Object-Oriented Programming

Object-Oriented Programming

Something to Ponder

Suppose that you want to assemble your own PC, you go to a hardware store and pick up a motherboard, a processor, some RAMs, a hard disk, a casing, a power supply, and put them together. You turn on the power, and the PC runs. You need not worry whether the CPU is 1-core or 6-core; the motherboard is a 4-layer or 6-layer; the hard disk has 4 plates or 6 plates, 3 inches or 5 inches in diameter; the RAM is made in Japan or Korea, and so on. You simply put the hardware componentstogether and expect the machine to run. Of course, you have to make sure that you have the correctinterfaces, i.e., you pick an IDE hard disk rather than a SCSI hard disk, if your motherboard supports only IDE; you have to select RAMs with the correct speed rating, and so on. Nevertheless, it is not difficult to set up a machine from hardwarecomponents.

Similarly, a car is assembled from parts and components, such as chassis, doors, engine, wheels, brake and transmission. The components are reusable, e.g., a wheel can be used in many cars (of the same specifications).

Hardware, such as computers and cars, are assembled from parts, which are reusable components.

How about software? Can you "assemble" a software application by picking a routine here, a routine there, and expect the program to run? Unlike hardware, it is very difficult to "assemble" an application fromsoftware components. Since the advent of computer 70 years ago, we have written tons and tons of programs. However, for each new application, we have to re-invent the wheels and write the program from scratch.

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Overview

In the early 1970s, the US Department of Defense (DoD) commissioned a task force to investigate why its IT budget always went out of control; but without much to show for. The findings are:

1. 80% of the budget went to the software (with the remaining 20% to the hardware).

2. More than 80% of the software budget went to maintenance (only the remaining 20% for new software development).

3. Hardware components could be applied to various products, and their integrity normally did not affect other products. (Hardware can share and reuse! Hardware faults are isolated!)

4. Software procedures were often non-sharable and not reusable. Software faults could affect other programs running in computers.

The task force proposed to make software behave like hardware OBJECT. Subsequently, DoD replaces over 450 computer languages, which were then used to build DoD systems, with an object-oriented language called Ada.

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Object-Oriented Programming (OOP)Definition

Object-oriented programming (OOP) is a programming language model organized aroundobjectsrather than "actions" and data rather than logic.

It is aprogramming paradigmbased on the concept of "objects", which aredata structures that containdata, in the form offields, often known asattributes;and code, in the form of procedures, often known asmethods. Historically, a program has been viewed as a logical procedure that takes input data, processes it, and produces output data.

The programming challenge was seen as how to write the logic, not how to define the data. Object-oriented programming takes the view that what we really care about are the objects we want to manipulate rather than the logic required to manipulate them. Examples of objects range from human beings (described by name, address, and so forth) to buildings and floors (whose properties can be described and managed) down to the littlewidgetson a computer desktop (such as buttons and scroll bars). In OO programming, computer programs are designed by making them out of objects that interact with one another.There is significant diversity in object-oriented programming, but most popular languages areclass-based, meaning that objects areinstancesofclasses, which typically also determines theirtype.Object-oriented modeling Object-oriented modeling (OOM) is the construction of objects using a collection of objects that contain stored values of the instance variables found within an object. Unlike models that are record-oriented, object-oriented values are solely objects. Object-oriented modeling is the process of preparing and designing what the models code will actually look like. During the construction or programming phase, the modeling techniques are implemented by using a language that supports the object-oriented programming model. Object-oriented modelingis an approach to modeling an application that is used at the beginning of thesoftware life cyclewhen using an object-oriented approach to software development.

The software life cycle is typically divided up into stages going from abstract descriptions of the problem to designs then to code and testing and finally to deployment.

Modeling is done at the beginning of the process. The reasons to model a system before writing the code are:

Communication.

Users typically cannot understand programming language code.

Model diagrams can be more understandable and can allow users to give developers feedback on the appropriate structure of the system.

A key goal of the Object-Oriented approach is to decrease the "semantic gap" between the system and the real world, to have the system be constructed using terminology that is the same as the functions that users perform.

Abstraction. A goal of most software methodologies is to first address "what" questions and then address "how" questions. I.e., first determine the functionality the system is to provide without consideration of implementation constraints and then consider how to take this abstract description and refine it into an implementable design and code given constraints such as technology and budget.

Modeling enables this by allowing abstract descriptions of processes and objects that define their essential structure and behavior.

Object-oriented modeling provides a vehicle to represent the properties, behavior and interaction of things. Object-oriented modeling is typically done viause casesand abstract definitions of the most important objects. The most common language used to do object-oriented modeling is theObject Management Group'sUnified Modeling Language (UML) In order to implement these models so they can be used through a computer, a programming language is required these are called object-oriented programming (OOP) languages.

Object-Oriented Programming Languages

Many of the most widely used programming languages are multi-paradigm programming languages that support object-oriented programming to a greater or lesser degree, typically in combination with imperative, procedural programming. There is a wide range of OOP languages from which to choose. Different languages support different degrees of object-orientation, but all provide mechanisms to implement the basic concepts.

