Path: utzoo!attcan!uunet!lll-winken!lll-lcc!ames!nrl-cmf!ukma!rutgers!att!mtuxo!mtgzz!drutx!druhi!dlm
From: dlm@druhi.ATT.COM (Dan Moore)
Newsgroups: comp.sys.atari.st
Subject: Re: bios function 0x7f
Message-ID: <3767@druhi.ATT.COM>
Date: 14 Dec 88 17:20:37 GMT
References: <12076@hall.cray.com>
Organization: AT&T, Denver, CO
Lines: 22

in article <12076@hall.cray.com>, rosenkra@hall.cray.com (Bill Rosenkranz) says:
> after disassembling a code i found on some bbs which doubles the effective
> on-screen travel of the mouse form, i found it ixecutes bios function 0x7F

	There isn't a bios function 0x7f.  But it is a useful bios call
if you intended to patch the bios handler on the ST.  When the ST bios
or xbios handler receives an illegal function number it returns an error
code and a pointer to the bios/xbios function pointer table.  I believe
it returns the pointer in A0.  You need this pointer if you are going to
have your own code handle the bios/xbios traps. 

	This is a trick Dave Small and I used in the MOUSE program in STart
#2 or #3.  MOUSE kept the mouse out of the menu bar unless you pressed the
right button.



				Dan Moore
				AT&T Bell Labs
				Denver
				dlm@druhi.ATT.COM
					or
				dlm@druwy.ATT.COM