Files under SCCS are composed of one or more sets of changes applied to the original version of the file. A set of changes depends on all the previous sets. For SCCS to keep track of the changes, any alterations to a file are stored separately in another file called a delta.
Each delta is assigned a name known as an SCCS IDentification string (SID). An SID contains four components. The first two are the release and level numbers, separated by a period. The next two are the branch and sequence numbers, also separated by a period. This is explained in ``Delta numbering''.
The SID for any original file turned over to SCCS is composed of
release number 1 and level number 1, stated as 1.1.
The SID for the first set of changes made to that file
(that is, its first delta) is release 1 and version 2, or 1.2.
The next delta would be 1.3, the next 1.4, and so on.
There will be more on delta numbering later.
At this point, it is enough to know that, by default, SCCS
assigns SIDs automatically.