Programs that are in a very early stage of development 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. Alpha- and beta-version software is often given numerical versions less than 1 (such as 0.9), to suggest their approach toward a public "1.0" release. 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.
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 version is actually released, the "rc" tag disappears.
Usaly but not always. There are many factors: bugs, add-ons, choice of the DEV team(s).
I have seen many times that software is updated:
2 stages of Alpha
4 stages of Beta
2 stages of RC
Last edited by Zachariah; March 30th, 2006 at 08:14 AM.