)
Values for DOS Plus v2.1 XIOS functions:
 00h	terminate program
 01h	???
 02h	check for console input status
 03h	read character from console
 04h	write character to console
 05h	write character to list device
 06h	write character to auxiliary device
 07h	read character from auxiliary device
 0Fh	get list device status
 10h-14h reserved
 15h	device initialization
 16h	check console output status
 17h-7Fh reserved
---BBC Acorn---
 80h	get XIOS version
 81h	get Tube semaphore
 82h	release Tube semaphore
 83h	select text/graphics
 84h	update B&W graphics rectangle
 85h	update color graphics rectangle
 86h	get/release/update mouse
 87h	get system error info
 88h	entry in CLOCK called by WatchDog RSP
 89h	BBC OSBYTE function
 8Ah	BBC OSWORD function
SeeAlso: #04019