RCS vs SCCS

The majority of the replies (in a recent poll) were in favor of RCS, a
few for SCCS, and a few suggested alternatives such as CVS.

Functionally RCS and SCCS are practically equal, with RCS having a bit
more features since it continues to be updated.

Note that RCS learned from the mistakes of SCCS...
  
1.  Interface

  RCS has an easier interface for first time users.  There are less
  commands, it is more intuitive and consistent, and it provides more
  useful arguments.

  Branches have to be specifically created in SCCS.  In RCS, they are
  checked in as any other version.
  
2.  What's in a Revision File?

  RCS keeps history in files with a ",v" suffix.  SCCS keeps history
  in files with a "s." prefix.

  RCS looks for RCS files automatically in the current directory or in
  a RCS subdirectory, or you can specify an alternate RCS file.  The
  sccs front end to SCCS always uses the SCCS directory.  If you don't
  use the sccs front end, you must specify the full SCCS filename.

  RCS stores its revisions by holding a copy of the latest version and
  storing backward deltas.  SCCS uses a "merged delta" concept.

  All RCS activity takes place within a single RCS file.  SCCS
  maintains several files.  This can be messy and confusing.
  
  Editing either RCS or SCCS files is a bad idea because mistakes are
  so easy to make and so fatal to the history of the file.  Revision
  information is easy to edit in both types, whereas one would not
  want to edit the actual text of a version in RCS.  If you edit an
  SCCS file, you will have to recalculate the checksum using the admin
  program.
  
3.  Keywords

  RCS and SCCS use different keywords that are expanded in the text.
  For SCCS the keyword "%I%" is replaced with the revision number if
  the file is checked out for reading.  

  The RCS keywords are easier to remember, but keyword expansion is
  more easily customized in SCCS.

  In SCCS, keywords are expanded on a read-only get.  If a version
  with expanded keywords is copied into a file that will be deltaed,
  the keywords will be lost and the version information in the file
  will not be updated.  On the other hand, RCS retains the keywords
  when they are expanded so this is avoided.
  
4.  Symbolic Names

  RCS allows you treat a set of files as a family of files while SCCS
  is meant primarily for keeping the revision history of files.
  
  RCS accomplishes that with symbolic names: you can mark all the
  source files associated with an application version with `rcs -n',
  and then easily retrieve them later as a cohesive unit.  In SCCS you
  would have to do this by writing a script to write or read all file
  names and versions to or from a file.
  
5.  Performance

  Since RCS stores the latest version in full, it is much faster in
  retrieving the latest version.  After RCS version 5.6, it is also
  faster than SCCS in retrieving older versions.
  
6.  Version Identification

  SCCS is able to determine when a specific line of code was added to
  a system.
  
7.  Problems

  If you are missing the sccs or rcs tools, or the RCS or SCCS file is
  corrupt and the tools don't work on it, you can still retrieve the
  latest version in RCS.  Not true with SCCS.
  
8.  Conversion

  RCS provides a program to convert from SCCS to RCS.  One would have
  to write his own program to convert from RCS to SCCS.
  
9.  Support

  SCCS is supported by AT&T.  RCS is supported by the Free Software
  Foundation.  Therefore RCS runs on many more platforms, including
  PCs. 

  Most make programs recognize SCCS's "s."  prefix while GNU make is one
  of the few that handles RCS's ",v" suffix.

  Some tar programs have a -F option that ignores either RCS
  directories, or SCCS directories or both.
  
10. Command Comparison

  SCCS				RCS		Explanation
  sccs admin -i -nfile file	ci file		Checks in the file for the
						first time, creating
						the revision history file.
  sccs get file			co file		Check out a file for reading.
  sccs edit file		co -l file	Check out a file for
						modification.
  sccs delta file		ci file		Check in a file previously
						locked.

  what file			ident file	Print keyword information.
  sccs prs file			rlog file	Print a history of the file.

  sccs sccsdiff -rx -ry file	rcsdiff -rx -ry file	Compare two revisions.
  sccs diffs file		rcsdiff file	Compare current with last
						revision.
  sccs edit -ix-y file		rcsmerge -rx-y file 	Merge changes between
						two versions into file.

  ???				rcs -l file	Lock the latest revision.
  ???				rcs -u file	Unlock the latest revision.
						Possible to break another's 
						lock, but mail is sent to the
						other person explaining why.