The document discusses various C++ concepts related to classes and objects including friend functions, friend classes, passing objects as arguments, returning objects, dynamic memory allocation using pointers to objects, copy constructors, different types of constructors, generic functions, and generic classes. Some key points covered are: 1. Friend functions and classes allow non-member functions and other classes to access private and protected members of a class. 2. Objects can be passed as arguments to functions and returned from functions. 3. Dynamic memory is allocated using pointers to objects and arrays of objects. 4. Copy constructors are used to initialize objects with other existing objects. 5. Different types of constructors - default

1. 1 | P a g e A n a n d a K u m a r H N
UNIT - 03 / CLASSES AND OBJECT - II
Friend Function:
class x{
public:
float a,b;
void add()
{
cout<<"add:"<<a+b<<endl;
}
friend void avg(x); //friend function declaration
using friend prefix
};
void avg(x x1) //function definition
{
cout<<"avg:"<<((x1.a+x1.b)/2);
}
int main()
{
x a,b;
cout<<"enter two valuesn";
cin>>a.a>>a.b;
a.add(); //member function call using object
reference
avg(a); // no need of object reference since it is
friend function
}
OUTPUT:
Friend Classes:
class x
{
private: int a,b; //private data members
public:
//initializing data members of class x
void init(int u, int t)
{
a=u;
b=t;
}
friend class y; //making class y as friend of x
};
class y
{
public:
int m,n;
//initializing data members of class y
void init(int q, int p)
{
m=q;
n=p;
}
// member function of class of y is accessing private
data members of class of x
void print(x x1)
{
cout<<"adding a+m:"<<x1.a+m<<endl;
cout<<"adding b+n:"<<x1.b+n<<endl;
}
};
int main()
{
x xx;
xx.init(11,22);
y yy;
yy.init(33,44);
yy.print(xx);
}
OUTPUT:
Friend Classes with common non member
function as friend:
class y; //forward declaration of class y
class x{
int a,b; //private data members

2. 2 | P a g e A n a n d a K u m a r H N
public:
int e,f; //public data members
//initializing data members of class x
void initx(int x,int y,int o,int n)
{
a=x;
b=y;
e=o;
f=n;
}
//making non member function as friend of class x
friend void show(x x1,y y1);
friend class y; //making class y as friend of class x
};
class y{
int c,d;
public:
//initializing data members of class y
void inity(int t, int u)
{
c=t;
d=u;
}
//making non member function as friend of class x
friend void show(x x1,y y1);
};
//definition of non member of function
void show(x x1,y y1)
{
cout<<"a:"<<x1.a<<endl;
cout<<"b:"<<x1.b<<endl;
cout<<"c:"<<y1.c<<endl;
cout<<"d:"<<y1.d<<endl;
cout<<"a+c="<<x1.a+y1.c<<endl;
cout<<"b+d="<<x1.b+y1.d<<endl;
}
int main()
{
x x1;
y y1;
x1.initx(10,20,3,4);
y1.inity(25,40);
show(x1,y1); //calling friend function without object
reference
}
OUTPUT:
Passing objects as arguments:
class x{
public:
int a,b;
void add(x x1) //reciving object as a parameter
{
cout<<"add:"<<x1.a+x1.b<<endl;
}
float avg(x); //member function declaration
};
float x::avg(x x2) //defining function outside the class
{
return ((x2.a+x2.b)/2.0); //returning float value
}
int main()
{
x n1,n2;
cout<<"enter two valuesn";
cin>>n1.a>>n1.b;
n2.add(n1); //passing object n1 as parameter
cout<<"avg:"<<n2.avg(n1);
}
OUTPUT:
Returning objects:
class complex{
private:
int real;
int img;

