int latchPin = 5;  // Latch pin of 74HC595 is connected to Digital pin 5
int clockPin = 6;  // Clock pin of 74HC595 is connected to Digital pin 6
int dataPin = 4;   // Data pin of 74HC595 is connected to Digital pin 4

byte leds = 0;  // Variable to hold the pattern of which LEDs are currently turned on or off

void setup() {
  // Set all the pins of 74HC595 as OUTPUT
  pinMode(latchPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
  pinMode(clockPin, OUTPUT);

  Serial.begin(9600);
  while (!Serial)
    ;

  leds = 0;  // Initially turns all the LEDs off, by giving the variable 'leds' the value 0
  updateShiftRegister();
  delay(1000);
}

void loop() {

	// τα led ανάβουν διαδοχικά

        for (int i = 7; i >= 0; i--)  // Turn all the LEDs ON one by one.
        {
          bitSet(leds, i);  // Set the bit that controls that LED in the variable 'leds'
          updateShiftRegister();
          delay(100);
        }

        delay(1000);
    
    // τα led σβήνουν διαδοχικά

        for (int i = 0; i < 8; i++)  // Turn all the LEDs ON one by one.
        {
          bitClear(leds, i);  // Set the bit that controls that LED in the variable 'leds'
          updateShiftRegister();
          delay(100);
        }

        delay(1000);
}


void updateShiftRegister() {
  digitalWrite(latchPin, LOW);
  shiftOut(dataPin, clockPin, LSBFIRST, leds);
  digitalWrite(latchPin, HIGH);
}