Process flows from getting a requirement to designing a software package

The international standard for describing the method of selecting, implementing and monitoring the life cycle for software is ISO/IEC 12207.

Planning

An important task in creating a software program is extracting the requirements or requirements analysis ^[1]. Customers typically have an abstract idea of what they want as an end result, but not what software should do. Skilled and experienced software engineers recognize incomplete, ambiguous, or even contradictory requirements at this point. Frequently demonstrating live code may help reduce the risk that the requirements are incorrect.

Once the general requirements are gathered from the client, an analysis of the scope of the development should be determined and clearly stated. This is often called a scope document.

Certain functionality may be out of scope of the project as a function of cost or as a result of unclear requirements at the start of development. If the development is done externally, this document can be considered a legal document so that if there are ever disputes, any ambiguity of what was promised to the client can be clarified.

Implementation, testing and documenting

Implementation is the part of the process where software engineers actually program the code for the project.

Software testing is an integral and important phase of the software development process. This part of the process ensures that defectsare recognized as soon as possible.

Documenting the internal design of software for the purpose of future maintenance and enhancement is done throughout development. This may also include the writing of an API, be it external or internal. The software engineering process chosen by the developing team will determine how much internal documentation (if any) is necessary.Plan-driven models (e.g., Waterfall) generally produce more documentation than Agile models.

[edit]Deployment and maintenance

Deployment starts after the code is appropriately tested, approved for release, and sold or otherwise distributed into a production environment. This may involve installation, customization (e.g. by setting parameters to the customer's values), testing, and possibly an extended period of evaluation.^{[citation needed]}

Software training and support is important, as software is only effective if it is used correctly.^{[citation needed]}

Maintaining and enhancing software to cope with newly discovered faults or requirements can take substantial time and effort, as missed requirements may force redesign of the software.^{[citation needed]}