12 Aug
2004
12 Aug
'04
2:06 a.m.
Am 11 Aug 2004 14:47 meinte Steve Thatcher:
I realize that the idea is to create a format to make
re-creation
of media possible for a variety of platforms. We can certainly do
that and have its only function be to maintain a physical data
format. My added idea is that the data and the formatting be
separated so that a simple utility on a non-target platform could
extract data from the image file.
Well, physical format and data is not always seperable. In some
circumstances the physical format is part of the onformation an
application needs, and differs form media to media (e.g. copy
protection schemes)
If we create a physical description only and do not
abstract
the data then any emulator must understand the OS file
structure in order to retrieve any internal file representation.
My idea would make the file re-creation simple in that the xml
image file would be parsed for the actual file data that an
emulator would need. This makes the emulator easier.
But what if the emulator needs the physical format information?
To retrieve a file from the physical layout that it at
the end
of this message, the emulator must know the actual disk format
that is used on the target system (the one the image file was
made for). I have seen cp/m systems where the actual physical
sectors were sequential on disk and the OS file sector was
actually virtual to increase speed. Not my idea of the way to
do it. It is much easier to make the physical sectors slewed
so that a physical sector is a file sector. These are the types
of issues you will have to overcome if an emulator must totally
understand each and every file system for a cp/m version for
example.
At least within a CP/M system it usualy doesn't matter at all
how the files are stored on a disk. Except for some odd apps
who tried to implement system specific copy protection schemes,
all and every CP/M app accesses files just via BDOS which already
hides the real disk strukture.
Gruss
H.
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