#include <stdio.h>

void order_chars(char *c1, char *c2, char *c3);
void swap(char *p, char *q);

int main(void) {

  char c1 = 'c', c2 = 'b', c3 = 'd';

  printf("%c, %c, %c\n", c1, c2, c3);
  order_chars(&c1, &c2, &c3);
  printf("%c, %c, %c\n", c1, c2, c3);
  
  return 0;
}

void order_chars(char *c1, char *c2, char *c3){
  if (*c3 < *c2) swap(c2,c3);
  if (*c2 < *c1) swap(c1,c2);  
  if (*c3 < *c2) swap(c2,c3);  
}

void swap(char *p, char *q){
   int   tmp;

   tmp = *p;
   *p = *q;
   *q = tmp;
}