boolean running = false;
int LedPin = 13;
int switchPin = 5;

void setup() {
  // put your setup code here, to run once:
pinMode(LedPin, OUTPUT);
pinMode(switchPin, INPUT_PULLUP);
digitalWrite(switchPin, HIGH);
}

void loop() {
  // put your main code here, to run repeatedly:
if (digitalRead(switchPin)==LOW){
  delay(100);
  running = !running;
  digitalWrite(LedPin, running);
  }
}