const int proximity=5;    //pin5 of port P1 connected to IR sensor

int value=0;  

void setup() {  

  Serial.begin(9600);               

  pinMode(proximity, INPUT); //declared as input

  delay(100);

}

void loop() {

  value=digitalRead(proximity); // storing sensor data in a variable.

  delay(1000);

  if(!value)                    //check for an obstacle if present.

  {

    Serial.println("obstacle detected.."); //display this message when obstacle detects

  }

}