View source for Software versioning

{{short description|Unique identification of incremental software updates}}
{{Use mdy dates|date=October 2021}}
{{redirect|Version number|versioning of other products|Mark (designation)}}
{{condensed|date=February 2022}}
'''Software versioning''' is the process of assigning either unique ''version names'' or unique ''version numbers'' to unique states of computer software. Within a given version number category (e.g., major or minor), these numbers are generally assigned in increasing order and correspond to new developments in the software. At a fine-grained level, [[revision control]] is used for keeping track of incrementally-different versions of information, whether or not this information is computer software, in order to be able to roll any changes back.

Modern computer software is often tracked using two different software versioning schemes: an ''internal version number'' that may be incremented many times in a single day, such as a revision control number, and a ''release version'' that typically changes far less often, such as semantic versioning<ref name="semver" /> or a project code name.

==History==
File numbers were used especially in public administration, as well as companies, to uniquely identify files or cases. For computer files this practice was introduced for the first time with MIT's ITS file system, later the TENEX filesystem for the PDP-10 in 1972.<ref>[https://www.researchgate.net/publication/220421975_TENEX_a_paged_time_sharing_system_for_the_PDP_-_10 TENEX, a paged time sharing system for the PDP - 10], Bobrow, Burchfiel, Murphy, Tomlinson, March 1972, Communications of the ACM 15(3):135-143.</ref>

Later lists of files including their versions were added, and dependencies amongst them. Linux distributions like Debian, with its [[dpkg]], early on created package management software which could resolve dependencies between their packages. Debian's first try was that a package knew other packages which depended on it. From 1994 on this idea was inverted, so a package that knew the packages it needed. When installing a package, dependency resolution was used to automatically calculate the packages needed as well, and install them with the desired package. To facilitate upgrades, minimum package versions were introduced. Thus the numbering scheme needed to tell which version was newer than the required one.<ref>[https://lists.debian.org/debian-devel/1994/02/msg00026.html package interdependencies], Robert Sanders, 1994-02-25.</ref><ref>[<https://lists.debian.org/debian-devel/1995/07/msg00085.html Bug#1167: ELF development packages fail or have missing dependencies], Ian Jackson, 1995-07-30.</ref><ref>[https://www.debian.org/doc/manuals/project-history/project-history.en.pdf A Brief History of Debian], Javier Fernández-Sanguino et al, 2021-10-26.</ref>

==Schemes==
A variety of version numbering schemes have been created to keep track of different versions of a piece of software. The ubiquity of computers has also led to these schemes being used in contexts outside computing.

===Based on sequence identifiers===
[[File:VersionNumbers.svg|thumb|upright=0.5|An example version number sequence]]
In sequence-based software versioning schemes, each [[software release]] is assigned a unique identifier that consists of one or more sequences of numbers or letters.<ref>{{Cite web |title=PEP 440 – Version Identification and Dependency Specification {{!}} peps.python.org |url=https://peps.python.org/pep-0440/ |access-date=2023-04-19 |website=peps.python.org}}</ref> This is the extent of the commonality; schemes vary widely in areas such as the number of sequences, the attribution of meaning to individual sequences, and the means of incrementing the sequences.

==== Change significance ====
In some schemes, sequence-based identifiers are used to convey the significance of changes between releases. Changes are classified by significance level, and the decision of which sequence to change between releases is based on the significance of the changes from the previous release, whereby the first sequence is changed for the most significant changes, and changes to sequences after the first represent changes of decreasing significance.

Depending on the scheme, significance may be assessed by lines of code changed, function points added or removed, the potential impact on customers in terms of work required to adopt a new version, risk of bugs or undeclared breaking changes, degree of changes in visual layout, the number of new features, or almost anything the product developers or marketers deem to be significant, including marketing desire to stress the "relative goodness" of the new version.

<!-- [[Semantic versioning]] and [[SemVer]] redirect here -->
==== Semantic versioning ====
[[File:Semver.jpg|thumb|Semantic versioning three-part version number]]
'''{{Visible anchor|Semantic versioning}}''' (aka '''SemVer''')<ref name="semver">
Preston-Werner, Tom (2013).
[https://semver.org/ Semantic Versioning] 2.0.0. Creative Commons.
Retrieved from https://semver.org/spec/v2.0.0.html.
</ref> is a widely-adopted version scheme<ref>{{cite book|last1=Lam|first1=Patrick|last2=Dietrich|first2=Jens|last3=Pearce|first3=David J.|date=August 16, 2020|title=Proceedings of the 2020 ACM SIGPLAN International Symposium on New Ideas, New Paradigms, and Reflections on Programming and Software|chapter=Putting the semantics into semantic versioning |pages=157–179 |doi=10.1145/3426428.3426922 |arxiv=2008.07069|isbn=9781450381789 |s2cid=221139849 }}</ref> that encodes a version by a three-part version number (Major.Minor.Patch), an optional pre-release tag, and an optional build meta tag. In this scheme, risk and functionality are the measures of significance. Breaking changes are indicated by increasing the major number (high risk); new, non-breaking features increment the minor number (medium risk); and all other non-breaking changes increment the patch number (lowest risk). The presence of a pre-release tag (-alpha, -beta) indicates substantial risk, as does a major number of zero (0.y.z), which is used to indicate a work-in-progress that may contain any level of potentially breaking changes (highest risk). As an example of inferring compatibility from a SemVer version, software which relies on version 2.1.5 of an API is compatible with version 2.2.3, but not necessarily with 3.2.4.

==== Other schemes based on sequence identifiers ====
Developers may choose to jump multiple minor versions at a time to indicate that significant features have been added, but are not enough to warrant incrementing a major version number; for example, [[Internet Explorer 5]] from 5.1 to 5.5 or [[Adobe Photoshop]] 5 to 5.5. This may be done to emphasize the value of the upgrade to the software user or, as in Adobe's case, to represent a release halfway between major versions (although levels of sequence-based versioning are not necessarily limited to a single digit, as in [[Blender (software)|Blender]] version 2.91 or ''[[Minecraft]]'' Java Edition starting from 1.7.10).

