#define vs const declaration in global scope

#define NAME VAL

When compiled, the compiler will simply just replace all instances of NAME throughout the program. It has no type, and does not take up any memory (RAM). (preprocessor)

const type name = val;

int main(void)
{
    ... /* some code executed */
    
    /* and you can access the variable with */
    extern name ... /* some action to the external value */
}

In this version, name is a variable, and takes up memory, has a type, and could be manipulatable (by removing the const). The Handling Multiple Files could be omitted in this situation (same file), but it is still advisable to add it (because if you have multiple files, you’d need the extern).

#C