Editing Patch (computing) (section)

==Application==
The size of patches may vary from a few [[byte]]s to hundreds of [[megabyte]]s; thus, more significant changes imply a larger size, though this also depends on whether the patch includes entire files or only the changed portion(s) of files. In particular, patches can become quite large when the changes add or replace non-program data, such as graphics and sounds files. Such situations commonly occur in the patching of [[computer game]]s.  Compared with the initial installation of software, patches usually do not take long to apply.

In the case of [[operating system]]s and [[computer server]] software, patches have the particularly important role of fixing security holes.  Some critical patches involve issues with drivers.<ref>{{cite book
|last1= Liu
|first1= Ashok
|title= Computercare's Laptop Repair Workbook: The 300 Cases of Classic Notebook Computers Troubleshooting and Repair
|date= June 2012
|url= https://books.google.com/books?id=qCA9tMQ_BlAC
|publisher= AuthorHouse
|publication-date= 2012
|page= 591
|isbn= 9781477205402
|access-date= 2015-01-08
|quote= Uninstall High Definition Audio driver patch KB835221 & KB888111 [...]
}}</ref>  Patches may require prior application of other patches, or may require prior or concurrent updates of several independent software components. To facilitate updates, operating systems often provide automatic or semi-automatic updating facilities. Completely automatic updates have not succeeded in gaining widespread popularity in corporate computing environments, partly because of the aforementioned glitches, but also because administrators fear that software companies may gain unlimited control over their computers.{{Citation needed|date=May 2009}} [[Package management system]]s can offer various degrees of patch automation.

Usage of completely automatic updates has become far more widespread in the consumer market, due largely{{citation needed|date=January 2015}} to the fact that [[Microsoft Windows]] added support for them{{when|date=January 2015}}, and [[Windows XP#Service Pack 2|Service Pack 2 of Windows XP]] (available in 2004) enabled them by default.  Cautious users, particularly system administrators, tend to put off applying patches until they can verify the stability of the fixes. Microsoft [[Windows Server Update Services|(W)SUS]] supports this. In the cases of large patches or of significant changes, distributors often limit availability of patches to qualified developers as a [[Development stage#Beta|beta test]].

Applying patches to [[firmware]] poses special challenges, as it often involves the provisioning of totally new firmware images, rather than applying only the differences from the previous version.  The patch usually consists of a firmware image in form of binary data, together with a supplier-provided special program that replaces the previous version with the new version; a [[motherboard]] [[BIOS]] update is an example of a common firmware patch. Any unexpected error or interruption during the update, such as a power outage, may render the motherboard unusable.  It is possible for motherboard manufacturers to put safeguards in place to prevent serious damage; for example, the update procedure could make and keep a backup of the firmware to use in case it determines that the primary copy is corrupt (usually through the use of a [[checksum]], such as a [[Cyclic redundancy check|CRC]]).