serialDemo.pde

void setup()
{
  Serial.begin(9600); // Use serial with 9600 baud rate
  pinMode(13, OUTPUT);
}

void loop()
{
  
  if(Serial.available()) // Check if there is something for Arduino to read
  {
    char a = Serial.read(); // Read a character

    switch(a)
    {
      case '0':
        digitalWrite(13, LOW);
        break;
        
      case '1':
        digitalWrite(13, HIGH);
        break;
        
      case '2':
        if(digitalRead(13) == HIGH)
        {
          Serial.print('1'); // Write a character to serial port
        }
        else
        {
          Serial.print('0');
        }
        break;
    }
  }
  
}