Arduino Uno - Makes a single LED blink for 1 second

A001-LED-Blink.ino

void setup() {
  pinMode(13, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
  delay(500);                       
  blink();
  delay(500);
  blink();
}

void blink() {
  digitalWrite(LED_BUILTIN, HIGH);   
  delay(1000);                       
  digitalWrite(LED_BUILTIN, LOW);    
  delay(1000);                      
}