// The statement we call it as a type
// define type
// every class has at least one type.
// In Kotlin at least 2 types. show the example
//just like an inherited class becomes subclass of a class.
// The ype of subclass also becomes subtype of parent class type
//show the example
// also show non nullable type is a subtype of nullable type
// val x: String = "John"
//val y: String? = x

open class Person(val name: String)

class Student(name: String): Person(name)

fun main() {
    //type
    val age: Int = 22
    val rollNumber: Int? = 4

    //subtype
    val student: Student = Student("John")
    val person: Person = student

}