Path: utzoo!attcan!uunet!aplcen!uakari.primate.wisc.edu!zaphod.mps.ohio-state.edu!usc!apple!jkc
From: jkc@Apple.COM (John Kevin Calhoun)
Newsgroups: comp.sys.mac.hypercard
Subject: Re: Compatibility of stacks and Hypercard 2.0
Message-ID: <43360@apple.Apple.COM>
Date: 26 Jul 90 16:49:46 GMT
References: <1133@cs.nps.navy.mil>
Organization: Apple Computer Inc, Cupertino, CA
Lines: 38


>  Will stacks written using Hypercard version 1.2.x run under version 2.0?

Yes.  Until you convert them to the new 2.0 file format, they'll operate
as read-only stacks in 2.0, just as they operate in 1.2.x when they live
on locked disks, for example.

The conversion is easy.  When you open a 1.x with 2.0, the "Compact Stack"
item in the File menu changes to "Convert Stack".  Choose "Convert Stack"
and HyperCard does the rest.  It's just as painless as compaction (and
in fact is really the same thing internally).  Once a stack is converted,
however, you can't open it anymore with 1.x.  There's nothing wrong with
that, unless you discover an incompatibility between your stack and
HyperCard 2.0.  It's wise, then, to convert a copy of the stack and check
it out under 2.0 before chucking your old copy of HyperCard.

So, the following question will undoubtedly come up:  what incompatibilities
are likely to arise?  We've seen two, both of which occur infrequently--
  1)  An XCMD that worked fine under 1.x has trouble under 2.0.  The
      cause is usually that the XCMD made some assumption about HyperCard's
      world--it's use of memory, for example--that is no longer valid.
      The vast majority of XCMDs continue to work under 2.0.
  2)  A script has an error in code that never executes.  The old interpreter
      would never see the offending line, and so the script would work.  The
      compiler knows all, sees all, and will refuse to run the script.
      Although you may be thinking to yourself, gosh, I wonder if this will
      happen to me, I doubt that you'll run into this.  It's more of a
      theoretical worry than a practical problem.  It hasn't come up very
      often in our testing.

Anyway, although incompatibilities will be rare, they will arise.  So, my
advice is to convert a copy and check it out.  Then, when you come to know
and love 2.0 the way we do, you can abandon the past and take advantage of
the many, many improvements.

Kevin Calhoun
Software engineer
Apple Computer