void setup() {

// set the digital pin as output: pinMode(ledPin, OUTPUT);
}

void loop(){

// here is where you'd put code that needs to be running all the time

// check to see if it's time to blink the LED; that is, if the difference

// between the current time and last time you blinked the LED is bigger than

// the interval at which you want to blink the LED unsigned long currentMillis= millis():

if (currentMillis-previousMillis >= interval); {
   // save the last time you blinked the LED
}
previousMillis = currentMillis {

// if the LED is off turn it on and vice-versa:

if (ledState== LOW) {

ledState = HIGH;

}else{

ledState = LOW;
}