When do we use virtual function? Differentiate early and late binding.

Virtual functions are used in object-oriented programming to achieve polymorphism. In particular, virtual functions are used in the following scenarios:

1. When a base class pointer points to an object of the derived class, and we want to call a member function of the derived class through the base class pointer. This is known as runtime polymorphism, and it requires the use of virtual functions.
2. When a base class has one or more functions that are intended to be overridden by derived classes. In this case, the base class should declare these functions as virtual, so that the derived classes can override them as needed.

In general, virtual functions are used to provide a way for derived classes to customize the behavior of a base class, while still remaining a common interface with other classes in the inheritance hierarchy. This makes it easier to write code that can work with object of different derived classes, without having to know the details of each class's implementation.

Early binding and late binding are two concepts related to polymorphism in object-oriented programming languages like C++ and Java. Here are the difference between the two:

Early Binding:

1. Also known as static binding, compile-time binding, or overloading resolution at compile time.
2. The binding of a function call to a function implementation happens at compile time, based on the static type of the object or pointer.
3. It is efficient because the binding is resolved at compile time, which saves time during runtime.
4. It is used when the type of object or pointer is known at compile time.

Late Binding:

1. Also known as dynamic binding, runtime binding or overriding resolution at runtime.
2. The binding of a function call to a function implementation happens at runtime, based on the actual type of the object or pointer.
3. It is less efficient because the binding is resolved at runtime, which takes more time during execution.
4. It is used when the type of object or pointer is not known until runtime