void setup()
{
  Serial.begin(9600);
  pinMode(13, OUTPUT);
  pinMode(A0, INPUT_PULLUP);
  DDRD |= 0b00111100; //pin 5-4-3-2
}
void loop()
{
  //if (digitalRead(A0) == 0)
    if (digitalRead(A0) > 0)//no switch
  {
    for (int z = 0; z < 16; z++)
    {
      PORTD = z << 2;
      delay(750);
    }
    digitalWrite(13, 1);
    Serial.println("Hello Computer");
  }
}