Object Oriented Programming Developments in software technology continue to be dynamic. This maid the software industry and software engineers to continuously look for new approaches to software design and development. Rapid advances appear to have created a situation of crisis within the industry.
Object Oriented Programming Major issues need to resolved: How to represente real-life entites How to ensure reusability and extensibility of modules How to develop modules that are tolerant to any changes in future How to improve software productivity and decrease software cost How to improve the quality of software How to manage time schedules
Object Oriented Programming Studies and other reports on software implementation suggest that software products should be evaulated carefully for their quality before they are delivered and implemented.
Software Evolution To built today’s complex software it is just not enough to put together a squence of programming statements and sets of procedures and modules; we need to incorporate sound construction techniques and program structures that are easy to comprehend, implement and modify. Since the invention of the computer, many programming approaches have been tried.
Software Evolution Such as Modular programming, top-down programming, bottom-up programming and structured programming. The primary motivation in each case has been the concern to handle the increasing complexity of programs that are reliable and maintainable.
C vs C++ C – Structured programming became very popular and was the main technique of the 1980. Structured programming enable programmers to write moderately complex programs fairly easily. However as the programs grew larger, even the structured approach failed to show the desired results in terms of bug-free, easy-to-maintain and reusable programs.
C vs C++ C++ - Object-Oriented Programming (OOP) is an appraoch to program organization and development that attempts to elimate some of the pitfalls of conventional programming methods by incorporating the best of structured programming features with several powerful new concepts.
Procedure-Oriented Programming Conventional programming using high level language such as COBOL, FORTRAN and C is commonly known as Procedure-oriented programming. In the Procedure-oriented approach the problem is viewed as a sequence of things to be done such as reading, calculating and printing. The primary focus is on functions.
Structure of Procedure-oriented Main Program Function 1 Function 2 Function 3 Function 4 Function 5
Procedure-Oriented Programming Procudure-oriented programming basically consists of writing a list of instructions for the computer to follow and organizing these instructions into groups known as functions. We normally use a flowchart to organize these actions and represent the flow of control from one action to another. More importance to functions very little attention to data that are being used by the functions.
Structure of Procedure-oriented Global data Global data Function 1 Function 2 Function 3 Local data Local data Local data
Procedure-Oriented Programming What happens to data? How are they affected by the functions that work on them? In multi-function program many important data items are placed as global so that they may be accessed by all the functions.Each function may have its own local data. In large program it is very difficult to identify what data is used by which function. In case we need to revise an external data structure we also need to revise all function that access it.
Object-Oriented Programming OOP treats data as a critical element in the program development and does not allow it to flow freely around the system. It ties data more closely to the functions that operate on it, and protects it from accidental modification from outside functions. OOP allows decomposition of a problem into a number of entites called objects.
Organization of data & function OOP Object A Object B Object A Object B Data Data Functions Functions Object C Data Functions
Striking features of OOP Emphasis is on data rather than procedure. Programs are divided into what are known as objects Functions that operate on the data of an object are tied together in the data structure Data is hidden and cannot be accessed by external functions Objects may communicate with each other through functions New data and functions can be easily added whenever necessary.
Object-oriented programming Object-oriented programming is an approach that provides a way of modularizing programs by creating partitioned memory area of both data and fucntions that can be used as templates for creating copies of such modules on demand. Object is considered to be a partitoned area of computer memory that stores data and set of operations that can access that data.
Basic concepts of OOP Objects Class Data Abstration Data Encapsulation Inheritance Polyomorphism Dynamic binding Message PassingThe three pillars of object-oriented development: Encapsulation, Inheritance, and Polymorphism.
Objects 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 that the program must handle. Program objects should be chosen such that they match closely with the real-world objects. Objects take up space in the memory and have an associated address like sturcture in C. When a program is executed the objects interact by sending messages to one another.
Objects Ways to represent an Object Object: STUDENT DATA Name Marks FUNCTIONS Total Display
Classes 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 variable of type class. Once a class has been defined we can create any number of objects belonging to that class. A class is thus a collection of objects of similar type. Classes are user-defined data types and behave like the built-in types of a programming language.
Classes Syntax used to create an object is no different than the syntax used to create an integer object in C. Fruit is a class defined as a Class. fruit f1; Here fruit is Class. And f1 is an object of fruit Class.
Encapsulation The wrapping up of data and functions into a single unit is known as Encapsulation The data is not accessible to the outside world and only those functions which are wrapped in the class can access it. This insulation of the data from direct access by the program is called data hiding or information hiding.
Data Abstraction Abstraction refers to the act of representing essential features without including the background details or explanations. Classes use the concept of abstraction and are defined as a list of abstract attributes such as size, weight and cost, and functions to operate on these functions. Since the classes use the concept of data abstraction, they are known as Abstract Data Types.
Inheritance Inheritance is the process by which objects of one class acquire the properties of objects of another class. The principle behind this sort of division is that each derived class shares common characteristics with the class from which it is derived. 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.
Inheritance The real power of inheritance mechanism is that it allows the programmer to reuse a class that is almost but not exactly, what he wants, and to tailor the class in such a way that it does not introduce any undesirable side-effects into the rest of the classes. Bird Flying Bird No flying Bird
Polymorphism Polymorphism means the ability to take more than one form. That is an operation may exhibit different behaviours in different instances. The behaviour depends upon the types of data used in the operation. Example: Operation of addition. For two numbers the operation will generate a sum. If the operands are strings, then the operation would produce a third string by concatenation.
Polymorphism The process of making an operator to exhibit different behaviours in different instances is known as operator overloading. Using a single function name to perform different types of taks is known as function overloading.
Dynamic Binding Binding refers to the linking of a porcedure 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 It is associated with polymorphism and inheritance.
Message Communication An object-orineted program consits of a set of objects that communicate with each other. Object communicate with one another by sending and receiving information much the same way as people pass message to one another. Message passing involves specifying the name of the object, the name of the funciton (message) and the information to be sent. emp.salary(emp_name); message object information
Benefits of OOP Through inheritance we can elimate the redundant code and extend the use of existing code Data hiding helps the programmer to build secure programs that cannot be invaded by code in other parts of the program It is possible to have mulitple instances of an objects to co-exist without any interference. It is possible to map objects in the problem domain to those objects in the program Easy to partition the work in a project based on objects
Benefits of OOP Data-centred design approach enables us to capture more details of a model in implementable form Object-oriented systems can be easily upgraded from small to large systems Software complexity can be easily managed.
Object-Oriented Languages The lanugages should support several of the OOP concepts to claim that they are object-oriented. Depending upon the features they support, they can be classified into the following two categories: Object-based programming lanugages Object-oriented programming languages
Object-based programming Languages Object-based programming is the style of programming that primarily supports encapsulation and object identify. Major features: Data encapsulation Data hidding and access mechanisms Automatic initialization and clear-up objects Operator overloading They do not support inheritance and dynamic binding.
Object-oriented programming Languages Object-oriented programming incorporates all of object-based programming features along with two additional features, namely, iheritance and dynamic binding. Object-based features + inheritance + dynamic binding
References Object-Oriented Programming with C++ by E Balagurusamy