[Coco] OS-9 Floppy

[Luis Fernández]

Interesting
I could do that easily in virtual disks


> Date: Sun, 17 Mar 2013 18:34:34 -0400
> From: robert.gault at att.net
> To: coco at maltedmedia.com
> Subject: Re: [Coco] OS-9 Floppy
> 
> Melanie and John Mark Mobley wrote:
> > Can I write a DECB (Disk Extended Color BASIC) file to an OS-9 disk without
> > disturbing the OS-9 portion of the disk?
> >
> 
> It is possible to format a disk for both DECB and OS-9 but you need much manual 
> work to get it right. It is only practical if you force the first half of the 
> disk to be OS-9 and the second half to be DECB.
> 
> Here is how you must do it to get it to work. Format the disk for OS-9 as a 
> single sided disk. Now use dEd to mark as used the allocation bit map in LSN1 so 
> that OS-9 can't make use of track 17 and beyond. So fill LSN2 bytes $26- with $FF.
> Now format a different disk with DECB. Place the OS-9 disk in drive0 and the 
> DECB disk in drive1. Run the following program.
> 10 CLEAR 512
> 20 FOR S=1TO18
> 30 DSKI$1,17,S,A$,B$:DSKO$0,17,S,A$,B$
> 40 NEXT
> That will place a DECB directory onto the OS-9 disk. You now need to mark the 
> file allocation sector T17S2 to show that the sectors used for OS-9 are not 
> available. You can write a DECB program to do this but using a raw disk editor 
> is easier. Again assuming the first half of the disk is OS-9 fill T17S2 bytes 
> 0-$21 with $EE to mark it used.
> 
> Now you could right either a Basic09 or DEC Basic program to do the above but it 
> probably won't be worth the effort. Why not put OS-9 on the front side of the 
> disk and DECB on the back side of the disk?
> 
> Robert
> 
> 
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