const uint8_t segmentCodes[] = {
  0x3F, 0x06, 0x5B, 0x4F, 0x66, 0x6D, 0x7D, 0x07, 0x7F, 0x6F
};

const int segmentPins[] = {2, 3, 4, 5, 6, 7, 8};

void setup() {
  for (int i = 0; i < 7; i++) {
    pinMode(segmentPins[i], OUTPUT);
  }
}

void displayDigit(int digit) {
  if (digit < 0 || digit > 9) return;

  uint8_t segments = segmentCodes[digit];

  for (int i = 0; i < 7; i++) {
    digitalWrite(segmentPins[i], (segments >> i) & 0x01);
  }
}

void loop() {
  for (int i = 0; i <= 9; i++) {
    displayDigit(i);
    delay(1000);
  }
}