Path: utzoo!attcan!uunet!lll-winken!xanth!ames!pasteur!ucbvax!tut.cis.ohio-state.edu!unmvax!indri!uflorida!haven!umd5!zben From: zben@umd5.umd.edu (Ben Cranston) Newsgroups: comp.sys.mac.programmer Subject: Re: Standard File and Desk Accessories Summary: Actually, I like the store-into-code idea... Message-ID: <4988@umd5.umd.edu> Date: 8 Jun 89 18:42:18 GMT References: <50967@tut.cis.ohio-state.edu> <7547@hoptoad.uucp> <4972@umd5.umd.edu> <51276@tut.cis.ohio-state.edu> <2015@husc6.harvard.edu> <1241@speedy.mcnc.org> Reply-To: zben@umd5.umd.edu (Ben Cranston) Organization: University of Maryland, College Park Lines: 29 Actually, of all the ideas presented, I like the store-into-our-code idea the best. Yes, self-modifying code is not a good thing. But, it is the ONLY way to properly manage A5 in the MultiFinder world, given that CurrentA5 may be swapped out by MF. The only problem I have with the technique is that the people who designed the MC680x0 had the same tunnel vision. "Storing into our own code is a *BAD* thing!", they thought, so they omitted any kind of PC relative store instruction! So you gotta do something like this: LEA blappo,A1 Move.L A5,(A1) Oh, well, it's only one extra instruction... My suggestion of using A4 or A6 was not real. Nobody should depend on the structure of another program like that. The point about SetupA4 and RestoreA4 is well taken. I wonder how they are implemented, though. The old SetupA5 and RestoreA5 used a reserved low memory location (CurrentA5) and I wonder if there is some kind of reservation for A4 in low memory (deal between Apple and developers?) and if there is a similar MultiFinder problem with the low-core location. This would show up in background event handling in MF-aware programs, also in handling raw IO interrupts etc... Q. How many computer professionals does it take to change a lightbulb? A. Three One customer engineer to decide the problem is software. One systems programmer to decide the problem is applications software. One applications programmer to reprogram the light switch... -- Ben Cranston (Kingdom of Merryland UniSys 1100/92) Copyright 1989 (you may redistribute ONLY if your recipients can).