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int pin1 = 13; //the LED is on pin number 13


void setup() {
 

  pinMode(pin1, OUTPUT); //to say if the pin 13 is going to be input or output, output because its going to produce an effect

  Serial.begin(9600); //the quantity of data sent between the board and the computer
} // end setup()




float time_clock; // the actual time of the microcontroller in seconds

float time_p = 0.0;//the initial time 

int pin_state = LOW; //if the pin has power in it or not; 0V(doesnt power the LED) or 5V(power the LED)


void loop() 
{

 while(1){  //question 1 : why do we need a while loop when the loop() function is a loop itself ?

    float dt = time_clock - time_p; // the difference in time between the actual time and the initial time.
    time_clock = micros()*1.0e-6;

  

  if(dt > 0.5) // question 2 : why the change doesnt happen at exactly 0.5 seconds so at dt == 0.5 ?
  { 

    if(pin_state == LOW) // if the pin isnt powered (5v), power it
    { 

        pin_state = HIGH;  
        digitalWrite(pin1, HIGH); // set to 5V TO to turn the LED on
        
    } //end if #2
     
   else // if the pin is powered, stop current (0v)
   {

    pin_state = LOW;
    digitalWrite(pin1, LOW); // set to 5V TO to turn the LED on

   } //end else

     Serial.print("\ntime =");
     Serial.print(time_clock);


    time_p = time_clock; // question 3 : time_p is the initial time and time_clock is the actual time, if they're equal  then dt = 0, so dt isnt superior than 0.5, i don't understand.

    break;
    
  }//end if #1


  
 } //end while

 //digitalWrite(pin1, HIGH); // set to 5V TO to turn the LED on
 



} //end void loop()