07_objects_and_classes.ppt

7/27/2019 07_Objects_and_Classes.ppt.............

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Programming Concepts in C++CT025-3-2

Classes and Objects



CT025-3-2-PCPP (Programming Concepts in C++) Classes and Objects Slide 2 (of 9)

Topic and structure of the lesson

• Classes and Objects

– Specifying a class

– Defining member variables and functions – Nesting of member functions

– Arrays within a class

– Static Data Members and Member Functions

– Arrays of objects

– Objects as function arguments




Learning Outcomes

• By the end of this session, you should be

able to:

– create, debug and run a simple C++ programsusing functions and applying concepts such

as classes and objects




Key terms to be used

• If you have mastered this topic, you should

be able to use the following terms correctly

in your assignments and exams: –class

–objects



CT025-3-2-PCPP (Programming Concepts in C++) Classes and Objects

Definition of class

• A class is the collection of related data and

function under a single name.

• Class is user defined data type.• Class consists of Data members and

methods(functions).




• A Class is a blueprint for objects

• When a class is defined, no memory is

allocated.• Object doesn't exist until an instance of the

class has been created;

• When the object is physically created,space for that object is allocated in RAM.

• Class is just the specification for objects

and object bears the property of that class.

http://cplus.about.com/od/introductiontoprogramming/g/ramdefn.htm

http://cplus.about.com/od/introductiontoprogramming/g/ramdefn.htm


http://slidepdf.com/reader/full/07objectsandclassesppt 7/26CT025-3-2-PCPP (Programming Concepts in C++) Classes and Objects

Defining the Class in C++

• Class is defined using keyword class followed by

identifier(name of class).

• Body of class is defined inside curly brackets an

terminated by semicolon at the end in similar way as structure.

class class_name

{access_specifier_1: member1;

access_specifier_2: member2;

...

} object_names;



• Where class_name is a valid identifier for

the class.

• object_names is an optional list of namesfor objects of this class.

• The body of the declaration can contain

members, that can be either data or function declarations,

• and optionally access specifiers.



Class Members

• Data Members and methods must be

declared within the class definition.

• A member cannot be redeclare within aclass.

• No member can be added elsewhere other

than in the class definition.

•



Access specifiers

• Access specifier : is one of the following three

keywords:

• private,

• public

• protected.

• These specifiers modify the access rights that

the members following them acquire:private members: of a class are accessible only

from within other members of the same class or

from their friends.



• protected members are accessible from

members of their same class and from

their friends, but also from members of

their derived classes.

public members are accessible from

anywhere where the object is visible



Accessing the Data Members

• Accessing a data member depends solely

on the access control of that data member.

• If its public, then the data member can beeasily accessed using the direct member

access (.) operator with the object of that

class.



• If, the data member is defined as private

or protected, then we cannot access the

data variables directly.

• we create special public member

functions to access,to use or to initialize

the private and protected data members.

• These member functions are

called getter and setter functions.



Accessing Private Data

Members

• The setter function will set the value

passed as argument to the private data

member, and

• getter function will return the value of the

private data member to be used.

• Both getter and setter function must bedefined public.



Accessing Protected Data

Members

• Protected data members, can be

accessed directly using dot (.) operator

inside the subclass of the current class.,

• For non-subclass we follow the steps

same as to access private data member.



class Student

{

public: int rollno;

string name;};

int main()

{

Student A;

Student B;

A.rollno=1;

A.name=“Raju";

B.rollno=2;

B.name=“suresh"; cout <<"Name and Roll no of A is:"<<A.name << A.rollno;

cout <<"Name and Roll no of B is :"<< B.name << B.rollno;

}



class Student {

private: // private data member

int rollno;

public: // public accessor and mutator functions

int getRollno(){

return rollno;

}

void setRollno(int i)

{

rollno=i;}

};

int main()

{

Student A;

A.rollono=1; //Compile time error

cout<< A.rollno; //Compile time error A.

setRollno(1); //Rollno initialized to 1

cout<< A.getRollno(); //Output will be 1 }




• class Box

{

public:

double length; // Length of a box

double breadth; // Breadth of a box

double height; // Height of a box

};

int main( )

{

Box Box1; // Declare Box1 of type Box

Box Box2; // Declare Box2 of type Box

double volume = 0.0; // Store the volume of a box here

// box 1 specification

Box1.height = 4.0;Box1.length = 6.0;

Box1.breadth = 3.0;

// box 2 specification

Box2.height = 10.0;

Box2.length = 12.0;

Box2.breadth = 12.0;

// volume of box 1volume = Box1.height * Box1.length * Box1.breadth;

cout << "Volume of Box1 : " << volume <<endl;

// volume of box 2

volume = Box2.height * Box2.length * Box2.breadth;

cout << "Volume of Box2 : " << volume <<endl;

return 0;

}




• Volume of Box1 : 72

Volume of Box2 : 1440




Nesting of member functions

• A member function of a class can be

called only by an object of that class using

a dot operator.

• A member function can be called by using

its name inside another member function

of the same class.

• This is known as nesting of member

functions.




• #include

using namespace std;

class set

{

int m,n;

public:

void input(void);void display(void);

void largest(void);

};

int set :: largest(void)

{

if(m >= n)

return(m);

else

return(n);}

void set :: input(void)

{

cout << "Input value of m and n"<<"\n";

cin >> m>>n;

}

void set :: display(void)

{

cout << "largest value=" << largest() <<"\n";}

int main()

{

set A;

A.input();

A.display();

• return 0;

}




Arrays within a class




Follow up Assignment

1. Write a complete C++ program that uses inline function

sphereVolume to prompt the user for radius of a sphere, and

to calculate and print the volume of that sphere using the

assignment

volume = (4/3)*3.14159*pow(radius, 3);

2. Do question 3.12 (Deitel & Deitel)







Summary of key points



– Defining member variables and functions

– Nesting of member functions







Highlight of next session



– Defining member variables and functions

– Nesting of member functions





07_objects_and_classes.ppt

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