4digit7segment2.ino

int digit1 = 2;
int digit2 = 3;
int digit3 = 4;
int digit4 = 5;
int clock = 10;
int latch = 11;
int data = 12;

//initialize the digital pin  as an outout
void setup() {
  pinMode(latch, OUTPUT);
  pinMode(clock, OUTPUT);
  pinMode(data, OUTPUT);

  pinMode(digit1, OUTPUT);
  pinMode(digit2, OUTPUT);
  pinMode(digit3, OUTPUT);
  pinMode(digit4, OUTPUT);
}

void display(int digit, int num)
{
  digitalWrite(digit1, LOW);
  digitalWrite(digit2, LOW);
  digitalWrite(digit3, LOW);
  digitalWrite(digit4, LOW);
  
  digitalWrite(latch, HIGH);
  shiftOut(data, clock, MSBFIRST, num);
  digitalWrite(latch, LOW);

  switch(digit) {
    case 1: digitalWrite(digit1, HIGH); break;
    case 2: digitalWrite(digit2, HIGH); break;
    case 3: digitalWrite(digit3, HIGH); break;
    case 4: digitalWrite(digit4, HIGH); break;
  }

  digitalWrite(latch, HIGH);
  shiftOut(data, clock, MSBFIRST, 0);
  digitalWrite(latch, LOW);
}

void loop() {
  display(1, B01000000);
  
  display(2, B00100000);

  display(3, B00010000);

  display(4, B00001000);
}