#include <iostream>

class DivisionByZero {};

float dezimal(int zaehler, int nenner)
{
  if (nenner == 0) throw DivisionByZero();
  return float(zaehler) / nenner;
}

int main()
{
  char const* const prompt = "Eingabe Zaehler Nenner: ";
  int z, n;   

  while (std::cout << prompt && cin >> z >> n)
  {
    try
    {
      float bruch = dezimal(z, n);
      std::cout << "Dezimalbruch = " << bruch << '\n';
    }
    catch(DivisionByZero& error)
    {
      std::cerr << "Nenner darf nicht Null sein!" << '\n';          
    }
  }           
}