Alarm system

int trigPin = 9;//first we should the pins
int echoPin = 10;
int buzzer  = 7;
void setup() {
  Serial.begin (9600);//to print on serial moniter we should start the serial baud
  pinMode(trigPin, OUTPUT);//we should declare trigpin as output and echo pin as input
  pinMode(echoPin, INPUT);
  pinMode(buzzer, OUTPUT);
}

void loop() {
  //block of code used to find the distance of an object in cm 
  long duration, distance;
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  distance = (duration / 2) / 29.1;
  
  if (distance <= 10)// if the distance is less than 10 or = 10 
                    //than the buzzer will make sound
  {
    digitalWrite(buzzer,HIGH);
    Serial.print(distance);//to print the distance in serial moniter
    Serial.println("");
  }
  else {
   digitalWrite(buzzer,LOW);//else it will turn off
   Serial.print(distance);//to print the distance in serial moniter
   Serial.println("");
  }
  delay(10);
}