int ledPin = 13;

void setup() {
  pinMode(ledPin, OUTPUT);
  Serial.begin(9600);
  Serial.println("Type 'ON' or 'OFF' to control the LED.");
}

void loop() {
  if (Serial.available()) {
    String command = Serial.readStringUntil('\n');
    command.trim();

    if (command.equalsIgnoreCase("ON")) {
      digitalWrite(ledPin, HIGH);
      Serial.println("LED Turned ON");
    }
    else if (command.equalsIgnoreCase("OFF")) {
      digitalWrite(ledPin, LOW);
      Serial.println("LED Turned OFF");
    }
    else {
      Serial.println("Unknown Command: " + command);
    }
  }
}