[Coco] OS9 vs RSDOS disks

[Bob Devries]

Robert,

Your explanation of the LSN0 structure is great, but it only holds true with 
Single-sided disks. On a double-sided disk, the directory sector could 
possibly be on the other side of the disk, which, from the point of view of 
writing a DECB identifier, wuld open a large can of worms.

Regards, Bob Devries
Dalby, QLD, Australia

----- Original Message ----- 
From: "Robert Gault" <robert.gault at att.net>
To: "CoCoList for Color Computer Enthusiasts" <coco at maltedmedia.com>
Sent: Friday, June 14, 2013 8:56 AM
Subject: Re: [Coco] OS9 vs RSDOS disks


> Bill Pierce wrote:
>>
>> Hi guys,
>> Is there a simple way to tell an OS9 disk from an RSDOS disk? Maybe 
>> something constant in LSN0 on the OS9 disk?
>> It would be nice to identify the disks through software
>>
>> Thanks
>>
>> Bill Pierce
>
> Bill,
>
> Unfortunately there is no sure fire method. What might work most of the 
> time is to see if there is a root directory in the correct location. If 
> there is, then the disk is at least formatted for OS-9 but might also be 
> formatted for Disk Basic.
>
> LSN0 bytes $08, $09, $0A are DD.DIR - address of starting sector of root 
> directory
>
> DD.DIR bytes $10, $11, $12 - indicate address of first sector of directory 
> listing
>
> First sector of listing for any directory
>
> bytes
> $00   $2E $AE
> $20   $AE
> These are the .. and . entries in any OS-9 directory but they are never 
> printed by the command dir.
>
> Robert
>
>
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