Object-Oriented Programming Overview   The concepts of Object-Oriented (OO) programming have been around for over four decades. Initially developed in the field of artificial intelligence, OO programming was embraced by Xerox as a means of developing systems that better reflected real life needs and were more user friendly. OO’s popularity and sophistication has increased in the past several years as businesses are abandoning their mainframe systems and incorporating more client-server models to run their businesses and are integrating web technology as a business tool. A change in the overall pace of business has also contributed to the increased popularity of OO programming. One of the primary features of OO programming is its relative flexibility and adaptability to changing business needs. How is OO programming different from traditional procedural programming? Traditional programming has the following characteristics: Functions are written sequentially, so that a change in programming can affect any code that follows it. If a function is used multiple times in a system (i.e., a piece of code that manages the date), it is often simply cut and pasted into each program (i.e., a change log, order function, fulfillment system, etc). If a date change is needed (i.e., Y2K when the code needed to be changed to handle four numerical digits instead of two), all these pieces of code must be found, modified, and tested. Code (sequences of computer instructions) and data (information on which the instructions operates on) are kept separate. Multiple sets of code can access and modify one set of data. One set of code may rely on data in multiple places. Multiple sets of code and data are required to work together. Changes made to any of the code sets and data sets can cause problems through out the system. Object-Oriented programming takes a radically different approach: Code and data are merged into one indivisible item – an object (the term “component” has also been used to describe an object.) An object is an abstraction of a set of real-world things (for example, an object may be created around “date”) The object would contain all information and functionality for that thing (A date object it may contain labels like January, February, Tuesday, Wednesday. It may contain functionality that manages leap years, determines if it is a business day or a holiday, etc., See Fig. 1). Ideally, information about a particular thing should reside in only one place in a system. The information within an object is encapsulated (or hidden) from the rest of the system.  A system is composed of multiple objects (i.e., date function, reports, order processing, etc., See Fig 2). When one object needs information from another object, a request is sent asking for specific information. (for example, a report object may need to know what today’s date is and will send a request to the date object) These requests are called messages and each object has an interface that manages messages. OO programming languages include features such as “class”, “instance”, “inheritance”, and “polymorphism” that increase the power and flexibility of an object. What are the advantages of Object-Oriented programming? One of the main advantages of OO programming is its ease of modification; objects can easily be modified and added to a system there by reducing maintenance costs. OO programming is also considered to be better at modeling the real world than is procedural programming. It allows for more complicated and flexible interactions. OO systems are also easier for non-technical personnel to understand and easier for them to participate in the maintenance and enhancement of a system because it appeals to natural human cognition patterns. For some systems, an OO approach can speed development time since many objects are standard across systems and can be reused. Components that manage dates, shipping, shopping carts, etc. can be purchased and easily modified for a specific system. Are there specific programming languages needed for OO? There are almost two-dozen major OO languages, the leading commercial OO languages are: C++  Smalltalk  Java C++ C++ is an OO version of C. It is compatible with C (it is actually a superset), so that existing C code can be incorporated into C++ programs. C++ programs are fast and efficient.  Smalltalk Smalltalk is a pure OO language. A rich class library and a dynamic development environment makes Smalltalk a favorite of OO developers. Java Java is the latest, flashiest OO language. It has taken the software industry by storm due to its close ties with the Internet and Web browsers. Java is a mixture of C++ and Smalltalk. It is important to note that OO programming is less a function of what programming language is used but rather the use of a programming style and philosophy. Many programmers use OO languages but do not have the training or experience in creating true OO programs and systems. The programs they create do not take advantage of OO’s strengths, instead they are still essentially procedural programs. An experienced OO programmer can create an OO program using a non-OO language, although it is more time consuming and difficult.

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