C++ Tutorial Index

C++ Tutorial C++ History C++ Installation C++ First Program C++ cin and cout C++ Data type C++ Variable C++ operator C++ Keywords

C++ Control Statements

C++ If C++ Nested if C++ If-else C++ If-else-if C++ Switch C++ Break C++ Continue C++ Goto C++ For loop C++ While loop C++ Do while loop

C++ Functions

C++ Call by Value C++ Call by Reference C++ Recursion Function C++ Inline function C++ Friend function

C++ Arrays

Single dimension array Two dimension array

C++ Strings

C++ Strings

C++ Inheritance

C++ Inheritance Single level Inheritance Multilevel Inheritance Multiple Inheritance Hierarchical Inheritance Hybrid Inheritance

C++ Polymorphism

C++ Polymorphism C++ Overloading C++ Overriding C++ Virtual Function

C++ Pointers

C++ Pointers C++ this pointer

C++ Exception Handling

C++ Exception Handling

C++ Constructors

C++ Constructors Default Constructor Parameterize Constructor Copy constructor Constructor Overloading Destructor

C++ File Handling

C++ File Handling C++ Writing to file C++ Reading file C++ Close file

Miscellaneous

C Vs C++ C++ Comments C++ Data Abstraction C++ Identifier C++ Memory Management C++ Storage Classes C++ Void Pointer C++ Array To Function C++ Expressions C++ Features C++ Interfaces C++ Encapsulation std::min in C++ External merge sort in C++ Remove duplicates from sorted array in C++ Precision of floating point numbers Using these functions floor(), ceil(), trunc(), round() and setprecision() in C++ C++ References C++ Friend Functions C++ Mutable keyword Unary Operators in C++ Initialize Array of objects with parameterized constructors in C++ Differences between #define & const in C/C++ C++ Program to Implement Shell Sort C++ Program to Implement Merge Sort Storage Classes in C Vector resize() in C++ Passing by Reference Vs. Passing by the pointer in C++ Free vs delete() in C++ goto statement in C and C++ C++ program to read string using cin.getline() C++ String Concatenation Heap Sort in C++ Swap numbers in C++ Input Iterators in C++ Fibonacci Series in C++ C ++ Program: Alphabet Triangle and Number Triangle C++ Program: Matrix Multiplication C++ Program to Print Fibonacci Triangle Stack in C++ Maps in C++ Queue in C++ C++ Bitset C++ Algorithms Priority Queue in C++ C++ Multimap C++ Deque Function Pointer in C++ Sizeof() Operators in C++ C++ array of Pointers free() Vs delete in C Timsort Implementation Using C++ CPP Templates C++ Aggregation C++ Enumeration C++ Math Functions C++ Object Class C++ Queue Initialize Vector in C++ Vector in C++ C++ STL Components Function overloading in C++ C++ Maximum Index Problem C++ find missing in the second array C++ Program to find the product array puzzle C++ Program To Find Largest Subarray With 0 Sum C++ Program To Move All Zeros To The End Of The Array C++ Program to find the element that occurs once C++ Program to find the largest number formed from an array Constructor Vs Destructor C++ Namespaces C++ OOPs Concept C++ Static C++ Structs C++ Try-Catch C++ User Defined Exceptions C++ Virtual Destructor C++ vs C# Malloc() and new in C++ Palindrome Number Program in C++ Snake Code in C++ Splitting a string in C++ Structure Vs Class in C++ Virtual Function Vs Pure Virtual Function C++ Bidirectional Iterators C++ Forward Iterators C++ Iterators C++ Output Iterators C++ Range-based For Loop Converting string into integer in C++ LCM Program in C++ Type conversion in C++ Add two numbers using the function in C++ Advantage and disadvantage friend function C++ Armstrong Number Program in C++ ATM machine program in C++ using functions Binary to Decimal in C++ Bit Manipulation in C++ C++ Constructor C++ Dijkstra Algorithm Using the Priority Queue C++ int into String C++ Signal Handling Decimal to Binary in C++ Decimal to Hexadecimal in C++ Decimal to Octal in C++ Factorial Program in C++ Function in C++ Hexadecimal to Decimal in C++ Octal to Decimal in C++ Reverse a Number in C++ Structure Vs Class in C++ C++ Forward Iterators C++ Output Iterators C++ Prime number program Char Array to String in C++ Constructor Overloading in C++ Default arguments in C++ Different Ways to Compare Strings in C++ Dynamic Binding in C++ Program to convert infix to postfix