void setup() {
  // initialize digital pin 3 as an output.
  // Output means that you can turn pin 3 High or LOW.
  pinMode(3, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(3, HIGH); // turn the LED on (HIGH is the voltage level)
  delay(1000);                       // wait for a second
  digitalWrite(3, LOW);  // turn the LED off by making the voltage LOW
  delay(1000);                       // wait for a second
}