Object-Orientated Programming (IB)
Encapsulation is the wrapping of data and functions together as a single unit.
By default, data is not accessible to the outside world and they are only accessible through the functions which are wrapped in a class.
Prevention of data direct access by the program is called data hiding or information hiding
Abstraction refers to the act of representing essential features without including the background details or explanation.
Classes use the concept of abstraction and are defined as a list of attributes such as size, weight, cost and functions to operate on these attributes.
They encapsulate all essential properties of the object that are to be created.
The attributes are called data members as they hold data, and the functions that operate on these data are called member functions.
Class use the concept of data abstraction so they are called abstract data type (ADT)
Polymorphism comes from the Greek words “poly” and “morphism”.
“Poly” means many and “morphism” means form i.e. many forms.
Polymorphism means the ability to take more than one form.
For example, an operation has different behaviour in different instances.
The behaviour depends upon the type of data used in the operation.
Different ways to achieve polymorphism in C++ programs:
Function overloading
Operator overloading
Inheritance is the process by which one object can acquire the properties of another.
Inheritance is the most promising concept of OOP, which helps realise the goal of constructing software from reusable parts, rather than hand-coding every system from scratch.
Inheritance supports reuse across systems and directly facilitates extensibility within a system. Inheritance coupled with polymorphism and dynamic binding minimises the existing code to be modified while enhancing a system.
When the class child, inherits the class parent, the class child is referred to as a derived class (sub-class) and the class parent as a base class (superclass).
In this case, the class child has two parts:
a derived part
an incremental part.
The derived part is inherited from the class parent.
The incremental part is the new code written specifically for the class child.
Binding refers to linking of procedure call to the code to be executed in response to the call.
Dynamic binding(or late binding) means the code associated with a given procedure call in not known until the time of call at run time.
An object-oriented program consists of a set of objects that communicate with each other.
Objects communicate with each other by sending and receiving information.
A message for an object is a request for the execution of a procedure and therefore invoke the function that is called for an object and generates the result.
Reusability: In OOPs programs functions and modules that are written by a user can be reused by other users without any modification.
Inheritance: Through this we can eliminate redundant code and extend the use of existing classes.
Data Hiding: The programmer can hide the data and functions in a class from other classes. It helps the programmer to build the secure programs.
Reduced complexity of a problem: The given problem can be viewed as a collection of different objects. Each object is responsible for a specific task.
The problem is solved by interfacing the objects.
This technique reduces the complexity of the program design.
Easy to Maintain and Upgrade: OOP makes it easy to maintain and modify existing code as new objects can be created with small differences to existing ones.
Software complexity can be easily managed.
Message Passing: The technique of message communication between objects makes the interface with external systems easier.
Modifiability: It is easy to make minor changes in the data representation or the procedures in an
OO program. Changes inside a class do not affect any other part of a program, since the only
public interface that the external world has to a class is through the use of methods.
A class is a user-defined data type.
It consists of data members and member functions, which can be accessed and used by creating an instance of that class.
It represents the set of properties or methods common to all objects of one type.
A class is like a blueprint for an object.
Here’s the definition (sometimes called a specifier) for the class smallobj, copied from the SMALLOBJ listing:
class smallobj //define a class
{
private:
int somedata; //class data
public:
void setdata(int d) //member function to set data
{ somedata = d; }
void showdata() //member function to display data
{ cout << “\nData is “ << somedata; }
};The definition starts with the keyword class, followed by the class name—smallobj in this example.
Like a structure, the body of the class is delimited by braces and terminated by a semicolon.
(Don’t forget the semicolon. Remember, data constructs such as structures and classes end with a semicolon, while control constructs such as functions and loops do not.)
Private and Public:
A key feature of object-oriented programming is data hiding.
This term does not refer to the activities of particularly paranoid programmers; rather it means that data is concealed within a class so that it cannot be accessed mistakenly by functions outside the class.
The primary mechanism for hiding data is to put it in a class and make it private. Private data or functions can only be accessed from within the class.
Public data or functions, on the other hand, are accessible from outside the class.
The smallobj class contains one data item: somedata, which is of type int.
The data items within a class are called data members (or sometimes member data).
There can be any number of data members in a class, just as there can be any number of data items in a structure.
The data member somedata follows the keyword private, so it can be accessed from within the class, but not from outside.
An object is an instance of a class. It is a self-contained entity that consists of both data (attributes) and procedures (methods) that operate on the data.
Objects are the fundamental building blocks of Object-Oriented Programming (OOP).
Each object can represent a real-world entity or concept, encapsulating its state and behavior.
class Car:
def __init__(self, make, model, year):
self.make = make
self.model = model
self.year = year
def start_engine(self):
print(f"The {self.make} {self.model}'s engine has started.")
my_car = Car('Toyota', 'Corolla', 2020)In this example, my_car is an object of the Car class.
A method is a function that is defined within a class and is associated with the objects of that class.
Methods describe the behaviors and actions that an object can perform.
They can manipulate the object's attributes and interact with other objects.
An attribute is a variable that is bound to an instance of a class.
Attributes hold data that is associated with an object.
They represent the state or properties of the object. Attributes are defined within the class and are accessed using dot notation.
Example:
class Car:
def __init__(self, make, model, year):
self.make = make
self.model = model
self.year = year
my_car = Car('Toyota', 'Corolla', 2020)
print(my_car.make) # Output: Toyota
print(my_car.model) # Output: Corolla
print(my_car.year) # Output: 2020In this example, make, model, and year are attributes of the Car class.
These definitions and examples illustrate the core concepts of objects, methods, and attributes in Object-Oriented Programming, highlighting how they interact to form the basis of OOP design.
