OOP-1.pptx

Object Oriented
Programming
Course Instructor: Dr Mrs I. Botchway Essandoh
Computer Science & Engineering Department
University of Mines & Technology (UMaT) 1

Introduction
The Concept of Programming
• What is Programming?
Do I need to be good in maths?
What about logic?
• What is Computer Programming?
Designing and building executable computer programs
Object Oriented Programming 2
Computer Programs
do real world things
on their own.

Why do we need to learn about Object-Oriented Programming?
• Object-Oriented Programming was developed because
limitations were discovered in the earlier programming
approaches.
Introduction
Evolution of Programming Techniques
• Procedural Programming (PP);
• Structured Programming; and
• Object Oriented Programming.

• Views a program as a series of steps (procedures) to be
carried out;
 Uses a list of instructions; and
 Takes inputs and returns outputs.
 E.g. C, FORTRAN, Cobol, Pascal
• Division into functions
Each function has a clearly defined purpose and a clearly
defined interface to the other functions in the program.
The idea of breaking a program into functions can further be
extended by grouping a number of functions together into a
larger entity called a module.
Procedural Programming

Main Program
Function 1 Function 3
Function 2
Function 4 Function 5
Function 8
Function 7
Function 6

• In multi-function programs, important data items are placed
as global data so that they may be accessed by all functions.
• Each function may as well have its own local data.
Global
Data
Global
Data
Global
Data
Function 1 Function 2 Function 3 Function 4

Problems with Procedural Languages
• Since every function has complete access to the global data,
a new programmer can corrupt the data accidentally;
• Cannot cope with very large project sizes (Complexity) since
it is difficult to identify the data used by a specific function;
• Difficult to modify and maintain;
• Codes are often not reusable;
• We can access the data of one function from another, hence,
there is security unfriendliness due to code exposure; and
• Program codes become difficult to write when working with a
larger project.

Causes of Problems
• Unrestricted Access to Data
 Global data/variable is allowed
 Access to data by multiple functions means many connections
between functions
 Programs become more difficult to understand
• Poor Modeling of Real World Things
 Real world things are integral collections of data
(Attributes/properties/features) and functions (Behaviour)
 e.g. a car: has data (make, model etc.) and functions (acceleration)
 Procedural languages do not tie up data with functions

Characteristics:
• Large programs are divided into smaller programs known as
functions.
• Most of the functions share global data.
• Data can move openly around the system from function to
function.
• Employs the top-down approach in program design.
The top-down programming approach
This is the process of breaking tasks into component parts
called modules and the subdivide each component module
until the lowest level of detail has been reached.

• Structured Programming can be defined as a programming
approach in which the program is made as a single
structure.
• It means that the code will execute the instruction one after
the other.
• It doesn’t support the possibility of jumping from one
instruction to some other with the help of any statement like
GOTO, etc.
• Therefore, the instructions in this approach will be executed
in a serial and structured manner.
• Organizes Procedural Programming into functions and
modules.
• E.g. Pascal, Cobol, C
Structured Programming

Object Oriented Language
• OOP was introduced to overcome the
flaws in procedural programming such
as reusability and maintainability.
• Views a program as a group of objects
that have certain properties and can
perform certain functions.
• E.g. C++, Java, C#, Python
Object-Oriented Programming
Object:
John

• Clearer, more reliable, more easily maintained programs;
• More effective way of coping with program complexity;
• It basically supports encapsulation, abstraction, inheritance
and polymorphism; and
• It also includes data hiding features therefore it is more
secure.
Goal of OOP

• The fundamental idea is to combine into a single unit both
data/variable (features) and functions that operate on the
data.
• Such a unit is called an “Object”.
• In OOP, problems are divided into the number of entities
(objects) and then builds data and functions around these
entities (objects).
• It ties the data more closely to the functions that operate on
it and protects it from accidental modification from outside
functions.
The Object-oriented Approach

• Data of an object can be accessed only by the functions
associated with that object.
• Communication of objects is done through functions.
• Data and its function are said to be encapsulated into a
single entity called a class.
• Data encapsulation and data hiding are key elements of
object-oriented languages.

• If you want to modify data in an object, you know exactly
what functions interact with it (i.e. the member functions of
the object).
• This simplifies writing, debugging, and maintaining the
programs.

