Advantages of Modules

One way to reduce potential confusion when you use the same source code in several projects is to organize the routines into modules. There are two main uses for modules in Visual Fortran:

• Internal encapsulation – A single complex program can be made up of many modules. Each module can be a self-contained entity, incorporating all the procedures and data required for one of your program's tasks. When a task is encapsulated, it is easy to share the code between two different projects.

  In this case, all the modules should be included in the main project directory. If many projects all share the same module, the module should reside in only one directory. All projects that use it should specify the /I compiler option to indicate the location of the module.

• External modules – If you use a module provided from an outside source, you need only the .MOD file at compile time, and the .OBJ file at link time. Use the /[no]include[path] (or /Ipath) command line option (or the INCLUDE environment variable) to specify the location of these files, which will probably not be the same as your project directory.

During the building of a project, the compiler scans the project files for dependencies. If you specify the /[no]include[path] (or /Ipath) command line option or the INCLUDE environment variable, the compiler is able to find the external modules.

Store precompiled module files, with the extension .MOD, in a directory included in the path. When the compiler sees the USE statement in a program, it finds the module based on the name given in the USE statement, so there is no need to maintain several copies of the same source or object code.

Modules are excellent ways to organize programs. You can set up separate modules for:

• Commonly used routines
• Data definitions specific to certain operating systems
• System-dependent language extensions