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From: lotto@wjh12.HARVARD.EDU (Jerry Lotto)
Newsgroups: comp.sys.ibm.pc
Subject: ^PrtSc handler is a mystery to me
Message-ID: <79@wjh12.HARVARD.EDU>
Date: Fri, 26-Jun-87 10:01:35 EDT
Article-I.D.: wjh12.79
Posted: Fri Jun 26 10:01:35 1987
Date-Received: Sat, 27-Jun-87 09:22:29 EDT
Reply-To: lotto@wjh12.UUCP (Jerry Lotto)
Organization: Harvard Univ. Chem. Dept.
Lines: 19
Keywords: control PrtSc

I had to write a few procedures for someone recently that did, among
other things, a toggle of the ^PrtSc style printer echo without any
keyboard input. I never realized just how barren the DOS documentation
could be on a topic! I found a minor ref. to it in the keyboard handler
BIOS listing and a ref. under the extended scan codes tables. That's
it. I resorted to sticking the key-code into the active keyboard buffer
by hand, but this is not emotionally satisfying (although it works).

Who knows the mechanism that DOS (x.y) uses for printer echo?
A memory dump state diff. between the two was not helpful, although
the mechanism might be invisible with redirected output. Nothing
in the video driver that I found helped. The printer was out of the
reach of anyone in the room at the time!

Thanks in advance for some insight into this.
-- 
Gerald Lotto - Harvard Chemistry Dept.
UUCP:  {seismo,harpo,ihnp4,linus,allegra,ut-sally}!harvard!lotto
ARPA:  lotto@harvard.harvard.edu