OOPS - [Fundamentals: Characteristics]

♠ Posted by Unknown in Fundamentals,OOPS at 04:26

Object-Oriented Programming&Characteristics

Object-oriented programming (OOP) is a powerful way to approach the task of programming. At each critical point in the evolution of programming, a new approach was created to help the programmer handle increasingly complex programs. OOP takes the best of the ideas embodied in structured programming and combines them with powerful new concepts that allow you to organize your programs more effectively. Object-oriented programming encourages you to decompose a problem into its constituent parts.

Each components becomes a self-contained object that contains its own instruction and data that relate to that object. In this way, complexity is reduced and data that relate to that object. In this way, complexity is reduced and the programmer can manage larger programs.

All OOP languages, including C++, share three common defining traits: Encapsulation, Polymorphism, and Inheritance.

Characteristics:

1. ENCAPSULATION/DATA ABSTRACTION/DATA HIDING :- 

Encapsulation is that mechanism that binds together code and the data it manipulates, and keeps both stage from outside interference and misuse. In an object-oriented language, code and data can be combined in such a way that a self-contained “black-box” is created. When code and data are linked together in this fashion, an object is created. In other words, an object is the device that supports encapsulation.

Within an object, code, data, or both may be private to that object or public. Private code or data is known to and accessible only by another part of the object.  That is, private code or data cannot be accessed by a piece of the program that exists outside the object. When code or data is public, other parts of your program can access it even though it is defined within an object.

For all intents and purposes, an object is a variable of a user-defined type. It may seem strange that an object that links both code and data can be thought of as a variable. However, in Object-Oriented programming, this is precisely the case. Each time you define a new type of object, you are creating a new data type. Each specific instance of this data type is a compound variable.

2. POLYMORPHISM :-

Polymorphism (from the Greek, meaning “many forms”) is the quality that allows one name to be used for two or more related but technically different purposes. As it relates to OOP, polymorphism allows one name to specify a general class of actions. For example, in C, which goes not significantly support polymorphism, the absolute value action requires three distinct function names: abs(), labs(),  and fabs(). These functions compute and return the absolute value of an integer, a long integer, and a floating point value respectively. However, in C++ , which supports polymorphism, each function can be called by the same name such as abs(). The type of data used to call the function determines which specific version of the function is actually executed. As you will see, in C++ it is possible to use one function name for many purposes. This is called function overloading.

Polymorphism can be applied to operators, too. Virtually all programming languages contain a limited of polymorphism as it relates to the arithmetic operators. For example, in C, the + sign is used to add integers, long integers, characters, and floating-point values. In these cases, the compiler automatically knows which type of arithmetic to apply. In C++, you can extend this concept to other types of data that you define. This type of polymorphism is called Operator Overloading.

3. INHERITANCE/REUSABILITY/Extendibility:- 

Inheritance is the process by which one object can acquire the properties of another. More specifically, an object can inherit a general set of properties to which it can add those features that are specific only to itself. Inheritance is important because it allows an object to support the concept of hierarchical classification. In each case, the child class inherits all those qualities associated with the parent and adds to them its own defining characteristics. Without the use of ordered classifications, each object would have to define all characteristics that relate to it explicitly. However , through inheritance, it is possible to describe an object by stating what general class (or classes) it belongs to along with those specific traits that makes is unique.

4. Object & Classes :-                                                                                  

Objects are the basic Run-Time entities in an object Oriented System. They may represent a person, a place, a bank account. A table of data or any item.

Programming problem is analyzed in terms of objects and the nature of communication between them. Objects take up space in the memory and have an associated address like a record in PASCAL or a structure in C.

When a program is executed the objects interact by sending messages to one another for example if “Customer” and “Account” are tow objects in a program, then the customer object may send a message. It is sufficient to know the type of message accepte3d and the type of response returned by the objects.

We just mentioned that objects contain data and code to manipulate the data. the entire set of data and code of an object can be made a user-defined data type with the help of a class. Objects are variables of the type class. Each objects is associated with the data of type class with which they are created. A class is has a collection of objects of similar type. Classes are user defined data types and behave like the built-in types of a programming language. If “Fruit” has been defined as a class : 

                                                     

Fruit Mango;

Will create an object Mango belonging to the class “Fruit”.

5. Dynamic Binding :-

Binding refers to the linking of a procedure call to the code to be executed in response to the call. Dynamic binding means that the code associated with a given procedure call is not known until the time of the call at run-time the dynamic type of that reference.

6. Message Passing :-

An object Oriented Program consists of a set of objects that communicate with each other. The process of programming in an object oriented language. Therefore involves the following basic steps:

1. Creating classes that define objects and their behavior.
2. Creating objects from class definitions and establishing communication among objects.

Objects communicate with one another by sending and receiving information much the same way as people pass messages to one another.

A message for an object is a request for execution of a procedure, and therefore will invoke a function in the receiving object that generate the desired result.

Objects have a life cycle. They can be created and destroyed. Communication with an object is feasible as long as it is alive.

7. Abstract Class :

An Abstract class is on that is not used to create objects. An abstract class is designed only to act as a base class (to be inherited by other classes). It is a design concept in program development and provides a base upon which other classes may be built.