[Oberon] OFS directory-format documented ?

[B. Smith-Mannschott]

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:

Quote:
    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.

Source:
    Project Oberon "Edition 2005", Page 174
    http://www.oberon.ethz.ch/WirthPubl/ProjectOberon.pdf

// Ben