Date   : Sun, 09 Aug 2009 18:07:36 +0100
From   : info@... (Sprow)
Subject: Level 4 FS Y2K query

In article <Marcel-1.53-0809113737-0b0xSBG@...>,
   Johan Heuseveldt <johan@...> wrote:

[snip]

> It is not hard to see that the two systems of use and
> interpretation, clashes enormously!
>
>     It's a mystery to me why Acorn didn't get this right
>     in the first place, e.g. a bit in the attributes field.
>     Even when restricted to 8 bits - not touching the other
>     24 bits of the 32 bits sized attributes field - there is
>     still space to a dedicated bit for this purpose.

The top 24 bits of the attributes are private to the filing system. Some
will just preserve but ignore them, others will make them read only, others
use them to contain private meta data.

For example, NetFS stores the date in them

  byte 0 = common FS attributes per AUG
  byte 1 = bits 0-4 day of month
           bits 5-7 year high bits
  byte 2 = bits 0-3 month
           bits 4-7 year low bits
  byte 3 = unused

All 8 bits of the common FS attributes have already been used up, so there's
no where left to store the flag.

As you state, the two systems do overlap considerably,
Sprow.