Chapter: 11th Computer Science : Chapter 14 : Classes and objects
Example C++ Programs: Classes and objects
Illustration 14.1 Inline and Outline member function
Absence of access specifier means that members are private by default..
# include <iostream>
using namespace std;
class Box
{
double width; // no access specifier mentioned
public:
double length;
void printWidth( ) //inline member function definition
{
cout<<”\n The width of the box is...”<<width;
}
void setWidth( double w ); //prototype of the function
};
void Box :: setWidth(double w) // outline member function definition
{
width=w;
}
int main( )
{
Box b; // object for class Box
b.setWidth(10.0); // Use member function to set the width.
b.printWidth( ); //Use member function to print the width.
return 0;
}
Output:
The width of the box is... 10
Illustration 14.2 The use of local object
A global object can be declared only for global class. If a class definition is specified outside the body of all functions in a program then it is called global class
#include <iostream>
#include <conio>
using namespace
std class add //Global class
{
int a,b;
public:
int sum;
void getdata()
{
a=5;
b=10;
sum = a+b;
}
} a1;
add a2;
int main()
{
add a3; //Local object for a global class
a1.getdata();
a2.getdata();
a3.getdata(); //public data member accessed from outside the class
cout<<a1.sum;
cout<<a2.sum;
cout<<a3.sum;
return 0;
}
Output:
151515
Illustration 14.3 Memory allocation for objects
include <iostream>
using namespace std;
//The members will be allocated with memory space only after the creation of the class type object
class product
{
int code, quantity;
float price;
public:
void assignData();
void Print();
};
int main()
{
product p1, p2;
cout<<”\n Memory allocation for object p1 ” <<sizeof(p1);
cout<<”\n Memory allocation for object p2 ” <<sizeof(p2);
return 0;
}
Output:
Memory allocation for object p1 12
Memory allocation for object p2 12
Illustration 14.4 C++ program to illustrate the communication of object:
Calling a member function of an object is also known as sending message to object or communication with the object.
#include<iostream>
using namespace std;
class compute
{
int n1,n2; //private by default
public :
int n;
int add (int a, int b) //inline member function
{
int c=a+b; //int c ; local variable for this function
return c;
}
int prd (int a, int b) //inline member function
{
int c=a*b;
return c;
}
}; // end of class specification
compute c1,c2; //global object
int main()
{
c1.n =c1.add(12,15); //member function is called
c2.n =c2.add(8,4);
cout<<"\n Sum of object-1 "<<c1.n;
cout<<"\n Sum of object-2 "<<c2.n;
cout<<"\n Sum of the two objects are "<<c1.n+c2.n;
c1.n=c1.prd(5,4);
c2.n=c2.prd(2,5);
cout<<"\n Product of object-1 "<<c1.n;
cout<<"\n Product of object-2 "<<c2.n;
cout<<"\n Product of the two objects are "<<c1.n*c2.n;
return 0;
}
Output:
Sum of object-1 27
Sum of object-2 12
Sum of the two objects are 39
Product of object-1 20
Product of object-2 10
Product of the two objects are 200
Illustration 14.5 Array of objects
gets () can accept a string with space which is not possible by cin.
#include<iostream>
#include<stdio.h>
using namespace std;
class stock
{
int itemno;
char itemname[10]; // array as member variable
float price;
public:
void getdata()
{
cin>>itemno>>price;
gets(itemname);
}
void putdata()
{
cout<<’\n’<<itemno<<’\t’<<itemname<<’\n’<<price;
}
};
int main()
{
stock s[10];
int i;
cout<<”Enter the details\n”;
for( i=0;i<10;i++)
s[i].getdata();
cout<<”\n Item Details\n”;
cout<<”\nITEM NO \t ITEM NAME\t PRICE”<<endl;
for( i=0;i<10;i++)
s[i].putdata();
return 0;
}
Output
Item Details
ITEM NOITEM NAME PRICE
101 APSARA PENCIL Price10.5
102 FABER CASTELL PENCIL Price12.0001
103 NATARAJ PENCIL Price9.75
201 PILOT V7 PEN Price50
201 CELLO BUTTERFLOW Price10
202 PARKER PEN Price450
202 PILOT FOUNTAIN PEN Price600
301 APSARA ERASER Price5
302 FABER CASTELL ERASER Price15.0001
303 NATARAJ ERASER Price3
Illustration 14.6 Inline Outline and function
#include<iostream>
using namespace std
class sales
{
int sno;
char sname [15];
float hrwrk,wage,totwage;
void calcwg( )
{
totwage=hrwrk * wage;
}
public :
void in_data();
void out_data();
};
void sales :: in_data()
{
wage=75.26;
totwage=0.0;
cout<<"\nEnter the salesperson id";cin>>sno;
cout<<"\nEnter the name" ;gets(sname);
cout<<"\nEnter the hours worked" ;cin>>hrwrk;
calcwg(); //member function called inside by another member function
}
void sales :: out_data()
{
cout<<"\n Wage slip ";
cout<<"\n ~~~~~~~~ ";
cout<<"\nID : " << sno;
cout<<"\nName : " <<sname ;
cout<<"\nHours worked :" <<hrwrk;
cout<<"\nTotal Wage :"<<setprecision(2)<<totwage;
}
int main()
{
sales sal;
sal.in_data();
sal.out_data();
return 0;
}
Output:
Enter the salesperson id 1201
Enter the name ARUL
Enter the hours worked 7
Wage slip
~~~~~~~~
ID : 1201
Name : ARUL
Hours worked :7
Total Wage :526.82
Illustration 14.7 The use of Nesting of Member Function
A member function can call another member function of the same class for that you do not need an object.
