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C++ program to demonstrate example of friend function with class

Learn about the friend function in C++, how to implement friend function using C++ program?
[Last updated : March 01, 2023]

Friend Function in C++

Friend function is a special type of function, which declares inside the class. Friend function can access the private, protected and public data of the class.
A keyword friend is used before return type of the function declaration/prototype.

Friend Function Program in C++

// C++ program to demonstrate example of
// friend function with class

#include <iostream>

using namespace std;

class Number {
private:
    int a;

public:
    void getNum(int x);
    //declaration of friend function
    friend void printNum(Number NUM);
};

//class member function definitions
void Number::getNum(int x)
{
    a = x;
}

//friend function definition,
//no need of class name with SRO (::)
void printNum(Number NUM)
{
    cout << "Value of a (private data member of class Number): " << NUM.a;
}

int main()
{
    Number nObj; //Object declaration
    
    nObj.getNum(1000);
    printNum(nObj);
    
    return 0;
}

Output

Value of a (private data member of class Number): 1000