[Coco] DECB FAT question

[Roger Taylor]

At 01:26 AM 1/17/2007, you wrote:
>Actually, Willard, there is a bad granule code. Any granule marked $C0 in
>the granule map will, I believe be treated as allocated, and ignored.
>--


True, Bob.   $C0-$C9 should be the codes for allocated granules.  $C0 
or (%11000000) has a sector count of 0.

Almost all Disk BASIC floppy disks have lots of "free space" on them 
even when the disks report as being FULL.  How so?  The reason is 
that the File Allocation system reserves 9 sectors at a time, no 
matter if the files need them or not.

The granule code $C1 would mean the granule (9-sector chunk) only has 
1 valid sector in it.  The remaining 8 are "VOID".  For this reason, 
a disk tool could be written that combs a disk for all the unused 
sectors and store any kind of data there without trashing the disk or 
file system.

I'm curious to know how many free sectors could be claimed on any 
given file disk and what kind of ideas can be thought of for using 
those sectors.  The same applies to the CoCo hard drives, especially 
from within OS-9.