About class assign for public or private variable.

About_Class_assign_size.cpp

#include <iostream>
#include <stdio.h>

class aClass
{
private:
    int a1=1;
public:
    aClass():a1(2), a2(3)
    {
        printOut();
        a1=a2;
        printOut();
    }
    int a2=1;
    void printOut()
    {
        printf("a1 = %d, a2=%d\n", a1, a2);
    }
    void change_A1()
    {
        a1=7;
    }
};

class bClass :public aClass
{
private:
    int b1=1;

public:
    bClass():b1(2), b2(3)
    {
        aClass::printOut();
        b1=b2;
        printOut();
    };
    virtual void printOut()
    {
        printf("b1 = %d, b2=%d\n", b1, b2);
    }
    int b2=1;
};

int main(int argc, const char * argv[])
{
    aClass A1;
    printf("memory address of A1=%d\n", &A1);
    aClass A2;
    printf("memory address of A2=%d\n", &A2);
    
    bClass B1;
    printf("memory address of B1=%d\n", &B1);
    
    //Class variable assignment.
    A1.a2=5;
    A1.change_A1();
    A2=A1;
    printf("memory address of A2=%d, after assign!\n", &A2);
    A2.printOut();
    // Class instance address will not change.
    // No matter pulick or private member variable will assign fro A1 to A2.

    //Inherience variable assignment.
    //B1 = A1;  will failed.
    
    printf("size of A1=%d\n", sizeof(A1));  // size = a1(4) + a2(4) = 8
    printf("size of B1=%d\n", sizeof(B1));  // size = a1(4)+a2(4) + b1(4) + b2(4) + virtual vptr(8)=24
    
    return 0;
}