[Coco] Re: Disk Basic and 512 byte block floppies.

[Amardeep S Chana]

<KnudsenMJ at aol.com> wrote in message
news:f8.35b0f62a.2d404a62 at aol.com...
> In a message dated 1/20/04 10:06:38 PM Eastern Standard Time,
> alxevans at concentric.net writes:
>
> > All CP/M disk formats use virtual 128 byte sectors, and a few (very
> >  few) use physical 128 byte sectors.
>
> ISTR that in CP/M, the 128th byte of each sector points to the next sector
in
> the file, so you get only 127 bytes per sector, and some real
opportunities
> to screw up your file system :-)  Also, this would limit a disk to 256
sectors
> total, so maybe I'm not remembering quite right.  --Mike K.
>

CP/M doesn't do that.  All 128 bytes of a logical (and sometimes physical)
record is available for data.  Allocation is done right in the directory
area and each addressable group of sectors has a unique scalar value.

Some 68xx OS's did put a link vector in the last few bytes of each record.
Smoke Signal Broadcasting DOS/68 comes to mind. I analyzed a few diskettes I
picked up at a Hamfest.  I think Flex/09 did as well according to an
80-Micro article I'm currently reading.  Atari DOS also does that.  Seems it
was not an uncommon allocation mechanism.

Amardeep