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Object Orientation, sometimes called object technology, is a set of still-evolving theories, techniques and tools for developing complex software systems. It is based on the idea that software systems are best thought of as set of interacting parts, objects, that do the work of the system by sending messages to each other. (Although the Internet is not an object-oriented system, it is quite useful to think of object-oriented systems as working in a similar way.) Object technology has particular strengths because it allows developers to move in a relatively smooth fashion from that part of the world that the software has to simulate to the software itself. For example, in an object-oriented implementation of a banking system (i.e. in the code) you should find customer objects that directly and straightforwardly represent how actual bank customers behave. Most software development technologies evolve after a language has emerged that best represents the ideas. The programming languages Simula and Smalltalk were the starting points for object technology. Then came C++ and Java. C++ has some support for object concepts and became hugely popular because of its relationship with C. Java has given a further boost to object technology because of the Web, not to mention its superficial relationship with C++ and its inclusion of many ideas from Smalltalk.– Java is a relatively new programming language developed by Sun Microsystems, Inc. Java started out in 1991 as a project code-named Green and the language was at one stage called Oak. Java is thought by many to have been a compromise between what its two inventors, James Gosling and Bill Joy, wanted. An early motivation was to design a language for embedded systems, however other desirable language features were added and Java is the result. There are many existing computer programming languages, however Java has certain features that motivated its creation and widespread adoption by software developers and universities. One of these features is the portability of Java software – the same ‘pure’ Java software can run on many different types of computer system with no changes, including PC-compatibles, Macintosh, and computers running a variety of Unix systems. Another feature of Java is that it is possible to create Java software (called ‘applets’) that can be included as part of a web page, and so run on any computer with no software required except a Java-enabled web browser. A strength of Java is that it implements most of the concepts of object-oriented systems. As will become apparent as you progress through the module, object technology encourages and facilitates both software reuse, and the development of programs that can model and respond well to modern, event-driven multi-tasking, graphical user interfaces-based software systems. Before learning about Java in the following units of the module, it is important to understand the fundamental concepts behind computers, software systems and object-oriented systems. This unit has been written in a way that presents ideas about systems, software systems and object concepts first in abstract terms, then in more concrete terms. There are a lot of new concepts introduced in this unit, some are core concepts, others are important background concepts for anyone studying and working with computer systems. Use the activities and unit test questions to help focus on understanding and apply the important concepts. You will probably find your self revisiting this unit each time you complete a later unit, as your personal model of computing and computer systems developed through the learning of object-oriented technology with the Java programming language.
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