[Coco] values other than 0 or 1 for byte 14 of decb dir entry

Luis Fernández luis46coco at hotmail.com
Sun Mar 25 14:07:08 EDT 2012


No 
DECB use these 2 bytes for the number of bytes in the last sector, should be 1 to 256 (sector 0 would be used).
Only some. Dsk, have in some file, not all, the number of bytes in the last granule (but this is the exepcion, not the rule)
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CoCoDskUtilPack V 1.0.10.zip  
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> Date: Sun, 25 Mar 2012 13:23:29 -0500
> From: hhos at st-tel.net
> To: coco at maltedmedia.com
> Subject: Re: [Coco] values other than 0 or 1 for byte 14 of decb dir entry
> 
> > Hi,
> >
> > According to my docs, bytes 14 and 15 are the number of bytes used in
> > the last sector of the file.
> > Since we have sectors of only 256 bytes, I think that means you'd
> > either see 0 in 14 and any value in 15, or 1 in 14 with 0 in 15.
> >
> > That rule holds true for a vast majority of the disk images I have
> > here, however there are some disks with files that seem to be claiming
> > to use more than 256 bytes in their last sector.  I'm not sure what
> > this means.  Am I misinterpreting the docs?
> >
> > I've values of 2, 7 and 8 in byte 14, and a couple instances of a 1 in
> > 14 and a non zero value in 15.
> >
> > -Aaron
> 
> I am definitely confused here. Are any of these images you're looking at
> showing a value over $900? It's been a while since I looked at
> documentation about this subject, but my memories tell me that DECB uses
> granule sizes of 2304 bytes. I remember that number quite well mainly
> because it is one of the main reasons why I despise the DECB file
> structure. Wouldn't the value in bytes 14/15 therefore be the # of bytes
> used in the last GRANULE, not the last sector, and could be as high as
> $900?
> 
> > Dragon Use 1 byte for bytes in last sector
> > and say
> > if 0 then 256 bytes in last sector
> 
> The Dragon disk file structure differs from the DECB structure. It does
> manage them on a sector by sector basis.
> 
> HH
> 
> 
> 
> 
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