const int switchPin = 8;
const int ledPin = 13;
int switchState = 0;      
int previousSwitchState = 0;
void setup() {
pinMode(ledPin, OUTPUT);
pinMode(switchPin, INPUT);
}
void loop() {
  switchState = digitalRead(switchPin);
  if (switchState != previousSwitchState) {
    if (switchState == HIGH) {
      digitalWrite(ledPin, HIGH);
    } else {
      digitalWrite(ledPin, LOW);
    }
    previousSwitchState = switchState;
  }
}