Let's start sort of from scratch here.
So far we have the following (high level) criterion for a disk archive
standard:
1. Host computer type (2 bytes allowing up to 65536 models to be
specified)
2. Track format (host computer specific)
3. Sector format (single-density, double-density, etc)
4. Sector data format - this will specify what format the archived sector
is in (raw data? logical bytes?)
5. Bytes per sector
6. Bits per byte
What else?
I will be the first to say that this is may not be very logically
structured. What I am attempting to do is give a suggestion for a high
level header that identifies what each chunk of data in the archive can
represent. In this way, disks that are formatted with several different
formats can be described.
I think what this may evolve into is a Data Definition Language. The DDL
will be encoded along with the disk data and will describe the format of
the data on the disk as it is being read.
This comes back to the fact that utilities will have to be written for
each computer we decide to support (I assume it will be all of them) to
both read and write native diskettes. I also assume the data will be
passed between the archive host and the target machine via serial link?
In case my mostly random thoughts above don't make sense, here is what I
would have in mind for the Apple ][:
The disk can be read in either standard, logical format (13 or 16 sectors
per track, 256 bytes per sector) or "raw" format (raw disk bytes are read
from the track). There would also have to be format descriptions for
specially formatted tracks such as the 18-sector type I mentioned.
As for reading the raw bytes, the Apple ][ had what were called
"synchronization" bytes, which were 10 bits long, the two extra bits being
used to synchronize the head with the start of the track. I could go into
a technical discussion of this but would have to pull out some reference
material to refresh my memory of how it all worked. Anyway, these bytes
would have to be specially encoded in the archive.
Sellam International Man of Intrigue and Danger
-------------------------------------------------------------------------------
Looking for a six in a pile of nines...
Coming soon: VCF 4.0!
VCF East: Planning in Progress
See
http://www.vintage.org for details!
Received on Tue May 30 2000 - 01:50:03 BST