int main() {
  int a[2] = {  0 }; //all elements 0
  printf("%i\n", a[0]);
  printf("%i\n", a[1]);
  int b[2] = { -1 }; //all elements -1!!!!
  printf("%i\n", b[0]);
  printf("%i\n", b[1]);
  return 0;
}

0
0
-1
0