Control LEDs Using Arduino And Bluetooth

char junk;
String inputString="";

void setup()                    
{
 Serial.begin(9600);            
 pinMode(13, OUTPUT);
pinMode(10,OUTPUT);
pinMode(7,OUTPUT);
}

void loop()
{
  if(Serial.available()){
  while(Serial.available())
    {
      char inChar = (char)Serial.read(); 
      inputString += inChar;       
    }
    Serial.println(inputString);
    while (Serial.available() > 0)  
    {
 junk = Serial.read() ; 
}      
    if(inputString == "a")
{         
      digitalWrite(13, HIGH);  
    }
else if(inputString == "b")
{  
      digitalWrite(10, HIGH);
    }
else if(inputString == "c")
{  
      digitalWrite(7, HIGH);
    }
else if(inputString == "x")
{  
      digitalWrite(10, LOW);
 digitalWrite(13, LOW);
 digitalWrite(7, LOW);
    }
    inputString = "";
  }
}