Virtual functions in C++ - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a virtual function named display in the base class.

C++

class Base {
public:
    virtual void [1]() {
        std::cout << "Base display" << std::endl;
    }
};

Drag options to blanks, or click blank then click option'

Ashow

Bdisplay

Cprint

Doutput

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different function name than 'display'.

Forgetting to declare the function as virtual.

The virtual function must be named display as declared in the base class.

2fill in blank

medium

Complete the code to override the virtual function display in the derived class.

C++

class Derived : public Base {
public:
    void [1]() override {
        std::cout << "Derived display" << std::endl;
    }
};

Drag options to blanks, or click blank then click option'

Adisplay

Boutput

Cprint

Dshow

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different function name than 'display'.

Omitting the override keyword (though optional, it helps).

The derived class overrides the base class virtual function named display.

3fill in blank

hard

Fix the error in the code to call the derived class display function through a base class pointer.

C++

Base* ptr = new Derived();
ptr->[1]();

Drag options to blanks, or click blank then click option'

Ashow

Boutput

Cprint

Ddisplay

Attempts:

3 left

💡 Hint

Common Mistakes

Calling a function name not declared in the base class.

Not using the virtual function name.

Calling display on the base class pointer invokes the derived class version because display is virtual.

4fill in blank

hard

Fill both blanks to declare a pure virtual function show in the base class and override it in the derived class.

C++

class Base {
public:
    virtual void [1]() [2];
};

Drag options to blanks, or click blank then click option'

Ashow

Bdisplay

C= 0

D{}

Attempts:

3 left

💡 Hint

Common Mistakes

Not using '= 0' to make the function pure virtual.

Using the wrong function name.

A pure virtual function is declared with = 0 and must be overridden in derived classes.

5fill in blank

hard

Fill all three blanks to implement the derived class overriding the pure virtual function show and calling it.

C++

class Derived : public Base {
public:
    void [1]() override [2];
};

int main() {
    Base* obj = new Derived();
    obj->[3]();
    delete obj;
    return 0;
}

Drag options to blanks, or click blank then click option'

Adisplay

Bshow

C()

D{}

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong function names.

Missing function body braces.

Incorrect function call syntax.

The derived class overrides show with an empty body {} and calls show() through the base pointer.