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From: dlm@druwy.ATT.COM (Dan Moore)
Newsgroups: comp.sys.atari.st
Subject: Re: Atari ST Screen Dump Info Sought
Message-ID: <3856@druwy.ATT.COM>
Date: 6 Mar 89 16:16:20 GMT
References: <3292@hermes.ai.mit.edu>
Organization: AT&T, Denver, CO
Lines: 21

in article <3292@hermes.ai.mit.edu>, jpexg@hermes.ai.mit.edu (John Purbrick) says:
>> ... for the Atari Laser Printer (SLM804) there's a screen dumper that
>> steals the Alt-Help and outputs the correct data over the DMA to print
>> to the laser printer...
>> --Kenneth Soohoo	(soohoo@cory.Berkeley.Edu)
> 
> How does a program do this? Presumably terminate-and-stay-resident, but how
> does it intercept keypresses?

	You don't have to intercept the keypress data.  There is a
documented low memory vector to the screen dump routine.  All you need
to do is take over that vector, whenever the user presses Alt-HELP your
code will be run.  Check the "Hitch Hiker's Guide to the BIOS", it has
the official list of low memory vectors and variables.


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