View source for Source Code Control System

{{Short description|Version control system for source code}}
{{More citations needed|date=March 2010}}
{{Infobox software
| name                   = Source Code Control System (SCCS)
| logo                   =
| screenshot             =
| caption                =
| author                 = [[Marc Rochkind|Marc J. Rochkind]]
| developer              = [[Bell Labs]]<!-- no official active development -->
| released               = {{Start date and age|1973}}
| latest release version = 
| latest release date    =
| latest preview version =
| latest preview date    =
| programming language   = First version: [[SNOBOL|SNOBOL4]]<br />Rewrite: [[C (programming language)|C]]
| operating system       = [[OS/360]], [[Unix]], [[Unix-like]]
| platform               = [[IBM System/370]], [[PDP-11]], [[IA-32]]
| genre                  = [[Version control]]
| license                = proprietary licenses, [[Common Development and Distribution License]]
| repo                   = N/A
| website                = {{URL|http://pubs.opengroup.org/onlinepubs/9699919799/utilities/sccs.html| The Open Group Base Specifications Issue 7, IEEE Std 1003.1-2008, 2016 Edition}}
}}
'''Source Code Control System''' ('''SCCS''') is a [[version control|version control system]] designed to track changes in [[source code]] and other text files during the development of a piece of software. This allows the user to retrieve any of the previous versions of the original source code and the changes which are stored. It was originally developed at [[Bell Labs]] beginning in late 1972 by [[Marc Rochkind]] for an [[IBM System/370]] computer running [[OS/360]].<ref name = "r1">{{Citation |last=Rochkind |first=Marc J. |url=http://basepath.com/aup/talks/SCCS-Slideshow.pdf |title=The Source Code Control System |periodical=IEEE Transactions on Software Engineering |volume=SE-1 |issue=4 |date=December 1975 |pages=364–370 |doi=10.1109/tse.1975.6312866 |bibcode=1975ITSEn...1..364R |s2cid=10006076 |access-date=2005-07-08 |archive-date=2011-05-25 |archive-url=https://web.archive.org/web/20110525193926/http://basepath.com/aup/talks/SCCS-Slideshow.pdf |url-status=dead }}</ref>

A characteristic feature of SCCS is the ''sccsid'' string that is embedded into source code, and automatically updated by SCCS for each revision.<ref name="Oracle">{{Cite web|url=http://docs.oracle.com/cd/E19504-01/802-5880/6i9k05dhp/index.html|title=Chapter 5 SCCS Source Code Control System|last=Oracle|website=Programming Utilities Guide}}</ref> This example illustrates its use in the [[C (programming language)|C programming language]]:
<syntaxhighlight lang="c">
 static char sccsid[] = "@(#)ls.c        8.1 (Berkeley) 6/11/93";
</syntaxhighlight>
This [[String (computer science)|string]] contains the file name, date, and can also contain a comment. After compilation, the string can be found in binary and object files by looking for the pattern <code>@(#)</code> and can be used to determine which [[source code]] files were used during compilation. The <code>what</code> command is available to automate this search for version strings.<ref>{{cite web |url=https://pubs.opengroup.org/onlinepubs/9699919799/utilities/what.html |title=what |author=<!--Not stated--> |date=n.d. |publisher=IEEE and The Open Group |access-date=November 28, 2022}}</ref>

==History==
In 1972, [[Marc Rochkind]] developed SCCS in [[SNOBOL|SNOBOL4]] at [[Bell Labs]] for an [[IBM System/370]] computer running [[OS/360]] [[Multiprogramming with a Variable number of Tasks|MVT]].<ref name = "r1"/> He rewrote SCCS in the C programming language for use under [[UNIX]], then running on a [[PDP-11]], in 1973.

The first publicly released version was SCCS version 4 from February 18, 1977.<ref>https://sccs.sourceforge.net/PWB.html AT&T Announcement for SCCSv4</ref> It was available with the [[PWB/UNIX|Programmer's Workbench]] (PWB) edition of the [[operating system]]. Release 4 of SCCS was the first version that used a text-based history file format; earlier versions used binary history file formats. Release 4 was no longer written or maintained by Marc Rochkind. Subsequently, SCCS was included in [[AT&T]]'s commercial [[UNIX System III|System III]] and [[UNIX System V|System V]] distributions.  It was not licensed with [[UNIX/32V|32V]], the ancestor to [[Berkeley Software Distribution|BSD]].<ref>SCCS [http://minnie.tuhs.org/cgi-bin/utree.pl?file=4BSD/usr/man/cat1/what.1 what(1)] manpage from 4BSD, 1980, on the website of [http://www.tuhs.org/ The Unix Heritage Society] {{webarchive|url=https://web.archive.org/web/20050831153956/http://www.tuhs.org/ |date=2005-08-31 }}.</ref> The SCCS command set is now part of the [[Single UNIX Specification]].

