#Diff between HSF & 9660
5 messages in this thread
Any High Sierra / 9660 format experts out there?
I got some old code out last week and realised that there are major differences
between the volume descriptor layout it dealt with and ISO9660 spec. I guess
that the code was written for the original High Sierra Format proposal. can
anyone enlighten / remind me of the answers to the following questions:
1. Is it right that the first byte in the primary volume descriptor is 01 hex
for ISO 9660 conformant CDs and 10 hex for the original High Sierra Format?
2. Are there any other sorts of volume descriptor layouts apart from these two?
3. Why were these major changes to the volume descriptor made? The data in
there seems much the same, just re-organised.
4. Or, in other words, what are the major changes and justifications for the
differences?
5. The only other difference I spotted was that the directory ID length and its
location are interchanged in the path tables between the HSF and 9660 formats.
Again why make such a trivial change, the data seems much the same?
6. Are there any other differences between HSF and 9660 that I havn't spotted?
7. Is it, in fact, a requirement that general purpose code still deals with
both formats? I have a number of old HSF ROMs that I still use from time to
time.
Thanks for any info.
Chris
INTERNET:cbt@cam-orl.co.uk
A good place to find out the differences between the two is download a file
from the December 1992 issue of Dr. Dobbs Journal. The C source code and
structures show you the differences between the two. (GO DDJFOR) and the search
the library with the keyword DEC92 or CD-ROM and you will find it.
Albert
OK got it thank you very much. I see the differences and I guess that there are
only these two formats around. But, I'd still like to hear from anyone who can
comment on why such major and incompatible changes were made.
Thanks
Chris
INTERNET:cbt@cam-orl.co.uk
Chris,
The simple answer was that that the HSF format came out quite early in the
evolution of CD-ROM. The choice was :
(1) Use what was there, HSF , even if it had some problems,
(2) Stay with Proprietary formats.
(3) Wait for the ISO format to be ratified, a moderate to long process.
Microsofts' MSCDEX and a documented low level CD-ROM interface that protected
vendors from having to write multiple low-level hardware drivers also was a big
factor.
Glen Chapman
Its the nature of standards bodies to change things. Adding things like offset
to GMT and escape sequences/character sets is a must to get an international
standard. Also, everybody wants to get in their two cents worth.
We've been going through this with ECMA 167/ISO DIS 13346 (a file system
standard designed for WORM and rewritable optical). Bit positions for certain
fields get changed with no other reason than somebody thought it was more
logical.
David