#define LED   13


void setup() {

pinMode(LED, OUTPUT);

}

void  BlinkLED(int pin, int *whichState)
             
{
            
digitalWrite(pin, *whichState);   // turn the LED on (HIGH is the voltage level)
             
delay(1000);                      // wait for a second
             
 *whichState = !(*whichState);     // Change state

}

void loop() {

static int state = HIGH;
BlinkLED(LED,&state);

}