6. Implementation of classes_and_its_advantages.pdf

CSE201
Unit – II
Implementation of classes
25-03-2023 Ref. "Object-Oriented Programming in C++" by Robert Lafore

Object-Oriented Approach
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Ref. "Object-Oriented Programming in C++" by Robert Lafore
Data
Functions
that operate
on data
Object

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Roll_no
M1,M2,M3
calTotal()
student

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Data
Functions
that operate
on data
Object
An object’s functions, called member
functions in C++, typically provide the
only way to access its data

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Data
Member
Functions
Object - 1
member functions or methods
Attributes or instance variables

Classes
• In OOP, Objects are instances of classes
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Class
Attributes
Member functions
Object-1
Attributes
Member functions
Object-2
Attributes
Member functions
Object-1 & 2 are of type
class

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class firstClass
{
int a,b;
int add(int x, int y)
{
a=x; b=y;
return (a+b);
}
};
Class
Attributes
Member functions

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Data
Member
Functions
Object - 1
Data is
hidden So, its safe from accidental
alteration – DATA HIDING

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class firstClass
{
int a,b; // should be accessed by member function only
int add(int x, int y) // can be accessed by main ()
{
a=x; b=y;
return (a+b);
}
}; Set rights or give the access
specifications using “Access Specifier”

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class firstClass
{
private: // access specifier
int a,b;
public: // access specifier
{
a=x; b=y;
return (a+b);
}
};
Class is ready!!

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class firstClass
{
int a,b;
{
a=x; b=y;
return (a+b);
}
};
int main()
{
firstClass obj; //declaring an obj
int sum;
sum=obj.add(5,6); //msg passing
cout<<“Sum =”<<sum;
}

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class firstClass
{
int a,b;
{
a=x; b=y;
return (a+b);
}
};
int main()
{
firstClass obj; //declaring an obj
int x, y, sum;
cout<<“Enter values for x and y:”;
cin>>x>>y;
sum=obj.add(x,y); //msg passing
cout<<“Sum =”<<sum;
}

Classes
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• Class Data: The data items within a class are called data members (or
sometimes member data).
• Member Functions: Member functions are functions that are included
within a class.
• int add(int x, int y);
• Defining class: Defining objects in this way means creating them. This is
also called instantiating them.
• firstClass obj;
• The term instantiating arises because an instance of the class is created. An
object is an instance of a class.
• Objects are sometimes called instance variables.

Classes
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• Calling member function: The data items within a class are called
data members (or sometimes member data).
• obj.add(x, y); - The dot operator is also called the class member access
operator.)

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#include <iostream>
using namespace std;
class Distance
{
private:
int feet;
float inches;
public:
void setdist(int ft, float in)
{ feet = ft; inches = in; }
void getdist()
{
cout << “nEnter feet: “; cin >> feet;
cout << “Enter inches: “; cin >> inches;
}
void showdist() //display distance
{ cout << feet << “’-” << inches << ‘”’; }
};
int main()
{
Distance dist1, dist2;
dist1.setdist(11, 6.25);
dist2.getdist();
cout << “ndist1 = “; dist1.showdist();
cout << “ndist2 = “; dist2.showdist();
cout << endl;
return 0;
}

More On Classes and Objects
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17
Dr. J. Sangeetha/CSE/SRC/SASTRA

18

19

20

Dr. J. Sangeetha/CSE/SRC/SASTRA 21

23
Method : 1 – Defining member function inside the class –
By default inline

Ex : 2

Ex : 3

27

Ex: 4

Method 2 : Member function definition outside the class

Difference between Classes and Structures
• In C++, a structure works the same way as a class, except for just two
small differences. The most important of them is hiding
implementation details.
• A structure will by default not hide its implementation details from
whoever uses it in code, while a class by default hides all its
implementation details and will therefore by default prevent the
programmer from accessing them.
• The following table summarizes all of the fundamental differences.
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Example – Employee details
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Example: Student details
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Reference
• Robert Lafore. Object oriented programming in C++, Pearson
Education, Fourth Edition, 2012.
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6. Implementation of classes_and_its_advantages.pdf

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6. Implementation of classes_and_its_advantages.pdf