expression in C++ SET Data Structure in C++ Upcasting and Downcasting in C++ Reverse an Array in C++ Fast Input and Output in C++ Delete Operator in C++ Copy elision in C++ C++ Date and Time C++ Bitwise XOR Operator Array of sets in C++ Binary Operator Overloading in C++ Binary Search in C++ Implementing the sets without C++ STL containers Scope Resolution Operator in C++ Smart pointers in C++ Types of polymorphism in C++ Exception Handling in C++ vs Java Const Keyword in C++ Type Casting in C++ Static keyword in C++ vs Java Inheritance in C++ vs Java How to concatenate two strings in C++ Programs to Print Pyramid Patterns in C++ swap() function in C++ Structure of C++ Program Stringstream in C++ and its applications rand() and srand() in C / C++ C++ Ternary Operator C++ Scope of Variables While Loop Examples in C++ Star pattern in C++ using For Loops For Loop Examples in C++ Do-While Loop Examples in C++ Top 5 IDEs for C++ That You Should Try Once Assertions in C/C++ C++ Convert Int to String Continue in C++ While loop Diamond Pattern in C++ using For Loop How to Reverse a String in C++ using Do-While Loop How to Reverse a String in C++ using For Loop How to Reverse a String in C++ using While Loop Infinite loop in C++ Loops in C++ Returning Multiple Values from a Function using Tuple and Pair in C++ wcscpy(), wcslen(), wcscmp() Functions in C++ Auto keyword in C++ C++ 11 vs C++ 14 vs C++ 17 C++ STL (Standard Template Library) Differences Between C Structures and C++ Structures Divide by Zero Exception in C++ Dynamic Constructor in C++ Dynamic Memory Allocation in C++ Find the Size of Array in C/C++ without using sizeof() function Floating Point Operations and Associativity in C, C++ and Java Hello World Program in C++ How to create a table in C++ How to Setup Environment for C++ Programming on Mac Implementation of a Falling Matrix in C++ Message Passing in C++ Pointer to Object in C++ Templates in C++ vs Generics in Java Ways to Copy a Vector in C++ What does Buffer Flush mean in C++ sort() function in C++ Structure Sorting (By Multiple Rules) in C++ Similarities between C++ and Java std::distance in C++ Array program in C++ C++ Tricks for Competitive Programming Desired Capabilities in Selenium Web Driver in C++ Socket Programming in C++ Template Specialization in C++ Classes and Objects in C++ Convex hull Algorithm in C++ DES in C++ C++ vardiac() function Difference between Two Sets in C++ Difference between Exit and Return Structured Binding in C++ Differences between Local and Global Variable Bitwise Operator vs Logical Operator Difference between OOP and POP in C++ Fork in C++ Functors in C++ How to call a void function in C++ How to create a directory or folder in C/C++ How to create a library in C++ How to create a stack in C++ How to create the Processes with Fork in C++ How to Handle Divide by Zero Exception in C++ Lambda Expression in C++ Pattern programs in C++ Roadmap to C++ Programming Substring in C++ Virtual base class in C++ Bits stdc++.h in C++ Top 14 Best Free C++ IDE (Editor & Compiler) for Windows in 2022 Bitmasking in C++ Auto Keyword in C++ Features of OOPS in C++ Hospital Management Project in C++ How to Declare Unordered Sets in C++ How to Sort an Array in C++ Include Guards in C++ Iostream in C++ Method overriding in C++ How to run program in turbo c++ How to Use Getline in C++ Leap Year Program in C++ Naming Convention in C++ New Operator in C++ Nullptr in C++ Object Slicing in C++ Principles of Object-Oriented Programming in C++ Processing strings using std string stream in C++ Pure Virtual Function in C++ With Example Program Random Number Generator in C++ Singleton Design Pattern in C++ Size_t Data Type in C++ Skyline Problem in C++ System() function in C++ Web Development in C++ Data Hiding in C++ Difference between exit() and _Exit() in C++ Hashing in C++ Object in C++ Sum of all Elements between k1’th and k2’th Smallest Elements Virtual class in C++ Vector Size in C++ Top best IDEs for C/C++ Developers in 2022 Tensorflow in C++ Sliding Window Technique in C++ Reverse String Word-Wise in C++ Returning a Function Pointer from a Function in C/C++ RTTI in C++ Pthreads or POSIX Threads in C++ Reserved Keywords in C++ Passing