#define LED_1 (13)  // Define LED pin 13
int blink = 0;  // Flag blink led

void setup()
{
  // initialize the digital pin as an output.
  // Pin 13 has an LED connected on most Arduino boards:
  pinMode (LED_1, OUTPUT) ;
}
void loop()
{
  blink^=1;
  digitalWrite(LED_1, blink);  //set the LED on
  delay(1000);
/*
digitalWrite(LED_1, HIGH);   //set the LED on
delay(1000);               //wait for a second
digitalwrite(LED_1, LOW);    //set the LED off
delay (1000);              //wait for a second
*/
}