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?
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.