Wirt Atmar writes:

>...some of our most intensely
>used software only runs on older versions (we've been Mac users since 1984
>and
>we're still buying Mac Plusses because of this). This lack of forward
>incompatibility is one of the primary reasons that we've switched over to
>PCs,
>regardless of how high a regard I hold Macs.

This is an issue that, oddly enough, is directly relevant to HP 3000
software development. I have Mac programs that I wrote under System 4
(around 1986) that work fine on System 8.1, despite the fact that so many
things have changed -- not least of which is the processor architecture.
I don't know what Wirt did to write incompatible programs, but I know
what he didn't do: follow Apple's guidelines.

Unlike Microsoft and HP, Apple publishes nearly all of their technical
information: operating system internal calls, operating system internal
table layouts, disc layouts, control flow, register-level hardware
descriptions, the works. Much of the more esoteric information is
prefaced with a warning that the information may change in future
hardware and future versions of the operating system.

Thus, given a choice between publishing information that may change and
keeping all internal information secret, Apple opted to do what most of
us software developers would have wished: they published nearly
everything, with notes saying what was part of the official API and what
wasn't. Programmers who've gone ahead and used the "internals"
information to write application programs have no cause whatever to
complain when something breaks in a new OS, just as HP 3000 programmers
who write privileged code have no cause to complain when something breaks
in a new OS.

Wirt's reaction is a big part of the reason that companies like HP refuse
to publish OS internal information. No matter how big they make the
notice that the information may change, someone always starts to rely on
it, then complains when it does. For Wirt to have to continue buying Mac
Pluses to run his Mac software, he must be doing things like direct
access to hardware. I wouldn't expect a program that does this to be
compatible with today's Macintoshes any more than I'd expect a Series III
disc driver to work on today's HP 3000s.

-- Bruce


--------------------------------------------------------------------------
Bruce Toback    Tel: (602) 996-8601| My candle burns at both ends;
OPT, Inc.            (800) 858-4507| It will not last the night;
11801 N. Tatum Blvd. Ste. 142      | But ah, my foes, and oh, my friends -
Phoenix AZ 85028                   | It gives a lovely light.
[log in to unmask]                   |     -- Edna St. Vincent Millay