int ledPin[] = {7,8,9,10};

void setup()
{
  for (int i =0;i<4;i++)
  {
    pinMode(ledPin[i], OUTPUT);
  }
}

void loop()
{
  for (byte counter =0;counter<=15; counter++)
  {
    display(counter);
    delay(300);
  }
}

void display(byte num)
{
  for (int i =0;i<4;i++)
  {
    if (bitRead(num, i)==1)
    {
      digitalWrite(ledPin[i], HIGH);
    }
    else
    {
      digitalWrite(ledPin[i], LOW);
    }
  }

}