>Thanks for sharing this info Colin. I really appreciate it. I was curious to
>know what multitasking in OS 9 was supposed to be all about. None of my
>colleagues could explain it to me. But it's really been a part of the mac OS
>since system 6? That really helps explain the function of cpuHogTicks.

Glad to help. Here's some more system trivia:

As I mentioned in the other message, system 4.2 was the first to have 
multifinder, which was were background applications could stay open 
and continue to work. There were no systems between 4.3 and 6.0, the 
Finder and the System were always a bit out of sync. The Finder that 
came with System 3.2 was 4.something, the one that came with System 
4.1 was 5.5. That took the integers past 5, and so a system of 
version 5 would have involved a Finder version number that was going 
backwards. And so both jumped to version 6.

Of course, life isn't that simple, and in no time the Finder had a .1 
difference. Also, 6.0 had so many problems that it wasn't even 
released overseas (I was working at Apple UK during this whole period 
from before 4.2 until after 7.0). 6.01 took care of those, but by the 
time it was ready to go, 6.02 was being worked on. Us Europeans 
didn't see System 6 (officially anyway) until 6.02.

What caused a lot of upset was that many applications (Word in 
particular) had System 6 versions that would not even launch in 
earlier systems. What were Microsoft thinking! Well, there was a 
significant change that was done in System 6, and Microsoft had taken 
advantage of that, and so were not backward compatible.

Prior to System 6, you would have to write your application so that 
it knew whether it was running under single Finder or multifinder. If 
it was on single Finder, your program had to do a GetNextEvent to 
find out what it had to do next. If it was multifinder, it would do a 
WaitNextEvent (this is where the whole business of cooperative 
multitasking comes in, because one of the parameters of WaitNextEvent 
is how long you are willing to wait, the default being one second).

With System 6, single Finder also worked with WaitNextEvent, 
developers could skip the whole Finder/multifinder test, and could 
have just one routine that did a WaitNextEvent. A single Finder 
System 6 could cope with that. This allowed people like Microsoft to 
be a little lazy, at the cost of backward compatibility.




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