//print Hello world and blink LED 

//Define global variables 
int LED = 2;

// Define pin mode
void setup() {
  Serial.begin(9600); // initialize Serial
  Serial.println("Hello world"); // print "Hello world"
  pinMode(LED, OUTPUT);
}

// Main program
void loop() {
  digitalWrite(LED, HIGH);
  delay(500);
  digitalWrite(LED, LOW);
  delay(500);
}