A different approach is to use the ''major'' and ''minor'' numbers along with an alphanumeric string denoting the release type, e.g. "alpha" (a), "beta" (b), or "release candidate" (rc). A [[software release train]] using this approach might look like 0.5, 0.6, 0.7, 0.8, 0.9 → 1.0b1, 1.0b2 (with some fixes), 1.0b3 (with more fixes) → 1.0rc1 (if it is stable ''enough''), 1.0rc2 (if more bugs are found) → 1.0. It is a common practice in this scheme to lock out new features and breaking changes during the release candidate phases and, for some teams, even betas are locked down to bug fixes only, to ensure convergence on the target release.

Other schemes impart meaning on individual sequences:
:''<nowiki>major.minor[.build[.revision]]</nowiki>'' (example: ''1.2.12.102'')
:''<nowiki>major.minor[.maintenance[.build]]</nowiki>'' (example: ''1.4.3.5249'')

Again, in these examples, the definition of what constitutes a "major" as opposed to a "minor" change is entirely subjective and up to the author, as is what defines a "build", or how a "revision" differs from a "minor" change.

Shared libraries in [[Linux]] and [[Oracle Solaris|Solaris]] may use the ''<nowiki>current.revision.age</nowiki>'' format where:<ref name="libinterface">{{cite web|url=http://static.usenix.org/publications/library/proceedings/als00/2000papers/papers/full_papers/browndavid/browndavid_html/|title=Library Interface Versioning in Solaris and Linux}}</ref><ref>{{cite web |title=Libtool's versioning system |url=https://www.gnu.org/software/libtool/manual/libtool.html#Versioning |website=Libtool documentation}}</ref>
:''current'': The most recent interface number that the library implements.
:''revision'': The implementation number of the current interface. 
:''age'': The difference between the newest and oldest interfaces that the library implements. This use of the third field is specific to [[libtool]]: others may use a different meaning or simply ignore it.

A similar problem of relative change significance and versioning nomenclature exists in book publishing, where [[edition (book)#Revised edition|edition numbers or names]] can be chosen based on varying criteria.

In most proprietary software, the first released version of a software product has version 1.{{Citation needed|date=December 2020}}

==== Degree of compatibility ====
Some projects use the major version number to indicate incompatible releases. Two examples are [[Apache Portable Runtime]] (APR)<ref name="apr">{{cite web|url=http://apr.apache.org/versioning.html|title=Versioning Numbering Concepts – The Apache Portable Runtime Project|access-date=April 11, 2009}}</ref> and the FarCry CMS.<ref name="farcry">{{cite web|url=http://blog.daemon.com.au/archives/000276.html|title=Daemonite: The science of version numbering|date=September 14, 2004|access-date=April 11, 2009}}</ref>

Often programmers write new software to be [[backward compatible]], i.e., the new software is designed to interact correctly with older versions of the software (using old protocols and file formats) and the most recent version (using the latest protocols and file formats). For example, IBM [[z/OS]] is designed to work properly with 3 consecutive major versions of the operating system running in the same sysplex.
This enables people who run a [[high availability]] computer cluster to keep most of the computers up and running while one machine at a time is shut down, upgraded, and restored to service.<ref>
Frank Kyne, Bert de Beer, Luis Martinez, Harriet Morril, Miha Petric, David Viguers, Suzi Wendler.
[https://books.google.com/books?id=UxjCAgAAQBAJ "System z Parallel Sysplex Best Practices"].
2011.
p. 6.
</ref>

Often [[packet header]]s and [[file format#Internal metadata|file format]] include a version number – sometimes the same as the version number of the software that wrote it; other times a "protocol version number" independent of the software version number.
The code to handle old [[deprecated]] protocols and file formats is often seen as [[cruft]].

==== Designating development stage ====
Software in the experimental stage ([[Alpha test|alpha]] or [[Betaware|beta]]) often uses a zero in the first ("major") position of the sequence to designate its status. However, this scheme is only useful for the early stages, not for upcoming releases with established software where the version number has already progressed past 0.<ref name="semver" />

A number of schemes are used to denote the status of a newer release:
* ''Alphanumeric suffix'' is a common scheme adopted by semantic versioning.<ref name="semver" /> In this scheme, versions have affixed a dash plus some alphanumeric characters to indicate the status.
* ''Numeric status'' is a scheme that uses numbers to indicate the status as if it's part of the sequence. A typical choice is the third position for the four-position versioning.
* ''Numeric 90+'' is another scheme that uses numbers, but apparently under a number of a previous version. A large number in the last position, typically 90 or higher, is used. This is commonly used by older open-source projects like [[Fontconfig]].

{| class="wikitable"
|+ Comparison of development stage indicators
|-
! Development<br>stage !! Semantic<br>versioning !! Numeric<br>status !! Numeric<br>90+
|-
| Alpha || 1.2.0-a.1 || 1.2.0.1 || 1.1.90
|-
| Beta  || 1.2.0-b.2 || 1.2.1.2 || 1.1.93
|-
| Release candidate (RC) || 1.2.0-rc.3 || 1.2.2.3 || 1.1.97
|-
| Release || 1.2.0 || 1.2.3.0 || 1.2.0
|-
| Post-release fixes || 1.2.5 || 1.2.3.5 || 1.2.5
|}

The two purely numeric forms remove the special logic required to handle the comparison of "alpha &lt; beta &lt; rc &lt; no prefix" as found in semantic versioning, at the cost of clarity.

==== Incrementing sequences ====
There are two schools of thought regarding how numeric version numbers are incremented. Most [[free and open-source software]] packages, including [[MediaWiki]], treat versions as a series of individual numbers, separated by periods, with a progression such as 1.7.0, 1.8.0, 1.8.1, 1.9.0, 1.10.0, 1.11.0, 1.11.1, 1.11.2, and so on.

On the other hand, some software packages identify releases by decimal numbers: 1.7, 1.8, 1.81, 1.82, 1.9, etc. Decimal versions were common in the 1980s, for example with [[NetWare]], [[Timeline of DOS operating systems|DOS]], and [[Timeline of Microsoft Windows|Microsoft Windows]], but even in the 2000s have been for example used by [[Opera (web browser)|Opera]]<ref>{{cite web|title=Opera Changelogs for Windows|publisher=[[Opera Software]]|year=2014|access-date=November 6, 2014|url=http://www.opera.com/docs/changelogs/windows/}}</ref> and [[Movable Type]].<ref>{{cite web|title=Home|work=Movable Type Documentation Wiki|date=June 25, 2013|access-date=November 6, 2014|url=https://github.com/movabletype/Documentation/wiki/Home/4aa709ba079523d7a64cab4a86650f8a8b7a9121}}</ref> In the decimal scheme, 1.81 is the minor version following 1.8, while maintenance releases (i.e. bug fixes only) may be denoted with an alphabetic suffix, such as 1.81a or 1.81b.

