Making a function static hides it from other translation units, which helps provide encapsulation.
helper_file.c
int f1(int); /* prototype */
static int f2(int); /* prototype */
int f1(int foo) {
return f2(foo); /* ok, f2 is in the same translation unit */
/* (basically same .c file) as f1 */
}
int f2(int foo) {
return 42 + foo;
}
main.c:
int f1(int); /* prototype */
int f2(int); /* prototype */
int main(void) {
f1(10); /* ok, f1 is visible to the linker */
f2(12); /* nope, f2 is not visible to the linker */
return 0;
}