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Object Oriented Programming using C++

lecture 08(Access Specifiers)

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Object Oriented Concepts

Compare and contrast the structure, and

class in C++

OOP Features

What is the concept of CLASS?

How to define and implement a class?

Can we access the class members? Why Public or Private?

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Structure in C++ vs. Classes

Similarities Both are derivedtypes. Both present similar features Both are automatictypedefs

Class private members by default

Structure public members by default

The data members are thus accessible out of thestructure implementation, e.g., Client program

Classes are more advanced than structures

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OOP Features

Abstraction

Encapsulation and data hiding

InheritancePolymorphism

Reusable CODE

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Class

Class is an Object-Oriented ProgrammingConcept.

A class is a programmer-defined data

type. It consists of data members andfunctions which operate on that data.

Data Members define Object attributes

Functions define Object Behavior

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C++ Class

Classes are derivedtypes.

Class enables the programmer to model

objects that have attributes (represented as

data members), and behaviors or

operations or functionality(represented asmember functions).

Member functions are sometimes calledmethodsin otherobject-oriented languages.

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C++ Class Example1 class Time {

2public:

3 Time();

4 void setTime( int, int, int );

5 void printMilitary();

6 void printStandard();

7private:

8 int hour; // 0 - 23

9 int minute; // 0 - 59

10 int second; // 0 - 59

11};

Public: and Private:

are member-access

specifiers.

setTime,printMilitary,

andprintStandardare

member functions.Time is the constructor.

hour,minute, and

secondare data

members.

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C++ Class Declaration

To declare a class

Theclass keyword is used

The declaration is enclosed in braces {};

The class definition ends with a semicolonEvery piece of code inside the braces is

called class body

The class body thus contains classmembers

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C++ Class Class Members

A classs declaration declares the classs

members, which may consist of

The data members

The constructor & destructorfunctions

Specialized member functions

Othermember functionsInclude the functionality that can be invokedon the object of this class (or type)

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Data Members

A data member can be of any valid C++

data type. For example

Ordinary variableprimitive type

An instance variable of another class

programmer defined type

A pointer or reference variable

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public:

Public members can be accessed bymember functions as well as by functions

that declare the objects of that class.

A struct has all members public bydefault.

Normally, for classes, those member

functions are made public which mustinteract with the outside world.

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private:

Private memberscan only be accessed

by member functions.

This means they can only be accessed inthe member function body.

Remember the members mean both

variables and functions.By default all class members are private,

unless declared otherwise.

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public: OR private:

It is not compulsory for all members

functions to be public and all data

members to be private.

Some member functions can also be

private.

Similarly, data members can also be

public.

Violation ofEncapsulationprinciple

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protected:

Similar to private they cannot be

accessed directly from the outside world

Mainly used with inheritance

We will study this later Inheritance in

C++

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Initialization

Class data membercannot be initializedat declaration time.

By default all data members have

garbage value.If all members are declared public then,they can be initialized at objectdeclaration time.

Similar to structure initialization time.

Otherwise we require a constructorforthis.

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MemberFunctions

Member functions are those functions that you

declare within the class definition.

Definition of these functions must be provided,

like any other function.There are a number of categories of functions.

Constructor/Destructor

Regular member functions

Overloaded operator functions

Virtual functions

Friend functions