SCCS was the dominant version control system for Unix until later [[version control]] systems, notably the [[Revision Control System|RCS]] and later [[Concurrent Versions System|CVS]], gained more widespread adoption.  Today, these early version control systems are generally considered obsolete, particularly in the [[open-source software|open-source]] community, which has largely embraced [[distributed version control]] systems.  However, the SCCS file format is still used internally by a few newer version control programs, including ''[[BitKeeper]]'' and ''[[TeamWare]]''. The latter is a frontend to SCCS. Sablime<ref name="sablime">{{cite web|title=Sablime Webpage|website=Alcatel-Lucent|url=http://sablime.alcatel-lucent.com|archive-url=https://web.archive.org/web/20160722092853/http://sablime.alcatel-lucent.com/|archive-date=2016-07-22|url-status=dead }}</ref> has been developed from a modified version of SCCS<ref>Estublier, Jacky, David Leblang, [[André van der Hoek]], Reidar Conradi, Geoffrey Clemm, Walter Tichy, and Darcy Wiborg-Weber. “Impact of software engineering research on the practice of software configuration management.” ACM Transactions on Software Engineering and Methodology (TOSEM) 14 (October 2005): 383–430.</ref> but uses a history file format that is incompatible with SCCS.  The SCCS file format uses a storage technique called [[interleaved deltas]] (or the weave<ref>{{Citation |last=Hudson |first=Greg |url=http://web.mit.edu/ghudson/thoughts/file-versioning |title=Notes on keeping version histories of files |publisher=Unpublished personal notes |date=2002-10-03}}</ref>).  This storage technique is now considered by many [[version control]] system developers as foundational to advanced [[Merge (version control)|merging]] and versioning techniques,<ref>Estublier, Jacky, David Leblang, [[André van der Hoek]], Reidar Conradi, Geoffrey Clemm, Walter Tichy, and Darcy Wiborg-Weber. “Impact of software engineering research on the practice of software configuration management.” ACM Transactions on Software Engineering and Methodology (TOSEM) 14 (October 2005): p.398.</ref> such as the "Precise Codeville" ("pcdv") merge.

Apart from correcting [[Year 2000 problem]]s in 1999, no active development has taken place on the various UNIX vendor-specific SCCS versions.<ref>
[https://www.gnu.org/software/cssc/ What is SCCS], GNU operating System</ref>
In 2006, [[Sun Microsystems]] (today part of [[Oracle Corporation|Oracle]]) released their [[Solaris (operating system)|Solaris]] version of SCCS as [[open-source software|open-source]] under the [[Common Development and Distribution License|CDDL license]] as part of their efforts to open-source Solaris.<ref>{{cite web|url=http://mail.opensolaris.org/pipermail/opensolaris-announce/2006-December/000364.html |title=SCCS/make source available |date=2006-12-19 |access-date=2011-11-14 |author=Stephen Lau, [[Sun Microsystems]] |url-status=dead |archive-url=https://web.archive.org/web/20120425142501/http://mail.opensolaris.org/pipermail/opensolaris-announce/2006-December/000364.html |archive-date=April 25, 2012 }}</ref>

==Background==

The Source Code Control System (SCCS) is a system for controlling file and history changes. Software is typically [[Source upgrade|upgraded]] to a new version by fixing bugs, optimizing algorithms and adding extra functions.<ref>Home Organization Selection {{ProQuest|215925387}}</ref> Changing software causes problems that require version control to solve.<ref name = "r1"/>
* 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–server model|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<ref>The evolution of a Source Code Control System. Alan L.Glasser, published in sigmetrics, Nov 1978 when SCCS on UNIX was a version 4</ref>
Two specific implementations using SCCS are: PDP 11 under Unix and IBM 370 under the OS.<ref name = "r1"/>

