Smartplug with Arduino UNO and HC-05 Bluetooth module

1int relay = 12;//variable for assigning the relay module
2int state  = 0;//variable for assigning the value communicated by bluetooth module
3int flag  = 0; //variable for assigning flag to for a desirable operation
4void setup()
5{
6  pinMode(relay, OUTPUT);//setting relay as output
7  digitalWrite(relay, LOW);//  initializing the output as off
8  Serial.begin(9600); // default connection rate  for the BT module
9}
10void loop()
11{
12  if (Serial.available() > 0) //checking  if connection available with bluetooth module
13  {
14    state = Serial.read();//assigning  the value communicated by bluetooth module
15    flag = 0;//initial value set for  flag
16  } 
17  if (state == '0') // LOW value communicated by bluetooth module
18  {
19    digitalWrite(relay , LOW);//relay is switched OFF
20    if (flag ==  0) //initial flag
21    {
22      Serial.println("POWER: Off");//display on  the smartphone app
23      flag = 1;//flag toggled
24    }
25  } 
26  else if  (state == '1') //HIGH value communicated by bluetooth module
27  {
28    digitalWrite(relay,  HIGH);// relay is turned ON
29    if (flag == 0)//initial flag
30    {
31      Serial.println("POWER:  On");//display on the smartphone app
32      flag = 1;//flag toggled
33    }
34  }
35}