Re: OS400 release levels

Well, the unzip from WinXP to Win3.1 might work... if the file names
are in the short (8.3) format that Win3.1 supports.

However, the .EXE and .COM files compiled on WinXP won't work on Win3.1.
If there are data files in the .zip, you MIGHT be able to use them, but
if they're access databases or something like that you'd probably have
to export them in an older format...   So, things aren't completely
compatible.

The same is basically true of OS/400 save files.  The format of the save
files themselves has changes, so you have to specify what OS level you're
saving at, so that the newer OS knows to use the older format of the file.
Just like exporting an excel or access file to an older version.

The executables compiled on a RISC system won't run on a CISC system.
It's actually a nice feature of OS/400 to stop you from trying to
save/restore them, rather than actually restoring them and then having
problems as would be the case with a WinXP executable that you restored
on Win3.1.

But, I think the really major difference is the architecture of the
operating system.  On either Windows or Unix, there aren't really
different "object types".   Everything is just a "stream file" (as we call
them in the OS/400 world.)  In OS/400, each object type has data
structures associated with it that are managed by the operating system.
These "object descriptions" contain lots of useful information that the
other operating systems don't keep track of.   Since that structure
changes from release to release, object conversion must be done when
saving & restoring across releases.

You can see why, with all of these extra issues to deal with, IBM doesn't
want to maintain support for every previous release..   things would get
very messy!  to say the least...


On Fri, 6 Sep 2002, James Rich wrote:
>
> Of course, I forgot to mention that.  And it is true that my tarballs
> compressed with bzip2 can't be restored on my 1994 Slackware 3.0 machine,
> but I could compress with gzip (or even plain old compress) and I would be
> able to restore them on good old linux 1.2.14.  And I'm reasonably certain
> that something zipped on WinXP can be unzipped on Win3.1 (though I don't
> know for sure).
>
> James Rich
>