== Composition ==
SCCS consists of two parts: SCCS commands and SCCS files.<ref name="SCCS">{{Cite web|url=http://www-h.eng.cam.ac.uk/help/tpl/languages/sccs.html|title=SCCS|website=www-h.eng.cam.ac.uk|access-date=2016-09-12}}</ref> All basic operations (e.g., create, delete, edit) can be realized by SCCS commands.<ref name="SCCS"/> SCCS files have a unique format prefix <code>s.</code>, which is controlled by SCCS commands.<ref name="Oracle"/>

== SCCS files ==
An SCCS file consists of three parts:<ref name=":0">{{Cite web|url=https://www.ibm.com/support/knowledgecenter/ssw_aix_53/com.ibm.aix.genprogc/doc/genprogc/sccs.htm|title=General Programming Concepts: Writing and Debugging Programs|last=IBM|website=IBM Knowledge Center|date=7 June 2018 }}</ref>   
* 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.<ref name=":0" />

=== Control and tracking flags in SCCS files ===
Every operation of each SCCS file is tracked by flags. Their functions are as below:<ref name=":0" />
* 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 control records are stored in the body along with the original text records.<ref name = "r1"/>

==SCCS basic commands==
SCCS provides a set of commands in the form of macro invocations that perform or initiate source code management functions with a simple syntax, such as create, get, edit, prt.<ref>[https://sccs.sourceforge.net/man/sccs.me.html  An Introduction to the Source Code Control System ] Eric Allman, Project Ingres, University of California at Berkeley</ref><ref>[http://docs.oracle.com/cd/E19504-01/802-5880/6i9k05dhp/index.html  Source Code Control System] Programming Utilities Guide</ref> It also provides access to the revision history of files under management. These commands are implemented as argument verbs to the driver program ''sccs''.

=== Create ===
The sccs command ''create'' uses the text of a source file to create a new history file. For example:
<syntaxhighlight lang="console">
$ sccs create program.c
program.c:
1.1
87 lines
</syntaxhighlight>
The outputs are name, version and lines.

The command is a macro that expands to ''admin'' to create the new history file followed by ''get'' to retrieve the file.

=== Edit ===
<syntaxhighlight lang="console">
$ sccs edit program.c
1.1
new delta 1.2
87 lines
</syntaxhighlight>
Edit a specific file.

The command is a macro that expands to ''get -e''.

=== Delget ===
<syntaxhighlight lang="console">
$ sccs delget program.c
comments? main function enhanced
1.2
10 inserted
0 deleted
87 unchanged
1.2
97 lines
</syntaxhighlight>
Check in new version and get the new version from sccs.

The command is a macro that expands to ''delta'' to check in the new version file followed by ''get'' to retrieve the file.

=== Get ===
<syntaxhighlight lang="console">
$ sccs get program.c
1.1
87 lines
</syntaxhighlight>
The outputs are version and lines you want to get from specific file.

=== Prt ===
<syntaxhighlight lang="console">
$ sccs prt program.c
</syntaxhighlight>
This command produces a report of source code changes.

==Implementations==

=== UNIX SCCS versions ===
Most [[UNIX]] versions include a version of SCCS, which, however, is often no longer actively developed.<ref>Koike, Hideki, and Hui-Chu Chu. "VRCS: Integrating version control and module management

using interactive three-dimensional graphics." Visual Languages, 1997. Proceedings. 1997

IEEE Symposium on. IEEE, 1997.</ref>{{better source needed|date=September 2016}}

=== Jörg Schilling's fork ===
The late {{ill|Jörg Schilling|de}} (who requested the release of SCCS in the early days of the [[OpenSolaris]] project)<ref>{{cite web|title=os.solaris.opensolaris.rfe - Re: star - msg#00001 - Recent Discussion OSDir.com|url=http://osdir.com/ml/os.solaris.opensolaris.rfe/2006-05/msg00001.html|website=osdir.com|access-date=10 September 2016}}</ref> maintained a [[Fork (software development)|fork]] of SCCS<ref name="schily-sccs">[https://sccs.sourceforge.net/ Jörg Schilling's SCCS development website]</ref><ref>{{cite web |url=https://codeberg.org/schilytools/schilytools/src/branch/master/AN-2022-10-16 |title=A collection of tools written or formerly managed by Jörg Schilling. |author=<!--Not stated--> |date=22 October 2022 |website=[[Codeberg]] |access-date=28 November 2022 |quote=development has been picked up by a group of volunteers who would like to keep the project alive and well}}</ref> that is based on the OpenSolaris source code. It has received major feature enhancements but remains compatible with the original SCCS versions unless using the "new project" mode.<ref>[https://sccs.sourceforge.net/#compatibility Schily SCCS web site]: "Will the upcoming SCCSv6 stay compatible with POSIX and with historic SCCS implementations?"</ref>

