// int trig=8;
// int echo=7;
#define trig 8  //this is not a variable but similer to constunt variable
#define echo 7
void setup() {
  pinMode(trig, OUTPUT);
  pinMode(echo, INPUT);
  Serial.begin(9600);

}

void loop() {
  //Triggering
  digitalWrite(trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(trig, LOW);

  //echo
   unsigned long t=pulseIn(echo, HIGH); //duration in micro seconds
   //distance calculator
   float d = 340*(t/1000000.0)/2.0;
   Serial.println(d);
   delay(100);

}