In CVS, revision numbers are per file. This is because CVS stores its data in RCS files; each file has a corresponding RCS file in the repository, and the repository is roughly laid out according to the structure of your project tree.
In Subversion, the repository looks like a single filesystem. Each commit results in an entirely new filesystem tree; in essence, the repository is an array of trees. Each of these trees is labeled with a single revision number. When someone talks about “revision 54”, he's talking about a particular tree (and indirectly, the way the filesystem looked after the 54th commit).
Technically, it's not valid to talk about “revision 5
foo.c.” Instead, one would say
foo.c as it appears in revision
5.” Also, be careful when making assumptions about the
evolution of a file. In CVS, revisions 5 and 6 of
foo.c are always different. In Subversion,
it's most likely that
not change between revisions 5 and
Similarly, in CVS, a tag or branch is an annotation on the
file or on the version information for that individual file,
whereas in Subversion, a tag or branch is a copy of an entire
tree (by convention, into the
tags/ directories that appear at the top
level of the repository, beside
the repository as a whole, many versions of each file may be
visible: the latest version on each branch, every tagged
version, and of course the latest version on the trunk
itself. So, to refine the terms even further, one would often
foo.c as it appears in
branches/REL1 in revision
For more details on this topic, see the section called “Revisions”.