Controls the meaning of variable parameters declared using the string keyword.

The $P- State

In the $P- state, variable parameters declared using the string keyword are normal variable parameters. This allows compatibility with earlier versions of Turbo Pascal.

The $P+ State

In the $P+ state, variable parameters declared using the string keyword are open string parameters. Regardless of the setting of the $P directive, the OpenString identifier can always be used to declare open string paraemters.

The actual parameter of an open-string parameter can be a variable of any string type, and within the procedure or function, the size attribute (maximum length) of the formal parameter will be the same as that of the actual parameter.