//Turn on LED when button is pressed and keep it on after release
//If LED is on and button is pressed turn it off

#define LED 9 //the pin for the LED
#define BUTTON 7 //the input pin where the push button is connected

int val = 0;  //integer variable "val" used to store the state of the input (button) pin

int old_val = 0;  //integer variable "old_val" used to store previous value of "val"

int state = 0;  //0 = LED off and 1 = LED on

void setup() {
  pinMode(LED, OUTPUT); //tell Arduino LED is an output - the "load" of the circuit
  pinMode(BUTTON, INPUT); //tell Arduino BUTTON is the input
}

void loop() {
  val = digitalRead(BUTTON); //read input value and store it
  
  //check whether the input is HIGH (button pressed)
  if ((val == HIGH) && (old_val == LOW)) {
    state = 1 - state;
    delay(10);
  }
  
  old_val = val; //val is now old, store it
  
  if (state == 1) {
    digitalWrite(LED, HIGH); //turn LED on
  } else {
    digitalWrite(LED, LOW); //otherwise turn LED off
  }
}