[unios] runtime example I

[Pieter Dumon]

I was rather surprised when I read the "run time example #1". Some comments.

The example is actually rather an exaple of an OS that is not generic,
and not transparant. 

The article was pretty amusing, up to the point when Bob discovers the
Fat32(1) partition. This is just an example of how whe shouldn't do
this. The file system (or whatever storage system UniOS uses) should
be completely transparent. The user mustn't be confronted with cryptic
names like Fat32(1) and more important, it doesn't mather,certainly to
a home user, what file system resides on the disk, which disk it is or
whatever. This does not mean he can't ask the system what type of file
system it uses on a certain partition, but the system mustn't confront
the user with it automatically. Take a look at Unix: the user sees a
file system which starts at the / (root) directory , and with a lot of
subdirs. Somewhere, he has a home directory, eg /home/bob. He does not
need to know that the /home directory is on another disk than the /
and possible also uses a completely different filesystem.
You can in Unix for example use a filesystem mounted over NFS as the
root filesystem, so that filesystem would be called NFS(1) or
something in your example. The /home directory could be on a local
file system using the NTFS file system , so it would be called
NFS(1)/NTFS(1) or something, and the user's home directory could be
mounted over the network from a Netware server using the NCP
filesystem, so the complete name would be called
NFS(1)/NTFS(1)/NCP(3102) or what? Doesn't make sense, does it?
/home/bob is a lot easier and generic. If the user is interested in
what disks are mounted usign which filesystems, in Unix the user can
simply do 'df' and he gets the complete picture. But teh main thing is
he _can_ do this but he doesn't _need_ to.

If you make UniOS really transparent, the second example in the
document is also not very 'clean': the user shouldn't be confronted
with the fact that the image is BMP or TIFF or whatever, but if the
user would like, to he/she _can_ get the information, convert image
formats to each other etc...


The shutdown thing is, on the other hand, a good example: 
an OS called UniOS Home PC needs to be able to be shut down easily
by a normal user. Let's not forget this is not the fact for lots of
computers. The computer on which I'm sitting right now typing this is
our local Linux web/proxy/mail server. You cannot let such a system be
shut down by a normal user. Only a privileged (on Unix 'root') user
must be able to do that. But, indeed, for home users, shutting down
their computer must be possible whithout trouble.


 Pieter

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Pieter.Dumon@rug.ac.be
pdumon@vtk2.rug.ac.be

http://studwww.rug.ac.be~/pdumon

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