static void Main(string[] args)
{
var john = new Person();
john.FirstName = "John";
john.LastName = "Smith";
john.Introduce();
var calculator = new Calculator();
int result = calculator.Add(1, 2);
System.Console.WriteLine(result);
var chapter4 = new Chatper4();
chapter4.NonPrimitive();
int number = 1;
Increment(number);
System.Console.WriteLine(number);
var person = new PersonAge()
{
Age = 20
};
MakeOld(person);
System.Console.WriteLine(person.Age);
}
public static void MakeOld(PersonAge person)
{
person.Age += 10;
}