Toggle Button

/* Arduino Toggle Button Code */
bool ledState = LOW;        // store state of LED.
int currentButtonState = LOW;           // track when button has changed states
int previousButtonState = LOW;

void setup() {
  pinMode(13, OUTPUT);      // built-in LED
  pinMode(12, INPUT);      // button
  digitalWrite(12, HIGH);   // turn on internal pull-up
}

void loop() {
  digitalWrite(13, ledState);     // keep LED on pin 13 in sync

  currentButtonState = digitalRead(12);    // get current state of button
  if ((previousButtonState==HIGH) && (currentButtonState == LOW)) {  // has the button changed?
    delay(100);  // let the button de-bounce
    ledState = !ledState;       // changes value of ledState from HIGH to LOW or LOW to HIGH.
  }

  if ((previousButtonState==LOW) && (currentButtonState == HIGH))
     delay(100); // de-bounce again

  previousButtonState = currentButtonState;
}