How to include a module from a different file in Fortran 95?

Question

The question is obvious I think, although I googled it, I could not find any solutions. I want to split my source code to keep it more maintainable. How can I reference a module in another file?

Answer 1

I think that you are looking for the use statement. You might, for example, have one source file containing the definition of a module, outline:

module abstract_types
    implicit none
    ! declarations
  contains
    ! procedure definitions
end module abstract_types 

and then, in another source file, a program which uses the module, outline:

program hello_there
    use abstract_types
    implicit none
    ! declarations
    ! executable statements
end program hello_there

Note:

• Any use statements precede the implicit statement.

• The use statement refers to the module by name.

When it comes to compilation, make sure that you compile the module source file before the program source file; at compilation time (not at link time) the compiler will look for a module file (often called a mod file) to satisfy the reference to the module in the use statement. The mod file is a bit like a header file, but it's created by the compiler.

Later, when you link your program you'll need the object files for both module and program.