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From: authorplaceholder@gorgo.UUCP.UUCP
Newsgroups: comp.sys.m6809
Subject: Re: os9 level II full screen editor
Message-ID: <58400009@gorgo.UUCP>
Date: Mon, 18-May-87 09:28:00 EDT
Article-I.D.: gorgo.58400009
Posted: Mon May 18 09:28:00 1987
Date-Received: Sat, 23-May-87 00:47:59 EDT
References: <20@abvax.abnet.com>
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Nf-From: gorgo.UUCP!bsteve    May 18 08:28:00 1987


Jim Omura replies :
>
>>In article <58400005@gorgo.UUCP> bsteve@gorgo.UUCP writes:
>>
>>Larry Harmon writes:
>>
>>>	One of the minor complaints I have with OS9 level II is the
>>>lack of a full screen editor.  I purchased a copy of tsedit and tsword
>>>for OS9 level I, but they don't seem to work with level II.
>>...
>>I believe that you are wrongly critical. OS9 Level II is a different operating
>>system from OS9 Level I. It is only by lucky coincedence that Level I binaries
>>run under Level II. More often than not level I binaries make assumptions
>>that the entire address-space of the machine is available, when with hardware
>>memory management, it is not. I believe that this is the fundamental problem
>
>     Whaaaaat?  Where the heck did you get a silly set of ideas like
>this?  The point of OS-9 is that the majority of code properly written
>following the OS-9 conventions are directly usable under both OS-9
>Level I or Level II.  This is possible because addressing within the
>program is all relative and addressing of data is all base register
>relative.

THIS IS NOT A SILLY IDEA. The outward structure is pretty much the same and
in fact several system calls did change between the versions. Software
vendors took advantage of the fact that the full address-space was available
in level I. Programs written with portability to Level II in mind work just
fine... This is to say that I can run the level I C compiler on my level II
system. It just can be guarenteed to work unless the author of the software
fails to stick to the rules.

>     It's certainly no accident or matter of luck that code is portable
>between Level I and Level II.

This is true. The mechanism for upward portability was built into both
level I and level II. I wish more software authors had followed it. Folks
need to know about this so that they don't get burned by it.


   Steve Blasingame (Oklahoma City)
   ihnp4!gorgo!bsteve