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.Table 1 in Chapter 1, Software engineering is related to the disciplines of computer science, computer engineering, management, mathematics, project management, quality management, software ergonomics, and systems engineering.Table 2 in Chapter 1,

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

main: Controversies over the term Engineer

Typical formal definitions of software engineering are:

• "the application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software".“IEEE Standard Glossary of Software Engineering Terminology,” IEEE std 610.12-1990, 1990.
• "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.