//BLOCKING

// 1. MAKE PIN HIGH AND LOW
/*
const int led_pin = 9;
#define LED_PIN = 9;

cannot be changed

void setup()
{
  pinMode(led_pin, OUTPUT);
}

void loop()
{
  digitalWrite(led_pin, HIGH);
  delay(1000);
  digitalWrite(led_pin, LOW);
  delay(1000);
}

// 2. USING FOR LOOP

const int led_pin = 9;
const int blink_times = 3;
const int blink_delay = 1000;
int repeats = 0;

void setup()
{
  pinMode(led_pin, OUTPUT);
  blink_led(blink_times, blink_delay);
}

void loop()
{

}

void blink_led(int blink_times, int blink_delay)
{
  for (repeats; repeats < blink_times; repeats++)
  {
    digitalWrite(led_pin, HIGH);
    delay(blink_delay);
    digitalWrite(led_pin, LOW);
    delay(blink_delay);
  }
}

// 2. READ PIN STATE AND WRITE THE OPPOSITE

const int led_pin = 9;
byte led_pin_state = 0;

good practice to initialise a varible with zero

better use byte 
byte can store maximum value of 255 or 8 bits

int can store maximun value of 32000 32 bits or 4 bytes


void setup()
{
  pinMode(led_pin, OUTPUT);
}

void loop() 
{
  digitalWrite(led_pin, !digitalRead(led_pin));
  delay(1000);
}

//NON BLOCKING

// 3. USING DIVISON REMINDER TO SET PIN STATE

const int led_pin = 9;
byte led_pin_state = 0;
int blink_delay = 1000;

//if you plant to change it in the code use a variable 

void setup()
{
  pinMode(led_pin, OUTPUT);
}

void loop()
{
  led_pin_state = (millis() / (blink_delay / 2)) % 2;
  digitalWrite(led_pin, led_pin_state);
  Serial.println(led_pin_state);
}

*/

#define LED 13                  // Defining an LED variable as 13 because our LED is connected to pin 13
unsigned long previousMillis;   // variable for comparing millis counter
bool ledState = false;       // will determine current led state
void setup() {
  pinMode(LED, OUTPUT);         // Set LED pin as OUTPUT
}

void loop() {
  if (millis() - previousMillis >= 1000)  // check that 1000ms is pass
  {
    if (ledState == false) {              // check the leddState and toggle it. 
      ledState = true;
    }
    else {
      ledState = false;
    }
    digitalWrite(LED, ledState);          // Set LED state to ledState 
    previousMillis = millis();            // set previousMillis to current millis
  }
}

const int led_pin = 9;
const int blink_times = 3;
const int blink_delay = 1000;
int repeats = 0;

void setup()
{
  pinMode(led_pin, OUTPUT);
  blink_led(blink_times, blink_delay);
}

void loop()
{

}

void blink_led(int blink_times, int blink_delay)
{
  for (repeats; repeats < blink_times; repeats++)
  {
    digitalWrite(led_pin, HIGH);
    delay(blink_delay);
    digitalWrite(led_pin, LOW);
    delay(blink_delay);
  }
}