Arduino UNO blinker

blink.ino

// Arduino UNO
// Programmer: AVRISP mkII


/*
  Blink

  Most Arduinos have an on-board LED you can control. On the UNO, MEGA and ZERO
  it is attached to digital pin 13, on MKR1000 on pin 6. LED_BUILTIN is set to
  the correct LED pin independent of which board is used.
  If you want to know what pin the on-board LED is connected to on your Arduino
  model, check the Technical Specs of your board at:
  https://www.arduino.cc/en/Main/Products
*/
int COUNTER;

void setup() {
  COUNTER = 0;
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(LED_BUILTIN, OUTPUT);

  // when arduino starts, it prints its baud rate (bits per second). then we set its rate here
  Serial.begin(115200);
}

void loop() {
  
  digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(800);                       // wait for a second
  digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW
  delay(400);                       // wait for a second

  COUNTER = COUNTER + 1;
  
  // after baud rate is set we can open port monitor (rightmost button in arduino IDE)
  // and set it's read rate same as arduinos write rate. then we can print in java-like style :)
  Serial.println("hello!");
  Serial.println(COUNTER);
}