Aprogramming paradigmis a fundamentalstyleofcomputer programming, serving as a way of building the structure and elements of computer programs. Capabilities and styles of variousprogramming languagesare defined by their supported programmingparadigms; some programming languages are designed to follow only one paradigm, while others support multiple paradigms. Amulti-paradigm programming languageis aprogramming languagethat supports more than one programming paradigm. AsLedadesignerTimothy Buddputs it: "The idea of a multi-paradigm language is to provide a framework in which programmers can work in a variety of styles, freely intermixing constructs from different paradigms." The design goal of such languages is to allow programmers to use the best tool for a job, admitting that no single paradigm solves all problems in the easiest or most efficient way. Simula was the first object-oriented programming language.Java,Python,C++,Visual Basic .NETandRubyare the most popular OOP languages today. The Java programming language is designed especially for use in distributed applications on corporate networks and the Internet. Ruby is used in many Web applications. Significant object-oriented languages include Python, C++, Objective-C, Smalltalk, Delphi, Java, C#, Perl, Ruby and PHP. The most popular programming languages are Java, C++ and Visual Basic.

Java Java is one of the purest OOP languages. It was designed from the ground up with objects in mind and is widely used in a range of Internet as well as stand-alone applications. Additionally, the majority of applications running on mobile phones and some PDAs are developed in Java.

C++ One of the most popular programming languages among computer programmers is C. About a decade ago it was extended with object-oriented elements and was then called C++. The majority of applications running on Microsoft Windows, Mac OS and Linux are

written in C++.

Microsoft has recently introduced C# (speak: C sharp) which is a popular variant of C++ that has been integrated in the Microsoft.Net Framework.

Visual Basic One of the most popular programming languages is Microsoft Visual Basic. Visual Basic, like C, was initially designed as a procedural programming language. In recent versions, object-oriented elements have been added and, since it has been integrated in the Microsoft.Net Framework, it is now widely accepted as an OOP language.

OOP Flow and Control

OOP languages, in contrast to the other programming techniques, have a web of interacting objects sending messages to each other.Strengths of OOPs

More opportunity for reuse

Models the real world more accurately

Naturalness ("objects concept")

Increased quality

Encapsulation and abstraction (higher cohesion/lower coupling)

Easier maintenance

Enhanced modifiabilityWeaknesses of OOPs

Can run slower

Can be complex

Can take more memory

Benefits of OOP

The procedural-oriented languages focus on procedures, with function as the basic unit. You need to first figure out all the functions and then think about how to represent data.

The object-oriented languages focus on components that the user perceives, with objects as the basic unit. You figure out all the objects by putting all the data and operations that describe the user's interaction with the data.

Object-Oriented technology has many benefits:

Ease in software design:as you could think in the problem space rather than the machine's bits and bytes. You are dealing with high-level concepts and abstractions. Ease in design leads to more productive software development.

Ease in software maintenance: object-oriented software are easier to understand, therefore easier to test, debug, and maintain.

Reusable software: you don't need to keep re-inventing the wheels and re-write the same functions for different situations. The fastest and safest way of developing a new application is to reuse existing codes - fully tested and proven codes.

Object Oriented Programming versus Procedural Programming Object Oriented Programming (OOP) and Procedural Programming are two programming paradigms.

A programming paradigm is a fundamental style of computer programming, and they differ in the way different elements of the program are represented and how steps for solving problems are defined.

As the name suggests, OOP focuses on representing problems using real-world objects and their behavior while, Procedural Programming deals with representing solutions to problems using procedures, which are collections of code that run in a specific order.

There are programming languages that support key aspects of OOP (called OOP languages), Procedural (called Procedural languages) and both. But one important thing to note is that OOP and Procedural are two ways of representing problems to be solved, and it does not matter which language is used.

In other words, OOP languages can be used for Procedural Programming while Procedural languages can sometimes be used for OOP, with some effort.

Procedural Programming is a way of programming by identifying the set of steps to solve a certain problem and the exact order that they should be executed to reach the desired outcome or state.

For example, if you want to calculate the month-end closing balance for a bank account, then the required steps would be as follows.

First, you acquire the starting balance of the account and then you reduce all the debit amounts occurred during the month.

After that, you add all the credit amounts occurred during the month. At the end of the process, you will get the month-end closing balance of the account.

One of the main concepts of Procedural Programming is the Procedure call. A procedure also known as a subroutine, method or a function contains an ordered list of instructions to be carried out.

A procedure can be called at any time during the execution by any other procedure or by itself. Examples of Procedural programming languages are C and Pascal.

In Object Oriented Programming, the focus is on thinking about the problem to be solved in terms of real-world elements and representing the problem in terms of objects and their behavior.

Object is a data structure that closely resembles some real-world object. Objects contain data fields and methods that represent attributes and behavior of real-world objects.

There are several important OOP concepts such as Data abstraction, Encapsulation, Polymorphism, Messaging, Modularity and Inheritance.

Some popular OOP languages are Java and C#. However, they can be used to perform Procedural Programming as well.

The key difference between OOP and Procedural Programming is that:

The focus of Procedural Programming is to break down the programming task in to a collection of variables and subroutines.

The focus of OOP is to break down the programming task in to objects, which encapsulate data and methods. Most notable difference could be that while Procedural Programming uses procedures to directly operate on data structures, OOP will bundle the data and methods together so that an object will operate on its own data. When it comes to the nomenclature, procedure, module, procedure call and variable in Procedural Programming are often referred to as method, object, message and attribute in OOP, respectively.

5 | ITEP309 Object Oriented ProgrammingPercival A. Fernandez