// Globale Variablen
byte zaehler = 0;
byte bitwert;

void setup() {

  pinMode(8,  OUTPUT);
  pinMode(9,  OUTPUT);
  pinMode(10, OUTPUT);
  pinMode(11, OUTPUT);
}

void loop() {
  
  for (byte n = 0; n <= 3; n++) 
  {
    bitwert = (zaehler & (1<<n));

    if (bitwert == (1<<n))
      digitalWrite(n+8, HIGH);
    else
      digitalWrite(n+8, LOW);
  }

  delay(1000);
  
  if (zaehler >= 15)
    zaehler = 0;
  else
    zaehler++;

}