3. 2 | P a g e A n a n d a K u m a r H N
public:
int e,f; //public data members
//initializing data members of class x
void initx(int x,int y,int o,int n)
{
a=x;
b=y;
e=o;
f=n;
}
//making non member function as friend of class x
friend void show(x x1,y y1);
friend class y; //making class y as friend of class x
};
class y{
int c,d;
public:
//initializing data members of class y
void inity(int t, int u)
{
c=t;
d=u;
}
//making non member function as friend of class x
friend void show(x x1,y y1);
};
//definition of non member of function
void show(x x1,y y1)
{
cout<<"a:"<<x1.a<<endl;
cout<<"b:"<<x1.b<<endl;
cout<<"c:"<<y1.c<<endl;
cout<<"d:"<<y1.d<<endl;
cout<<"a+c="<<x1.a+y1.c<<endl;
cout<<"b+d="<<x1.b+y1.d<<endl;
}
int main()
{
x x1;
y y1;
x1.initx(10,20,3,4);
y1.inity(25,40);
show(x1,y1); //calling friend function without object
reference
}
OUTPUT:
Passing objects as arguments:
class x{
public:
int a,b;
void add(x x1) //reciving object as a parameter
{
cout<<"add:"<<x1.a+x1.b<<endl;
}
float avg(x); //member function declaration
};
float x::avg(x x2) //defining function outside the class
{
return ((x2.a+x2.b)/2.0); //returning float value
}
int main()
{
x n1,n2;
cout<<"enter two valuesn";
cin>>n1.a>>n1.b;
n2.add(n1); //passing object n1 as parameter
cout<<"avg:"<<n2.avg(n1);
}
OUTPUT:
Returning objects:
class complex{
private:
int real;
int img;

4. 2 | P a g e A n a n d a K u m a r H N
public:
int e,f; //public data members
//initializing data members of class x
void initx(int x,int y,int o,int n)
{
a=x;
b=y;
e=o;
f=n;
}
//making non member function as friend of class x
friend void show(x x1,y y1);
friend class y; //making class y as friend of class x
};
class y{
int c,d;
public:
//initializing data members of class y
void inity(int t, int u)
{
c=t;
d=u;
}
//making non member function as friend of class x
friend void show(x x1,y y1);
};
//definition of non member of function
void show(x x1,y y1)
{
cout<<"a:"<<x1.a<<endl;
cout<<"b:"<<x1.b<<endl;
cout<<"c:"<<y1.c<<endl;
cout<<"d:"<<y1.d<<endl;
cout<<"a+c="<<x1.a+y1.c<<endl;
cout<<"b+d="<<x1.b+y1.d<<endl;
}
int main()
{
x x1;
y y1;
x1.initx(10,20,3,4);
y1.inity(25,40);
show(x1,y1); //calling friend function without object
reference
}
OUTPUT:
Passing objects as arguments:
class x{
public:
int a,b;
void add(x x1) //reciving object as a parameter
{
cout<<"add:"<<x1.a+x1.b<<endl;
}
float avg(x); //member function declaration
};
float x::avg(x x2) //defining function outside the class
{
return ((x2.a+x2.b)/2.0); //returning float value
}
int main()
{
x n1,n2;
cout<<"enter two valuesn";
cin>>n1.a>>n1.b;
n2.add(n1); //passing object n1 as parameter
cout<<"avg:"<<n2.avg(n1);
}
OUTPUT:
Returning objects:
class complex{
private:
int real;
int img;

5. 5 | P a g e A n a n d a K u m a r H N
class emp
{
private:
char name[50];
int ID;
float salary;
public:
void read()
{
cout<<"enter name, ID and salaryn";
cin>>name>>ID>>salary;
}
void display( )
{
cout<<"NAME"<<"t"<<"ID"<<"t"<<"SALARYn";
cout<<name<<"t"<<ID<<"t"<<salary<<endl;
}
};
int main()
{
emp *e;
e=new emp;
e->read();
e->display();
}
OUTPUT:
class emp
{
private:
char name[50];
int ID;
float salary;
public:
void read( )
{
cout<<"enter name, ID and salaryn";
cin>>name>>ID>>salary;
}
void display( )
{
cout<<name<<"t"<<ID<<"t"<<salary<<endl;
}
};
int main()
{
int sizee;
cout<<"enter how many employee:"<<endl;
cin>>sizee;
emp *e=new emp[sizee];
for(int i=1;i<=sizee;i++)
{
cout<<"enter "<<i<<" employe name ID
salary:"<<endl;
e[i].read();
}
cout<<"employe details:"<<endl<<endl;
cout<<"NAME"<<"t"<<"ID"<<"t"<<"SALARY"<<e
ndl;
for(int i=1;i<=sizee;i++)
{
e[i].display();
}
delete [ ] e;
}

