void setup() {
  pinMode(12, OUTPUT);
  pinMode(3, INPUT);
  Serial.begin(9600);
}

void loop() {
 int x = digitalRead(3);
 if (x==0)
 {
  digitalWrite(12, HIGH);
  Serial.println("Switch ON , LED ON");
 }
else
{
  digitalWrite(12, LOW);
  Serial.println("SWITCH OFF , LED OFF");
}
}