[Oberon] OFS directory-format documented ?
benpsm at gmail.com
Thu Nov 29 12:58:52 MET 2007
On Nov 28, 2007 8:08 AM, <easlab at absamail.co.za> wrote:
> In fact for a big-directory all the 'arg-words' are
> multiples of 29; and the 1st chronologically entered
> File's arg-word: 5829; equals 201*29.
I can't answer your more general question about documentation of the
on-disk format of OFS, but the book Project Obeorn provides some
insight into the magic number 29:
3. Sector pointers are represented by sector numbers of type
LONGINT. Actually, we use the numbers multiplied by 29. This implies
that any single-bit error leads to a number which is not a multiple of
29, and hence can easily be detected. Thereby the crucial sector
addresses are software parity checked and are safe (against single-bit
errors) even on computers without hardware parity check. The check is
performed by procedures Kernel.GetSector and Kernel.PutSector.
Project Oberon "Edition 2005", Page 174
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