Bluetooth Robo UNO Atmega328 Development Board

int ENA=9; //Connect on Pin 9
int IN1=4; //Connect on Pin 4
int IN2=5; //Connect on Pin 5
int ENB=10; //Connect on Pin 10
int IN3=6; //Connect on Pin 6
int IN4=7; //Connect on Pin 7

char old;

void setup() {
Serial.begin(9600);
while (!Serial) {
; // wait for serial port to connect. Needed for Leonardo only
}

pinMode(ENA,OUTPUT);
pinMode(ENB,OUTPUT);
pinMode(IN1,OUTPUT);
pinMode(IN2,OUTPUT);
pinMode(IN3,OUTPUT);
pinMode(IN4,OUTPUT);
digitalWrite(ENA,HIGH);// Activate motor A
digitalWrite(ENB,HIGH);// Activatemotor B
Stop();
delay(500);
}
void loop(){
if (Serial.available())
{
char rec=Serial.read();
//A Serial.write(rec);
if(old!=rec)
{
if(rec=='F')
Forword();
else if(rec=='B')
Back();
else if(rec=='R')
Right();
else if(rec=='L')
Left();
else if(rec=='S')
Stop();
old=rec;
}

}
}
void Left()
{
Stop();
delay(500);
digitalWrite(IN1,LOW);
digitalWrite(IN2,HIGH);
digitalWrite(IN3,LOW);
digitalWrite(IN4,HIGH);
}

void Right()
{
Stop();
delay(500);
digitalWrite(IN1,HIGH);
digitalWrite(IN2,LOW);
digitalWrite(IN3,HIGH);
digitalWrite(IN4,LOW);
}

void Forword()
{
Stop();
delay(500);
digitalWrite(IN1,LOW);
digitalWrite(IN2,HIGH);
digitalWrite(IN3,HIGH);
digitalWrite(IN4,LOW);
}
void Back()
{
Stop();
delay(500);
digitalWrite(IN1,HIGH);
digitalWrite(IN2,LOW);
digitalWrite(IN3,LOW);
digitalWrite(IN4,HIGH);
}
void Stop()
{
digitalWrite(IN1,LOW);
digitalWrite(IN2,LOW);
digitalWrite(IN3,LOW);
digitalWrite(IN4,LOW);
}