void setup ( ) {
  int trigger_pin = 2;
  int echo_pin = 3;
  int buzzer_pin = 10;
  int time = 0 ;
  int distance = 0 ;

  Serial.begin (9600);
  pinMode (2, OUTPUT);
  pinMode (3, INPUT);
  pinMode (10, OUTPUT);
}

void loop ( ) {
  digitalWrite (2, HIGH);
  delayMicroseconds (10);
  digitalWrite (2, LOW);

  int time = pulseIn (3, HIGH);
  int distance = (time * 0.034) / 2;
  if (distance <= 10) {
      Serial.println (" Door Open ");
      Serial.print (" Distance= ");
      Serial.println (distance);
      digitalWrite (10, HIGH);
      delay (500);
    }

  else {
    Serial.println (" Door closed ");
    Serial.print (" Distance= ");
    Serial.println (distance);
    digitalWrite (10, LOW);
    delay (500);
  }
}