Base Class Pointer derived Class Object in C++

This pointer of base class will be able to temper functions and variables of its own class and can still point to derived class object. A base class pointer can point to a derived class object we can only access base class membera using the base class pointer because object slicing happens when a derived class object is assigned to a base class object.

The program demonstrates inheritance in object-oriented programming using C++. It defines a base class car with a single method start() that prints the message "Car Start". Then it defines a derived class BMW, which inherits from the car base class and adds a new method AdvanceGear() that prints the message "BMW Advance Gear".

In the main() function, an object b of class BMW is created. Then a pointer p of type car is created and assigned the address of b. Since BMW is derived from car, a pointer of type car can point to an object of type BMW.

Finally, the start() method of the car class is called using the p pointer. This demonstrates the concept of virtual functions in C++, where a function in the base class can be overridden by a function in the derived class.

Note that the commented-out lines in main() demonstrate an alternate way to call the methods directly on the object o of class BMW.

Source Code

//Base Class Pointer derived Class Object
#include<iostream>
using namespace std;
 
class car  //Base Class
{
public:
    void start()
    {
        cout<<"Car Start"<<endl;
    }
};
 
class BMW:public car  //Derived Class
{
public:
    void AdvanceGear()
    {
        cout<<"BMW Advance Gear"<<endl;
    }
};
 
int main()
{
    /*BMW o;
    o.start();
    o.AdvanceGear();*/
    BMW b;
    car *p=NULL;
    p=&b;
    p->start();
    return 0;
}

Output

Car Start

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