#include<iostream>
using namespace std
class nest
{
int a;
int square_num( )
{
return a* a;
}
public:
void input_num( )
{
cout<<”\nEnter a number ”;
cin>>a;
}
int cube_num( )
{
return a* a*a;
}
void disp_num()
{
int sq=square_num(); //nesting of member function
int cu=cube_num(); //nesting of member function
cout<<”\nThe square of “<<a<<” is ” <<sq;
cout<<”\nThe cube of “<<a<<” is ” <<cu;
}
};
int main()
{
nest n1;
n1.input_num();
n1.disp_num();
return 0;
}
Output:
Enter a number 5
The square of 5 is 25
The cube of 5 is 125
Illustration 14.8 The use of scope resolution operator
Recall :: is also used to identify the class to which a member function belongs to.
#include<iostream>
using namespace std;
int a=100;
class A
{
int a;
public:
void fun()
{
a=20;
a+=::a; //using global variable value
cout<<a;
} };
int main()
{
clrscr(); A a1;
a1.fun();
retun 0;
}
Output:
120
Illustration 14.9 C++ program to illustrate how the pass by value method work
we can assign one object to another object, Similar to structure object
#include <iostream>
using namespace std;
class Sample
{
private:
int num;
public:
void set (int x)
{
num = x;
}
void pass(Sample obj1, Sample obj2) //objects are passed
{
obj1.num=100; // value of the object is changed inside the function
obj2.num=200; // value of the object is changed inside the function
cout<<"\n\n Changed value of object1 "<<obj1.num;
cout<<"\n\n Changed value of object2 "<<obj2.num;
}
void print( )
{
cout<<num;
}
};
int main()
{
//object declarations
Sample s1;
Sample s2;
Sample s3;
//assigning values to the data member of objects
s1.set(10);
s2.set(20);
cout<<"\n\t\t Example program for pass by value\n\n\n"; //printing the values before passing the object
cout<<"\n\nValue of object1 before passing";
s1.print();
cout<<"\n\nValue of object2 before passing ";
s2.print();
passing object s1 and s2
s3.pass(s1,s2);
//printing the values after returning to main
cout<<"\n\nValue of object1 after passing ";
s1.print();
cout<<"\n\nValue of object2 after passing ";
s2.print();
return 0;
}
Output:
Example program for PASS BY VALUE
Value of object1 before passing 10
Value of object2 before passing 20
Changed value of object 1 100
Changed value of object 200
Value of object 1 after passing 10
Value of object 2 after passing 20
Illustration 14.10 C++ program to illustrate how the pass by reference method work
#include <iostream>
using namespace std;
class Sample
{
private:
int num;
public:
void set (int x)
{
num = x;
}
void pass(Sample &obj1, Sample &obj2) //objects are passed
{
obj1.num=100; // value of the object is changed inside the function
obj2.num=200; // value of the object is changed inside the function
cout<<"\n\n Changed value of object1 "<<obj1.num;
cout<<"\n\n Changed value of object2 "<<obj2.num;
}
void print()
{
cout<<num;
}
};
int main()
{
clrscr();
//object declarations
Sample s1;
Sample s2;
Sample s3;
//assigning values to the data member of objects
s1.set(10);
s2.set(20);
cout<<"\n\t\t Example program for pass by reference\n\n\n";
//printing the values before passing the object
cout<<"\n\nValue of object1 before passing"; s1.print();
cout<<"\n\nValue of object2 before passing "; s2.print();
//passing object s1 and s2 s3.pass(s1,s2);
//printing the values after returning to main
cout<<"\n\nValue of object1 after passing "; s1.print();
cout<<"\n\nValue of object2 after passing ";
s2.print();
return 0;
}
Output:
Example program for PASS BY REFERENCE
Value of object1 before passing10
Value of object 2 before passing 20
Changed value of object1 100
Changed value of object2 200
Value of object1 after passing 100
Value of object2 after passing 200
