arduino pir example Crossroads

byte pirPin = 2;  // define the IO pins
byte ledPin = 13;
void setup(){
  pinMode (pirPin, INPUT); // set them as inputs/outputs
  pinMode (ledPin, OUTPUT);
}
void loop(){
  if (digitalRead (pirPin) == LOW){  // read the input pin
    digitalWrite (ledPin, HIGH);       // and drive the LED on
  }
  else {                                     // pirPin is high, so
    digitalWrite (ledPin, LOW);      // drive the LED off
  }
}