The standard [[GNU]] version numbering scheme is major.minor.revision,<ref>{{cite web|url=https://www.gnu.org/prep/standards/html_node/Releases.html#index-version-numbers_002c-for-releases |title=GNU Coding Standards: Releases |publisher=[[GNU Project]] |date=May 13, 2014 |access-date=May 25, 2014 |quote=You should identify each release with a pair of version numbers, a major version and a minor. We have no objection to using more than two numbers, but it is very unlikely that you really need them.}}</ref> but [[Emacs]] is a notable example using another scheme where the major number (1) was dropped and a ''user site'' revision was added which is always zero in original Emacs packages but increased by distributors.<ref name="advogato"/> Similarly, [[Debian]] package numbers are prefixed with an optional "epoch", which is used to allow the versioning scheme to be changed.<ref>Debian Policy Manual, [http://www.debian.org/doc/debian-policy/ch-controlfields.html#version 5.6.12 Version]</ref>

==== Resetting ====
In some cases, developers may decide to reset the major version number. This is sometimes used to denote a new development phase being released. For example, ''[[Minecraft]]'' Alpha ran from version 1.0.0 to 1.2.6, and when Beta was released, it reset the major version number and ran from 1.0 to 1.8. Once the game was fully released, the major version number again reset to 1.0.0.<ref>{{cite web |url=https://minecraft.wiki/w/Java_Edition_version_history |title=Java Edition version history |work=Minecraft Wiki |access-date=24 September 2023 |language=en}}</ref>

==== Separating sequences ====
When printed, the sequences may be separated with characters. The choice of characters and their usage varies by the scheme. The following list shows hypothetical examples of separation schemes for the same release (the thirteenth third-level revision to the fourth second-level revision to the second first-level revision):{{or inline|date=December 2020}}

* A scheme may use the same character between all sequences: 2.4.13, 2/4/13, 2-4-13
* A scheme choice of which sequences to separate may be inconsistent, separating some sequences but not others: 2.413
* A scheme's choice of characters may be inconsistent within the same identifier: 2.4_13 (for instance, ''[[Minecraft]]'' Beta incremented from 1.7 to 1.7_01 to 1.7.2)

When a period is used to separate sequences, it ''may'' or ''may not'' represent a decimal point—see "[[#Incrementing sequences|Incrementing sequences]]" section for various interpretation styles.

==== Number of sequences ====<!-- This looks more like a&nbsp;part of&nbsp;another section. Somebody care to&nbsp;merge? -->
There is sometimes a fourth, unpublished number which denotes the [[software build]] (as used by [[Microsoft]]). [[Adobe Flash]] is a notable case where a four-part version number is indicated publicly, as in 10.1.53.64. Some companies also include the build date. Version numbers may also include letters and other characters, such as [[Lotus 1-2-3]] Release 1a.

==== Negative numbers ====
Some projects use negative version numbers. One example is the [[SmartEiffel]] compiler which started from −1.0 and counted upwards to 0.0.<ref name="advogato">{{cite web|url=http://www.advogato.org/article/40.html|title=Advogato: Version numbering madness|access-date=April 11, 2009|date=February 28, 2000}}</ref>

====Version number ordering systems====
Historically, software versioning schemes which use numbers broadly evolved from simple integers (1, 2, ...) to decimal numbers (2.08, 2.09, 2.10)
and then to non-numeric "numbers" such as 4:3.16.3-2. These complex version numbers are therefore better treated as character strings. Operating systems that include package management facilities (such as all non-trivial Linux or [[*BSD|BSD]] distributions) will use a distribution-specific algorithm for comparing version numbers of different software packages. For example, the ordering algorithms of [[Red Hat Enterprise Linux|Red Hat]] and derived distributions differ to those of the Debian-like distributions.

As an example of surprising version number ordering implementation behavior, in Debian, leading zeroes are ignored in chunks, so that 5.0005 and 5.5 are considered as equal, and 5.5{{nbsp}}<{{nbsp}}5.0006. This can confuse users; string-matching tools may fail to find a given version number; and this can cause subtle bugs in [[package management]] if the programmers use string-indexed data structures such as version-number indexed [[hash table]]s.

To ease sorting, some software packages represent each component of the ''major.minor.release'' scheme with a fixed width. Perl represents its version numbers as a floating-point number; for example, Perl's 5.8.7 release can also be represented as 5.008007. This allows a theoretical version of 5.8.10 to be represented as 5.008010. Other software packages pack each segment into a fixed bit width; for example, on Microsoft Windows, version number 6.3.9600.16384 would be represented as [[hexadecimal]] 0x0006000325804000. The floating-point scheme breaks down if any segment of the version number exceeds 999; a packed-binary scheme employing 16 bits apiece breaks down after 65535.

====Odd-numbered versions for development releases====
Between the 1.0 and the 2.6.x series, the [[Linux kernel]] used [[even and odd numbers|odd]] minor version numbers to denote development releases and [[even and odd numbers|even]] minor version numbers to denote stable releases. For example, Linux 2.3 was a development family of the second major design of the Linux kernel, and Linux 2.4 was the stable release family that Linux 2.3 matured into. After the minor version number in the Linux kernel is the release number, in ascending order; for example, Linux 2.4.0 → Linux 2.4.22. Since the 2004 release of the 2.6 kernel, Linux no longer uses this system, and has a much shorter release cycle.

