Page 11 - DCAP404 _Object Oriented Programming

Object-oriented Programming

Notes 3. Data Abstraction: Abstraction refers to the act of representing essential-features without
including the background details or explanations. Abstraction is indispensable part of the
design process and is essential for problem partitioning. Partitioning essentially is the
exercise in determining the components of the system. However, these components are
not isolated from each other, they interact with each other. Since the classes use the concept
of data abstraction, they are known as Abstract Data Types (ADT).

Example: We can represents essential features without including background details
and explanations.

index of text book.
class School
{
void sixthc lass();
void seventhclass();
void tenthclass();

}
4. Data Encapsulation: The wrapping up to data and functions into a single unit (class) is
known as encapsulation. Data encapsulation is the most striking feature of a class. The
data is not accessible to the outside world and only those functions that are wrapped in the
class can access it. These functions provide the interface between the object’s data and the
program. This insulation of the data from direct access by the program is called data
hiding.
5. Inheritance: Inheritance is the process by which objects of one class acquire the properties
of objects of another class. It supports the concept of hierarchical classification. For example,
an manager class is a type of the class employee, which again is a type of the class person
as illustrated below.
The principle behind this sort of division is that each derived class shares common
characteristics with the class from which it is derived. The power of inheritance lies in the
fact that all common features of the subclasses can be accumulated in the super class. In
other words, a feature is placed in the higher level of abstraction. Once this is done, such
features can be inherited from the parent class and used in the subclass directly. This
implies that if there are many abstract class definitions available, when a new class is
needed, it is possible that the new class is a specialization of one or more of the existing
classes.
In OOP, the concept of inheritance provides the idea of reusability. This means that we can
add additional features to an existing class without modifying it. This is possible by
deriving a new class from the existing one. The new class will have the combined features
of both the classes. Each subclass defines only those features that are unique to it. In OOP,
The concept of inheritance provides the idea of reusability. This means that we can add
additional features to an existing class without modifying it. This is possible by deriving
a new class from the existing one. The new class will have the combined features of both
the classes.

!
Caution Keep in mind that each subclass defines only those features that are unique to it.

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