Editing Software (section)

==Software development and maintenance==
[[File:Traditional software development life cycle diagram.png|thumb|upright=2.5|center|Diagram for a traditional [[software development life cycle]] from 1988. The numbers represent the typical cost of each phase.]]

Software companies aim to deliver a high-quality product on time and under budget. A challenge is that [[software development effort estimation]] is often inaccurate.{{sfn|O'Regan|2022|p=7}} [[Software development]] begins by conceiving the project, evaluating its feasibility, analyzing the business requirements, and making a [[software design]].{{sfn|O'Regan|2022|p=5}}{{sfn|Dooley|2017|p=1}} Most software projects speed up their development by [[software reuse|reusing]] or incorporating existing software, either in the form of [[commercial off-the-shelf]] (COTS) or [[open-source software]].{{sfn|O'Regan|2022|pp=18, 110-111}}{{sfn|Tracy|2021|pp=43, 76}} [[Software quality assurance]] is typically a combination of manual [[code review]] by other engineers{{sfn|O'Regan|2022|pp=117-118}} and automated [[software testing]]. Due to time constraints, testing cannot cover all aspects of the software's intended functionality, so developers often focus on the most critical functionality.{{sfn|O'Regan|2022|p=54}} [[Formal method]]s are used in some safety-critical systems to prove the correctness of code,{{sfn|O'Regan|2022|p=267}} while [[user acceptance testing]] helps to ensure that the product meets customer expectations.{{sfn|O'Regan|2022|p=20}} There are a variety of [[software development methodologies]], which vary from completing all steps in order to concurrent and iterative models.{{sfn|O'Regan|2022|p=9}} Software development is driven by [[software requirements|requirements]] taken from prospective users, as opposed to maintenance, which is driven by events such as a change request.{{sfn|Tripathy |Naik|2014|p=26}}

Frequently, software is [[software release life cycle|released]] in an incomplete state when the development team runs out of time or funding.{{sfn |Reifer|2012|p=22}} Despite [[software testing|testing]] and [[Software quality assurance|quality assurance]], virtually all software contains [[software bug|bugs]] where the system does not work as intended. Post-release [[software maintenance]] is necessary to remediate these bugs when they are found and keep the software working as the environment changes over time.{{sfn|Tripathy |Naik|2014|pp=4, 27}} New features are often added after the release. Over time, the level of maintenance becomes increasingly restricted before being cut off entirely when the product is withdrawn from the market.{{sfn|Tripathy |Naik|2014|p=89}} As software [[software aging|ages]], it becomes known as [[legacy software]] and can remain in use for decades, even if there is no one left who knows how to fix it.{{sfn|Tracy|2021|p=3}} Over the lifetime of the product, software maintenance is estimated to comprise 75 percent or more of the total development cost.{{sfn|Varga|2018|p=6}}{{sfn|Ulziit ''et al.''|2015|p=764}}

Completing a software project involves various forms of expertise, not just in [[software programmer]]s but also testing, documentation writing, [[Software project management|project management]], [[graphic design]], [[user experience]], user support, [[marketing]], and fundraising.{{sfn|Tucker |Morelli |de Silva |2011|p=7}}{{sfn|Stull|2018|pp=24-25}}{{sfn|Dooley|2017|p=1}}