Blink pin 13 (LED) at Arduino

Blink.ino

/*
Blink
Turns on an LED on for one second, then off for one second, repeatedly.
This example code is in the public domain.
*/
// Pin 13 has an LED connected on most Arduino boards.
// give it a name:

int led = 13;

// the setup routine runs once when you press reset:
void setup() {
	// initialize the digital pin as an output.
	pinMode(led, OUTPUT);
}

// the loop routine runs over and over again forever:
void loop() {
	digitalWrite(led, HIGH); // turn the LED on (HIGH is the voltage level)
	delay(1000); // wait for a second
	digitalWrite(led, LOW); // turn the LED off by making the voltage LOW
	delay(1000); // wait for a second
}