multiple file scope question

[owi_just]

I am making a program with multiple *.c files and multiple *.h files.
I want to declare a "typedef struct" like this:

typedef struct node{
    char data;
    struct node* next;
)NODE;

Where do I have to declare it in order for it to be recognized throughout the whole program?

Do I have to make it external?
thanks.

[jim mcnamara]

One way is to put it in an include file that is included in every module, with something like this:

#ifndef NODE_DEF
#define NODE_DEF 
 typedef struct node
 {
     char data;
     struct node* next;
 ) NODE;
#endif

[itsme86]

Do I have to make it external?

The extern keyword is used to tell one file that the actual declaration of that variable/struct/whatever is in another file.

For example, if you have a global variable in one .c file declared as int ImAGlobalVariable;, then you could put extern int ImAGlobalVariable; in a header file that you include in other .c files.

[owi_just]

thanx for the replies,
i was playing around with it a little more,
whould it work if i declared the struct in one of the .h files and include it in main.c,
whould all the files recognize it that way?

[itsme86]

It's fine to define a struct in a header file, but you want to declare instances of the struct in .c files. So you might have this:

// file.c

struct somestruct foo;

// file.h
#ifndef FILE_C_
#define FILE_C_

struct somestruct
{
  int a;
  int b;
};

extern struct somestruct foo;
#endif

And then any .c file in which you include file.h can use struct somestruct and will also have access to the foo instance of that struct.

[Aerie]

I'd been meaning to ask this exact question(well, I thought that's how it worked, but I wanted to make sure it was okay).