lab4.ino

const int latchpin = 8;
const int clockpin = 12;
const int datapin = 11;

const int bits[10] = {0x3f, 0x06, 0x5b, 0x4f, 0x66, 0x6d, 0x7d, 0x07, 0x7f, 0x67};

int curVal = 99;

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

void loop() {
  sendNumber(curVal);
  
  delay(500);
  if (curVal == 0) {
    curVal = 99;
  } else {
    curVal--;
  }
}

void sendNumber(int twodig) {
  digitalWrite(latchpin, LOW);
  sendDigit(twodig % 10);
  sendDigit(twodig / 10);
  digitalWrite(latchpin, HIGH);
}

void sendDigit(int digit) {
  shiftOut(datapin, clockpin, MSBFIRST,  bits[digit]);
}