=== Heirloom Project ===
The [[Heirloom Project]] includes a version of SCCS derived from the [[OpenSolaris]] source code<ref>{{cite web |url=https://heirloom.sourceforge.net/devtools.html |title=The Heirloom Development Tools |author=Gunnar Ritter |date=20 June 2010 |access-date=4 November 2011}}</ref> and maintained between December 2006 and April 2007.<ref>https://heirloom.cvs.sourceforge.net/viewvc/heirloom/heirloom-devtools/sccs/ see CVS history</ref>

=== GNU conversion utility ===
[[GNU]] offers the SCCS compatible program [https://www.gnu.org/software/cssc/ GNU CSSC] ("Compatibly Stupid Source Control"), which is occasionally used to convert SCCS archives to newer systems like [[Concurrent Versions System|CVS]] or [[Subversion (software)|Subversion]];<ref>[http://sccs2svn.berlios.de/ SCCS2SVN conversion utility] {{webarchive|url=https://web.archive.org/web/20091222091016/http://sccs2svn.berlios.de/ |date=2009-12-22 }}, which works with both SCCS and CSSC</ref> it is not a complete<ref>[https://www.gnu.org/s/cssc/manual/Incomplete.html#Incomplete GNU CSSC list of limitations in its documentation]</ref> SCCS implementation and not recommended for use in new projects, but mostly meant for converting to a modern version control system.

=== Other version control systems ===
Since the 1990s, [[List of version control software|many 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.<ref>{{cite web|title=revtool|work=BitKeeper Documentation|url=https://www.bitkeeper.org/man/revtool.html}}</ref><ref>{{cite web|title=Introduction to Sun WorkShop TeamWare|url=https://docs.oracle.com/cd/E19957-01/806-3573/intro.html|website=docs.oracle.com|access-date=10 September 2016}}</ref>

On BSD systems, the SCCSID is replaced by a RCSID starting and ending with {{mono|$}}; the corresponding tool is {{mono|ident}}.<ref>{{Man|1|ident|NetBSD}}</ref> This system is originally used by [[Revision Control System|RCS]] and added automatically on checkout. The resulting source code revision control identifiers are documented in the [[NetBSD]]<ref>{{cite web|title=src/share/misc/style revision 1.64|url=http://cvsweb.netbsd.org/bsdweb.cgi/src/share/misc/style?rev=1.64&content-type=text/x-cvsweb-markup|publisher=NetBSD CVS repository}}</ref> and [[FreeBSD]]<ref>{{Man|9|style|FreeBSD}}</ref> style guides for their own code bases. NetBSD defines the custom keyword {{mono|$NetBSD: ...$}} while FreeBSD defines {{mono|$FreeBSD: ...$}} and a macro renamed {{mono|__FBSDID}}.

The SRC version control system can also use the SCCS file format internally (or [[Revision Control System|RCS]]'s) and aims to provide a better user interface for SCCS while still managing only single-file projects.<ref>{{cite web |url=http://www.catb.org/esr/src/ |title=Resource page for src 1.29 |author=<!--Not stated--> |date=January 21, 2022 |access-date=November 28, 2022 |quote=}}</ref>

==References==
{{Reflist|30em}}

==Further reading==
* [https://sccs.sourceforge.net/sccs_invention.html Essay from Marc Rochkind on how SCCS was invented]
* {{man|1|sccs|SUS}}
* {{man|1|sccs|FreeBSD}}
* {{man|1|sccs|Solaris}}
* {{man/format|1|sccs|3=https://www.ibm.com/docs/en/aix/7.3?topic=s-sccs-command}} – AIX 7.3 manual page
* {{man|1|sccs|HP-UX}}
* {{man|1|sccs|IRIX}}

==External links==
* [https://codeberg.org/schilytools/schilytools Schily's SCCS on Codeberg]

{{Version control software}}
{{Authority control}}

[[Category:1972 software]]
[[Category:Version control systems]]
[[Category:Free version control software]]
[[Category:Unix archivers and compression-related utilities]]
[[Category:Unix SUS2008 utilities]]
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[[Category:Software using Common Development and Distribution License]]