void setup(){
  //initialize digital pin 9 as an output.
  pinMode(9, OUTPUT);
}
//the loop function runs over and over again forever
void loop(){
  digitalWrite(9, HIGH); //turn the LED on (HIGH is the voltage level)
  delay(500); // wait for a second
  digitalWrite(9, LOW); // turn the LED off by making the
delay(1000); // wait for a second
}