十進位(Decimal) 轉成 八進位(Octal)

int main()
{
  int r, num10, num8, multi;
  r=num8=0;
  multi=1;   /* for counting power(10,i) */

  printf ("input decimal: ");
  scanf ("%d", &num10);

  while (num10 > 0)
  {
    r = num10 % 8;
    num8 = num8 + (multi * r);
    multi = multi * 10;
    num10 = num10/8;
  }

 return 0;
}