Starting with the main development branch after X11R6.7, the X.Org versions are numbered according to the scheme outlined here.
The version numbering format is
the major version number,
m is the minor version number,
P is the patch level, and
s is the snapshot number.
Full releases have
P set to zero, and it is incremented for
each subsequent bug fix release on the post-release stable branch. The
s is present only for between-release snapshots
of the development and stable branches.
Immediately after forming a release stable branch, the patch level
number for the main development branch is bumped to 99, and the snapshot
number is reset. The snapshot number is incremented for each tagged
development snapshot. The CVS tag for snapshots is
XORG-M_m_P_s". When the development branch enters feature
freeze, the snapshot number is bumped to 900. A stable branch may be
created for the next full release at any time after the feature freeze.
When it is, the branch is called "
snapshot number is incremented from there until the release is
finalised. Each of these snapshots is a "release candidate". When the
release is finalised, the minor version is incremented, the patch level
is set to zero, and the snapshot number removed.
Here's an example which shows the version number sequence for the development leading up to version 6.8:
The first snapshot of the pre-6.8 development branch.
The twenty-third snapshot of the pre-6.8 development branch.
The start of the 6.8 feature freeze.
The third 6.8 release candidate.
The 6.8 release.
The first pre-6.9 development snapshot, which is the first main branch snapshot after creating the 6.8 stable branch.
After a full release, the stable branch for the release will be
maintained with bug fixes and important updates until the next full
release. Any snapshots on this branch are considered "release
candidates", which is indicated by setting
s to a number above
900. The snapshot number is incremented for each release candidate
until the update release is finalised. The patch level value
P) is incremented for each update release.
Here's an example which shows a version number sequence for a 6.8.x stable branch:
The 6.8 release.
The first pre 6.8.1 snapshot.
The third pre 6.8.1 snapshot, also known as the third 6.8.1 release candidate.
The 6.8.1 release.
The first pre 6.8.2 snapshot.
The 6.8.2 release.