The same odd-even system is used by some other software with long release cycles, such as [[Node.js]] up to version 0.12 as well as [[WineHQ]].<ref>{{Cite news |url= http://nodesource.com/blog/nodejs-is-semver/ |title=Node.js is SemVer |date= September 15, 2015 |work=The NodeSource Blog – Node.js Tutorials, Guides, and Updates|access-date=March 26, 2018 |id= introduced Node with a Linux kernel-style odd/even versioning scheme.}}</ref>

===Based on date of release identifiers===
[[File:Street Fighter EX Opening Version Number.png|thumb|''Street Fighter EX'' [[splash screen]] showing release number in [[CalVer (software)|CalVer]] format: "961219 USA"]]
Many projects use a date-based versioning scheme called '''Calendar Versioning'''<!-- bolded per [[WP:MOSBOLD]] as a redirect target --> (aka '''CalVer'''<!-- bolded per [[WP:MOSBOLD]] as a redirect target --><ref>{{Cite web|url=https://calver.org/ |title=Calendar Versioning — CalVer|website=calver.org |access-date=October 10, 2019}}</ref>).

[[Ubuntu]] is one example of a project using calendar versioning; Ubuntu 18.04, for example, was released in April 2018. This has the advantage of being easily relatable to development schedules and support timelines. Some video games also use date as versioning, for example the [[arcade game]] ''[[Street Fighter EX]]''. At startup it displays the version number as a date plus a region code, for example ''961219 ASIA''.{{citation needed|date=November 2020}}

When using dates in versioning, for instance, file names, it is common to use the [[ISO 8601]] scheme<ref name="ISO Date">{{cite web|url=http://www.cl.cam.ac.uk/~mgk25/iso-time.html|title=International standard date and time notation|author=Markus Kuhn|access-date=April 11, 2009|date=December 19, 2004|publisher=[[University of Cambridge]]}}</ref> ''YYYY-MM-DD'', as this is easily string-sorted in increasing or decreasing order. The hyphens are sometimes omitted. The [[Wine (software)|Wine]] project formerly used a date versioning scheme, which used the year followed by the month followed by the day of the release; for example, "Wine 20040505".{{citation needed|date=November 2020}} ''[[Minecraft]]'' had a similar version formatting, but instead used DDHHMM, ex: rd-132211, 13 being the 13th of May, and 2211 being 22:11.

[[Microsoft Office]] build numbers are an encoded date:<ref name="ms">{{cite web|url=https://blog.codinghorror.com/whats-in-a-version-number-anyway/|title=Coding Horror: What's In a Version Number, Anyway?|date=February 15, 2007|access-date=November 15, 2016|author=Jeff Atwood}}</ref> the first two digits indicate the number of months that have passed from the January of the year in which the project started (with each major Office release being a different project), while the last two digits indicate the day of that month. So 3419 is the 19th day of the 34th month after the month of January of the year the project started.{{citation needed|date=November 2020}}

Other examples that identify versions by year include [[Adobe Illustrator]] 88 and [[WordPerfect Office]] 2003. When a year is used to denote version, it is generally for marketing purposes, and an actual version number also exists. For example, [[Windows 95]] is internally versioned as [[MS-DOS 7.00]] and Windows 4.00; likewise, [[Windows 2000]] is internally versioned as NT 5.0.<ref>{{cite web|url=https://pc.net/helpcenter/answers/what_nt_stands_for|title=What does the "NT" stand for in Windows NT?|date=October 20, 2006|access-date=August 13, 2022|author=Per Christensson}}</ref>

=== Other schemes ===
Some software producers use different schemes to denote releases of their software. The Debian project uses a major/minor versioning scheme for releases of its operating system but uses code names from the movie ''[[Toy Story]]'' during development to refer to stable, unstable, and testing releases.<ref>{{cite web|title=Debian FAQ: 6.2.2 Where do these codenames come from?|url=https://www.debian.org/doc/manuals/debian-faq/ftparchives.en.html#sourceforcodenames|access-date=January 2, 2021|archive-url=https://web.archive.org/web/20201210165704/https://www.debian.org/doc/manuals/debian-faq/ftparchives.en.html#sourceforcodenames|archive-date= December 10, 2020}}</ref>

[[BLAG Linux and GNU]] features very large version numbers: major releases have numbers such as 50000 and 60000, while minor releases increase the number by 1 (e.g. 50001, 50002). Alpha and beta releases are given decimal version numbers slightly less than the major release number, such as 19999.00071 for alpha 1 of version 20000, and 29999.50000 for beta 2 of version 30000. Starting at 9001 in 2003, the most recent version {{As of|2011|alt=as of 2011}} is 140000.<ref>{{cite web|title=BLAG Linux And GNU|url=http://www.blagblagblag.org/download/index.html|work=DistroWatch.com|access-date=September 29, 2011}}</ref><ref>{{cite web|title=News and Updates: BLAG|url=http://distrowatch.com/index.php?distribution=blag|work=DistroWatch.com|access-date=September 29, 2011}}</ref><ref>{{cite web|title=blag download|url=http://www.blagblagblag.org/download/index.html|work=blag|access-date=September 29, 2011}}</ref>

[[Urbit]] uses ''Kelvin versioning'' (named after the absolute [[Kelvin]] temperature scale): software versions start at a high number and count down to version 0, at which point the software is considered finished and no further modifications are made.<ref>{{Cite web|title=Kelvin Versioning · jtobin.io|url=https://jtobin.io/kelvin-versioning|access-date=March 17, 2021|website=jtobin.io}}</ref><ref>{{Cite web|last=urbit.org|title=Toward a Frozen Operating System – Urbit|url=https://urbit.org/blog/toward-a-frozen-operating-system/|access-date=March 17, 2021|website=urbit.org|language=en}}</ref>

==Internal version numbers==
Software may have an "internal" version number which differs from the version number shown in the product name (and which typically follows version numbering rules more consistently). [[Java Platform, Standard Edition|Java SE]] 5.0, for example, has the internal version number of 1.5.0, and versions of Windows from NT 4 on have continued the standard numerical versions internally: Windows 2000 is [[Windows NT|NT]] 5.0, XP is Windows NT 5.1, [[Windows Server 2003]] and [[Windows XP Professional x64 Edition]] are NT 5.2, [[Windows Server 2008]] and Vista are NT 6.0, [[Windows Server 2008 R2]] and Windows 7 are NT 6.1, [[Windows Server 2012]] and [[Windows 8]] are NT 6.2, and [[Windows Server 2012 R2]] and [[Windows 8.1]] are NT 6.3. Windows 10 was initially intended to be NT 6.4, as the earliest Technical Preview build shared to the public is numbered 6.4.9841. However, that did not last as the version of Windows 10 was quickly artificially increased to 10.0<ref>{{Cite web |last=Tyrsina |first=Radu |date=2014-11-21 |title=Windows 10 NT kernel gets bumped from 6.4 to 10 in recent internal builds |url=https://windowsreport.com/windows-10-nt-kernel-gets-bumped-64-10-recent-internal-builds/ |access-date=2024-07-07 |website=Windows Report |language=en-US}}</ref> to align with the commercial name, resulting in the first released version of the operating system being numbered 10.0.10240. Note, however, that Windows NT is only on its fifth major revision, as its first release was numbered 3.1 (to match the then-current Windows release number) and the Windows 10 launching made a version leap from 6.3 to 10.0.

