new version control systems have been developed and become popular that are designed for managing projects with a large number of files and that offer advanced functionality such as multi-user operation, access control, automatic building, network support, release management and distributed version control. Bitkeeper and TeamWare use the SCCS file format internally and can be considered successors to SCCS. On BSD systems, the SCCSID is replaced by a RCSID starting and ending with ; the corresponding tool is . This system is originally used by RCS and added automatically on checkout. The resulting source code revision control identifiers are documented in the NetBSD and FreeBSD style guides for their own code bases. NetBSD defines the custom keyword while FreeBSD defines and a macro renamed . The SRC version control system can also use the SCCS file format internally (or RCS's) and aims to provide a better user interface for SCCS while still managing only single-file projects. References Further reading Essay from Marc Rochkind on how SCCS was invented – AIX 7.3 manual page External links Schily's SCCS on Codeberg 1972 software Version control systems Free version control software Unix archivers and compression-related utilities Unix SUS2008 utilities Self-hosting software Software using the CDDL license