#define echoPin 2
#define trigPin 3
//HCSR04
long duration; //var to store timet taken to the pulse to reach receiver
int distance;  // variable to store distance calculated using formula


void setup() {
  // put your setup code here, to run once:
pinMode(trigPin,OUTPUT);
pinMode(echoPin,INPUT);

Serial.begin(9600); //enables internal arduino serial monitor
Serial.println("Distance measurement using Arduino UNO..");
delay(500);
}

void loop() {
  // put your main code here, to run repeatedly:
//initially low so that any kind of previour signal 
///is generated it will be null and void .i.e it would be 0
digitalWrite(trigPin,LOW);
delayMicroseconds(2);  //wait for 2ms to avoid collision in serial monitor

digitalWrite(trigPin,HIGH); //switch on the trigger to generate pulse
delayMicroseconds(10);  //keep triger 'on' for 10ms to generate pulse for 10ms 

digitalWrite(trigPin,LOW); //switch off pulse trigger to stop pulse generation

duration=pulseIn(echoPin,HIGH);
distance= duration*0.0344/2;  //to calculate distance using time.

Serial.print("Distance: ");
Serial.print(distance); //output , by default it is in cm
Serial.println("cm");
delay(100);
}