First, though there can be many "declarations" (and in many translation units) of a single "global" (strictly speaking, "external") variable or function, there must be exactly one "definition".
(The definition is the declaration that actually allocates space, and provides an initialization value, if any.)
The best arrangement is to place each definition in some relevant .c file, with an external declaration in a header (".h") file, which is #included wherever the declaration is needed.
The .c file containing the definition should also #include the same header file, so that the compiler can check that the definition matches the declarations.

Only registered users can write comments.
Please login or register.