global variables in C

Your wording is extremely confusing.
Example:

A.c
int my_int = 10;

B.c
extern int my_int; /* Accesses my_int from A.c */
/* ... */
my_int = 20; /* Now my_int from A.c == 20 */

C.c
static int my_int = 20;

D.c
extern int my_int;
my_int = 30; /* Linking error: undefined symbol: myint. */

Quote:

---

Originally Posted by -EquinoX-

I see so static are only used inside the file and global can be used in other file using the extern files? is that the difference?

---

Pretty much. Static variables may undergo heavier optimization than non-static ones, as well.

yes that clears everything up.. thanks all