Software engineering

Software engineering is the application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software. It encompasses techniques and procedures, often regulated by a software development process, with the purpose of improving the reliability and maintainability of software systems. The effort is necessitated by the potential complexity of those systems, which may contain millions of lines of code.

The term software engineering was coined by Brian Randell and popularized by F.L. Bauer during the NATO Software Engineering Conference in 1968. The discipline of software engineering includes knowledge, tools, and methods for software requirements, software design, software construction, software testing, and software maintenance tasks. Software engineering is related to the disciplines of computer science, computer engineering, management, mathematics, project management, quality management, software ergonomics, and systems engineering.

In 2004, the U. S. Bureau of Labor Statistics counted 760,840 software engineers holding jobs in the U.S.; in the same time period there were some 1.4 million practitioners employed in the U.S. in all other engineering disciplines combined. Due to its relative newness as a field of study, formal education in software engineering is often taught as part of a computer science curriculum, and as a result most software engineers hold computer science degrees. The term software engineer is used very liberally in the corporate world. Very few of the practicing software engineers actually hold Engineering degrees from accredited universities. In fact, according to the Association for Computing Machinery, "most people who now function in the U.S. as serious software engineers have degrees in computer science, not in software engineering".

Ambiguity and controversy

Typical formal definitions of software engineering are:

• "the application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software".
• "an engineering discipline that is concerned with all aspects of software production"
• "the establishment and use of sound engineering principles in order to economically obtain software that is reliable and works efficiently on real machines"

The term has been used less formally:

• as the informal contemporary term for the broad range of activities that were formerly called programming and systems analysis;
• as the broad term for all aspects of the practice of computer programming, as opposed to the theory of computer programming, which is called computer science;
• as the term embodying the advocacy of a specific approach to computer programming, one that urges that it be treated as an engineering discipline rather than an art or a craft, and advocates the codification of recommended practices.

Some people believe that software engineering implies a certain level of academic training, professional discipline, and adherence to formal processes that often are not applied in cases of software development. A common analogy is that working in construction does not make one a civil engineer, and so writing code does not make one a software engineer. It is disputed by some - in particular by the Canadian Professional Engineers Ontario (PEO) body, that the field is not mature enough to warrant the title "engineering". The PEO disputed that "software engineering" was not an appropriate name for the field since those who practiced in the field and called themselves "software engineers" were not properly licensed professional engineers, and that they should therefore not be allowed to use the name.

In each of the last few decades, at least one radical new approach has entered the mainstream of software development (e.g. Structured Programming, Object Orientation), implying that the field is still changing too rapidly to be considered an engineering discipline. Proponents argue that the supposedly radical new approaches are evolutionary rather than revolutionary.

Individual commentators have disagreed sharply on how to define software engineering or its legitimacy as an engineering discipline. David Parnas has said that software engineering is, in fact, a form of engineering. Steve McConnell has said that it is not, but that it should be. Donald Knuth has said that programming is an art and a science. Edsger W. Dijkstra claimed that the terms software engineering and software engineer have been misused, particularly in the United States.