My book is widely used across the world as a student text, has been translated into many languages and, in different editions and languages, has sold almost a million copies. This is the website for the 10th edition, which includes additional learning materials — case studies, presentations and videos — for students and educators. The website for the 9th edition is still available but is not maintained. So I have lived through changes to computer generations from mainframes to minicomputers to PCs and mobile devices. I started using the Internet in the early s and my first web site was published in I have worked in several areas of software engineering — software tools and environments, requirements engineering, dependable systems and large-scale complex systems.

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I introduce important concepts such as software processes and agile methods, and describe essential software development activities, from initial software specification through to system evolution. The chapters in this part have been designed to support a one-semester course in software engineering.

Chapter 1 is a general introduction that introduces professional software engineering and defines some software engineering concepts. I have also written a brief discussion of ethical issues in software engineering. I think that it is important for software engineers to think about the wider implications of their work. This chapter also introduces three case studies that I use in the book, namely a system for managing records of patients undergoing treatment for mental health problems, a control system for a portable insulin pump and a wilderness weather system.

Chapters 2 and 3 cover software engineering processes and agile development. In Chapter 2, I introduce commonly used generic software process models, such as the waterfall model, and I discuss the basic activities that are part of these processes.

Chapter 3 supplements this with a discussion of agile development methods for software engineering.

I mostly use Extreme Programming as an example of an agile method but also briefly introduce Scrum in this chapter. The remainder of the chapters in this part are extended descriptions of the software process activities that will be introduced in Chapter 2.

Chapter 4 covers the critically important topic of requirements engineering, where the requirements for what a system should do are defined. Chapter 5 introduces system modeling using the UML, where I focus on the use of use case diagrams, class diagrams, sequence diagrams, and state diagrams for modeling a software system.

Chapter 6 introduces architectural design and I discuss the importance of architecture and the use of architectural patterns in software design. Chapter 7 introduces object-oriented design and the use of design patterns. I also introduce important implementation issues here—reuse, configuration management, and host-target development and discuss open source development.

Chapter 8 focuses on software testing from unit testing during system development to the testing of software releases. I also discuss the use of test-driven development—an approach pioneered in agile methods but which has wide applicability. Finally, Chapter 9 presents an overview of software evolution issues. I cover evolution processes, software maintenance, and legacy system management.

Contents 1. National infrastructures and utilities are controlled by computer-based systems and most electrical products include a computer and controlling software. Industrial manufacturing and distribution is completely computerized, as is the financial system. Entertainment, including the music industry, computer games, and film and television, is software intensive.

Therefore, software engineering is essential for the functioning of national and international societies. Software systems are abstract and intangible. They are not constrained by the properties of materials, governed by physical laws, or by manufacturing processes. This simplifies software engineering, as there are no natural limits to the potential of software.

However, because of the lack of physical constraints, software systems can quickly become extremely complex, difficult to understand, and expensive to change. There are many different types of software systems, from simple embedded systems to complex, worldwide information systems. It is pointless to look for universal notations, methods, or techniques for software engineering because different types of software require different approaches.

Developing an organizational information system is completely different from developing a controller for a scientific instrument. Neither of these systems has much in common with a graphics-intensive computer game. All of these applications need software engineering; they do not all need the same software engineering techniques. Software engineering is criticized as inadequate for modern software development.

However, in my view, many of these so-called software failures are a consequence of two factors: 1. Increasing demands As new software engineering techniques help us to build larger, more complex systems, the demands change. Systems have to be built and delivered more quickly; larger, even more complex systems are required; systems have to have new capabilities that were previously thought to be impossible. Existing software engineering methods cannot cope and new software engineering techniques have to be developed to meet new these new demands.

Low expectations It is relatively easy to write computer programs without using software engineering methods and techniques.

Many companies have drifted into software development as their products and services have evolved. They do not use software engineering methods in their everyday work. Consequently, their software is often more expensive and less reliable than it should be. We need better software engineering education and training to address this problem.

