const int PIR_PIN = 8;
const int BUZ_PIN = 7;
const int LED_PIN = 6;
const int BTN_PIN = 2;

int state;

void setup()  {
  Serial.begin(115200); // initializing BAUD RAte 
  pinMode(BTN_PIN, INPUT_PULLUP); // configure as input pin 
  pinMode(PIR_PIN, INPUT_PULLUP); // Some PIR sensors are open-collector
  pinMode(BUZ_PIN, OUTPUT);
  pinMode(LED_PIN, OUTPUT);
  state = 0;
}

void loop() {
  if (state == 0) {
    // Check the PIR sensor
    if (digitalRead(PIR_PIN))  {  // turn everything on
      tone(BUZ_PIN, 440);
      digitalWrite(LED_PIN, HIGH);
      Serial.print("Motion detected!\t");
      Serial.println("Alarm ON");
      state = 1;
    }
  } else  { // here state must be 1...
    // Check the button
    if (!digitalRead(BTN_PIN) )  {  // turn everything off
      noTone(BUZ_PIN);
      digitalWrite(LED_PIN, LOW);
      Serial.print("Alarm cancelled \t");
      Serial.println("Alarm OFF\n");
      state = 0;
    }
  }
}