SCCS file format uses a storage technique called interleaved deltas (or the weave). This storage technique is now considered by many version control system developers as foundational to advanced merging and versioning techniques, such as the "Precise Codeville" ("pcdv") merge. Apart from correcting Year 2000 problems in 1999, no active development has taken place on the various UNIX vendor-specific SCCS versions. In 2006, Sun Microsystems (today part of Oracle) released their Solaris version of SCCS as open-source under the CDDL license as part of their efforts to open-source Solaris. Background The Source Code Control System (SCCS) is a system for controlling file and history changes. Software is typically upgraded to a new version by fixing bugs, optimizing algorithms and adding extra functions. Changing software causes problems that require version control to solve. Source code takes up too much space because it is repeated in every version. It is hard to acquire information about when and where changes occurred. Finding the exact version which the client has problems with is difficult. SCCS was built to solve these problems. SCCS from AT&T had five major versions for the IBM OS and five major versions for UNIX Two specific implementations using SCCS are: PDP 11 under Unix and IBM 370 under the OS. Composition SCCS consists of two parts: SCCS commands and SCCS files. All basic operations (e.g., create, delete, edit) can be realized by SCCS commands. SCCS files have a unique format prefix s., which is controlled by SCCS commands. SCCS files An SCCS file consists of three parts: Delta table Access and tracking flags Body of the text Delta table In SCCS, a delta is a single revision in an SCCS file. Deltas are stored in a delta table, so each SCCS file has its own record of changes. Control and tracking flags in SCCS files Every operation of each SCCS file is tracked by flags. Their functions are as below: Setting permissions for editing of every SCCS file. Control each release of every SCCS file. Permitting collaborative editing of every SCCS file. Mutual-referencing changes of every SCCS file. Body SCCS uses three types of control records for keeping track of insertions and deletions applied in different deltas. They are the insertion control record, the deletion control record, and the end control record. Whenever a user changes some part of the text, a control record is inserted surrounding the change. The