixed with Win32 subsystem libraries, Win32 versions of C and C++ that need Fortran libraries cannot use them from Interix. This leaves stand-alone Fortran 77 applications that interoperate with stdin and stdout as the best candidates for a UNIX style port to Interix.