void setup()
{
  //put your setup code here , to run once:
  Serial.begin(115200);
  pinMode(18, INPUT);
}

void loop()
{
int aa=digitalRead(18);
if(aa==1)
{
Serial.println("switch ON...");

}

if(aa==0)
{
  Serial.println("switch OFf...");

}

delay(10);//this speed up the simulation

}