a Vector to a function in C++ 10 Best C and C++ Books for Beginners & Advanced Programmers Add two numbers represented by two arrays in C++ Array of Object in C++ C++ Program For FCFS Containership in C++ Counting Frequencies of Array Elements in C++ Decltype type Specifier in C++ Dynamic _Cast in C++ Difference between int main() and int main(void) in C/C++ Depth First Search Program to Traverse a Graph in C++ Features and Use Of Pointers in C/C++ Fread Function in C++ Programming Fscanf Function in The C++ Functions in C++ With Types and Examples Gmtime Function in C/C++ How is Multiset Implemented in C++ How to Build a Program in C++ How to Declare a 2d Array Dynamically in C++ inheritance Program in C++ int Max and int Min in C/C++ is It Fine to Write Void Main Or Main in C/C++ How to create a button in C++ abs() function in C++ Compile Time Polymorphism in C++ Division in C++ Factorial of a Number in C++ using while Loop Multiset in C++ 4 Pillars of OOPs Approach in C++ Backtracking Time Complexity in C++ C++ Global Variable C++ Pipe Tutorial Observer Design Pattern in C++ Private Inheritance in C++ Pthread in C++ Parameters SDL library in C++ with Examples Pointers in C++ Abstract Factory Design Pattern in C++ Ascending order in C++ How the value is passed in C++ Call by Pointer in C++ Constexpr in C++ Deadlock in C++ Design 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How to use the string find() in C++ Dynamic Casting in C++ 2D Vector Initialization in C++ C++ GUI Visual Studio C++ IPC C++ Macro Function Example C++ Permutation Overloading Stream Insertion in C++ Overloading array Index operator in C++ Operators that cannot be overloaded in C++ Operator overloading in C++ isprint() function in c++ Is_trivial function in C++ Is assignment operator Inherited in C++ div() function in C++ Default Assignment Operator and References in C++ Copy Constructor vs Assignment Operator in C++ Conversion Operator in C++ Array sum in C++ STL C++ Define Macro C++ Design C++ Factory Pattern TCP Client Server Example in C++ Convert String to Uppercase in C++ exit() and _Exit() in C and C++ Initializer list in C++ Iterator invalidation in C++ Lower bound in C++ Modulus of Two float numbers or double number Pass by value in C++ Set insert function in C++ Std partition_point in C++ Unary Operator Overloading in C++ Using Default Arguments with Virtual Functions Virtual Functions and Runtime Polymorphism What is endl in C++ What is Unary Operator Overloading in C++ Which operators cannot be overloaded in C++ C++ Program to Divide the String Into N equal Parts Gray Code to Binary Code in C++ How to get the value of pi in C++ Multimap value_comp() function in C++ Vector of Vectors in C++ Naïve Bayes Algorithm in C++ Minimum Cost Path Problem in C++ 10 C++ Programming Tricks You Should Know btowc() function in C++ forward_list::cend() in C++ Unordered_multimap max_load_factor() function in C++ Cpp_int in c++ Dynamic Objects in C++ FLOCK() FUNCTION IN C++ Generate Random Double Numbers in C++ How to Assign Infinity to a Number in C++ Jump statements in C++ Multipath inheritance in C++ Out of Range Exception in C++ Size of Class in C++ Size of string in C++ std::binary_negate in c++ Thread_local in C++ Tokenizing a String in C++ Ancestors of a Node in Binary Search Tree C++ program for Double to String Conversion C++ Program to Demonstrate Use of Formatting Flags on Float Output Clamp in C++ K-Dimensional Tree in C++ Mutable Lambda in C++ Power Set in C++ Program to Find Sum of Geometric Progression Std::Back_inserter in C++ Strpbrk() function in C++ Size of int in C++ TYPES OF MANIPULATORS IN C++ Double colon in C++ How to sort vector in C++ How to use Setprecision in C++ How to write a Vector in C++ Insertion in Splay Tree in C++ Merge Sort Algorithm in C++ Printing a Character using ASCII value in C++ Regex in C++ Size of Data Types in C++ Abstract Factory Design Pattern in C++ Sqrtf() function in C++ Static Casting in C++ Using Range in Switch Case in C++ wcstoimax() and wcstoumax() function in C++ What is float in C++ What is the Diamond Problem in C++ Best way to learn C++ ios setstate() function in C++ Nested Namespace in C++ Single Inheritance in C++

