Arduino Bluetooth Controlled 4WD Car

1char t;
2 
3void setup() {
4pinMode(13,OUTPUT);   //left motors  forward
5pinMode(12,OUTPUT);   //left motors reverse
6pinMode(11,OUTPUT);   //right  motors forward
7pinMode(10,OUTPUT);   //right motors reverse
8pinMode(9,OUTPUT);   //Led
9Serial.begin(9600);
10 
11}
12 
13void loop() {
14if(Serial.available()){
15  t = Serial.read();
16  Serial.println(t);
17}
18 
19if(t == 'F'){            //move  forward(all motors rotate in forward direction)
20  digitalWrite(13,HIGH);
21  digitalWrite(11,HIGH);
22}
23 
24else if(t == 'B'){      //move reverse (all  motors rotate in reverse direction)
25  digitalWrite(12,HIGH);
26  digitalWrite(10,HIGH);
27}
28  
29else if(t == 'L'){      //turn right (left side motors rotate in forward direction,  right side motors doesn't rotate)
30  digitalWrite(11,HIGH);
31}
32 
33else  if(t == 'R'){      //turn left (right side motors rotate in forward direction, left  side motors doesn't rotate)
34  digitalWrite(13,HIGH);
35}
36
37else if(t ==  'W'){    //turn led on or off)
38  digitalWrite(9,HIGH);
39}
40else if(t == 'w'){
41  digitalWrite(9,LOW);
42}
43 
44else if(t == 'S'){      //STOP (all motors stop)
45  digitalWrite(13,LOW);
46  digitalWrite(12,LOW);
47  digitalWrite(11,LOW);
48  digitalWrite(10,LOW);
49}
50delay(100);
51}