Editing Revision Control System (section)

== History ==
=== Development ===
RCS was first released in 1982<ref name=":1">{{cite journal
| last = Tichy | first = Walter
| title = Design, implementation, and evaluation of a Revision Control System
| journal = ICSE '82 Proceedings of the 6th International Conference on Software Engineering
| year = 1982 | pages = 58–67
| url = http://dl.acm.org/citation.cfm?id=807748
| access-date = 12 June 2012
}}</ref>
by [[Walter F. Tichy]] at [[Purdue University]]. It was an alternative tool to the then-popular [[Source Code Control System]] (SCCS) which was nearly the first version control software tool (developed in 1972 by early Unix developers).<ref name=":0">{{Cite web|url=http://www.catb.org/~esr/writings/version-control/version-control.html|title=Understanding Version-Control Systems (DRAFT)|first=Eric|last=Raymond|website=www.catb.org|access-date=2017-02-13}}</ref> RCS is currently maintained by the [[GNU Project]].<ref>{{cite web |title = RCS|website = GNU Project|publisher = Free Software Foundation|access-date = 27 June 2015|url = https://www.gnu.org/software/rcs/|date = 22 January 2015}}</ref>

An innovation in RCS is the adoption of ''reverse deltas''. Instead of storing every revision in a file like SCCS does with [[interleaved deltas]], RCS stores a set of edit instructions to go back to an earlier version of the file. Tichy claims that it is faster for most cases because the recent revisions are used more often.<ref name=":1"/>

===Legal and licensing===
Initially (through version 3, which was distributed in 4.3BSD), its license prohibited redistribution without written permission from Walter Tichy:<ref>{{cite web |url=http://www.retro11.de/ouxr/43bsd/usr/src/new/rcs/src/rcsdiff.c.html |title=4.3BSD - /usr/src/new/rcs/src/rcsdiff.c |publisher=Walter's Retro Computing Corner Documentation |access-date = 15 November 2014 |date=19 May 1986}}</ref>

{{quote|Copyright (C) 1982 by Walter F. Tichy [...] All rights reserved. No part of this software may be sold or distributed in any form or by any means without the prior written permission of the author.}}

A [[README|READ_ME]] file accompanied some versions of RCS which further restricted distribution, e.g., in [[Berkeley Software Distribution#4.3BSD|4.3BSD-Reno]].<ref>{{Cite FTP |url=ftp://ftp.mrynet.com/operatingsystems/CSRG/cd2/4.3reno/usr/src/contrib/rcs/src/READ_ME |server=FTP server |url-status=dead |title=CSRG/cd2/4.3reno/usr/src/contrib/rcs/src/READ_ME |date=27 February 1989 }}</ref><!-- Better source needed -->

Ca. 1989, the RCS license was altered to something similar to the contemporary [[BSD licenses#Previous license|BSD licenses]], as seen by comments in the source code.<ref>{{Cite FTP |url=ftp://ftp.mrynet.com/operatingsystems/CSRG/cd2/4.3reno/usr/src/contrib/rcs/src/rcs.c |server=FTP server |url-status=dead |title=CSRG/cd2/4.3reno/usr/src/contrib/rcs/src/rcs.c |date=15 August 1989}}</ref><!-- Better source needed -->

{{quote|Redistribution and use in source and binary forms are permitted provided that the above copyright notice and this paragraph are duplicated in all such forms and that any documentation, advertising materials, and other materials related to such distribution and use acknowledge that the software was developed by Walter Tichy.}}

RCS 4.3, released 26 July 1990, was distributed "under license by the [[Free Software Foundation]]", under the terms of the [[GNU General Public License|GPL]].<ref>RCS 4.3 README file.</ref>{{full citation needed|date=January 2022}}

OpenBSD provides a different implementation called ''OpenRCS'', which is BSD-licensed.<ref>{{Cite web |title=rcs(1) - OpenBSD manual pages |url=https://man.openbsd.org/rcs.1#HISTORY |access-date=2024-09-05 |website=man.openbsd.org}}</ref>