Encapsulation is the wrapping of data and functions together as a single unit.
By default, data is not accessible to the outside world and they are only accessible through the functions which are wrapped in a class.
Prevention of data direct access by the program is called data hiding or information hiding
Abstraction refers to the act of representing essential features without including the background details or explanation.
Classes use the concept of abstraction and are defined as a list of attributes such as size, weight, cost and functions to operate on these attributes.
They encapsulate all essential properties of the object that are to be created.
The attributes are called data members as they hold data, and the functions that operate on these data are called member functions.
Class use the concept of data abstraction so they are called abstract data type (ADT)
Polymorphism comes from the Greek words “poly” and “morphism”.
“Poly” means many and “morphism” means form i.e. many forms.
Polymorphism means the ability to take more than one form.
For example, an operation has different behaviour in different instances.
The behaviour depends upon the type of data used in the operation.
Different ways to achieve polymorphism in C++ programs:
Function overloading
Operator overloading
Inheritance is the process by which one object can acquire the properties of another.
Inheritance is the most promising concept of OOP, which helps realise the goal of constructing software from reusable parts, rather than hand-coding every system from scratch.
Inheritance supports reuse across systems and directly facilitates extensibility within a system. Inheritance coupled with polymorphism and dynamic binding minimises the existing code to be modified while enhancing a system.
When the class child, inherits the class parent, the class child is referred to as a derived class (sub-class) and the class parent as a base class (superclass).
In this case, the class child has two parts:
a derived part
an incremental part.
The derived part is inherited from the class parent.
The incremental part is the new code written specifically for the class child.
Binding refers to linking of procedure call to the code to be executed in response to the call.
Dynamic binding(or late binding) means the code associated with a given procedure call in not known until the time of call at run time.
An object-oriented program consists of a set of objects that communicate with each other.
Objects communicate with each other by sending and receiving information.
A message for an object is a request for the execution of a procedure and therefore invoke the function that is called for an object and generates the result.
Reusability: In OOPs programs functions and modules that are written by a user can be reused by other users without any modification.
Inheritance: Through this we can eliminate redundant code and extend the use of existing classes.
Data Hiding: The programmer can hide the data and functions in a class from other classes. It helps the programmer to build the secure programs.
Reduced complexity of a problem: The given problem can be viewed as a collection of different objects. Each object is responsible for a specific task.
The problem is solved by interfacing the objects.
This technique reduces the complexity of the program design.
Easy to Maintain and Upgrade: OOP makes it easy to maintain and modify existing code as new objects can be created with small differences to existing ones.
Software complexity can be easily managed.
Message Passing: The technique of message communication between objects makes the interface with external systems easier.
Modifiability: It is easy to make minor changes in the data representation or the procedures in an
OO program. Changes inside a class do not affect any other part of a program, since the only
public interface that the external world has to a class is through the use of methods.
A class is a user-defined data type.
It consists of data members and member functions, which can be accessed and used by creating an instance of that class.
It represents the set of properties or methods common to all objects of one type.
A class is like a blueprint for an object.
Here’s the definition (sometimes called a specifier) for the class smallobj, copied from the SMALLOBJ listing:
class smallobj //define a class
{
private:
int somedata; //class data
public:
void setdata(int d) //member function to set data
{ somedata = d; }
void showdata() //member function to display data
{ cout << “\nData is “ << somedata; }
};The definition starts with the keyword class, followed by the class name—smallobj in this example.
Like a structure, the body of the class is delimited by braces and terminated by a semicolon.
(Don’t forget the semicolon. Remember, data constructs such as structures and classes end with a semicolon, while control constructs such as functions and loops do not.)
Private and Public:
A key feature of object-oriented programming is data hiding.
This term does not refer to the activities of particularly paranoid programmers; rather it means that data is concealed within a class so that it cannot be accessed mistakenly by functions outside the class.
The primary mechanism for hiding data is to put it in a class and make it private. Private data or functions can only be accessed from within the class.
Public data or functions, on the other hand, are accessible from outside the class.
The smallobj class contains one data item: somedata, which is of type int.
The data items within a class are called data members (or sometimes member data).
There can be any number of data members in a class, just as there can be any number of data items in a structure.
The data member somedata follows the keyword private, so it can be accessed from within the class, but not from outside.
An object is an instance of a class. It is a self-contained entity that consists of both data (attributes) and procedures (methods) that operate on the data.
Objects are the fundamental building blocks of Object-Oriented Programming (OOP).
Each object can represent a real-world entity or concept, encapsulating its state and behavior.
class Car:
def __init__(self, make, model, year):
self.make = make
self.model = model
self.year = year
def start_engine(self):
print(f"The {self.make} {self.model}'s engine has started.")
my_car = Car('Toyota', 'Corolla', 2020)In this example, my_car is an object of the Car class.
A method is a function that is defined within a class and is associated with the objects of that class.
Methods describe the behaviors and actions that an object can perform.
They can manipulate the object's attributes and interact with other objects.
An attribute is a variable that is bound to an instance of a class.
Attributes hold data that is associated with an object.
They represent the state or properties of the object. Attributes are defined within the class and are accessed using dot notation.
Example:
class Car:
def __init__(self, make, model, year):
self.make = make
self.model = model
self.year = year
my_car = Car('Toyota', 'Corolla', 2020)
print(my_car.make) # Output: Toyota
print(my_car.model) # Output: Corolla
print(my_car.year) # Output: 2020In this example, make, model, and year are attributes of the Car class.
These definitions and examples illustrate the core concepts of objects, methods, and attributes in Object-Oriented Programming, highlighting how they interact to form the basis of OOP design.