==Pre-release versions==
In conjunction with the various versioning schemes listed above, a system for denoting pre-release versions is generally used, as the program makes its way through the stages of the [[software release life cycle]].

Programs that are in an early stage are often called "alpha" software, after the first letter in the Greek alphabet. After they mature but are not yet ready for release, they may be called "beta" software, after the second letter in the Greek alphabet. Generally alpha software is tested by developers only, while beta software is distributed for community testing.

Some systems use numerical versions less than 1 (such as 0.9), to suggest their approach toward a final "1.0" release. This is a common convention in [[Open-source software development|open source software]].<ref name=toaru>{{cite news|title=ToaruOS 1.0 Open Source OS Released After 6+ Years Of Development|url=https://fossbytes.com/toaruos-1-0-open-source/|access-date=May 23, 2017|date=February 13, 2017}}</ref><ref name=wine>{{cite magazine|last1=Gilbertson|first1=Scott|title=Wine Headed For a 1.0 Release. Finally.|magazine=WIRED |url=https://www.wired.com/2008/05/wine_headed_for_a_1dot0_releasedot_finallydot/|publisher=Wired|access-date=May 23, 2017}}</ref> However, if the pre-release version is for an existing software package (e.g. version 2.5), then an "a" or "alpha" may be appended to the version number. So the alpha version of the 2.5 release might be identified as 2.5a or 2.5.a.

An alternative is to refer to pre-release versions as "release candidates", so that software packages which are soon to be released as a particular version may carry that version tag followed by "rc-#", indicating the number of the release candidate; when the final version is released, the "rc" tag is removed.

==Release train==
A '''software release train''' is a form of software release schedule in which a number of distinct series of versioned software releases for multiple products are released as a number of different "trains" on a regular schedule. Generally, for each product line, a number of different release trains are running at a given time, with each train moving from initial release to eventual maturity and retirement on a planned schedule. Users may experiment with a newer release train before adopting it for production, allowing them to experiment with newer, "raw", releases early, while continuing to follow the previous train's [[point release]]s for their production systems prior to moving to the new release train as it becomes mature.

Cisco's [[Cisco IOS|IOS]] software platform used a release train schedule with many distinct trains for many years. More recently, a number of other platforms including [[Firefox]] and Fenix for Android,<ref>{{Cite web|url=https://wiki.mozilla.org/Release_Management/Calendar|title=Firefox Release Calendar – MozillaWiki|website=wiki.mozilla.org}}</ref> [[Eclipse (software)|Eclipse]],<ref>{{Cite web|url=https://wiki.eclipse.org/Simultaneous_Release|title=Simultaneous Release – Eclipsepedia|website=wiki.eclipse.org}}</ref> [[LibreOffice]],<ref>{{Cite web|url=https://wiki.documentfoundation.org/ReleasePlan|title=ReleasePlan – The Document Foundation Wiki|website=wiki.documentfoundation.org}}</ref> [[Ubuntu]],<ref>{{Cite web|url=https://wiki.ubuntu.com/Releases|title=Releases – Ubuntu Wiki|website=wiki.ubuntu.com}}</ref> Fedora,<ref>{{Cite web|url=https://fedoraproject.org/wiki/Releases|title=Releases – Fedora Project Wiki|website=fedoraproject.org}}</ref> Python,<ref>{{Cite web|url=https://www.python.org/dev/peps/|title=PEP 0 – Index of Python Enhancement Proposals (PEPs)|website=Python.org}}</ref> digiKam<ref>{{Cite web|url=https://digikam.org/documentation/releaseplan/|title=Release Plan|date=March 25, 2018|website=digikam.org}}</ref> and [[VMware]]<ref>{{Cite web|url=https://www.virten.net/vmware/product-release-tracker/|title=VMware Product Release Tracker (vTracker)|date=February 13, 2015|website=Virten.net}}</ref> have adopted the release train model.

==Significance==

===Technical significance===

==== In software engineering ====
Version numbers are used in practical terms by the consumer, or [[consumer|client]], to identify or compare their copy of the software product against another copy, such as the newest version released by the developer. For the programmer or company, versioning is often used on a revision-by-revision basis, where individual parts of the software are compared and contrasted with newer or older revisions of those same parts, often in a collaborative [[version control system]].

In the 21st century, more programmers started to use a formalized version policy, such as the semantic versioning policy.<ref name="semver" /> The purpose of such policies is to make it easier for other programmers to know when code changes are likely to break things they have written. Such policies are especially important for [[software libraries]] and [[software framework|frameworks]], but may also be very useful for command-line applications (which may be called from other applications) and for other applications (which may be scripted and/or extended by third parties).

Versioning is also a required practice to enable many schemes of patching and upgrading software, especially to automatically decide what and where to upgrade to.

====In technical support====
Version numbers allow people providing support to ascertain ''exactly'' which code a user is running, so that they can rule out bugs that have already been fixed as a cause of an issue, and the like. This is especially important when a program has a substantial user community, especially when that community is large enough that the people providing technical support are ''not'' the people who wrote the code. The semantic meaning<ref name="semver" /> of version.revision.change style numbering is also important to information technology staff, who often use it to determine how much attention and research they need to pay to a new release before deploying it in their facility. As a rule of thumb, the bigger the changes, the larger the chances that something might break (although examining the Changelog, if any, may reveal only superficial or irrelevant changes). This is one reason for some of the distaste expressed in the "drop the major release" approach taken by Asterisk et alia: now, staff must (or at least should) do a full regression test for every update.