Illustration 14.11 C++ program to illustrate how an object is returned to the calling function
#include <iostream>
using namespace std;
class Sample
{
private:
int num;
public:
void set (int x)
{
num = x;
}
Sample pass(Sample obj1, Sample obj2) //
{
Sample s4;
s4.num=obj1.num+obj2.num;
return s4;
}
}
void print()
{
cout<<num;
}
};
int main()
{
//object declarations
Sample s1;
Sample s2;
Sample s3;
//assigning values to the data member of objects
s1.set(10);
s2.set(20);
cout<<"\n\t\t Example program for Returning an object \n\n\n";
//passing object s1 and s2
s3=s3.pass(s1,s2);
//printing the values of object
cout<<"\nThe value of s1.num is ";
s1.print();
cout<<"\nThe value of s2.num is ";
s2.print();
//printing the sum
cout<<"\nThe sum s3.num is ";s3.print();
return 0;
}
Output:
Example program for Returning an object
The value of s1.num is 10
The value of s2.num is 20
The sum s3.num is 30
Illustration 14.12 C++ program to illustrate the nested class
#include<iostream>
using namespace std;
class enclose
{
private:
int x;
class nest
{
private :
int y;
public:
int z;
void prn()
{
y=3;z=2;
cout<<"\n The product of"<<y<<'*'<<z<<"= "<<y*z<<"\n";
}
}; //inner class definition over
nest n1;
public:
nest n2;
void square()
{
n2.prn(); //inner class member function is called by its object x=2;
n2.z=4;
cout<<"\n The product of " <<n2.z<<'*'<<n2.z<<"= "<<n2.z*n2.z<<"\n";
cout<<"\n The product of " <<x<<'*'<<x<<"= "<<x*x; }
}; //outer class definition over
int main()
{
enclose e;
e.square(); //outer class member function is called
}
Output:
The product of 3*2=6
The product of 4*4=16
The product of 2*2=4
Illustration 14.13 C++ program to illustrate the containership
#include<iostream>
using namespace std;
class outer
{
int data;
public:
void get();
};
class inner
{
int value;
outer ot; // object ot of class outer is declared in class inner
public:
void getdata();
};
void outer :: get()
{
cout<<"\nEnter a value";
cin>>data;
cout<<"\nThe given value is "<<data;
}
void inner :: getdata()
{
cout<<"\nEnter a value";
cin>>value;
cout<<"\nThe given value is "<<value;
ot.get(); //calling of get() of class outer in getdata() of class inner
}
int main()
{
inner in;
in.getdata();
return 0;
}
Output:
Enter a value10
The given value is 10
Enter a value 20
The given value is 20
Illustration 14.14 A constructor defined inside the class specification.
#include<iostream>
using namespace std;
class Sample
{
int i,j;
public :
int k;
Sample()
{
i=j=k=0;//constructor defined inside the class
}
};
Illustration 14.15 A constructor defined inside the class specification.
#include<iostream>
using namespace std;
class Sample
{
int i,j;
public :
int k;
Sample()
{
i=j=k=0;//constructor defined inside the class
}
};
int main()
{
Samples1;
return 0;
}
Illustration 14.16 A constructor defined outside the class specification.
#include<iostream>
using namespace std;
class Data
{
int p,q;
public :
int r;
Data(); //only prototype to be specified here to intimate its access specifier
};
Data ::Data()
{
p=q=r=0; // constructor defined outside the class
}
int main()
{
Data d1;
return 0;
}
Illustration 14.17 illustrate a constructor defined inside the private visibility.
#include<iostream>
using namespace std;
class X
{
int num;
X()
{
num=k=0;
}
public:
int k;
};
int main()
{
X x; // The constructor of X cannot accessed by main() because main() is a
//non member function
//and the compiler throws error message [Error] 'X::X()' is private
return 0;
}
Illustration 14.18 illustrate a member function initializes the data member.
After creating the object the getvalue() should be explicitly called to initialize the object.
