Section 8 : Inheritance

Question 1

How does public inheritance affect visibility?

Answer 1

Public members stay public, protected stay protected, private stay private (not inherited directly). Visibility is preserved.

Question 2

How does protected inheritance affect visibility?

Answer 2

Both public and protected members become protected in the derived class.

Question 3

How does private inheritance affect visibility?

Answer 3

Public and protected members become private in the derived class.

Question 4

Do derived classes inherit private members of the base class?

Answer 4

No. They exist in the object, but cannot be accessed directly.

Question 5

What happens if access specifier is not specified during inheritance?

Answer 5

It defaults to private.

Question 6

What is method overriding?

Answer 6

When a derived class provides a new implementation for a method already defined in the base class.

Question 7

Does the function signature need to match for overriding?

Answer 7

Yes, the method in the derived class must have the same name and parameters as in the base class.

Question 8

What is the output of overriding example below?

Base b; b.work(); // base method
Derived d; d.work(); // overridden method

Answer 8

base is working…
derived is working…

Question 9

Are constructors inherited in C++?

Answer 9

❌ No. Constructors and destructors are not inherited and must be defined in the derived class if needed.

Question 10

What is the order of constructor calls in inheritance?

Answer 10

Base class constructor

Derived class constructor

Question 11

What is the order of destructor calls in inheritance?

Answer 11

Derived class destructor

Base class destructor

Question 12

Can you call a base class constructor from a derived class?

Answer 12

✅ Yes, using an initializer list:
Derived(int a, int b) : Base(a), val(b) { }

Question 13

Why use initializer lists in inheritance?

Answer 13

To initialize base class members (especially private ones) and member variables before the body of the derived constructor runs.

Question 14

Can you call a base constructor inside the derived constructor body?

Answer 14

❌ No. That would create a temporary object, not initialize the actual base part of the derived object.

Question 15

When is the base class constructor called?

Answer 15

Before the derived class constructor, even if not explicitly written (calls default constructor if available).

Question 16

What happens if base has no default constructor and the derived constructor doesn’t call it?

Answer 16

❌ Compiler error — must explicitly call the base constructor via initializer list.

Question 17

Are friend functions or classes inherited?

Answer 17

❌ No. Friends of a base class are not friends of the derived class. You must declare them again.

Question 18

Can you make a protected member in the base class public in the derived class?

Answer 18

❌ No. You can restrict visibility (e.g., public → private), but cannot widen it.

Question 19

Can you access protected members of the base in the derived class?

Answer 19

✅ Yes, they can be accessed directly in the derived class.

Question 20

What happens when you create an object of a derived class that doesn’t explicitly call a base constructor?

Answer 20

The default constructor of the base class is called automatically before the derived class constructor, even if the derived class constructor is parameterized.

Question 21

If a derived class constructor is parameterized but doesn’t use an initializer list, which base constructor is invoked?

Answer 21

The default constructor of the base class is used by default.
C++ does not automatically match constructor arguments from Derived(int) to Base(int) unless you explicitly tell it to via an initializer list.

Question 22

How can you explicitly call a base class’s parameterized constructor from a derived class

Answer 22

Using an initializer list:
Derived(int x, int y) : Base(x) {
cout &laquo_space;“Derived constructor with y = “ &laquo_space;y &laquo_space;endl;
}

Question 23

What will happen in this code?

class Base {
public:
Base(int x) { cout &laquo_space;“Base: “ &laquo_space;x &laquo_space;endl; }
};

class Derived: public Base {
public:
Derived(int a) {
cout &laquo_space;“Derived: “ &laquo_space;a &laquo_space;endl;
}
};

int main() {
Derived d(5);
}

Answer 23

compile-time error.
Reason: Base has no default constructor, and Derived does not explicitly call Base(int) — the compiler doesn’t know how to initialize the base part.

Question 24

How would you fix the above code?

Answer 24

Add an initializer list in Derived to call the base constructor:

Derived(int a) : Base(a) {
cout &laquo_space;“Derived: “ &laquo_space;a &laquo_space;endl;
}

Question 25

What is the order of constructor calls when creating a derived object?

Answer 25

The base class constructor is called first. The derived class constructor is called. Always.

Question 26

What is the order of destructor calls when deleting a derived object?

Answer 26

Derived class destructor is called first Then base class destructor (Reverse of construction)

Question 27

What happens if both base and derived have default and parameterized constructors, and you create a derived object with no arguments?

Answer 27

The default constructor of the base is called first, then the default constructor of the derived.

Question 28

What happens if you create a derived object with arguments, but don’t call a base constructor explicitly?

Answer 28

The base class's default constructor is used — if it doesn't exist, you get a compiler error.

Question 29

Why can't you call Base(x); inside the body of the Derived constructor?

Answer 29

That just creates a temporary object — it doesn’t initialize the base part of the derived object. Base must be initialized in the initializer list.

Question 30

Can initializer lists be used to initialize both base and member variables in one line?

Answer 30

Yes. Example: class Derived : public Base { int val; public: Derived(int x, int y) : Base(x), val(y) { } };