[Info-vax] Anyone interested in another public access system

[David J Dachtera]

Bill Gunshannon wrote:
> 
> In article <49DF8CAD.5618BE77 at spam.comcast.net>,
>         David J Dachtera <djesys.no at spam.comcast.net> writes:
> > [snip]
> 
> They are not organized. 

If that were true, it would be an incomprehensible jumble of nonesense.

C'mon, Bill, you're reaching so far for an argument you're starting to
sound like ... well, Boob has been quiet lately, so best to let that dog
sleep...

> An artificial structure is imposed at the
> application layer.  All computer data is composed of bytes. (well,
> bits if you go low enough)  Any "structure" is artificial and
> imposed after the fact.  There are no records in memory.  Just bytes.
> So then, why should one assume there is anything different anywhere
> else? 

Perhaps Hein could address that from RMS's point of view.

Let us also recall a class of devices from the past known as "unit
record" devices. (Note: Unit "record", not unit "byte"!)

> There are no records built into my disks. 

...and that's entirely true, so long as you do not wish to comprehend
its recorded contents.

On second thought, no it isn't true: every unit of magnetic disk media
I've ever seen has had the concept of a "sector": that segment of a
track between sector deliniations. The data content of a sector can
reasonably be called a disk "record", the smallest "piece" the device
will retrieve per host request.

In VMSland, we call that a disk "block": one track for one sector.

> A disk from one
> computer can be used on another.  I can take the disk from my VMS
> machine with all those "structured file types" put it in my unix
> machine and it works just fine.  The disk does not store things
> as anything but blocks containing bytes.  Any structure is artificial
> and at a very high level in the process.

Not true, as was just illustrated. The low-level "Structure" you cite,
"blocks containing bytes" is "the nature of the disk beast".

> I have never tried it, but I would imagine it is perfectly doable to
> take a VMS disk, hook it up to a unix box and read the data from it.

dd should do very nicely.

VMS will even read a UN*X(, DOS, Windows, ...) disk:

$ MOUNT/FOREIGN ddcu:
$ COPY ddcu: DISK.IMG
$! The COPY will complete with an error, but the disk image file
$! will be complete and intact.
$ DISMOUNT ddcu:

D.J.D.