#include<iostream>
using namespace std;
class Sample
{
int i, j;
public :
int k;
void getvalue()
{
i=j=k=0; //member function
}
int main()
{
Sample s1;
s1.getvalue(); //member function initializes the class object
return 0;
}
Illustration 14.19 illustrate the compiler generated constructor
#include<iostream>
using namespace std;
class Sample
{
int i, j;
public:
int k; //no user defined constructor in this program
void getvalue()//member function
{
i=j=k=0;
}
};
int main()
{
Sample s1; //uses the default constructor generated by the compiler
s1.getvalue();
return 0;
}
Illustration 14.20 to illustrate the constructor and other member function in a class
#include<iostream>
using namespace std;
class simple
{
private:
int a,b;
public:
simple()
{
a= 0 ;
b= 0;
cout<< "\n Constructor of class-simple ";
}
void getdata()
{
cout<<"\n Enter values for a and b (sample data 6 and 7)... ";
cin>>a>>b;
}
void putdata()
{
cout<<"\nThe two integers are... "<<a<<'\t'<< b<<endl;
cout<<"\n The sum of the variables "<<a<<" + "<<b<<" = "<<a+b;
}
};
int main()
{
simple s;
s.getdata();
s.putdata();
return 0;
}
Output:
Constructor of class-simple
Enter values for a and b (sample data 6 and 7)... 6 7
The two integers are... 6 7
The sum of the variables 6 + 7 = 13
Illustration 14.21 to illustrate the Parameterized constructor used for creating objects
#include<iostream>
using namespace std;
class simple
{
private:
int a,b;
public:
simple(int m, int n)
{
a= m ;
b= n;
cout<< "\n Parameterized Constructor of class-simple "<<endl;
}
void putdata()
{
cout<<"\nThe two integers are... "<<a<<'\t'<< b<<endl;
cout<<"\n The sum of the variables "<<a<<" + "<<b<<" = "<< a+b; }
};
int main()
{
simple s1(10,20),s2(30,45); //Created two objects with different values created
cout<<"\n\t\tObject 1\n";
s1.putdata();
cout<<"\n\t\tObject 2\n";
s2.putdata();
return 0;
}
Output:
Parameterized Constructor of class-simple
Parameterized Constructor of class-simple
Object 1
The two integers are .. 10 20
The sum of the variables 10 + 20 = 30
Object 2
The two integers are... 30 45
The sum of the variables 30 + 45 = 75
Illustration 14.22 to illustrate the creation of object with no argument after defining parameterized constructor throws error
Note:- Just like normal function parameterized constructor can also have default arguments.
#include<iostream>
using namespace std;
class simple
{
private:
int a,b;
public:
simple(int m, int n)
{
a= m ;
b= n;
cout<< "\n Parameterized Constructor of class-simple "<<endl;
}
void putdata()
{
cout<<"\nThe two integers are .. "<<a<<'\t'<< b<<endl;
cout<<"\n The sum of the variables "<<a<<" + "<<b<<" = "<< a+b; }
};
int main()
{
simple s,s1(10,20) // [Error] no matching function for call to 'simple::simple()'
s1.putdata();
s2.putdata();
return 0;
}
Illustration 14.23 to illustrate the default argument in parameterized constructor
#include<iostream>
using namespace std;
class simple
{
private:
int a,b;
public:
simple(int m, int n=100) //default argument
{
a= m ;
b= n;
cout<< "\n Parameterized Constructor with default argument"<<endl;
}
void putdata()
{
cout<<"\nThe two integers are... "<<a<<'\t'<< b<<endl;
cout<<"\n The sum of the variables "<<a<<" + "<<b<<" = "<< a+b; }
};
int main()
{
simple s1(10,20),s2(50);
cout<<"\n\t\tObject 1 with both values \n";
s1.putdata();
cout<<"\n\t\tObject 2 with one value and one deafult value\n";
s2.putdata();
return 0;
}
Output:
Parameterized Constructor with default argument
Parameterized Constructor with default argument
Object 1 with both values
The two integers are... 10 20
The sum of the variables 10 + 20 = 30
Object 2 with one value and one deafult value
The two integers are... 50 100
The sum of the variables 50 + 100 = 150
Illustration 14.24 to illustrate the significance of default constructor
#include<iostream>
using namespace std;
class simple
{
private:
int a, b;
public:
simple() //default constructor
{
a= 0;
b= 0;
cout<< "\n default constructor"<<endl;
}
int getdata();
};
int simple :: getdata()
{
int tot;
cout<<"\nEnter two values ";
cin>>a>>b;
tot=a+b;
return tot;
}
int main()
{
int sum=0;
