Static, define, and const in C

Question

I\'ve read that static variables are used inside function when one doesn\'t want the variable value to change/initialize each time the function is called. But what about def

Answer 1

... change/initialize each time the function is called

You use the words "change" and "initialize" as though they were the same, but they aren't

void f(void) {
  static int a = 0;
  a++; // changed!
  printf("%d\n", a);
}

int main(void) {
  f(); f();
}

/* 
  # 1
  # 2
*/

When at file-scope (outside functions) static does not mean "const" as in "static value", but it means that the identifier can only be referred to in that translation unit.

So your first m without const can still be changed. Only const guards against changes. But if you omit static then if you link in a library or another object file that has the same non-static identifier at file-scope you will get conflicts at link-time.