OS-9 Disk Format

#FILE: $RCSfile: os9formt.txt $
#DESC: OS9 Disk and File formats
#REV: $Revision: 1.1 $
#DATE: 06/04/94
#AUTHOR: Graham E.Kinns
#DISCLAIMER: All information provided as is etc.
#ARCHIVE: This file is part of the DRGNINFO collection of Dragon info files
#CONTACT: Comments, bugs, revisions, suggestions to Dragon@grempc.demon.co.uk
#HISTORY: 1.0 22/03/94 - Initial version
#RCSID: $Id: os9formt.txt 1.1 1995/08/18 14:33:17 Graham Exp $
#SOURCE: Dragon OS9 System Programmer's Manual + additional

0.  Introduction
================

This file represents all I've amassed about the OS9 disk and file
formats, particulartly OS9 level 1 as released by Dragon Data Ltd, UK
for the Dragon computer in 1983 shortly before their demise.  Incidently,
it is believed Microware never received any license royalties whatsoever.
Having never run OS9, I may be missing a few things which are obvious
to the experienced user.
All words are stored in Motorola hi-order format.

1.  Known disk formats
======================

2.  Sector organization
=======================

3.  Identification Sector
=========================

Identification Sector resides on LSN 0 and contains the Disk Descriptor:

Os9 ref	 Byte	Length	Description
	offset	(bytes)

DD.TOT	0x00	 3	Total number of sectors on media
DD.TKS	0x03	 1	Number of tracks
DD.MAP	0x04	 2	Number of bytes in allocation map
DD.BIT	0x06	 2	Number of sectors per cluster
DD.DIR	0x08	 3	Starting sector of root directory
DD.OWN	0x0b	 2	Owner's user number
DD.ATT	0x0c	 1	Disk attributes (to be clarified)
			bit 7:	D  -  Directory
			bit 6:	S  -  Shared
			bit 5:	PE -  Public Execute
			bit 4:	PW -  Public Write
			bit 3:	PR -  Public Read
			bit 2:	E  -  Execute
			bit 1:	W  -  Write
			bit 0:	R  -  Read
DD.DSK	0x0e	 2	Disk identification (for internal use)
DD.FMT	0x10	 1	Disk format:  density, number of sides
			bit 7:	
			bit 6:	
			bit 5:	
			bit 4:	
			bit 3:	
			bit 2:	
			bit 1:
			bit 0:
DD.SPT	0x11	 2	Number of sectors per track
DD.RES	0x13	 2	Reserved for future use (under Level 1)
DD.BT	0x15	 3	Starting sector of bootstrap file
DD.BSZ	0x18	 2	Size of bootstrap file (in bytes)
DD.DAT	0x1a	 5	Time of creation:  Y : M : D : H : M
DD.NAM	0x1f	32	Volume name:  last char has sign bit set

4.  Allocation Map
==================

5.  File / Directory storage
============================

The first sector of every file contains a file descriptor, which 
contains the logical and physical description of the file.  The table 
below describes the contents of the descriptor.

Os9 ref	 Byte	Length	Description
	offset	(bytes)

FD.ATT	0x00	  1	File Attributes:  D S PE PW PR E W R
			bit 7:	D  -  Directory
			bit 6:	S  -  Shared
			bit 5:	PE -  Public Execute
			bit 4:	PW -  Public Write
			bit 3:	PR -  Public Read
			bit 2:	E  -  Execute
			bit 1:	W  -  Write
			bit 0:	R  -  Read
FD.OWN	0x01	  2	Owner's User ID
FD.DAT	0x03	  5	Date Last Modified Y : M : D : H : M
FD.LNK	0x08	  1	Link Count
FD.SIZ	0x09	  4	File Size (number of bytes)
FD.DCR	0x0d	  3	Date Created:  Y : M : D
FD.SEG	0x10	240	Segment List:  see below

------------------------------------------------------------------------------

99.  Acknowledgements
=====================

David J. Linsley ( djl102@tower.york.ac.uk ) for the information
from the Dragon 6809/OS9 Lev 1 System Programmer's Manual



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