*** QUESTIONS ***
Forward declaration

1)
    defining the struct in the header file, as opposed to declaring it, prevents the end user from knowing
    the exact implementation of the struct and using it independently.
    by doing so, it allows for each including C file to have it's own implementation of the struct. thus
    not harming any existing code. this could, and should be resloved with #ifndf though. it's not really a
     disadvantage but rather a limitation that needs to be thought about.

2)  if a C file is including a header with a struct forward declaration, then they would have to actually
    implement the struct definition. the preprocessor simply puts the forward declaration at the top of the
     C file, where forward declarations usually come anyway. then the C file is compiled as usual, having
     the declared methods/structs already implemented, or not used.
     trying to create a declared struct without defining it would work, unless that struct is accessed.