===Political and cultural significance of version numbers===
====Version 1.0 as a milestone====
The [[Free software|free-software]] and [[Open-source software|open source]] communities tend to release software [[release early, release often|early and often]]. Initial versions are numbers less than 1, with these 0.x version used to convey that the software is incomplete and not reliable enough for general release or usable in its current state. Backward-incompatible changes are common with 0.x versions.
Version 1.0 is used as a major [[Milestone (project management)|milestone]], indicating that the software has at least all major features plus functions the developers wanted to get into that version, and is considered reliable enough for general release.<ref name=toaru/><ref name=wine/> A good example of this is the Linux kernel, which was first released as version 0.01 in 1991,<ref name="Linux001">Torvalds, Linus: ''[https://www.kernel.org/pub/linux/kernel/Historic/old-versions/RELNOTES-0.01 Notes for linux release 0.01]'' kernel.org, 1991.</ref> and took until 1994 to reach version 1.0.0.<ref>{{cite news|last1=Calore|first1=Michael|title=Aug. 25, 1991: Kid From Helsinki Foments Linux Revolution|url=https://www.wired.com/2009/08/0825-torvalds-starts-linux/|date=August 25, 2009|access-date=February 8, 2018|publisher=WIRED}}</ref>

The developers of the [[arcade game]] emulator [[MAME]] do not ever intend to release a version 1.0 of the program because there will always be more [[arcade game]]s to emulate and thus the project can never be truly completed. Accordingly, version 0.99 was followed by version 0.100.<ref name="mythTV">{{cite book|last1=Still|first1=Michael|last2=Smith|first2=Stewart|title=Practical MythTV: Building a PVR and Media Center PC|date=December 15, 2007|publisher=Springer-Verlag New York, Inc.|location=New York|isbn=978-1-59059-779-8|page=9|url=https://books.google.com/books?id=E5uAAw8l2C8C&q=there+will+never+be+a+version+1.0+of+mame&pg=PA9|access-date=April 15, 2018|ref=mythTV}}</ref>

Since the internet has become widespread, most commercial software vendors no longer follow the maxim that a major version should be "complete" and instead rely on [[Patch (computing)|patches]] with bugfixes to sort out the known issues which a solution has been found for and could be fixed.{{citation needed|date=December 2020}}

====Superstition====
*The Office 2007 release of Microsoft Office had an internal version number of 12. The next version, Office 2010, has an internal version of 14, due to superstitions surrounding [[13 (number)|the number 13]].<ref name="Super Site for Windows">{{cite web|url=http://www.winsupersite.com/office/office2010_faq.asp|title=Office 2010 FAQ|author=Paul Thurrott|date=May 14, 2009|access-date=December 30, 2009|url-status=dead|archive-url=https://web.archive.org/web/20090419113856/http://www.winsupersite.com/office/office2010_faq.asp|archive-date=April 19, 2009}}</ref> Visual Studio 2013 is Version number 12.0 of the product, and the new version, Visual Studio 2015 has the Version number 14.0 for the same reasons.
*[[Roxio Toast]] went from version 12 to version 14, likely in an effort to skip the superstitions surrounding the number 13. 
*[[Corel]]'s [[WordPerfect Office]], version 13 is marketed as "X3" ([[Roman numerals|Roman number]] 10 and "3"). The procedure has continued into the next version, X4. The same has happened with Corel's Graphic Suite (i.e. [[CorelDRAW]], [[Corel Photo-Paint]]) as well as its [[video editing software]] "Video Studio".
*[[Sybase]] skipped major versions 13 ''and'' 14 in its Adaptive Server Enterprise relational database product, moving from 12.5 to 15.0.
* [[ABBYY FineReader|ABBYY]] Lingvo Dictionary uses numbering 12, x3 (14), x5 (15).
* SUSE Linux Enterprise skipped version 13 and 14 after version 12 and directly released SLES 15 in July 2018.
* In the mid-1990s, the rapidly growing [[CMMS]], Maximo, moved from Maximo Series 3 directly to Series 5, skipping Series 4 due to that number's perceived marketing difficulties in the Chinese market, where the number 4 is associated with "death" (see [[tetraphobia]]). This did not stop Maximo Series 5 version 4.0 from being released. (The "Series" versioning has since been dropped, effectively resetting version numbers after Series 5 version 1.0's release.)

====Geek culture====
* The [[SUSE Linux]] distribution started at version 4.2, to reference [[42 (number)|42]], "the answer to the ultimate question of life, the universe and everything" mentioned in [[Douglas Adams]]' ''[[The Hitchhiker's Guide to the Galaxy]]''.
* A Slackware Linux distribution was versioned 13.37, referencing [[leet]].
* [[Finnix]] skipped from version 93.0 to 100, partly to fulfill the assertion, "There Will Be No Finnix '95", a reference to [[Windows 95]].<ref name="finnix">{{cite web|url=http://lists.colobox.com/pipermail/finnix/2010-October/000121.html|title=I'm sorry|last=Finnie|first=Ryan|date=October 23, 2010|access-date=February 9, 2012}}</ref>
* The [[Tagged Image File Format]] specification has used [[42 (number)|42]] as [[Tagged Image File Format#Byte order|internal version number]] since its inception, its designers not expecting to alter it anymore during their (or its) lifetime since it would conflict with its development directives.

==Marketing considerations==

===Version number increase as marketing tool===
A relatively common practice is to make major jumps in version numbers for marketing reasons. Sometimes software vendors just bypass the 1.0 release or quickly release a release with a subsequent version number because 1.0 software is considered by many customers too immature to trust with production deployments.{{citation needed|date=May 2020}} For example, as in the case of [[dBase II]], a product is launched with a version number that implies that it is more mature than it is.

Other times version numbers are increased to match those of competitors. This can be seen in many examples of product version numbering by Microsoft, [[America Online]], Sun [[Solaris (operating system)|Solaris]], [[Java Virtual Machine]], SCO Unix, [[WordPerfect]]. [[Microsoft Access]] jumped from version 2.0 to version 7.0, to match the version number of [[Microsoft Word]].

Microsoft has also been the target of "catch-up" versioning, with the [[Netscape (web browser)|Netscape]] browsers skipping version 5 to 6, in line with Microsoft's [[Internet Explorer]], but also because the Mozilla application suite inherited version 5 in its [[user agent]] string during pre-1.0 development and Netscape 6.x was built upon Mozilla's code base.