Software engineers can be rightly proud of their achievements. Of course we still have problems developing complex software but, without software engineering, we would not have explored space, would not have the Internet or modern telecommunications. All forms of travel would be more dangerous and expensive. Software engineering has contributed a great deal and I am convinced that its contributions in the 21st century will be even greater.

It became clear that individual approaches to program development did not scale up to large and complex software systems. These were unreliable, cost more than expected, and were delivered late. Throughout the s and s, a variety of new software engineering techniques and methods were developed, such as structured programming, information hiding and object-oriented development. Tools and standard notations were developed and are now extensively used.

People in business write spreadsheet programs to simplify their jobs, scientists and engineers write programs to process their experimental data, and hobbyists write programs for their own interest and enjoyment. However, the vast majority of software development is a professional activity where software is developed for specific business purposes, for inclusion in other devices, or as software products such as information systems, CAD systems, etc.

Professional software, intended for use by someone apart from its developer, is usually developed by teams rather than individuals. It is maintained and changed throughout its life. Software engineering is intended to support professional software development, rather than individual programming. It includes techniques that support program specification, design, and evolution, none of which are normally relevant for personal software development.

To help you to get a broad view of what software engineering is about, I have summarized some frequently asked questions in Figure 1. Many people think that software is simply another word for computer programs. However, when we are talking about software engineering, software is not just the programs themselves but also all associated documentation and configuration data that is required to make these programs operate correctly. A professionally developed software system is often more than a single program.

The system usually consists of a number of separate programs and configuration files that are used to set up these programs. It may include system documentation, which describes the structure of the system; user documentation, which explains how to use the system, and websites for users to download recent product information.

This is one of the important differences between professional and amateur software development. However, if you are writing software that other people will use and other engineers will change then you usually have to provide additional information as well as the code of the program. Computer programs and associated documentation. Software products may be developed for a particular customer or may be developed for a general market.

What are the attributes of good software? Good software should deliver the required functionality and performance to the user and should be maintainable, dependable, and usable.

What is software engineering? Software engineering is an engineering discipline that is concerned with all aspects of software production. What are the fundamental software engineering activities? Software specification, software development, software validation, and software evolution.

What is the difference between software engineering and computer science? Computer science focuses on theory and fundamentals; software engineering is concerned with the practicalities of developing and delivering useful software. What is the difference between software engineering and system engineering? System engineering is concerned with all aspects of computer-based systems development including hardware, software, and process engineering.

Software engineering is part of this more general process. What are the key challenges facing software engineering? Coping with increasing diversity, demands for reduced delivery times, and developing trustworthy software. What are the costs of software engineering? For custom software, evolution costs often exceed development costs.

What are the best software engineering techniques and methods? While all software projects have to be professionally managed and developed, different techniques are appropriate for different types of system. For example, games should always be developed using a series of prototypes whereas safety critical control systems require a complete and analyzable specification to be developed.

What differences has the Web made to software engineering? The Web has led to the availability of software services and the possibility of developing highly distributed service-based systems. Web-based systems development has led to important advances in programming languages and software reuse.

Figure 1. There are two kinds of software products: 1. Generic products These are stand-alone systems that are produced by a development organization and sold on the open market to any customer who is able to 1. Examples of this type of product include software for PCs such as databases, word processors, drawing packages, and project-management tools. It also includes so-called vertical applications designed for some specific purpose such as library information systems, accounting systems, or systems for maintaining dental records.

Customized or bespoke products These are systems that are commissioned by a particular customer. A software contractor develops the software especially for that customer. Examples of this type of software include control systems for electronic devices, systems written to support a particular business process, and air traffic control systems.

An important difference between these types of software is that, in generic products, the organization that develops the software controls the software specification. For custom products, the specification is usually developed and controlled by the organization that is buying the software.


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