class Person{
  private:
    String _name;
    int _age = 10;
    int _size = 10;
    int _ID_num;

  public:
  Person();
  Person(String name);
  Person(String name, int age);
  Person(String name, int age, int size, int ID_num = 99);  // will assign 99 to ID if parameter is not passed to constructor

  void showValues(){
    Serial.print("Person name: "); Serial.println(_name);
    Serial.print("Person age: "); Serial.println(_age);
    Serial.print("Person size: "); Serial.println(_size);
    Serial.print("Person ID: "); Serial.println(_ID_num);Serial.println();
  }
};
Person::Person(){
    _name = "no name";
    _age = 11;
    _size = 11;
    _ID_num = 11;
    showValues();
  }
Person::Person(String name){
  _name = name;
  showValues();
}
Person::Person(String name, int age)
{
  _name = name;
  _age = age;
  showValues();
}
Person::Person(String name, int age, int size, int ID_num)
{
  _name = name;
  _age = age;
  _size = size;
  _ID_num = ID_num;
  showValues();
}

void setup() {
Serial.begin(115200);
Person anon;
Person jack("Jack");
Person john("John", 55);
Person andy("andy",32, 33 );
}

void loop() {
}