Another example of keeping up with competitors is when [[Slackware]] Linux jumped from version 4 to version 7 in 1999.<ref>{{cite web|title=Slackware FAQ|url=http://www.slackware.com/faq/do_faq.php?faq=general#0}}</ref>

This approach, panned by many because it breaks the semantic significance of the sections of the version number, has been adopted by an increasing number of vendors including [[Mozilla]] (for [[Firefox]]) and [[Google]] (for [[Google Chrome]]).<ref>{{cite web|title=Firefox to Copy Google Chrome Development Schedule, New Versions Every Six Weeks|url=https://news.softpedia.com/news/Firefox-to-Copy-Google-Chrome-Development-Schedule-New-Versions-Every-Six-Weeks-190232.shtml}}</ref>

Some drawbacks to this approach include user apathy to new major versions (because for example major versions are in the hundreds and have happened several times a month for a few years), frequent nagging and/or frequent download, update, install, restart and clean-up (and/or leftovers) of software with all the possible problems that it might entail each time including user time-consumption, users not knowing about the potential significant changes from one version to another (because of the major update high-frequency and ensuing apathy), version testing and support problems for all stakeholders involved.

===Promoting minor as major===
Sun's [[Java (programming language)|Java]] has at times had a hybrid system, where the internal version number has always been 1.''x'' but has been marketed by reference only to the ''x'':
* JDK 1.0.3
* JDK 1.1.2 through 1.1.8
* J2SE 1.2.0 ("Java 2") through 1.4.2
* Java 1.5.0, 1.6.0, 1.7.0, 1.8.0 ("Java 5, 6, 7, 8")

Sun also dropped the first digit for Solaris, where Solaris 2.8 (or 2.9) is referred to as Solaris 8 (or 9) in marketing materials.

A similar jump took place with the [[Asterisk (PBX)|Asterisk]] open-source PBX construction kit in the early 2010s, whose project leads announced that the current version 1.8.x would soon be followed by version 10.<ref>{{cite web|author=Kevin P. Fleming|date=July 21, 2011|title=The Evolution of Asterisk (or: How We Arrived at Asterisk 10) &#124; Inside the Asterisk|work=Inside the Asterisk |url=http://blogs.digium.com/2011/07/21/the-evolution-of-asterisk-or-how-we-arrived-at-asterisk-10/|access-date=May 25, 2014|publisher=Digium, Inc}}</ref>

== Software examples ==

===Python===
The [[Python Software Foundation]] has published PEP 440 – Version Identification and Dependency Specification,<ref name="PEP440">{{cite web|url=https://www.python.org/dev/peps/pep-0440/|title=PEP 440 – Version Identification and Dependency Specification}}</ref> outlining their own flexible scheme, that defines an epoch segment, a release segment, pre-release and post-release segments and a development release segment.

===TeX===
[[TeX]] has an [[idiosyncratic]] version numbering system, an unusual feature invented by its developer [[Donald Knuth]]. Since version 3.1, updates have been indicated by adding an extra digit at the end, so that the version number [[asymptotically]] approaches the number [[pi|{{pi}}]], so 3.14 effectively means 3.2 in semantic versioning. (This is a form of [[Unary numeral system|unary numbering]]; the version number is the number of digits.) Since 2021, the version number has been 3.141592653 (3.9). This is a reflection of TeX being very stable, and only minor updates are anticipated. TeX developer Donald Knuth has stated that the ''"absolutely final change (to be made after [his] death)"'' will be to change the version number to {{pi}}, at which point all remaining bugs will become permanent features.<ref name="tb30knut">{{cite journal |last1=Knuth |first1=Donald E. |date=December 1990 |title=The Future of TeX and Metafont |url=https://tug.org/TUGboat/tb11-4/tb30knut.pdf |journal=TUGboat |volume=11 |issue=4 |pages=489 |access-date=7 September 2023}}</ref>

In a similar way, the version number of [[Metafont]] asymptotically approaches [[E (mathematical constant)|Euler's number, {{mvar|e}}]].<ref name="tb30knut" /> As of February 2021, the version number is 2.71828182 (2.8). Metafont was also devised by Donald Knuth as a companion to his TeX typesetting system.

===Apple===
During the era of the [[classic Mac OS]], minor version numbers rarely went beyond ".1". When they did, they usually jumped straight to ".5", suggesting the release was "more significant".{{efn|The complete sequence of classic Mac OS versions (not including patches) is: 1.0, 1.1, 2.0, 2.1, 3.0, 3.2 (skipping 3.1), 4.0, 4.1, 5.0, 5.1, 6.0, 7.0, 7.1, 7.5, 7.6, 8.0, 8.1, 8.5 (jumped), 8.6, 9.0, 9.1, 9.2.}} Thus, "8.5" was marketed as its own release, representing "Mac OS 8 and a half", and 8.6 effectively meant "8.5.1".

[[Mac OS X history|Mac OS X]] departed from this trend, in large part because "X" (the Roman numeral for 10) was in the name of the product. As a result, all versions of OS X began with the number 10. The first major release of OS X was given the version number 10.0, but the next major release was not 11.0. Instead, it was numbered 10.1, followed by 10.2, 10.3, and so on for each subsequent major release. Thus the 11th major version of OS X was labeled "10.10". Even though the "X" was dropped from the name as of [[MacOS Sierra|macOS 10.12]], this numbering scheme continued through macOS 10.15. Under the "X"-based versioning scheme, the third number (instead of the second) denoted a minor release, and additional updates below this level, as well as updates to a given major version of OS X coming after the release of a new major version, were titled Supplemental Updates.<ref>{{Cite news|url=https://www.macrumors.com/2018/02/19/apple-releases-macos-10-13-3-supplemental-update/|title=Apple Releases macOS 10.13.3 Supplemental Update With Telugu Crash Fix|access-date=March 26, 2018|language=en}}</ref>

The Roman numeral X was concurrently leveraged for marketing purposes across multiple product lines. Both [[QuickTime]] and [[Final Cut Pro]] jumped from version 7 directly to version 10, QuickTime X and Final Cut Pro X. Like Mac OS X itself, the products were not upgrades to previous versions, but brand-new programs. As with OS X, major releases for these programs incremented the second digit and minor releases were denoted using a third digit. The "X" was dropped from Final Cut's name with the release of macOS 11.0 (see below), and QuickTime's branding became moot when the framework was deprecated in favor of AVFoundation in 2011 (the program for playing QuickTime video was only named QuickTime Player from the start).

