Pointers and Runtime Polymorphism: Two Marks Important Questions and Answers

Object Oriented Programming – C++

Chapter 4: Pointers and Runtime Polymorphism

Two Marks Questions with Answers

1. Differentiate constant pointer and a pointer to a constant with an example.

Answer:  A constant pointer is a pointer that can not change the address it is holding. A pointer to a constant is a pointer using which one can not change the value of variable it points to.

2. What is the use of void pointer ?

Answer: The void pointer is a special type of pointer that can be used to point to the objects of any data type. It is also known as generic pointer.

The void pointer is declared like normal pointer declaration, using the keyword void.

For example:

void *ptr;

3. What is pointer arithmetic ?

Answer: Pointer arithmetic is a set of arithmetic operations by which we can ‒ 1. use ++ or ‒‒

operators using pointers. 2. We can add or subtract an integer to a pointer variable.

4. What are the two operators used in pointers ?

Answer: The two operators used in pointers are* and &. The* denotes the value at particular location while the & denotes the address of variable.

5. How are virtual functions declared in C++?

Answer: Virtual function is a member function that is declared within a base class and redefined by a derived class. The virtual keyword is preceded to the function name. This virtual function can be redefined in the derived class. The virtual function within the base class defined the form of the interface to that function. Each redefinition of the virtual function by a derived class indicate some different task related to derived class.

6. When do we make a virtual function "pure" ?

OR

Define pure virtual function and mention its usage.

Answer: The pure virtual function is used in abstract class. When we want to override the definition of some particular function in the derived class then we normally declare that function as pure virtual function in the base class.

7. What is the difference between compile time and run time polymorphism ?

Answer: Compile time polymorphism: The linking between method call and method definition takes place at compile time. Compiler knows the exact memory address of the function definition. The advantage of this approach is that the execution of the code becomes fast.

For example ‒ Function oveloading

Run time polymorphism: The linking between method call and method definition takes place at run time. The advantage of this approach is that size of compiled code get reduced.

For example ‒ Virtual functions

8. What is function overriding?

Answer: The function overriding means redefining of a function in a derived class.

9. Give the difference between the function overloading and function overriding.

Answer: In both the function overloading and function overriding the function names remain the same. But in function overloading the two functions of same name can have varying number of arguments. They can have different return types. But in function overriding the signature of the function must be the same. Only the body of the function differs.

10. Compare overloading and overriding.

Answer:

Overloading

1. In function overloading different number of parameters can be passed to the function.

2. The overloading function may have different return type.

3. This method allows defining multiple member functions with same name but different signature.

Overriding

1. In function overriding the number of parameters that are passed to the function must be the same.

2. The return type of base and derived member function must be the same.

3. Overriding is a method that allows a class to redefine the behaviour of member functions which the derived class inherits from the base class.

11. Define the virtual functions.

Answer: A virtual function is a member function that is declared within a base class and redefined by a derived class. For the virtual function the virtual keyword is preceded to the function name.