Type Conditional compilation
Syntax {$IFOPT switch}
Compiles the source code that
follows it if switch is currently in the specified state. switch consists of
the name of a switch option, followed by a + or a - symbol. For example,
{$IFOPT R+}
Writeln('Compiled with range-checking');
{$ENDIF}
compiles the Writeln statement if the $R option is currently active.