Apple's next macOS release, provisionally numbered 10.16,<ref name="Gallagher, AppleInsider 2020.06.22">{{cite news|last1=Gallagher|first1=William|date=June 22, 2020|title=Apple turns macOS up to 11 – or to 10.16|publisher=AppleInsider|url=https://appleinsider.com/articles/20/06/22/apple-turns-macos-up-to-11---or-to-1016}}</ref> was officially announced as [[macOS Big Sur|macOS 11]] at WWDC in June 2020, and released in November 2020.<ref>{{cite news|last1=Heater |first1=Brian|title=Apple unveils macOS 11.0 Big Sur|url=https://techcrunch.com/2020/06/22/apple-unveils-macos-10-16-big-sur/|website=TechCrunch|access-date=June 22, 2020|archive-url=https://web.archive.org/web/20200622183548/https://techcrunch.com/2020/06/22/apple-unveils-macos-10-16-big-sur/|archive-date=June 22, 2020|url-status=live}}</ref> The following macOS version, [[macOS Monterey]], was released in October 2021 and bumped its major version number to 12.<ref name="BGR, 2021.10.12">{{cite news|last1=De Looper|first1=Christian|date=Oct 12, 2021|title=Apple macOS Monterey: Everything we know so far|publisher=BGR|archive-url=https://web.archive.org/web/20211010180620/https://bgr.com/tech/apple-macos-monterey-news/|archive-date=October 10, 2021|url=https://bgr.com/tech/apple-macos-monterey-news/}}</ref>

In June 2025, Apple announced an unified versioning scheme, using the year next to the release date, similar to [[Model year|model years]] in vehicles. The versions to be released in the fall of 2025 will be [[iOS]] 26, [[macOS]] 26, [[iPadOS]] 26, [[tvOS]] 26, [[watchOS]] 26 and [[visionOS]] 26.<ref>{{Cite web |last=Dent |first=Steve |date=2025-06-09 |title=iOS 26 is official: Apple changes from version numbers to years for its OS names |url=https://www.engadget.com/apps/ios-26-is-official-apple-changes-from-version-numbers-to-years-for-its-os-names-172129166.html |access-date=2025-06-11 |website=Engadget |language=en-US}}</ref>

===Microsoft Windows===
The [[Microsoft Windows]] operating system was first labelled with standard version numbers for [[Windows 1.0]] through [[Windows 3.1x|Windows 3.11]]. After this Microsoft excluded the version number from the product name. For [[Windows 95]] (version 4.0), [[Windows 98]] (4.10) and [[Windows 2000]] (5.0), year of the release was included in the product title. After Windows 2000, Microsoft created the [[Windows Server]] family which continued the year-based style with a difference: For minor releases, Microsoft suffixed "R2" to the title, e.g., [[Windows Server 2008 R2]] (version 6.1). This style had remained consistent to this date. The client versions of Windows however did not adopt a consistent style. First, they received names with arbitrary alphanumeric suffixes as with [[Windows Me]] (4.90), [[Windows XP]] (5.1), and [[Windows Vista]] (6.0). Then, once again Microsoft adopted incremental numbers in the title, but this time, they were not versioning numbers; the version numbers of [[Windows 7]], [[Windows 8]] and [[Windows 8.1]] are respectively 6.1, 6.2 and 6.3. In [[Windows 10]], the version number leaped to 10.0<ref>{{cite web|title=Announcing Windows 10|work=Blogging Windows |date=September 30, 2014 |url=http://blogs.windows.com/bloggingwindows/2014/09/30/announcing-windows-10/}}</ref> and [[Windows 10 version history|subsequent updates to the OS]] only incremented build number (which is date-based) and update build revision (UBR) number.

The successor of Windows 10, [[Windows 11]], was released on October 5, 2021. Despite being named "11", the new Windows release didn't bump its major version number to 11. Instead, it stayed at the same version number of 10.0, used by Windows 10.<ref>{{cite web|title=Windows 11: A new era for the PC begins today|url=https://blogs.windows.com/windowsexperience/2021/10/04/windows-11-a-new-era-for-the-pc-begins-today/|date=Oct 4, 2021|website=Windows Blogs}}</ref>

==Non-software use==
Some [[file system|computer file systems]], such as the [[OpenVMS Filesystem]], also keep versions for files.

Versioning amongst documents is relatively similar to the routine used with computers and software engineering, where with each small change in the structure, contents, or conditions, the version number is incremented by 1, or a smaller or larger value, again depending on the personal preference of the author and the size or importance of changes made.

Software-style version numbers can be found in other media. 

In some cases, the use is a direct analogy (for example: [[Jackass 2.5]], a version of Jackass Number Two with additional special features; the second album by [[Garbage (band)|Garbage]], titled ''[[Version 2.0]]''; or ''[[Dungeons & Dragons]]'' 3.5, where the rules were revised from the third edition, but not so much as to be considered the fourth).

More often it's used to play on an association with high technology, and doesn't literally indicate a 'version' (e.g., ''[[Tron 2.0]]'', a video game followup to the film ''[[Tron]]'', or the television series ''[[The IT Crowd]]'', which refers to the second season as Version 2.0). A particularly notable usage is [[Web 2.0]], referring to websites from the early 2000s that emphasized [[user-generated content]], [[usability]] and [[interoperability]].

[[Technical drawing]] and [[Computer-aided design|CAD software]] files may also use some kind of primitive versioning number to keep track of changes.

==See also==
<!-- Please keep entries in alphabetical order & add a short description [[WP:SEEALSO]] -->
{{div col|colwidth=30em}}
*[[Continuous Data Protection]]
*[[Maintenance release]]
*[[Product life cycle management]]
*[[Release management]]
*[[Release notes]]
*[[Software engineering]]
{{div col end}}

==Notes==
{{notelist}}

==References==
{{Reflist|30em}}

==External links==
* [http://wiki.documentfoundation.org/ReleasePlan Document Foundation release plan for LibreOffice, showing release trains]

{{DEFAULTSORT:Software Versioning}}
[[Category:Version control]]
[[Category:Software version histories| ]]
[[Category:Software release]]