// the LED is attached to this digital output pin
int ledPin = 13;

// the pushbutton is attached to this digital input pin
int buttonPin = 9;

// the value read by the pin.
int buttonValue;

void setup() {
  // set ledPin to OUTPUT
  pinMode(ledPin, OUTPUT);

  // set buttonPin to INPUT and 
  // turn on internal pull up resistor 
  pinMode(buttonPin, INPUT);
  digitalWrite(buttonPin, HIGH);
} 

void loop() {
  // read the pushbutton state
  buttonValue = digitalRead(buttonPin);

  // and set the light to be the same value
  digitalWrite(ledPin, buttonValue);
}