C++ Interfaces

The C++ programming language provides programmers with a variety of capabilities and functions. It also enables object-oriented programming, which is essential while working on a project. It will be simple for you to learn C++ programming if you have already learnt C programming. Because some ideologies in C++ are very much same as those in C programming. Now, from here we'll go over a C++ concept known as Interface.

Interfaces are present in various languages but here we will only be focussed on the interfaces in C++ language, what they are, how they are used and how they are helpful for us.

In C++, an interface is just a means to define the behaviour of a class without committing to any specific implementation. It is a feature that C++ classes and objects provide as a complement. We'll show you how to take the next step in exploring the depths of object-oriented programming using classes and objects. It's worth noting that in C++, there's no distinction between interfaces and abstract classes.

So moving ahead, let's start C++ Interfaces.

What are interfaces in the C++ language :

A class having a pure virtual function is referred to as an abstract class in C++ programming.

Interfaces are very much related to the classes and the objects. As a result, it's reasonable to assume that the terms "Interfaces" and "Abstract Classes" are interchangeable. The difference between data abstraction and abstract classes is that the goal of data abstraction is to keep important details separate from other data. Interfaces and abstract classes are similar in such way that they express the same message.

It's crucial to understand the difference between abstract classes and data abstraction in C++, as data abstraction merely removes the relevant data from the implementation approaches.

C++ Pure Virtual Functions :

An abstract class in C++ is just a class having a pure virtual function, as previously stated. First we should know about virtual and pure virtual functions to grasp more knowledge.

Virtual function-

A virtual function is a member function declared in a base class that a derived class epitomises (bypasses). When you refer to a derived class object that used a pointer or a reference to the base class, you may call a virtual function for that object and have it to execute the derived class's version of the function. It is feasible to create a virtual function-based base class. Abstract classes are not at all those that have virtual functions. There will be no influence on the compilation if the derived class does not redefine the virtual function of the base class. Also

  • • Virtual functions guarantee that the correct function is called for an object, irrespective of the type of reference (or pointers) used to call it.
  • They're mostly utilised to achieve polymorphism at runtime.
  • The virtual keyword is used to declare functions in base classes.
  • The call to a function is resolved at runtime.

Drawbacks of Virtual Functions :

  1. The virtual mechanism causes the function call to take somewhat longer, making it more difficult for the compiler to optimise because it does not know which function will be called at build time and is thus slower.
  2. Virtual functions can make it a little more difficult to find out where a function is being called from in a complicated system.

Example –

#include <iostream>
using namespace std;
class Base {
   public:
    virtual void prints() {
        cout << "Base Func." << endl;
    }
};
class Derived : public Bases {
   public:
    void prints() {
        cout << "Derived Func." << endl;
    }
};
int main() {
    Derived derived01;


    // pointer of the Base type, points to the derived01
    Base* base01 = &derived01;


    // calls the member function of the earlier Derived class
    Base01->prints();


    return 0;
}

Output:

Derived Func.

In this example, the prints() method of Base has been designated virtual in this case. So, even if we use a reference of Base type that links to the Derived object derived01, this function is overwritten. Thus in the main, the pointer of the Base type points towards the Derived object derived01. Then further calling the member function prints() of this Derived class we printed the required output.

Pure virtual function-

Pure virtual function is a virtual function that is known to be existing but we can't implement that. It's just a mere declaration and is not a plan.

Virtual functions are utilised exclusively

  • if a method has no purpose in the base class
  • but it’s required to be implemented by all of its derived classes

It's worth remembering that a pure virtual function may only be declared, not defined. The definition of a function is not specified in the base class in the case of a pure virtual function. It will not produce an error if the derived class does not define the pure virtual function; rather, the derived class will become an abstract class.

