If this switch is on, all function or procedure parameters of type string are considered to be open string parameters; this parameter only has effect for short strings, not for ansistrings.
When using openstrings, the declared type of the string can be different from the type of string that is actually passed, even for strings that are passed by reference. The declared size of the string passed can be examined with the High(P) call.
By default, the use of openstrings is off.