10.4 Freeware SCM tools

---

In addition to commercial SCM tools, there is a large number of free SCM tools. It is interesting to note that two SCM tools dominate in free software market: RCS and CVS. We give a short description of them and a list of other free SCM tools.

10.4.1 RCS

RCS is one of the oldest SCM tools. It is very simple and includes rudimentary SCM functions applied on files. The simplicity of RCS is outstanding and the reason for its widespread use. RCS is also used as a basic tool for many other SCM tools. Even more interesting is that the principles introduced in RCS (and partially previously SCCS) are still applied in other, more advanced SCM tools.

RCS is file oriented, and the SCM repository is simply a directory that contains versioned files. One versioned file contains one or several versions of that file. Baselines are achieved by setting a label on specific versions of the files. RCS includes difference and merge functions, which can be used by users and by check-in and check-out commands.

The main features of RCS are:

• Contains basic SCM functions (versioning, check in, check out, baselines, difference, and merge);

• SCM repository is the RCS underlying directory;

• Simple and easy to use;

• Practical for using on individual bases or in small groups;

• Can be used as a base for building more sophisticated tools.

10.4.2 CVS

CVS uses RCS as a basic SCM tool. However, in contrast with RCS, it manages directory structures. All files in a directory tree structure can be checked out or synchronized with working versions of files. CVS supports multiuser projects directly, as it uses a server-client architecture. A TCP/IP connection is used for the client-server communication. There are many CVS clients, for example, WinCVS (www.wincvs.org), jCVS (www.jcvs.org), command-line interfaces, and emacs commands. In the same way as RCS, CVS is a widespread tool because of its simplicity and flexibility.

The main features of CVS are:

• Contains basic SCM functions (versioning, check in, check out, baselines, difference, and merge);

• It is a client-server application in which the server manages the file repository;

• Enables parallel development with concurrent changes of files;

• Includes monitoring of files—operations (e.g., check in and check out) on the specified files are reported to the users;

• Simple and efficient;

• Practical for use in small distributed groups.

10.4.3 List of free SCM tools

The first SCM tools were developed by researchers, which has an implication: Many SCM tools are freely available on the market. There are, however, different categories of free software [11] (e.g., public domain free software [11], open source [12], and free software [13, 14]), which treat the software ownership, maintenance, and support in different ways.

Table 10.3 lists some of the free SCM tools available on the market.

Table 10.3: SCM Tool Free Software

SCM Tool	Web Site
Aegis	http://aegis.sourceforge.net
CERN—CMZ	www.info.cern.ch/cmz
CVS	www.cvshome.org
DVS	www.cs.colorado.edu/serl/cm/dvs.html
Inversion	inversion.tigris.org
JCVS	www.jcvs.org
Keep-It	www.keep-it.com
ODE	www.accurev.com/ode/index.html
PRCS	http://prcs.sourceforge.net
RCS	www.gnu.org/software/rcs/rcs.html
SCCS (free implementations)	www.cvshome.org/cyclic/cyclic-pages/sccs.html
TCCS	www.oreilly.com/homepages/tccs
TkCVS	www.twobarleycorns.net/tkcvs.html

---