چاکر داش ساسان گل.
ما رو حرف ساسان جون حرف نمیزنیم مثل اینکه از نسخه سری 1 تا سری 2 کرنل ها توسعه دهنده ها از الگوی even-odd system version numbering system استفاده می کردند که همونطور که گفتم رقم دوم زوج معرف stable ها
Odd-numbered versions for development releases[edit]
Between the 1.0 and the 2.6.x series, the Linux kernel used odd minor version numbers to denote development releases and even minor version numbers to denote stable releases; see Linux kernel: Version numbering. 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.
هست البته درست میگی و rc مخفف release candidates هستش اما به هر حال جزئیات بیشتر رو می تونی در بخش version numbering تو لینک های wiki زیر بخونی:
http://en.wikipedia.org/wiki/Linux_kernel
http://en.wikipedia.org/wiki/Software_versioning#Odd-numbered_versions_for_development_releases