We are developing ROOT according to the principle of Release early and release often. However, since a very large portion of the user base requires a stable product we generally keep at least three versions of the system available for download. The development, production and old versions.
The development version evolves quickly, with monthly releases. Use this to get access to the latest and greatest, but as a side effect there might be some instabilities. However, by trying out the development version you can help us converge much more quickly to a stable version that can then become the new production version. If you are a new user we would advice you to try directly the development version.
The RC version is a Release Candidate of the next production release. We typically have two RC's (one month and two weeks) prior to a production release. The idea of the RC is to only contain bug fixes and to provide a stable test platform for users to ready their code for the new production release.
The production version is a version we feel comfortable with to exposing to a large audience for serious work. We may issue patch releases of production versions with bug fixes. The change rate of this version is much lower than for the development version. In the order of 6 months. The old version is the previous production version that people might need for some time before switching to the new version.
For each of the active three versions we provide the full source and pre-compiled binaries for most of the supported platforms. After downloading and unpacking please read the included README/README file on how to set the necessary environment variables.
The following versions are available for download: