DOS 3.3 MEMORY LAYOUT

$C000 --- TOP OF RAM
	
$B600 --- RWTS

$AAC9 --- FILE MANAGER

$9D00 --- MAIN DOS ROUTINES

$9600 -- DOS FILE BUFFERS (MAXFILES 3)


BD00 	- RWTS main entry
	- call with AY pointing at IOB

Input/Output Control Block

OFFSET	DESCRIPTION
$00	Table Type (must be 1)
$01	Slot Number times 0x10
$02	Drive Number ($01 or $02)
$03	Volume Number ($00 matches any volume)
$04	Track Number 
$05	Sector Number
$06/$07	Address (lo/hi) of Device Characteristics Table
$08/$09	Address (lo/hi) of 256 byte buffer for READ/WRITE
$0A	Not Used
$0B 	byte count for partial sector
$0c	Command Code
		$00 = SEEK
		$01 = READ
		$02 = WRITE
		$04 = FORMAT
$0d	Return Code (if non zero, carry flag should be set)
		$00 = no error
		$08 = error during initialization
		$10 = write protect error
		$20 = volume mismatch error
		$40 = drive error
		$80 = read error (obsolete)
$0e	volume number of last access
$0f	slot number of last acces * 16
$10	drive number of last access