Syntax:

Virtual float func() = 0;

Example –

In this example, we have assumed that we've descended from the Shapes class, the various shapes of figures and we want to determine the area of each of these forms.

In this situation, we may use the Shape to build a pure virtual function called area(). All derived classes of those shapes must implement the area() function since it is a pure virtual function.

The function body is not present in a pure virtual function, and it must conclude with = 0. As an example,

class Shapes {
    public:


      // we are creating a pure virtual function in c++
      virtual void area() = 0;
};

Note that the = 0 syntax does not imply that the function is set to zero but it is the predefined manner in which the pure virtual functions are defined in the C++ language.

The Significance of Interface in C++ :

Let us recognise the significance of pure virtual functions once we have developed a comprehension of them by addressing a small situational example. Assume you've made an Apples class containing data members iPhoneX, iPad Pro, and iPod, as well as member methods rate(), ring() and alarms().

Assume that the ratee of each product that is being sold is fixed and can’t be changed. We know that Apple goods come in a variety of pricing, such as the iPhone X, which costs $60,500, and the iPad Pro, which costs $45,000.

The only acceptable approach to implement the function rate() in the class Apples is to make it pure abstract, so that we don't have to implement it in the class Apples, but all the classes that inherit the Apples class must. We can assure that all Apples items have a set and unique pricing in this way.

In C++, there are two methods for implementing the friend function.

Here is a C++ application that will assist you in solving the problem indicated above:

Code:

#include<iostream>
using namespace std;


class Apples
{
public:
// Pure Virtual Funct 
virtual void rate() = 0;


// Member funct
void ring() 
{
cout<<"Ring-tone is: trumpets"<<endl;
}
};
class iPhoneX: public Apples
{
public:
void rate() 
{
cout<<"The rate is: 60,500"<<endl;
}
};


int main()
{


cout<<"Significance of interfaces in C++"<<endl<<endl;


iPhoneX i;
i.rate();
i.ring();
return 0;
}

Output:

Significance of interfaces in C++!
The rate is: 60,500
Ring-tone is: trumpets

Another example  –

Assume you've constructed an OS class having data members Windows, Linux, and Mac, as well as member methods like sizes(), types() and features().

Assume that each operating system's size is fixed and cannot be changed. Varied operating systems, on the other hand, have different sizes. You may implement the class OpS for the method sizes() in one approach by making it abstract. We can ensure that the size of all operating systems is set this way.

The code to address the problem is provided below.

#include <iostream>
using namespace std;
class OpS
{
public:
virtual void sizes() = 0;
void types()
{
cout<<"It’s windows OS!"<<endl;
}
};
class WindowsOS: public OpS
{
public:
void size()
{
cout<<"The size is 4.89GB!"<<endl;
}
};


int main()
{
cout<<"Interfaces in C++ !"<<endl<<endl;
WindowsOS data;
data.sizes();
data.types();
return 0;
}

Output:

Interfaces in C++!
The size is 4.890GB!
It’s windows OS!

In C++, several rules applied to interfaces are :

When dealing with interfaces/abstract classes in C++, there are a few principles to bear in mind.

  • Since it is not feasible to define a pure virtual function thus it can only be declared and not defined.
  • You can't provide the pure virtual function any other value than 0.
  • It is not feasible to establish a class instance.

Example- You can't build an Apples type object, like, using the software shown above. There would be a compilation fault as a result.

  • The derived class becomes an abstract class if it is unable to implement the base class's pure virtual function.
  • Using a reference to the base abstract class, it is possible to build a pointer that refers to the instance of the derived class.

Example-

Using the preceding programme as an example, you may do this task by writing the following statements:

Apples *object = new iPhoneX();
object -> rate();

Or

OpS *obj = new WindowsOS();
obj->sizes();

In both these examples, we used a reference object which refers to the instance of the derived classes here.

Summarizing the content :

Hope the distinction between interfaces and abstract classes in C++ is clearer now. In addition, we now know about how to use classes to build pure virtual functions in a real-world application. Finally, we went through some of the principles that apply to abstract classes, leaving no space for confusion.