void sort_words(char *w[], int n)   /* n elements are to be sorted */
{
   int    i, j;

   for (i = 0; i < n; ++i)
      for (j = i + 1; j < n; ++j)
	 if (strcmp(w[i], w[j]) > 0)
	    swap(&w[i], &w[j]);
}