Software engineering is the study and an application of engineering to the design, development, and maintenance of software.Typical formal definitions of software engineering are: "research, design, develop, and test operating systems-level software, compilers, and network distribution software for medical, industrial, military, communications, aerospace, business, scientific, and general computing applications." "the systematic application of scientific and technological knowledge, methods, and experience to the design, implementation, testing, and documentation of software"; "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"; and "the establishment and use of sound engineering principles in order to economically obtain software that is reliable and works efficiently on real machines."↑ ↑ ↑ ↑ ↑ ↑ ↑ ↑