Defining Disk Image Dump Standard

From: Sellam Ismail <>
Date: Thu Jun 1 17:00:06 2000

On Thu, 1 Jun 2000, John Wilson wrote:

> Who says it's software? What if it's a data disk? Or a totally
> unknown one? Or something that's portable (e.g. an interpreted
> language). It just seems like it could cause trouble if the image
> were hard-wired to claim it's from one particular place. Especially
> if they get tagged incorrectly, then utilities which *could* read the
> disk will refuse, and ones which *can't* will screw themselves up
> trying because they believe the header.

In that case perhaps we can have generic group meta codes, such as "CP/M",

> The opposite extreme is to not have it adopted because it's too complex to
> be practical. It's definitely a good thing to anticipate future needs, but
> I wouldn't get too hung up with the notion that this format will be all
> things to all people. There will always be a few oddballs out there which
> won't fit the framework, whatever it is.

Yes, but in it's current iteration it is not very complex at all.
Detailed, yes. Complex, no. It's being designed to allow a very simple,
straight foward archive to be created in the case of no special
considerations (i.e. a "standard" floppy disk) while still being powerful
enough to allow a very bizarre format to be described as well. I think
the balance is being achieved.

> Absolutely, that's why I jumped in. I've written a bunch of floppy
> utilities, and picturing extending any of them to work with verbose tagged
> free-form text files with redundant header descriptors and lots of magic
> numbers, is giving me a headache. One aspect of doing it right, is doing
> it so that it can be implemented cleanly.


> >I envision all the post- and pre-processing will be done on a more modern
> >host, such as a standard PC running Linux or whatnot. I would never want
> >the processing done on the target machine, especially if this standard
> >turns into a big messy markup language.
> Careful, this is a *very* common pitfall these days. "I'll just assume
> that everyone in the world has access to the same modern hardware and
> software that I do."

I don't imagine anyone will be attempting to create a multi-gigabyte
archive on a Sinclair ZX80. The point is this archive will be carried
forward onto ever more powerful computers, and limiting it to be feasible
on technology that has long been passed by makes no sense to me.

Linux will run on a 386, a 68K Mac, an Atari ST, and the Amiga. I'm
satisfied with that.

> This was my point about Teledisk (especially since it's a bit flakey even
> on a real PC). If I have a Pro/350 and I want to write a DECmate II disk,
> there's no technical reason why I can't do it (the low-level format is the
> same so it's trivial), so why create an artificial limitation by depending
> on a big complicated C program which doesn't run on the Pro?

Take the specification and write an archive application that will run on
the Pro/350. As stated above, the standard as it is being defined is not
difficult to implement. And as I mentioned before, I'm considering
writing a DOS application to implement the standrad once it's near
completion. The point is I don't see this as a legitimate concern. The
standard is not currently constructed to require a computer with gobs of
memory, even if it does evolve into a markup language.

> IMHO, that's *their* problem. If a disk format is so weird that there isn't
> even any way to decide what would come first in a binary snapshot, then *that*
> format should have a big tangled mass of header descriptors etc. But that
> doesn't mean that *every* format needs to have a hairy wad of descriptors
> intermingled with the data.

I agree, and the way I am seeing the standard evolve will not require
massive headers for standard formatted disks. It may not look like it now
but that is what is in the back of my mind as we move forward with this.
We're still really in the gathering phase so don't get frustrated just

As statedin so many words before, the standard will be designed
intelligently enough to archive a standard diskette in a simple, straight
forward manner, but also allow the complexity to archive a completely
non-standard diskette.

> As an analogy, I *really* like the Kermit file transfer protocol. It's
> designed to be a very good compromise between capability and ease of
> implementation. There are lots of possible bells and whistles but
> most of the time you can get away without them. It has a few basic
> assumptions which don't hold true for *all* systems (files are a
> linear sequence of 8-bit bytes, filenames can be represented in ASCII,
> the serial line can pass any ASCII printing character through), but
> they fit the vast majority of real systems. It works around most of
> the common problems in file transfer, but it's simple enough that you
> can write a basic native Kermit implementation for almost any
> architecture in a few days.

We'll try to develop this standard in the same spirit.

Sellam International Man of Intrigue and Danger
Looking for a six in a pile of nines...

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Received on Thu Jun 01 2000 - 17:00:06 BST

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