Attributes
Methods
Methods
Attributes
Methods
Methods
Attributes
Methods
Methods
object
object
The Object-oriented Paradigm

Characteristics:
• Programs are divided into entities known as objects.
• Data is hidden and cannot be accessed by external functions.
• Objects communicate with each other through functions.
• New data and functions can be easily added whenever
necessary.
• Employs the bottom up approach in program design.
Object-Oriented Programming
OOP is suitable when
you want to group
attributes and methods
together into a handy
packet of functionality

Procedural OOP
The program is divided into
small parts called functions.
The program is divided into
small parts called objects.
There is no use of access
modifiers.
Uses access modifiers like
private, public, protected, etc.
Does not have any proper way
of hiding data so it is less
secure.
Provides data hiding so it is
more secure.
Does not have the concept of
inheritance.
Supports inheritance
Absent of code reusability It offers code reusability by
using the feature of inheritance.
Procedural Vs. OOP

• The structure of object-oriented programming include the
following:
Structure of OOP Languages

• The Object-oriented approach relies on a number of concepts
that define object-oriented languages.
Concepts of OOP Languages
OOP
Concepts
Class
Objects
Abstraction
Encapsulation
Inheritance
Polymorphism
Dynamic
Binding
Message
Passing

Classes
Class
Data/Variables
Properties/
Features
Functions
Methods/
Behavior
Object

• A collection of data and features encapsulated in a single
unit.
• A class is a user-defined data type that we can use in our
program, and it works as a blueprint for creating objects but
it doesn’t actually provide any real content itself.
• The Dog( ) class may specify that the name and age are
necessary for defining a dog, but it will not actually state
what a specific dog’s name or age is.
Classes/ Objects
think of a class as an idea for how
something should be defined

• Classes enable the creation of specific instances of the
system being modeled (Object).
• Attributes and methods are basically variables and
functions that belongs to the class. These are often referred
to as class members.
Creating a Class in Python
• Use the class keyword, followed by the class name and a
colon
Syntax
class ClassName:
# class definition
Classes/ Objects

• When a class is defined, only the specification for the object
is defined; no memory or storage is allocated. To use the data
and access functions defined in the class, we need to create
objects.
• An object is created from a class. It is an instance of a class
with actual values.
Objects

• An object is a software item that contains variables and
methods.
• They may represent a person, a place, a bank account, or
any item that a program must handle.
• When a program is executed, the objects interact by sending
messages to one another.
• Objects have two components:
• Data (attributes)
• Behaviors (functions or methods)
Objects

Instantiating Object
• To create an object of a class, type the class name, followed
by ( ). Assign the class name to the object name.
Syntax
class ClassName:
pass
objectName = ClassName()
Access Class Attributes Using Objects
• The attributes of a class can be accessed using the dot (.)
notation on the object of the class.
Objects

Example 1: An Empty Class
Object Oriented Programming
class Student:
pass
stud1 = Student()
stud1.name='Amina'
stud1.age = 20
stud1.dpt = 'Electrical'
stud1.hostel = 'Gold Refinery Hall'
print(f'Name:
{stud1.name}nAge:{stud1.age}nDepartment:{stud1.dpt}
nHostel:{stud1.hostel}n')
27

Example 2: Multiple Objects
class Student:
pass
stud1 = Student()
stud2 = Student()
stud1.name='Amina'
stud1.age = 20
stud1.hostel = 'Gold Refinery Hall'
stud2.name='Abena'
stud2.age = 19
stud2.hostel = 'KT Hall'
print(f'Name:
{stud1.name}nAge:{stud1.age}nDepartment:{stud1.dpt}nHostel:
{stud1.hostel}n')
print(f'Name:
{stud2.name}nAge:{stud2.age}nDepartment:{stud2.dpt}nHostel:
{stud2.hostel}')
28

Example 3: Class with Attributes
class Cars:
name = ''
make = ''
model = ''
year = 0
car1 = Cars() # Creating first object
car1.name='Toyota'
car1.make = 'Corolla'
car1.model = 'LE'
car1.year = 2016
car2 = Cars() # Creating second object
car2.name='Honda'
car2.make = 'Civic'
car2.model = 'Hybrid'
car2.year = 2018
car3 = Cars() # Creating third object
car3.name='Mercedes Benz'
car3.make = 'C class'
car3.model = '300'
car3.year = 2000
print(f"The vehicle name is
{car1.name} and it's make is
{car1.make}. nThe model is
{car1.model} and it's year
is {car1.year}n")
is {car2.year}n")
is {car3.year}")

End of Lecture 2

OOP-1.pptx

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