Article View: comp.sys.atari.st
Article #36930Re: Atari ST Screen Dump Info Sought
From: Dan Moore
Date: Mon, 06 Mar 1989 16:16
Date: Mon, 06 Mar 1989 16:16
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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
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arc1-ca.pugleaf.net!utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!wasatch!cs.utexas.edu!rutgers!att!mtuxo!mtgzz!drutx!druwy!dlmReferences:
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!wasatch!cs.utexas.edu!rutgers!att!mtuxo!mtgzz!drutx!druwy!dlm 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