int tDelay = 100;
int latchPin = 6;      // (11) ST_CP [RCK] on 74HC595
int clockPin = 7;      // (9) SH_CP [SCK] on 74HC595
int dataPin = 3;     // (12) DS [S1] on 74HC595

byte leds = 0;
/*   The most common method of using 74CH595
 *   lctchPin->LOW : Begin transmitting signals.
 *   shiftOut(dataPin, clockPin, bitOrder, value)
 *   dataPin: the pin on which to output each bit. Allowed data types: int.
 *   clockPin: the pin to toggle once the dataPin has been set to the correct value. Allowed data types: int.
 *   bitOrder: which order to shift out the bits; either MSBFIRST or LSBFIRST. (Most Significant Bit First, or, Least Significant Bit First).
 *   value: the data to shift out. Allowed data types: byte. 
 *   lctchPin->HIch : The end of the transmission signal.
*/
void updateShiftRegister()
{
   digitalWrite(latchPin, LOW);
   shiftOut(dataPin, clockPin, LSBFIRST, leds);
   digitalWrite(latchPin, HIGH);
}

void setup() 
{
  pinMode(latchPin, OUTPUT);
  pinMode(dataPin, OUTPUT);  
  pinMode(clockPin, OUTPUT);
}

void loop() 
{
  //Turn off all led
  leds = 0;
  updateShiftRegister();
  delay(tDelay);
  //Create a for loop:i 0 through 7 have gradually increased
  for (int i = 0; i < 8; i++)
  {
    //turn on the led with the i transform
    bitSet(leds, i);
    updateShiftRegister();
    delay(tDelay);
  }
}