The simplest way to refer to a statement is by using its source line number, that is, the physical line number in the source file on which the statement starts.
If an unqualified source file line number is specified (no environment reference), the first executable statement on the specified line, if present, or the first executable line following that line is used by the debugger.
If a source file line number is qualified by an environment reference, for example, "SIFT\18", the translation of the line number to an executable statement is executed in the same manner as described for unqualified line numbers, except that the set of executable statements that the line number can be translated to is restricted to those contained in the specified environment block.