From Second Life Wiki
Second Life Viewer Versioning
The Second Life Viewer uses a four-place version convention that is common to the software industry. The four places in the w.x.y.z version string correspond to Major.Minor.Patch.Revision, and combine to indicate the nature of each release. Information describing circumstances under which each place is incremented has been provided in the following sections.
Note: Individual Second Life viewer versions may be formatted as either "w.x.y.z" or "w.x.y (z)". In 'Help > About Second Life', as well as in the release notes, we have standardized on the "w.x.y (z)" format, but either version format is considered correct.
W.x.y.z - Major Revision
The first place, or Major version, in each version number effectively represents the "generation" of Second Life. Changes in the Major revision are reserved for comprehensive changes in the way Second Life looks and/or functions. The best, and most recent example is Viewer 2, which constituted a significant change in the look, feel and operation of Second Life - thereby justifying the Major version increment from 1 to 2.
w.X.y.z - Minor Revision
The second place, or Minor version, is the most frequently incremented digit and is used to denote the addition of significant new features and enhancements, as well as releases in which many bugs are fixed. Releases including only minor enhancements and consisting predominantly of bug fixes, are often referred to as "maintenance releases", and also result in a change to the Minor revision number.
- Recent examples:
- 2.1.0 included the new Voice Morphing feature, as well as a significant number of crash and performance fixes, and much-requested Bottom Bar and Sidebar improvements
- 2.2.0 included further Bottom Bar improvements, the ability to un-dock the Sidebar, a "sit anywhere" option, a new "Translate chat" option, and many other improvements and bug fixes
- NOTE: To see what we've changed, from one release to the next, check out the release notes.
w.x.Y.z - Patch Revision
The third place, or Patch version, is reserved for releases needed to address extremely urgent bugs, or important security issues.
- NOTE: Prior to the release of Viewer 2, the Patch revision was incremented with each Beta or Release Candidate release. This practice has been discontinued to reserve the third place for legitimate Patch releases and to better distinguish between Major, Minor, and Patch releases.
w.x.y.Z - Build
The final place in the viewer version contains a Build number unique to each release. While official Second Life Release viewers are referred to using only the first three places (e.g. 2.1.1), each Second Life Beta Viewer release is distinguished from prior Betas by means of the Build number, which continues to increment with each release - e.g. 2.3.0 (213435). Build numbers are also used to distinguish one Development build from another, which is essential for developers who often need to identify the exact point at which the code was packaged.
Second Life Server Versioning
Prior to September 2010, the server was versioned much like the viewer. Since then we have moved to a new format that better supports the new server deploy plan. The versioning scheme is simple:
[2-digit year].[2-digit month].[2-digit day].[build number]
The date in the version is the date that the code was compiled. The build number is a unique, incrementing, number for each revision committed to our Source Configuration Management (SCM) system.