The control lines that bracket a piece of text indicate whether a piece of text was inserted or deleted, and in what version. When a particular version of a file is created from the SCCS file, the control lines identify the pieces of text that should be added or deleted for that version of the file. Control lines can be nested within one another, so the same portion of text can be bracketed by several sets of control lines. The body of a long SCCS file can be very complicated. The SCCS commands, however, provide a better way to understand the different versions of an SCCS file.
Number Indicates an insert control line.
The Number variable indicates the serial number that corresponds to the delta for the control line. Text inserted between this control line and an end control line with the same serial number was inserted as part of the delta that corresponded to the same serial number. The Number variable indicates the serial number that corresponds to the delta for the control line is indicated by the Number variable. Text deleted between this control line and an end control line with the same serial number was deleted as part of the delta that corresponded to the same serial number. The serial number that corresponds to the delta for the control line is indicated by the Number variable.