15 - External LED

int led = 13;
int led2 = 12;

// the setup routine runs once when you press reset:
void setup() {                
  // initialize the digital pin as an output.
  pinMode(led, OUTPUT); 
  pinMode(led2, OUTPUT);   
}

// the loop routine runs over and over again forever:
void loop() {
  digitalWrite(led, HIGH);   // turn the LED on (HIGH is the voltage level)
  digitalWrite(led2, HIGH);   
  delay(500);               // wait for a second
  digitalWrite(led, LOW);    // turn the LED off by making the voltage LOW
  digitalWrite(led2, LOW);    
  delay(500);               // wait for a second
}