CVS uses a client–server architecture: a server stores the current version(s) of a project and its history, and clients connect to the server in order to "check out" a complete copy of the project, work on this copy and then later "check in" their changes. CVS servers can allow "anonymous read access", wherein clients may check out and compare versions with either a blank or simple published password (e.g., "anoncvs"); only the check-in of changes requires a personal account and password in these scenarios. Several developers may work on the same project concurrently, each one editing files within their own "working copy" of the project, and sending (or "checking in") their modifications to the server. To avoid conflicts, the server only accepts changes made to the most recent version of a file. Developers are therefore expected to keep their working copy up-to-date by incorporating other people's changes on a regular basis. This task is mostly handled automatically by the CVS client, requiring manual intervention only when an edit conflict arises between a checked-in modification and the yet-unchecked local version of a file. Clients can also use the "update" command to bring their local copies up-to-date with the newest version on the server. Clients can also compare versions, request a complete history of changes, or check out a historical snapshot of the project (e.g.: based on a given date). If the check in operation succeeds, then the version numbers of all files involved automatically increment, and the server writes a user-supplied description line, the date and the author's name to its log files. CVS can also run external, user-specified log processing scripts following each commit. These scripts are installed by an entry in CVS's codice_1 file, which can trigger email notification or convert the log data into a Web-based format.