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From: harrow@exodus.dec.com (Jeff Harrow, NCSE BXB1-2/E02 DTN=293-5128)
Newsgroups: comp.sys.mac
Subject: Re: Program compatability between Mac ][ and Classic Mac...
Message-ID: <9575@decwrl.DEC.COM>
Date: Wed, 29-Apr-87 12:26:41 EDT
Article-I.D.: decwrl.9575
Posted: Wed Apr 29 12:26:41 1987
Date-Received: Sat, 2-May-87 02:39:38 EDT
Sender: daemon@decwrl.DEC.COM
Organization: Digital Equipment Corporation
Lines: 57

In response  to  my original question regarding the need to write 
conditional code for  use  of  some new calls/structures (such as 
color windows, etc), David Goldsmith of Apple replies:
 
>Some of the new features have been backpatched onto 128K ROM machines.
>Basically, most of the new functions (TextEdit, Menu Manager, etc) are
>available on anything with 128K or later ROMs running System 4.1 or
>later.  This is not true for any of the color functions; these are
>available only on the Mac II, so I'm afraid that "yuk!" is the order
>of the day.
>
>David Goldsmith
>Apple Computer, Inc.
>MacApp Group
 
David, I'd first like  to  sincerely thank you, Larry, and others 
at Apple who respond so  promptly  to questions posed here on the 
net;    this does a tremendous  service  to  prevent  rumors  and 
misinformation.

Regarding this issue, however, how about some  type of patches in 
the  "lower"  systems  (non  Mac  ][ at this  point)  which  will 
AUTOMATICALLY  translate   the  "color"  (and  other  unsupported 
calls/structures) into a form which WILL work.

Consider, although in  the  case  of the Mac ][ vs.  Classic  Mac
writing conditional code is  feasible (although NOT in the spirit 
of full backwards compatibility that  has  been maintained in the 
past), what will happen when the  NEXT  advance in Mac technology 
(you ARE working on such, aren't you?)  comes  along...   Will we 
have to have MULTIPLE levels of conditional code  based an a tree 
structure of growing complexity, just to figure out WHAT calls to 
issue?    This  strikes me as a significant burden on  developers 
causing  an    increase   in  time/cost  of  programs,  but  most 
importantly probably GUARANTEES  that  a  larger  percentage  of 
programs will NOT be fully backwards compatible.

You folks have done SUCH a good job on this in the past, and have 
come SO close even in  the  Mac ][ world (with as you pointed out 
backward patches to TextEdit, etc.), why  not  go that extra mile 
ONCE  so that each and every developer  won't  have  to  put  the 
effort in for EACH program?

Thanks for your consideration,

Jeff Harrow

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