This sketch uses an ultrasonic distance sensor to calculate the distance between the sensor and an object in front of it

distance.ino

#define trigPin 13
#define echoPin 12
void setup() {
	Serial.begin (9600);
	pinMode(trigPin, OUTPUT);
	pinMode(echoPin, INPUT);
}
void loop() {
	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 >= 200 || distance <= 0)
		{
			Serial.println("Out of range”);
		}
	else {
			Serial.print(distance);
			Serial.println(" cm");
		}	
	delay(500);
}