#include <EEPROM.h> // include to use EEPROM
int BPin = 5; // button Pin is declared
int LED = 11; // LED Pin is declared

int ledState;         // the current state of the LED
int presentBState;    // button's present state
int oldBState = HIGH;  // button's old state

/* time and debounce is assigned to unsigned long datatype to avoid 
overflow as millis () can increase rapidly*/
unsigned long time = 0; 
unsigned long debounce = 50;    
void setup() {
  pinMode(BPin, INPUT); // declare button Pin as input
  pinMode(LED, OUTPUT); // declare LED Pin as output

  // Initial LED state is set
  digitalWrite(LED, ledState);
}

void loop() {
  // read the state of the button
  int State = digitalRead(BPin); 

  // If the button is pressed, reset the debouncing timer
  if (State != oldBState) { 
    time = millis();
  }
  if ((millis() - time) > debounce) {

    // the following codes is to toggle LED by pressing button.
    if (State != presentBState) {
      if(ledState == HIGH){
      ledState = LOW; } 
      else {
      ledState = HIGH; }
    }
  
  digitalWrite(LED, ledState);
  // store present state of LED
  EEPROM.write(0, ledState);}

  // the old state value of the button is updated
  oldBState = State;
}