6. 6 | P a g e A n a n d a K u m a r H N
class student{
public:
char name[30];
int usn;
void read()
{
cin>>name>>usn;
}
void show()
{
cout<<name<<"t"<<usn<<endl;
}
};
int main()
{
student *s;
s=new student[3];
for(int i=1;i<=3;i++)
{
cout<<"enter name and usn for student "<<i;
s[i].read();
}
cout<<"nametusnn";
for(int i=1;i<=3;i++)
{
s[i].show( );
}
delete [ ] s;
}
OUTPUT:
Pointers to objects:
class emp
{
private:
char name[50];
int ID;
float salary;
public:
void read()
{
cout<<"enter name, ID and salaryn";
cin>>name>>ID>>salary;
}
void display()
{
cout<<"NAME"<<"t"<<"ID"<<"t"<<"SALARYn";
cout<<name<<"t"<<ID<<"t"<<salary<<endl;
}
};
int main()
{
emp e;

7. 7 | P a g e A n a n d a K u m a r H N
emp *d;
d=&e; // pointer to an object;
d->read(); //arrow to operator to access fuction
d->display();
}
class a
{
public:
int num;
a()
{
num=0;
}
a(int x)
{
num=x;
}
int get()
{
return num;
}
};
int main()
{
a a1(100);
a a2[5]={1,2,3,4,5};
a *x,*y;
x=&a1;
y=&a2[0];
cout<<x->get()<<endl;
for(int i=0;i<5;i++)
{
cout<<y->get()<<endl;
y++;
}
}
Copy constructors:
class X
{
public:
int a, b;
X()
{
cout<<"default constructor"<<endl;
}
void init(int x,int y)
{
a=x;
b=y;
}
X(X &m)
{
a=m.a;
b=m.b;
cout<<"copy constructor calledn";
}
void show()
{
cout<<"a:"<<a<<endl<<"b:"<<b<<endl;
}
};
int main()
{
X x1,x2; //default constructor is called
x1.init(99,88);
x1.show();
x2.init(55,11);//copy constructor is called
x2.show();
X x3=x1;//copy constructor is called
X x4(x2);//copy constructor is called
x3.show();
x4.show();
X x5;
x5=x3;// just copy , copy constructor is not called
x5.show();
}

8. 8 | P a g e A n a n d a K u m a r H N
/*All Type of CONSTRUCTORS*/
class X
{
public:
int a, b;
X( )
{
a=b=0;
cout<<"default constructor"<<endl;
}
X(int x)
{ a=b=x;
cout<<"constructor with one parametern";
}
X(int x,int y)
{
a=x;
b=y;
cout<<"constructor with two parameter"<<endl;
}
X(X &m)
{
a=m.a;
b=m.b;
cout<<"copy constructor calledn";
}
void show()
{
cout<<"a:"<<a<<endl<<"b:"<<b<<endl;
}
};
int main()
{
X x1; //default constructor is called
x1.show();
X x2(100);//constructor with single parameter
x2.show();
X x3(29,99);//constructor with two parameter
x3.show();
X x4=x3;//copy constructor is called
x4.show();
X x5(x2);//copy constructor is called
x5.show();
x5=x3;// just copy , copy constructor is not called
x5.show();
}
Generic functions:
/*Generic function with ONE Type*/
template <class T1>
void myfunc(T1 X)
{
cout<<X<<endl;
}
int main()
{
myfunc(10);
myfunc("ATME-570028");
myfunc(3333.333);
myfunc("3rd SEMESTER");
myfunc(0.7685);
}

