Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!clyde.concordia.ca!uunet!samsung!brutus.cs.uiuc.edu!jarthur!bridge2!mbt
From: mbt@bridge2.ESD.3Com.COM (Brad Turner)
Newsgroups: comp.binaries.ibm.pc.d
Subject: Re: C/Utilities Toolchest (MIX Software)
Summary: clearing the Application Communication Area
Keywords: unix, msdos
Message-ID: <1141@bridge2.ESD.3Com.COM>
Date: 11 Dec 89 19:00:06 GMT
References: <5678@cps3xx.UUCP> <1045@kosman.UUCP> <5720@cps3xx.UUCP>
Organization: 3Com Corp., Mt. View, CA
Lines: 75

In article <5720@cps3xx.UUCP>, usenet@cps3xx.UUCP (Usenet file owner) writes:
> I have found the problem with the C/Utilities Toolchest and BRIEF.  The
> problem lies only in how the two programs interact.  Both programs use
> memory location 004F1.
> 
> I have written a small program which I can run after I run the BRIEF
> editor that solves this problem.

So have I. Between the ---cut here--- lines are the input lines to DOS debug
that will create a short little program that will write 16 NULs starting
at 0000:04F0, hence zeroing out the Application Communication Area. I ran
into the same problems on a 3Com diskless workstation. It turns out that
the Network boot service uses that area, but doesn't clean it out after
boot up. I'm posting this since it is so trivial and ``source'' is included.

Save this article and snip out the section between the cut here lines.
Then feed the lines to DOS debug (e.g. C:\> debug < input ). This should
create an executable named CLACA.COM which is 34 bytes long. Below in the
----output section---- is what debug will echo to your screen as it is running.

Be forewarned!! CLACA is simple and stupid, it just zaps 16 bytes in memory.
It has taken me longer to post this article that it took to create CLACA.COM.
If you are running some application that expects this area to set to
something special, you probably should not be running this program.

enjoy,
-brad-

-------------cut here---------cut here----------------------------
nclaca.com
e cs:0100  B8 00 00 8E D8 A3 F0 04 A3 F2 04 A3 F4 04 A3 F6
e cs:0110  04 A3 F8 04 A3 FA 04 A3 FC 04 A3 FE 04 B8 00 4C 
e cs:0120  CD 21
u cs:100 l 22
r bx   
0000
r cx
0022
w
q
-------------cut here---------cut here----------------------------
------------------output section----------------------------------
-nclaca.com
-e cs:0100  B8 00 00 8E D8 A3 F0 04 A3 F2 04 A3 F4 04 A3 F6
-e cs:0110  04 A3 F8 04 A3 FA 04 A3 FC 04 A3 FE 04 B8 00 4C
-e cs:0120  CD 21
-u cs:100 l 22
23BD:0100 B80000        MOV	AX,0000                            
23BD:0103 8ED8          MOV	DS,AX                              
23BD:0105 A3F004        MOV	[04F0],AX                          
23BD:0108 A3F204        MOV	[04F2],AX                          
23BD:010B A3F404        MOV	[04F4],AX                          
23BD:010E A3F604        MOV	[04F6],AX                          
23BD:0111 A3F804        MOV	[04F8],AX                          
23BD:0114 A3FA04        MOV	[04FA],AX                          
23BD:0117 A3FC04        MOV	[04FC],AX                          
23BD:011A A3FE04        MOV	[04FE],AX                          
23BD:011D B8004C        MOV	AX,4C00                            
23BD:0120 CD21          INT	21                                 
-r bx 
BX 0000
:0000
-r cx
CX 0022
:0022
-w
Writing 0022 bytes
-q
------------------output section----------------------------------


-- 
v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v^v
Brad Turner |2081 Shoreline Blvd.|(415) 969-2099 ext 217  | I speak for myself
3Com Corp.  |Mtn. View, CA 94043 |mbt@bridge2.ESD.3Com.Com| NOT for my employer