Editing Source code (section)

== Purposes ==
===Estimation===
The number of lines of source code is often used as a metric when evaluating the productivity of computer programmers, the economic value of a code base, [[software development effort estimation|effort estimation]] for projects in development, and the ongoing cost of [[software maintenance]] after release.{{sfn|Foster|2014|pp=249, 274, 280, 305}}

===Communication===
Source code is also used to communicate [[algorithm]]s between people {{endash}} e.g., [[code snippets]] online or in books.<ref name=Spinellis>Spinellis, D: ''Code Reading: The Open Source Perspective''. Addison-Wesley Professional, 2003. {{ISBN|0-201-79940-5}}</ref>

[[Programmer|Computer programmers]] may find it helpful to review existing source code to learn about programming techniques.<ref name=Spinellis/> The sharing of source code between developers is frequently cited as a contributing factor to the maturation of their programming skills.<ref name=Spinellis/> Some people consider source code an expressive [[Media (arts)|artistic medium]].<ref>"''Art and Computer Programming''" [http://www.onlamp.com/pub/a/onlamp/2005/06/30/artofprog.html ONLamp.com] {{Webarchive|url=https://web.archive.org/web/20180220045508/http://www.onlamp.com/pub/a/onlamp/2005/06/30/artofprog.html |date=20 February 2018 }}, (2005)</ref>

Source code often contains [[comment (programming)|comment]]s—blocks of text marked for the compiler to ignore. This content is not part of the program logic, but is instead intended to help readers understand the program.{{sfn|Kaczmarek ''et al.''|2018|p=68}}

Companies often keep the source code confidential in order to hide algorithms considered a [[trade secret]]. Proprietary, secret source code and algorithms are widely used for sensitive government applications such as [[criminal justice]], which results in [[black box]] behavior with a lack of [[Transparency (behavior)|transparency]] into the algorithm's methodology. The result is avoidance of public scrutiny of issues such as bias.{{sfn|Katyal|2019|pp=1186–1187}}
===Modification===
{{see also|Software development|Software maintenance}}
Access to the source code (not just the [[object code]]) is essential to modifying it.{{sfn|Katyal|2019|p=1195}} Understanding existing code is necessary to understand how it works{{sfn|Katyal|2019|p=1195}} and before modifying it.<ref name=Offutt>{{cite web |last1=Offutt |first1=Jeff |author1-link=Jeff Offutt |title=Overview of Software Maintenance and Evolution |url=https://cs.gmu.edu/~offutt/classes/437/maintessays/maintEvolutionOverview.html |website=[[George Mason University]] Department of Computer Science |access-date=5 May 2024 |date=January 2018}}</ref> The rate of understanding depends both on the code base as well as the skill of the programmer.{{sfn|Tripathy |Naik|2014|p=296}} Experienced programmers have an easier time understanding what the code does at a high level.{{sfn|Tripathy |Naik|2014|p=297}}  [[Software visualization]] is sometimes used to speed up this process.{{sfn|Tripathy |Naik|2014|pp=318-319}} 

Many software programmers use an [[integrated development environment]] (IDE) to improve their productivity. IDEs typically have several features built in, including a [[source-code editor]] that can alert the programmer to common errors.{{sfn|O'Regan|2022|p=375}}  Modification often includes [[code refactoring]] (improving the structure without changing functionality) and restructuring (improving structure and functionality at the same time).{{Sfn|Tripathy |Naik|2014|p=94}} Nearly every change to code will introduce new bugs or unexpected [[ripple effect]]s, which require another round of fixes.<ref name=Offutt/> 

[[Code review]]s by other developers are often used to scrutinize new code added to a project.{{sfn|Dooley|2017|p=272}} The purpose of this phase is often to verify that the code meets style and [[maintainability]] standards and that it is a correct implementation of the [[software design]].{{sfn|O'Regan|2022|pp=18, 21}} According to some estimates, code review dramatically reduce the number of bugs persisting after [[software testing]] is complete.{{sfn|Dooley|2017|p=272}} Along with software testing that works by executing the code, [[static program analysis]] uses automated tools to detect problems with the source code. Many IDEs support code analysis tools, which might provide metrics on the clarity and maintainability of the code.{{sfn|O'Regan|2022|p=133}} [[Debuggers]] are tools that often enable programmers to step through execution while keeping track of which source code corresponds to each change of state.{{sfn|Kaczmarek ''et al.''|2018|pp=348-349}}

===Compilation and execution===
Source code files in a high-level programming language must go through a stage of preprocessing into [[machine code]] before the instructions can be carried out.{{sfn|Tracy|2021|p=121}} After being compiled, the program can be saved as an [[object file]] and the [[Loader (computing)|loader]] (part of the operating system) can take this saved file and [[execution (computing)|execute]] it as a [[process]] on the computer hardware.{{sfn|Tracy|2021|pp=122-123}} Some programming languages use an [[Interpreter (computing)|interpreter]] instead of a compiler. An interpreter converts the program into machine code at [[execution (computing)|run time]], which makes them 10 to 100 times slower than compiled programming languages.{{sfn|O'Regan|2022|p=375}}{{sfn|Sebesta|2012|p=28}}