9. 9 | P a g e A n a n d a K u m a r H N
/*Generic function with TWO Type*/
template <class T1,class T2>
void myfunc(T1 X,T2 Y)
{
cout<<X<<"tt"<<Y<<endl;
}
int main()
{
myfunc(10,25);
myfunc(11.222,44.567);
myfunc("ATME","570028");
myfunc(55,76.666);
myfunc("atme mysore",570028);
}
/*Overloading Generic Fuctions*/
template <class T1>
void myfunc(T1 X)
{
cout<<"single parameter: "<<X<<endl;
}
template <class T1,class T2>
void myfunc(T1 X,T2 Y)
{
cout<<"TWO parameters: "<<X<<" "<<Y<<endl;
}
int main()
{
myfunc(10,25.555);
myfunc(55,"ATME-570028");
myfunc(3333.333);
myfunc("atme","mysore");
myfunc(100,200);
myfunc("3rd Semester");
}
/*Overriding Generic Fuction*/
template <class T1>
void myfunc(T1 X)
{
cout<<"single parameter: "<<X<<endl;
}
template <class T1,class T2>
void myfunc(T1 X,T2 Y)
{
cout<<"TWO parameter: "<<X<<" "<<Y<<endl;
}
void myfunc(int m,int n)
{
cout<<"inside fuction myfuc: "<<m<<" "<<n<<endl;
}
int main()
{
myfunc(10,25.555); //calls generic function
myfunc(55,"ATME-570028"); //calls
generic function
myfunc(3333.333); //calls generic function
myfunc(1,2); //overrides generic function
myfunc("atme mysore"); //calls generic function
myfunc(100,200); //overrides generic function
}
Generic CLASSES:
/*Generic CLASS with ONE type*/
template <class T>
class x
{
public: T a;
T b;

10. 10 | P a g e A n a n d a K u m a r H N
x(T m,T n)
{
a=m;
b=n;
}
void add()
{
cout<<”sum(a,b)=”<<a+b<<endl;
}
};
int main()
{
x<int>x1(111,222);
x<float>x2(2.33,4.7);
x<double>x3(22.33,44.77);
x1.add();
x2.add();
x3.add();
}
/*Generic CLASS with TWO types*/
template <class T1,class T2>
class x
{
public: T1 a;
T2 b;
x(T1 m,T2 n)
{
a=m;
b=n;
}
void add()
{
cout<<"sum(a,b)="<<a+b<<endl;
}
};
int main()
{
x<int,int>x1(11,222);
x<int,float>x2(2,4.7);
x<double,float>x3(33.333,55.555);
x1.add();
x2.add();
x3.add(); }
Operator overloading
/*overloaing unary + operator
as a member fuction*/
class a
{
public:
int m,n;
void init(int x, int y)
{
m=x;
n=y;
}
//overloaing as member fuction;
a operator+()
{
a t;
t.m=+m;
t.n=+n;
return t;
}
void show()
{
cout<<m<<endl<<n<<endl<<endl;
}
};
int main()
{
a aa,cc;
aa.init(-1,-1);
aa.show();
cc=+aa;
cc.show();
}
/*overloaing unary - operator
as a member fuction*/
class a
{
public:
int m,n;
void init(int x, int y)
{
m=x;
n=y;
}

11. 11 | P a g e A n a n d a K u m a r H N
a operator-( )
{
a t;
t.m=-m;
t.n=-n;
return t;
}
void show( )
{
cout<<m<<endl<<n<<endl<<endl;
}
};
int main( )
{
a aa,bb,cc;
aa.init(-1,-1);
bb.init(-20,-40);
aa.show( );
bb.show( );
cc=-aa;
cc.show( );
cc=-bb;
cc.show( );
}