Welcome to C++ Programming Tutorial

Class and Object Definitions in C++

In C++, a class is a user-defined data type that represents a blueprint for objects. It encapsulates data and functions that operate on the data. Objects are instances of classes and can be used to model real-world entities.

Class Definition: A class defines the data members (variables) and member functions (methods) that operate on those data members. Access to these members can be controlled using access specifiers: private, protected, and public.

Object: An object is a variable of a class type. Each object can have its own values for the data members and can use the member functions to operate on these values.

Scope Resolution Operator: The :: operator is used to define the implementation of class member functions outside the class definition. It specifies that the function belongs to a particular class.

Code Example: Class with Member Functions in C++

This example demonstrates the use of classes, member functions, and the scope resolution operator in C++. Below is the code:

#include <iostream>

using namespace std;

class add
{
private:
    int a, b, c;
public:
    int x, y;
    
    // Member function declarations
    void fun1(int d, int e, int f);
    void fun2(int d, int e, int f);
    void fun3(){
        cout << x << endl;
        cout << y << endl;
    }
};

// Member function definitions outside the class using the scope resolution operator
void add::fun1(int d, int e, int f)
{
    int sum;
    sum = d + e + f;
    cout << sum << endl;
}

void add::fun2(int d, int e, int f)
{
    int sum;
    sum = d - e - f;
    cout << sum << endl;
}

int main()
{
    int nu1 = 55, nu2 = 55, nu3 = 8;
    add m1;
    
    // Setting values and calling member functions
    m1.x = 23;
    m1.y = 12;
    m1.fun1(12, 55, 66);  // Calls fun1 to add three integers
    m1.fun2(nu1, nu2, nu3);  // Calls fun2 to subtract three integers
    m1.fun3();  // Calls fun3 to print x and y
    
    return 0;
}

Explanation:

• Class Definition: The add class demonstrates how to define a class with private and public members. It includes private variables a, b, and c, and public variables x and y.
• Member Functions Defined Inside the Class: The fun3 function is defined inside the class definition. This method can directly access the private and public members of the class and is implemented as part of the class body.
• Member Functions Defined Outside the Class: The fun1 and fun2 functions are defined outside the class using the scope resolution operator ::. This allows the member functions to be implemented separately from the class definition.
• Scope Resolution Operator: The scope resolution operator :: is used to define member functions outside the class definition, allowing for a cleaner class definition and separate implementation of methods.
• Main Function: The main function creates an object of the add class, sets the values of x and y, and calls the member functions to perform operations and display results.