Object Oriented Programming - Essay Example

Object Oriented Programming OOP is an acronym for Object Oriented Programming. Traditionally, a computer program was seen as a collection offunctions or procedures or simply a list of instructions whereas with the advent of Object Oriented programming, each program may be seen as comprising a collection of individual units, or objects, that act on each other. In simpler terms, it is a type of programming in which programmers define not only the data type of a data structure, but also the types of operations (functions) that can be applied to the data structure. In this way, the data structure becomes an object that includes both data and functions. In addition, programmers can create relationships between one object and another. Each object is capable of receiving messages, processing data and sending messages to other objects. One of the principal advantages of object oriented programming techniques over procedural programming techniques is that they enable programmers to create modules that do not need to be changed when a new type of object is added. A programmer can simply create a new object that inherits many of its features from existing objects. This makes object-oriented programs easier to modify. Thus, it creates greater flexibility and maintainability in programming, and so is widely used in large-scale software engineering. The key Object Oriented terms and concepts includes the following : -> Classes and Sub classes: The collections of objects with identical characteristics are collectively known as a class. It is the basis of modularity and structure in an object oriented program. We can design our own classes and create instances of these and then assign them to variables. We can then pass messages to these objects which triggers the user defined methods. -> Encapsulation: Encapsulation means wrapping up of data and associated functions into a single unit i.e., class. The object encapsulates both data and the logical procedures required to manipulate data. An object remembers its data values and performs operations to manipulate and report its data values and also hides all its details, and only exposes its operation interface to its users - objects and classes. -> Reuse: Software reuse is another characteristics of object oriented design. One of the major ways to achieve software reuse is through inheritance. ->Inheritance: Inheritance is the mechanism for creating sub-classes, it provides a way to define a (sub) class as a specialization or an extension of a more general class or parent class. An object in a sub class inherits all the attributes of the parent and might have additional attributes and behaviors. The basic advantage of inheritance is that it provides reusability, like, adding additional features to an existing class without modifying it. -> Polymorphism: It is the concept which states that the same operation may apply to two or more classes in different way. It is the behavior which varies depending on the class in which the behavior is invoked, that is, two or more classes can react differently to the same message. The essence of this concept is that every class should handle different data types. Thus, Object oriented programming provides a clear modular structure for programs which makes it good for defining abstract datatypes where implementation details are hidden and the unit has a clearly defined interface. DSDM Dynamic Systems Development Method is abbreviated as DSDM. DSDM provides a framework for an iterative and incremental approach to the development of Information Systems. In simpler terms, it is a framework of controls for the development of IT systems to tight time scales. It is independent of any particular set of tools and techniques and can be used with object-oriented and structured analysis and design approaches. DSDM has been used successfully by organizations in both the public and private sectors. The DSDM Life Cycle : The DSDM framework consists of three sequential phases, namely the Pre-Project, Project and Post - Project phases. The Project Phase of DSDM is the most elaborate of the three phases. It consists of 7 stages that form an iterative step-by-step approach in developing an IS. Advantages of DSDM : -> Likely to satisfy eventual users due to constant consultation throughout the design process. Another very fast process, important in keeping ahead of competition. -> Clients understand the final product well as they are well involved in all aspects of the project and comprehensive documents are produced. Disadvantages of DSDM : -> Software isn't reusable, due to the ad hoc nature of the design and implementation of the project the software can't be developed elsewhere. ' Traditional approaches fix requirements whereas in DSDM time is fixed for the life of a project, resources are fixed as far as possible. Thus DSDM projects guarantee to satisfy at least minimum usable subset of requirements. UML UML is an acronym for Unified Modeling Language. It is a non- proprietary, object modeling and specification language used in software engineering.UML is a family of design notations that is rapidly gaining widespread acceptance as a de facto standard design language for Object Oriented software development. UML includes a standardized graphical notation that may be used to create an abstract model of a system : the UML model. A large number of diagrams and different models are used in this language. Advantages : UML provides a variety of useful capabilities to the software designer, including multiple, interrelated design views, a semi-formal semantics expressed as a UML meta model, and an associated language for expressing formal logic constraints on design elements. Disadvantages : However, UML currently lacks support for capturing, representing, expressing, and exploiting certain architectural concerns whose importance has been demonstrated through research on software architectures. In particular, UML lacks direct support for modeling and exploiting architectural styles, explicit software "connectors" and global architectural constraints While UML was designed to specify, visualize, construct, and document software-intensive systems, UML is not restricted to modeling software. UML has its strengths at higher levels and has been used for modeling hardware (engineering systems) and is commonly used for business process modeling, syatems engineering modeling, and representing organizational structure. REFERENCES : -> A. Moreira & J Hernandez, 1998: Object- Oriented Technology. -> D.E.Avison & G. Fitzgerald, 1985: Information Systems Development. -> Harmon Paul, 1997: Understanding UML: The Developer's guide. Read More