// the onboard LED is attached to pin 13
int ledPin = 13;

/*
    When the Arduino board is reset, this method is 
    run exactly once.  Its job is to put the board into
    the proper configuration.
*/
void setup() {
  // configure ledPin to be a digital output
  pinMode(ledPin, OUTPUT);
}

/*
    An Arduino program is generally not meant to stop.
    It is supposed to keep interacting with its environment.
    The loop method is run over and over until the power
    is removed from the board, or the board is reset.
*/
void loop() {
  // set the pin to output a HIGH value and turn the LED on
  digitalWrite(ledPin, HIGH);

  // wait for 1000 milliseconds
  delay(1000);

  // set the pin to output a LOW value and turn the LED off
  digitalWrite(ledPin, LOW);

  // wait for 1000 milliseconds
  delay(1000);
}