void div(unsigned int a, unsigned int b, unsigned int *q, unsigned int *r)
{
 *q = 0;
 *r = a;

 while (b >= *r) {
   assert( *q * b + *r == a);
   *r -=b;
   *q += 1;
 }
}

? Sinon y'a le code de PedroM.