int pin_A[4] = {2,3,4,5};
int pinVal_A[4] = {0,0,0,0};
int pin_B[4] = {6,7,8,9};
int pinVal_B[4] = {0,0,0,0};
int pin_C0 = 10;
int pinVal_C0 = 0;

void setup() {
  Serial.begin(115200);

  for(int i = 0; i <= 3; i++) {
    pinMode(pin_A[i], OUTPUT);
    pinMode(pin_B[i], OUTPUT);
  }


  for(int i = 0; i <= 3; i++) {
    digitalWrite(pin_A[i], pinVal_A[i]);
    digitalWrite(pin_B[i], pinVal_B[i]);
  }

  pinMode(pin_C0, OUTPUT);
  digitalWrite(pin_C0, pinVal_C0);


  
}

void loop() {
  
uint8_t aVal = random(0, 16);
  uint8_t bVal = random(0, 16);

  for (int i = 0; i < 4; ++i) {
    digitalWrite(pin_A[i], aVal >> i & 1);
  }

  for (int i = 0; i < 4; ++i) {
    digitalWrite(pin_B[i], bVal >> i & 1);
  }

  uint8_t cVal = random(0, 2);
  digitalWrite(pin_C0, cVal);

  uint16_t result =  aVal + bVal + cVal;
 

  Serial.print(aVal);
  Serial.print(" + ");
  Serial.print(bVal);
  Serial.print(" + ");
  Serial.print(cVal);
  Serial.print(" = ");
  Serial.println(result);

  delay(5000);


}