#define LED 11
char ch;
void setup()
{
Serial.begin(9600);
pinMode(LED, OUTPUT);
Serial.println("press o or c");
}

void loop()
{
    if(Serial.available())
    {
      ch = Serial.available();
if (ch == 'o')
digitalWrite(LED, 1);
if(ch== 'c');
digitalWrite(LED, 0);
    }
  }