Arduino hello world.

// This is where we name stuff
const int LED_PIN = LED_BUILTIN; // Uses the onboard LED (Pin 13 on most boards)

// This is where we init stuff
void setup() {
  pinMode(LED_PIN, OUTPUT);      // Initialize the onboard LED pin as an output
}

// This happens repeatadly
void loop() {
  digitalWrite(LED_PIN, HIGH);   // Turn the onboard LED ON
  delay(1000);                   // Wait for 1 second (1000 milliseconds)
  
  digitalWrite(LED_PIN, LOW);    // Turn the onboard LED OFF
  delay(1000);                   // Wait for 1 second
}