为什么printf（）不会给scanf（）带来任何错误和问题

Code:

int main(int argc,char **argv)
{
  int y,i;
  printf("Number of character you entered is : %d",printf("you entered age : %d\n",i,scanf("%d",&i),printf("Enter age : "))-19);
  printf("\n\n");
  scanf("%d ",&y,printf("Enter number(y) : "));
  printf("Value of y is %d",y);
}
int main(int argc,char **argv)
{
  int