simple s1[3];
cout<<"\n\t\tObject 1 with both values \n";
for (int i=0;i<3;i++)
sum+=s1[i].getdata();
cout<<"\nsum of all object values is"<<sum;
return 0;
}
Output:
default constructor
default constructor
default constructor
Object 1 with both values
Enter two values 10 20
Enter two values 30 40
Enter two values 50 50
sum of all object values is200
Illustration14.25 to illustrate implicit call and explicit call
#include<iostream>
using namespace std;
class simple
{
private:
int a, b;
public:
simple(int m,int n)
{
a= m ;
b= n;
cout<< "\n Constructor of class-simple invoked for implicit and explicit call"<<endl;
}
void putdata()
{
cout<<"\nThe two integers are... "<<a<<'\t'<< b<<endl;
cout<<"\n The sum of the variables "<<a<<" + "<<b<<" = "<<a+b; }
};
int main()
{
simple s1(10,20); //implicit call
simple s2=simple(30,45); //explicit call
cout<<"\n\t\tObject 1\n";
s1.putdata();
s2.putdata();
return 0;
}
Explicit call to constructor creates a temporary instance
Output:
Constructor of class-simple invoked for implicit and explicit call
Constructor of class-simple invoked for implicit and explicit call
Object 1
The two integers are... 10 20
The sum of the variables 10 + 20 = 30
Object 2
The two integers are... 30 45
The sum of the variables 30 + 45 = 75
Illustration 14.26 to illustrate Copy constructor
#include <iostream>
using namespace std;
class Test
{
private:
int X;
int Y;
public:
Test (int , int ); //parameterized constructor declaration
Test (Test &); //Declaration of copy constructor to initialize data members.
void Display();
};//End of class
Test:: Test(int a, int b) //Definition of parameterized constructor.
{
X = a;
Y = b;
}
Test::Test(Test &T) //Definition of copy constructor.
{
X = T.X;
Y = T.Y;
}
void Test:: Display()//Definition of Display () member function.
{
cout<<endl<< "X: " << X;
cout<<endl<< "Y: " << Y <<endl;
}
int main()
{
Test T1(10,20) ; //Parameterized Constructor automatically called when
//object is created.
cout<<endl<<"T1 Object: " <<endl;
cout<< "Value after initialization : " ;
T1.Display();
Test T2(T1);//Intialize object with other object using copy constructor cout<<endl<< "T2 Object: " <<endl;
cout<< "Value after initialization : ";
T2.Display();
return 0;
}
Output:
T1 Object:
Value after initialization :
X: 10
Y: 20
T2 Object:
Value after initialization :
X: 10
Y: 20
Illustration14.27 to illustrate order of execution of constructor
#include<iostream>
using namespace std;
class outer
{
int data;
public:
outer()
{
cout<<"\nconstructor of class outer ";
}
};
class inner
{
outer ot; // object ot of class outer is declared in class inner
public:
inner()
{
cout<<"\n constructor of class inner ";}
};
int main()
{
inner in;
return 0;
}
Output:
constructor of class outer
constructor of class inner
Illustration14.28 to illustrate dynamic initialization
#include<iostream>
using namespace std;
class X
{
int n;
float avg;
public:
X(int p,float q)
{
n=p;
avg=q;
}
void disp()
{
cout<<"\n Roll numbe:- " <<n;
cout<<"\nAverage :- "<<avg;
}
};
int main()
{
int a ; float b:
cout<<"\nEnter the Roll Number";
cin>>a;
cout<<"\nEnter the Average";
cin>>b;
X x(a,b); // dynamic initialization
x.disp();
return 0;
}
Output:
Enter the Roll Number 1201
Enter the Average 98.6
Roll numbe:- 1201
Average :- 98.6
Illustration14.29 to illustrate destructor function in a class
#include<iostream>
using namespace std;
class simple
{
private:
int a, b;
public:
simple()
{
a= 0 ;
b= 0;
cout<< "\n Constructor of class-simple ";
}
void getdata()
{
cout<<"\n Enter values for a and b (sample data 6 and 7)... ";
cin>>a>>b;
}
void putdata()
{
cout<<"\nThe two integers are .. "<<a<<'\t'<< b<<endl;
cout<<"\n The sum of the variables "<<a<<" + "<<b<<" = "<<a+b;
}
~simple()
{ cout<<”\n Destructor is executed to destroy the object”;} };
int main()
{
simple s;
s.getdata();
s.putdata();
return 0;
}
Output:
Constructor of class-simple
Enter values for a and b (sample data 6 and 7)... 6 7
The two integers are .. 6 7
The sum of the variables 6 + 7 = 13
Destructor is executed to destroy the object
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