ButtonGemma.ino

int buttonPin = 2;      // The number of the input pin for the button
int ledPin =  1;        // The number of the output pin for the LED

int buttonState = 0;    // variable for reading the pushbutton status

void setup() {
  // Tell the Gemma that the LED pin is an output
  pinMode(ledPin, OUTPUT);
  // Tell the Gemma that the pushbutton pin Is an input
  pinMode(buttonPin, INPUT);
}

void loop() {
  // Read the state of the pushbutton value.
  // digitalRead() returns one of two values.
  // If the button is pushed the reading will be HIGH (5V)
  // If the button is released the reading wll be LOW (0V)
  buttonState = digitalRead(buttonPin);
  
  // If the pushbutton is pressed...
  if (buttonState == HIGH) {
    // ...turn the LED on.
    digitalWrite(ledPin, HIGH);
  }
  else {
    // ...turn the LED off.
    digitalWrite(ledPin, LOW);
  }
}