Virtual Functions C++

A virtual function is a member function which is declared within a base class and is re-defined (overridden) by a derived class. When you refer to a derived class object using a pointer or a reference to the base class, you can call a virtual function for that object and execute the derived class’s version of the function. 

• Virtual functions ensure that the correct function is called for an object, regardless of the type of reference (or pointer) used for function call.
• They are mainly used to achieve Runtime polymorphism
• Functions are declared with a virtual keyword in base class.
• The resolving of function call is done at runtime.

Link to Repl

// CPP program to illustrate
// concept of Virtual Functions

#include<iostream>
using namespace std;

class base {
public:
	virtual void print()
	{
		cout << "print base class\n";
	}

	void show()
	{
		cout << "show base class\n";
	}
};

class derived : public base {
public:
	void print()
	{
		cout << "print derived class\n";
	}

	void show()
	{
		cout << "show derived class\n";
	}
};

int main()
{
	base *bptr;
	derived d;
	bptr = &d;

	// Virtual function, binded at runtime
	bptr->print();

	// Non-virtual function, binded at compile time
	bptr->show();
	
	return 0;
}