Pure virtual functions in C++ - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

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

C++

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

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

A= 0

B= 1

C{}

D;

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to add '= 0' makes the function not pure virtual.

Using '{}' instead of '= 0' defines a normal virtual function.

A pure virtual function is declared by assigning 0 to the function declaration, like virtual void display() = 0;.

2fill in blank

medium

Complete the code to make Base an abstract class by adding a pure virtual function show.

C++

class Base {
public:
    virtual void [1]() = 0;
};

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

Aprint

Bshow

Cdisplay

Drun

Attempts:

3 left

💡 Hint

Common Mistakes

Using a function name different from the one asked.

Adding a function body instead of '= 0;'.

The function name can be any valid identifier. Here, show is used as the pure virtual function name.

3fill in blank

hard

Fix the error in the derived class by correctly overriding the pure virtual function display.

C++

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

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

Adisplay

Brun

Cprint

Dshow

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different function name than the base class pure virtual function.

Forgetting to override the pure virtual function causes the derived class to be abstract.

The derived class must override the pure virtual function with the exact same name to provide implementation.

4fill in blank

hard

Fill both blanks to declare a pure virtual function calculate that returns an int.

C++

class Calculator {
public:
    virtual [1] [2]() = 0;
};

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

Aint

Bvoid

Ccalculate

Ddisplay

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping return type and function name.

Using wrong function names.

The function return type is int and the function name is calculate.

5fill in blank

hard

Fill all three blanks to define a pure virtual function process that takes an int parameter and returns bool.

C++

class Processor {
public:
    virtual [1] [2]([3] value) = 0;
};

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

Abool

Bprocess

Cint

Dvoid

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up return type and parameter type.

Using wrong function names.

The function returns bool, is named process, and takes an int parameter.