A software release refers to the phases of development for a piece of computer software. The "release" life cycle ranges from its initial development, to its eventual release, and includes updated versions of the released version to help improve software or fix bugs still present in the software.
The various stages of development include:
Pre-alpha - Pre-alpha refers to all activities performed during the software project prior to testing. These activities can include requirements analysis, software design, software development and unit testing. In typical open source development, there are several types of pre-alpha versions. "Milestone" versions include specific sets of functions and are released as soon as the functionality is complete.
Alpha - The alpha phase of the release life cycle is the first phase to begin software testing (alpha is the first letter of the Greek alphabet, used as the number 1). In this phase, developers generally test the software using white box techniques. Additional validation is then performed using black box or gray box techniques, by another testing team. Moving to black box testing inside the organization is known as alpha release.
Alpha software can be unstable and could cause crashes or data loss. The exception to this is when the alpha is available publicly (such as a pre-order bonus), in which developers normally push for stability so that their testers can test properly. External availability of alpha software is uncommon in proprietary software. However, open source software, in particular, often have publicly available alpha versions, often distributed as the raw source code of the software. The alpha phase usually ends with a feature freeze, indicating that no more features will be added to the software. At this time, the software is said to be a "feature complete."
Beta - Beta (named after the second letter of the Greek alphabet) is the software development phase following alpha. It generally begins when the software is feature complete. Software in the beta phase will generally have many more bugs in it than completed software, as well as speed/performance issues. The focus of beta testing is reducing impacts to users, often incorporating usability testing. The process of delivering a beta version to the users is called beta release and this is typically the first time that the software is available outside of the organization that developed it.
The users of a beta version are called beta testers. They are usually customers or prospective customers of the organization that develops the software, willing to test the software without charge, often receiving the final software free of charge or for a reduced price. Beta version software is often useful for demonstrations and previews within an organization and to prospective customers. Some developers refer to this stage as a preview, prototype, technical preview (TP), or early access. Note: Some software is kept in perpetual beta—where new features and functionality is continually added to the software without establishing a firm "final" release.
Open and closed beta - Developers release either a closed beta or an open beta; closed beta versions are released to a restricted group of individuals for a user test by invitation, while open beta testers are from a larger group, or anyone interested. The testers report any bugs that they find, and sometimes suggest additional features they think should be available in the final version. Open betas serve the dual purpose of demonstrating a product to potential consumers, and testing among an extremely wide user base likely to bring to light obscure errors that a much smaller testing team may not find.
Release candidate - A release candidate (RC) is a beta version with potential to be a final product, which is ready to release unless significant bugs emerge. In this stage of product stabilization, all product features have been designed, coded and tested through one or more beta cycles with no known showstopper-class bug.
A release is called "code complete" when the development team agrees that no entirely new source code will be added to this release. There may still be source code changes to fix defects, and changes to documentation and data files, and to the code for test cases or utilities.