Re: Writing an Operating System in Ada

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Tue, 12 Jan 2010 13:52:40 -0800 (PST), Maciej Sobczak wrote:

> On 12 Sty, 20:56, "Dmitry A. Kazakov" <mail...@dmitry-kazakov.de>
> wrote:
> 
>> There should be no file system at all. If you have objects, I mean if you
>> do have them consistently all the way, then you do not need files. Make
>> objects persistent in the corresponding device, that gives you all
>> functionality of any file. No I/O is ever needed. Map the object into the
>> memory, call its operations, what else any program would have to do?
> 
> Interact with other systems? You know, you might want to sometimes
> move your "persistent objects" to another machine.

Marshaling? In terms of ADT it is assignment. Create a local object of the
type. Assign the remote object to it. Done.

Provided you have the assignment defined.

> Did I mention that you might want to move you whole hard drive to
> another machine as well? :-)

Did you try? What happens with a NTFS drive in a Linux system? Can you
mount it as an ext4?

This is not a question of objects or raw blocks. If the OS recognizes the
pluggable component, there is no problem, if it does not there is a
problem. Nothing prevents a portable design of persistent storage.

Note that the file system itself is built on a layer of blocks and sectors.
So if your argument worked, there would be no need for a file system. We
would still read sectors and count drive heads...

> There is a reason why none of the pure-OO-OS-let's-do-it-correctly
> ever really took off.

Yes. There are many reasons. For all there is no consistently designed
OOPL, Ada included. Without MI, MD, tagged tasks, there is no chance to get
it right. But the major problem is lack of any interest, since the market
of operating system was burnt down to the ground.

>> The problem is that we followed the wrong path for too long.
> 
> There is nothing wrong with that path, as it happens to be very
> pragmatic.

Maybe. If we compared the computing power we had in i386 days with the
power of a modern machine (that includes not only the CPUs but also all
processors and micro controllers on board). Is this increase of power
matched by what the software provides? I don't think it is. The
"pragmatism" was, if you have a software problem, buy a new computer. That
might be economically OK, but it still is bad for the software. In long
term perspective we sooner or later will be forced to use computing
resources more efficiently.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de