#IF_NOT_DEFINED
This Compiler Directive is used to define conditional compilation similar to #IF_DEFINED.
- The code following the #IF_NOT_DEFINED and before #ELSE (or
before #END_IF, if #ELSE is not present) is compiled only if
symbolis not defined (see #DEFINE). - If
symbolis defined and the #ELSE directive is present, the code following #ELSE and before #END_IF is compiled instead.