const int PinLed = 8;     // define constant PinLed
bool      pinOn  = false; // define true/false boolean variable
                          // and initialize to false

void setup() {
  Serial.begin(115200);         // set serial interface speed
  pinMode (PinLed, OUTPUT);     // configure pin
}

void loop() {
  if (pinOn)  { // execute code w/in braces if pinOn is true
    digitalWrite (PinLed, LOW);   // turn off
    pinOn = false;
  }
  else {        // otherwise execute this block of code
    digitalWrite (PinLed, HIGH);   // turn on
    pinOn = true;
  }
  delay (500);                    // delay half second
}