In software development, version control is a class of systems responsible for managing changes to computer programs or other collections of information such that revisions have a logical and consistent organization. The following tables include general and technical information on notable version control and software configuration management (SCM) software. For SCM software not suitable for source code, see Comparison of open-source configuration management software. General information Table explanation Repository model describes the relationship between various copies of the source code repository. In a client–server model, users access a master repository via a client; typically, their local machines hold only a working copy of a project tree. Changes in one working copy must be committed to the master repository before they are propagated to other users. In a distributed model, repositories act as peers, and users typically have a local repository with version history available, in addition to their working copies. Concurrency model describes how changes to the working copy are managed to prevent simultaneous edits from causing nonsensical data in the repository. In a lock model, changes are disallowed until the user requests and receives an exclusive lock on the file from the master repository. In a merge model, users may freely edit files, but are informed of possible conflicts upon checking their changes into the repository, whereupon the version control system may merge changes on both sides, or let the user decide when conflicts arise. Distributed version control systems usually use a merge concurrency model. Technical information Table explanation Software: The name of the application that is described. Programming language: The coding language in which the application is being developed Storage Method: Describes the form in which files are stored in the repository. A snapshot indicates that a committed file(s) is stored in its entirety—usually compressed. A changeset, in this context, indicates that a committed file(s) is stored in the form of a difference between either the previous version or the next. Scope of change: Describes whether changes are recorded for individual files or for entire directory trees. Revision IDs: are used internally to identify specific versions of files in the repository. Systems may use pseudorandom identifiers, content hashes of revisions, or filenames with sequential version numbers (namespace). With Integrated Difference, revisions are based on the Changesets themselves, which can describe changes to more than one file. Network protocols: lists the protocols used for synchronization of changes. Source code