Date   : Thu, 03 Nov 1994 14:35:56 +0000
From   : jfid@... (James Fidell)
Subject: Re: Reading BBC disks

Peter Coghlan wrote:

> How about one of these solutions to hold the attributes:
>  
> 1. Create a single file per disk (or per directory) which holds the
>    BBC attributes of all files on the disk (or in the directory) which
>    are to be used with the emulator. The attributes would be held in text
>    form, one line per file. This would allow them to be added or modified
>    with any editor if required.

This is my preferred option.  A sort of equivalent of a disk directory.

> 2. A marker plus the attributes are added in text form at the top of
> any file to be used in the emulator system. As above, files which do
> not have attributes (ie the marker is not present) cannot be *RUN
> and cannot be loaded with Osfile unless a load address is specified.
> Attributes are not added to any file which does not have them as this
> would mess up other applications using the files.

I personally don't like this one because it requires modification of the
file as it appears on the Beeb.

> 3. A marker plus the attributes are added in text form to the end of
> any file to be used in the emulator system. Similar problems to scheme
> 2 except that it is easier to add attributes to existing files and
> less likely to end up thrashing the file by accident.

But it means that you have to mess around with file pointers to actually
read the attributes.  I don't really see any useful advantage over option
2 here.

An observation...

Using method one can, as I've already said, be considered a sort of
analogue of the disk catalog mechanism, but it should work fine for
emulating a tape mechanism.

To use the same method for emulating disks would require a slightly
different approach because disk files have more attributes, disk sizes
are fixed and there can be at most 31 files per disk (I'm talking about
the original Acorn DFS here.  I have no experience of the ADFS.  I'm
not even sure it was around when I left school).

How do you differentiate between the two systems ?  Do you bother ?

James.

-- 
 "Yield to temptation --             |     jfid@...        
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                                     |
        - Lazarus Long               |              James Fidell