This PPT contains all information about friend function in objective oriented programming. that is need, characteristic and syntax of friend function. Although I used cpp in this ppt.

1. By: Jagrati Mehra
Course: B. Sc. (CS) II year
Submitted to: Prof. Someshwar Joshi

2. Suppose there is two different objects of two
different classes.
class ABC
ABC a
int data
function()
{
........
}
class XYZ
XYZ x
int data
function()
{
........
}

3. class ABC
ABC a
int data
function()
{
........
}
class XYZ
XYZ x
int data
function()
{
........
}
But what if I need to access both data and
information ?
Here we use friend function.
Access not
possible
..!!!

4. Simple only add friend in front of member function. We
don’t need to write (friend) while defining out of class.
void display
{
//body
}
friend void display
{
//body
}
How is friend function is different from
normal function?
Let understand by a program-
Normal function Friend function

5. #include<iostream.h>
#include<conio.h>
class test
{
int data1,data2;
public:
test()
{}
test (int a, int b)
{
data1=a;
data2=b;
}
void display();//normal function
friend void multiply(test);//friend function
};

6. void test::display()//normal function in scope of class.
{
cout<<“data 1= ”<<data1;//directly access private variable
cout<<“data 2=“<<data2<<endl;
}
void multiply(test t)//object as argument.
{
int data0;
data0=t.data1*t.data2;//need object name and dot(.)
cout<<“multiplication =“<<data0;
}
void main()
{
test obj(100,200);
obj.display();//need object name and dot(.) while calling.
multiply(obj);//direct calling.
getch();
}

7.  friend function need not required scope
resolution operator.
 friend function can be declared in private or
public doesn’t matter.
 friend function can not be called using object of
the class.
 friend function need object name and dot (.) to
access private members.
 Usually it passes objects as arguments.
 The function can define anywhere like a normal
function.

8. friend void total(boss b,employee e);
class boss
boss b
int salary
void display()
{
........
}
class employee
employee e
int salary
void display()
{
........
}

9. #include<iostream.h>
#include<conio.h>
class boss
{
int salary;
public:
boss()
{}
boss(int a)
{
salary=a;
}
void display()
{
cout<<“Boss Salary =“<<salary;
}
friend void total(boss,employee);
};
class employee
{
int salary;
public:
employee()
{}
employee(int b)
{
salary=b;
}
void display()
{
cout<<“Employee Salary =“<<salary;
}
friend void total(boss,employee);
};

10. void total_salary(boss b,employee e)
{
int total;
total=b.salary+e.salary;
cout<<“Total Salary =“<<total<<endl;
}
void main()
{
boss b(50000);
b.display();
employee e(25000);
e.display();
total(b,e);
getch();
}
Boss Salary =50000
Employee Salary=25000
Total Salary = 75000