int datapin = 2; 
int clockpin = 3;
int latchpin = 4;

byte data = 0;


void setup()
{
  pinMode(datapin, OUTPUT);
  pinMode(clockpin, OUTPUT);  
  pinMode(latchpin, OUTPUT);
}


void loop()
{

  // allAtOnce();

  oneOnAtATime();

  // binaryCount();
}


void shiftWrite(int desiredPin, boolean desiredState){
  bitWrite(data,desiredPin,desiredState);

  shiftOut(datapin, clockpin, MSBFIRST, data);

  digitalWrite(latchpin, HIGH); 
  digitalWrite(latchpin, LOW); 
}


void allAtOnce()
{
  int index;

  for(index = 0; index <= 7; index++)
  {
    shiftWrite(index, HIGH);
  }

  delay(1000);

  for(index = 7; index >= 0; index--)
  {
    shiftWrite(index, LOW);
  }

  delay(1000);
}


void oneOnAtATime()
{
  int index;
  int delayTime = 500;

  for(index = 0; index <= 7; index++)
  {
    shiftWrite(index, HIGH);
    delay(delayTime);
    shiftWrite(index, LOW);
  }
}

void binaryCount()
{
  int delayTime = 100;

  shiftOut(datapin, clockpin, MSBFIRST, data);

  digitalWrite(latchpin, HIGH);
  digitalWrite(latchpin, LOW);

  data++;

  delay(delayTime);
}