🚀 go-pugleaf

In article <MUa8YYy00UhTQM00cm@andrew.cmu.edu> rs4u#@ANDREW.CMU.EDU (Richard Siegel) writes:
>
>Some questions:
>
>	1) Why the change? It seems to me that there's a large number
>of programs that have the "Transfer" feature (as it's usually called),
>that will suddenly stop working.

Not likely.  The sublaunch code simply adds a new feature to _Launch, it
doesn't change anything else.  The mechanism for passing additional
parameters to _Launch was implemented in the 128K ROM, and as far as I know
they have never been documented.

In the 128K ROM, these extra parameters were used to indicate that a program
should be launched read-only, which is useful if you are using a file
server.

>	2) For Old Mac and Mac Plus owners (Old Mac = 64K ROM), does
>this change come with System 4.x? Or is it simple a change in the ROM
>for the SE and Mac II, so the "Transfer" feature will only crash
>on the new machines?

The patch is definitely in System 4.1; I don't have a copy of System 4.0
around to see if it was in there as well.

>	3) *Flame On* Why is Apple doing this? I personally would simply
>add another trap (_SubLaunch or somehting) to the 256K ROMs, or
>make the existing _Launch trap smart enough to know when it's being

The new features are activated by a special signal to the _Launch trap.
Normally, _Launch takes a pointer to a parameter block in A0.  The first
long of the block points to the file name and the next 2 bytes to the
sound/screen page 2 options.  

If the 2 bytes after that is $4C43, then the extended parameter set is
assumed.  Following the code will be 4 bytes for the length of the extended
parameters, followed by a word of flags. Bit 6 of the low flag byte is 1 to
indicate a read-only launch.

As I mentioned before, I don't have a copy of the new set of Tech Notes,
which indicate how to specify a sublaunch.

>	4) By the way, will this interface change be backward compatible?

If the patch is not present, then the sublaunch will work, but (I assume
that) the application doing the launching would not regain control.


-- 
Larry Rosenstein

Object Specialist
Apple Computer

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