// outputs to driver for tube A
void displayA() {
  digitalWrite(oneA, bitRead(tubeA, 0) ? HIGH : LOW);
  digitalWrite(twoA, bitRead(tubeA, 1) ? HIGH : LOW);
}

// outputs to driver for tube B
void displayB() {
  digitalWrite(oneB, bitRead(tubeB, 0) ? HIGH : LOW);
  digitalWrite(twoB, bitRead(tubeB, 1) ? HIGH : LOW);
  digitalWrite(fourB, bitRead(tubeB, 2) ? HIGH : LOW);
  digitalWrite(eightB, bitRead(tubeB, 3) ? HIGH : LOW);
}

// output to C
void displayC(){
  digitalWrite(oneC, bitRead(tubeC, 0) ? HIGH : LOW);
  digitalWrite(twoC, bitRead(tubeC, 1) ? HIGH : LOW);
  digitalWrite(fourC, bitRead(tubeC, 2) ? HIGH : LOW);
}

// output to D
void displayD() {
  digitalWrite(oneD, bitRead(tubeD, 0) ? HIGH : LOW);
  digitalWrite(twoD, bitRead(tubeD, 1) ? HIGH : LOW);
  digitalWrite(fourD, bitRead(tubeD, 2) ? HIGH : LOW);
  digitalWrite(eightD, bitRead(tubeD, 3) ? HIGH : LOW);
}