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

[Robert Gault]

Aaron Wolfe wrote:
> 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
>

If not directory corruption, the above might be part of a copyright protection 
scheme. There are some programs that use sectors of sizes other than 256, and 
sector - track numbers higher than typical for RSDOS disks. These programs use 
their own routines to read disks and will reboot if the disk is not as expected. 
There are other tricks regards data address marks and crcs.

Post a url to one of these disk images.