I want to call my C or assembler function with a reference
 parameter in a string.  Why can't you just use the pointer returned
 by _parc() to modify a string parameter?

 Date: 23-Jul-91
 From: Ted Means <73067.3332@compuserve.com>

 Clipper 5.0 performed under-the-hood memory optimizations that
 sometimes resulted in two strings being assigned the same pointer.

 For example, if you did this:

        X := "Some string"
        Y := X

 In all likelihood Clipper would simply make a copy of the pointer
 rather than actually copying the string.  It sounds great in
 theory, because it saves memory.  But problems arose when a C or
 ASM routine attempted to modify X or Y by writing directly to the
 assigned memory.  Since the same pointer was assigned to two
 different memvars, they both got changed, even though that was
 not the intended effect.

 So with the release of Clipper 5.01, Nantucket graciously
 provided a method for accessing strings that is more convenient.
 If you call __StorCLen with a null pointer *before* calling
 __ParC, it warns Clipper that you plan to directly modify a
 __ParC pointer and Clipper will take whatever steps are necessary
 to make it safe to do so.

 This gives the best of both worlds, in that Clipper can still
 perform its memory optimizations, but C and ASM programmers get
 the benefit of being able to directly modify strings.  This is
 all documented in the Release Notes, but briefly, if you need to
 write directly to a string, use the following sequence:

      1)  Call __ParCLen to get the string's length.

      2)  Call __StorCLen with the length and a null pointer.

      3)  Call __ParC to get a pointer to the string.  This
          pointer will be safe to write to.

 Writing directly to a __ParC pointer without using this method is
 not sanctioned by Nantucket and is likely to cause problems.
 Note, though, that if you don't need to write to the string you
 can simply call __ParC by itself.