Controlling a LED with a button

1/***********************************************************
2File name:  _02_ButtonAndLed.ino
3Description: When you press the button, you can see the  state
4              of the LED will be toggled. (ON->OFFOFF->ON).
5Website:  www.quadstore.in
6***********************************************************/
7
8int  ledpin=11;            //definition digital 11 pins as pin to control the LED
9int  btnpin=2;             //Set the digital 2 to button interface 
10
11volatile int  state = LOW; // Defined output status LED Interface
12
13void setup()
14{
15  pinMode(ledpin,OUTPUT);//Set digital 11 port mode, the OUTPUT for the output
16  pinMode(btnpin,INPUT); //Set digital 2 port mode, the INPUT for the input
17}
18
19void  loop()
20{
21  if(digitalRead(btnpin)==LOW)          //Detection button interface  to low
22  {   
23      delay(10);                        //Delay 10ms for the  elimination of key leading-edge jitter
24      if(digitalRead(btnpin)==LOW)      //Confirm  button is pressed
25      {     
26        while(digitalRead(btnpin)==LOW);//Wait  for key interfaces to high
27        delay(10);                      //delay 10ms  for the elimination of key trailing-edge jitter
28        while(digitalRead(btnpin)==LOW);//Confirm  button release
29        state = !state;                 //Negate operation, each  time you run the program here, state the HGIH becomes LOW, or the state becomes  the LOW HGIH.
30        digitalWrite(ledpin,state);     //Output control status  LED, ON or OFF 
31      }
32   }
33}
34