Data members and member functions

DATA MEMBERS AND MEMBER
FUNCTIONS IN OBJECT
ORIENTED PROGRAMMING
Presented by :-
DC2016BTE0044 PUSPITA DAS
DC2016BTE0185 SHREYALAXMITALUKDAR
DC2016BTE0195 MARLOM BEY

 Introduction
 Static Data Members
 Accessing Data Members
 Defining Member Functions
 Types of Member Functions
 Conclusion
 References
Contents

Introduction
 Data Members:
O The variables declared inside the class are known as data members.
O Data members may be private or public.
 Member functions:
O The functions declared inside the class are known as member functions.
O Member functions are methods or functions that are defined inside of
objects.
O Generally used to manipulate data members and other object data.

Static Data Members
 Static Data Members are those which are declared by using the static
keyword in front of the data members.
 Static Data Members are always used in the static member function.
 The static data members are always assigned some values from the
outside of the class.
Syntax:
classWidget {
...
static unsigned int g_serial ;
...
} ;

Accessing Data Members
 Accessing Public Data Members
 Accessing Private Data Members
 Accessing Protected Data Members

Accessing Public Data Members
 Following is an example to show how to initialize and use the public data members
using the dot (.) operator and the respective object of class.
class Student
{
public:
int rollno;
string name;
};
int main()
{
StudentA;
Student B;
A.rollno=1;
A.name="Adam";
B.rollno=2;
B.name="Bella";
cout <<"Name and Roll no of A is :"<<A.name << A.rollno;
cout <<"Name and Roll no of B is :"<< B.name << B.rollno;
}

Accessing Private Data Members
 To access, use and initialize the private data member we need to create getter and setter
functions, to get and set the value of the data member.
class Student
{
private:
int rollno;
public: // public getter and setter functions
int getRollno()
{
return rollno;
}
void setRollno(int i)
{
rollno=i;
}
};
int main()
{
Student A;
A.rollono=1;
cout<< A.rollno;
A.setRollno(1);
cout<< A.getRollno(); //Output will be 1
}

Accessing Protected Data Members
 Protected data members, can be accessed directly using dot (.)
operator inside the subclass of the current class
 Protected data members can be accessed in the same way as
public data members f.rom friend functions or classes and from
derived classes.

Defining Member Function
 Inside the class definition
 Outside the class definition

InsideThe Class Definition
 A member function of a class can be defined inside the class. However,
when a member function is defined inside the class, the class name and
the scope resolution operator are not specified in the function header.
Example :
class book
{
char title[30];
float price;
public:
void getdata(char [],float); II declaration
void putdata()//definition inside the class
{
cout<<"nTitle of Book: "<<title;
cout<<"nPrice of Book: "<<price;
};

OutsideThe Class Definition
 Defining a member function outside a class requires the function declaration to be
provided inside the class definition.
Example:
Class book
{
// body of the class
} :
void book :: getdata(char a[],float b)
{
// defining member function outside the class
Strcpy(title,a):
price = b:
}
void book :: putdata ()
{
cout<<"nTitle of Book: "<<title;
cout<<"nPrice of Book: "<<price;
}

TYPES OF MEMBER FUNCTION
 Simple Function
 Static Function
 Const Function
 Inline Function
 Friend Function

Simple Function
 These are the basic member function, which don,t have any
special keyword like static etc. as prefix.
Example:
return_type functionName(parameter_list)
{
function body;
}

Static Member Function
 A function is made static by using static keyword with function name.
 It can be called using the object and the direct member access (.) operator.
But, its more typical to call a static member function by itself, using class
name and scope resolution (::) operator.
A function is made static by using static keyword with function name
Example:
class X
{
public:
static void f(){};
};
int main()
{
X::f(); // calling member function directly with class name
}

Const Member Functions
 Const keyword makes variables constant, that means once
defined, there values can't be changed.
 When used with member function, such member functions can
never modify the object or its related data members.
//Basic Syntax of const Member Function
void fun() const {}

Inline Member Functions
 All the member functions defined inside the class definition are by default
declared as Inline.
 Member functions containing a few lines of code are usually declared inline.
For example:
ClassY
{
char*a ;
public:
Char* f();{return a;}
};
Is equivalent to
Char Z
{
char*a;
Public:
char* f();
};
Inline char* Z::f()
{return a;}

Friend Member Functions
 Friend functions are made to give private access to non-class functions.You can
declare a global function as friend, or a member function of other class as friend.
Example:
class WithFriend
{
int i;
public:
friend void fun(); // Global function as friend
};
void fun()
{
withFriend wf;
wf.i=10; //Access to private data member
cout << wf.i;
}
int main()
{
fun(); //Can be called directly
}

Conclusion
 A static member function can only access static data members of the
class, it cannot access instance data members.
 A private member function can only be called by another function
that is a member class.
 Protected keywords are only used in the inheritance context.
 Objects created by object oriented programs can easily be reused in
other programs

References
■ Books
[1]. By E Balagurusamy “Object Oriented ProgrammingWith C++” ,TATA McGraw-
Hill Publishing Company Limited, 2008
■ Web Links
[2]. https://www3.ntu.edu.sg/home/ehchua/programming/cpp/cp3_OOP.html
---OOP Basics
[3]. http://www.studytonight.com/cpp/accessing-data-
members.php
---Accessing Data Members
[4]. http://www.studytonight.com/cpp/member-functions-cpp.php
---Member Functions
[5]. http://www.studytonight.com/cpp/types-of-member-function.php
---Types of Member Function

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