### 3.4 `delta`

The `delta` command is used to add a new revision to the ones already stored in an SCCS file. Before being able to do this you need to run `get -e` to check the file out for editing.

A new revision is created by the `delta` program. These revisions are each identified by a unique SID. A SID looks like ‘`1.2.3.4`’, where the four numbers are the release, level, branch and sequence numbers.

New revisions on the main sequence (the trunk) have no branch or sequence numbers and so just have two number components (‘`1.2`’, for example).

When a new version is checked in, `delta` usually prompts for comments describing the changes just made. At this point you can enter any comments, separating lines with backslash-newline pairs. An unescaped newline terminates the comment, allowing operation to continue.

Sometimes, running `delta` results in the creation of a branch in the SCCS file; this is controlled by the `get` command at the time the file is checked out for editing (see Making Branches).

The `delta` program checks to see if you are authorised to check in a delta to this file. The list of authorised users can be maintained with the `admin` program (see admin). If the MR-validation flag (see Flags) is set, you must also supply a valid MR-number in order to be able to check in your change.