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From: tsc2597@acf4.UUCP (Sam Chin)
Newsgroups: net.micro.pc
Subject: Re: Questions on Interrupts and DOS
Message-ID: <1050030@acf4.UUCP>
Date: Wed, 8-May-85 18:11:00 EDT
Article-I.D.: acf4.1050030
Posted: Wed May  8 18:11:00 1985
Date-Received: Fri, 10-May-85 09:05:22 EDT
References: <79@tekig5.UUCP>
Organization: New York University
Lines: 21

<>

>In addition, all the function keys, the unshifted keypad keys, and alt-key
>combinations return an ascii value of 0.  Their interpretation depends
>exclusively upon the "extended" code returned in the ah register (in place
>of their scan code).  Thus, the only way to handle programs that have
>special bells and whistles bound to specific PC keys is to create a
>translate table that will take the output of your Dos 7/6 calls and
>construct an IBM { scan code | extended code }, ascii value result.

I'm not sure if the extended code is returned in the ah register but the
standard way to read an extended code is to issue the read (function 1,6,7
or 8) again if the first result is 0. ie.

       if (0 == (c = getchar()))
           extended_code = getchar();

This is documented in the DOS 2.0 reference manual Appendix D-17 bottom note.
Sam Chin
allegra!cmcl2!acf4!tsc2597
tsc2597.acf4@nyu