int clockPin = 2;
int latchPin = 3;
int dataPin = 4;
int num;
int byte1;
int byte2_1 = ~0b10000000, byte2_2 = ~0b01000000, byte2_3 = ~0b00100000, byte2_4 = ~0b00010000;
void setup() {
  // put your setup code here, to run once:
  pinMode(clockPin, OUTPUT);
  pinMode(latchPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
}

byte numchecker(int a) {
  if (a == 1) {
    byte1 = ~0b10011111;
  }
  else if (a == 2) {
    byte1 = ~0b00100101;
  }
  else if (a == 3) {
    byte1 = ~0b00001101;
  }
  else if (a == 4) {
    byte1 = ~0b10011001;
  }
  else if (a == 5) {
    byte1 = ~0b01001001;
  }
  else if (a == 6) {
    byte1 = ~0b01000001;
  }
  else if (a == 7) {
    byte1 = ~0b00011111;
  }
  else if (a == 8) {
    byte1 = ~0b00000001;
  }
  else if (a == 9) {
    byte1 = ~0b00001001;
  }
  else if (a == 0) {
    byte1 = ~0b00000011;
  }
}

void byteconv(int num){
  int num1 = 0, num2 = 0, num3 = 0, num4 = 0;
    if (num >= 0 && num < 10){
      num1 = num;
    }
    else if (num >= 10 && num < 100){
      num2 = num/10;
      num1 = num - (num2*10);
    }
    else if (num >= 100 && num < 1000){
      num3 = num/100;
      num2 = (num - (num3*100))/10 ;
      num1 = (num - (num3*100) - (num2*10));
      
    }
    else if (num >= 1000 && num <= 9999){
      num4 = num/1000;
      num3 = (num - (num4*1000))/100 ;
      num2 = (num - (num4*1000) - (num3*100))/10 ;
      num1 = (num - (num4*1000) - (num3*100)-(num2*10)) ;
    }
    else if (num > 9999){
      num1 = num2 = num3 = num4 = 0 ;
    }
    numchecker(num1);
    digitalWrite(latchPin, LOW);
    shiftOut(dataPin, clockPin, LSBFIRST, byte2_1);
    shiftOut(dataPin, clockPin, LSBFIRST, byte1);
    digitalWrite(latchPin, HIGH);

    numchecker(num2);
    digitalWrite(latchPin, LOW);
    shiftOut(dataPin, clockPin, LSBFIRST, byte2_2);
    shiftOut(dataPin, clockPin, LSBFIRST, byte1);
    digitalWrite(latchPin, HIGH);

    numchecker(num3);
    digitalWrite(latchPin, LOW);
    shiftOut(dataPin, clockPin, LSBFIRST, byte2_3);
    shiftOut(dataPin, clockPin, LSBFIRST, byte1);
    digitalWrite(latchPin, HIGH);

    numchecker(num4);
    digitalWrite(latchPin, LOW);
    shiftOut(dataPin, clockPin, LSBFIRST, byte2_4);
    shiftOut(dataPin, clockPin, LSBFIRST, byte1);
    digitalWrite(latchPin, HIGH);
  return 0;
}

void loop() {
  // put your main code here, to run repeatedly:
  num = millis()/100;
  byteconv(num);
}