const int ledPin = 13;   // Pin connected to the LED
const int buttonPin = 2; // Pin connected to the button

void setup() 
{
  pinMode(ledPin, OUTPUT);   // Set the LED pin as an output
  pinMode(buttonPin, INPUT); // Set the button pin as an input
}

void loop() 
{
  while (digitalRead(buttonPin) == HIGH) 
  { // While the button is pressed
    digitalWrite(ledPin, HIGH); // Turn the LED on
    delay(500);                 // Wait for half a second
    digitalWrite(ledPin, LOW);  // Turn the LED off
    delay(500);                 // Wait for half a second
  }
}