The document discusses fundamentals of object-oriented programming. It defines objects as software bundles that model real-world objects using variables to represent states and methods to represent behaviors. Classes are blueprints that define common variables and methods for objects. Objects interact by sending messages to each other specifying a method and parameters. Object-oriented principles of abstraction, encapsulation, inheritance and polymorphism are covered.

1. Lecture 02
Fundamentals
of
Object-Oriented
Programming

2. What Are Objects?
Software objects model real-world objects or abstract concepts.
dog, bicycle, queue
Real-world objects have states and behaviors.
Dogs' states: name, color, breed, hungry
Dogs' behaviors: barking, fetching
How do software objects implement real-world objects?
Use variables/data to implement states.
Use methods/functions to implement behaviors.
An object is a software bundle of variables and related methods.

3. Software Object
Visual Representation
Instance Variables Vs Instance Methods

4. Software Bicycle
Visual Representation

5. What Are Classes?
• A class is a blueprint or prototype defining the
variables and methods common to all objects of
a certain kind.
• An object is an instance of a certain class.
• After you have created a class, you must create
an instance of it before you can use.
• Class variables and class methods.

6. What Are Messages?
Software objects interact and communicate with
each other by sending messages to each other.

7. Components Of A Message
The object to whom the message is addressed
(YourBicycle)
The name of the method to perform (changeGears)
Any parameters needed by the method (lowerGear)

8. O-O Principles
• Abstraction - take only important
information
• Encapsulation - hiding or combine data
and operations on data in a single unit.
• Inheritance - create new objects from
existing objects.
• Polymorphism-the ability to use the same
expression to denote different operations.

9. Encapsulation
• The objects' variables make up the center of
the object.
• Methods surround and hide the object's
center from other objects.
• Benefit of encapsulation: Modularity &
Information Hiding.
• For implementation or efficiency reasons, an
object may wish to expose some of its
variables or hide some of its methods.

10. Inheritance
• Inheritance allows classes to be defined in terms of
other classes.
• Each subclass inherits variables and methods from its
superclass.
• Subclasses can add variables and methods to the
ones they inherit from the superclass.
• Subclasses can also override inherited methods and
provide specialized implementations for those
methods.

11. Class Hierarchy
(Inheritance Hierarchy)
Superclass vs Subclass.
Base Class vs Derived Class.

12. Polymorphism and Overloading
• Polymorphism allows the use of operators or functions
in different ways, depending on the data they are
operating on.
• When an existing operator (eg. + or =) is given the
capability to operate on a new data type, it is said to
be overloaded.
• Overloading is a kind of polymorphism; it is also an
important feature of OOP.
• Example of operator overloading and polymorphism)
• the + operator know how to treat an integer and a float
differently.

13. Benefits of OOP
Reusability
• Once written, created, and debugged, a class can be
distributed to other programmers for use in their own
programs.
• Reusability facilitates component-based software
design and implementation.
• A programmer can also take an existing class and,
without modifying it, add additional features and
capabilities to it.

14. Benefits of OOP
Creating New Data Types
• Objects and classes give the programmer a
convenient way to construct new data types.
• Many features of C++ are intended to facilitate the
creation of new data types.
• The ability to create new data types leads to
extensible languages and programs.
• In C++, new data types can be built on top of existing
(system or user-defined) data types.

15. C++ Program Structure
#include <iostream.h>
Header files
preprocessor statements
class Data int main( ) // VOID
Members
{ …..
and Member {
} Functions
main( ) Variable
cout << “Welcome to C++”;
{ …… declarations & return 0;
valid C++
} statements
}

16. Example 2
#include <iostream.h> Sum = a + b + c;
int main ( ) cout << “ the sum is “<< sum;
{ int a , b, c, sum =0;
cout << “ enter a value “<<endl; OTHER DATA TYPES
cin >> a; Char
int
cout << “ enter b value “<<endl; long int
float
cin >> b;
double
cout << “ enter c value “<<endl;
cin >> c;

17. Input / Output
Cout - used for printing out the output
Syntax :
Cout << “Message if needed”<< variablename;
<< is called the insertion operator.
Cin - used for getting a input from the keyboard
Syntax:
Cin >> variable name;
>> is called the extraction operator

18. Other Points
Remark statement - it is a non executable statement
used for documentation
// or /* statements */
escape sequences:
n - new line
t - horizontal tab
r - carriage return
a - bell
- back slash ” - double quotations