Path: utzoo!attcan!lsuc!maccs!cs4g6ag
From: cs4g6ag@maccs.dcss.mcmaster.ca (Stephen M. Dunn)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Keyboard question
Message-ID: <25F9E71E.21473@maccs.dcss.mcmaster.ca>
Date: 11 Mar 90 05:50:22 GMT
References: <1990Mar9.070424.15361@cec1.wustl.edu>
Reply-To: cs4g6ag@maccs.dcss.mcmaster.ca (Stephen M. Dunn)
Distribution: na
Organization: McMaster University, Hamilton, Ontario
Lines: 37

In article <1990Mar9.070424.15361@cec1.wustl.edu> sjw2264@cec2.UUCP (Stephen John Von Worley) writes:
$I am programming a graphical terminal emulation package in TC 2.0, and
$have stumbled upon an interesting problem which someone perhaps can
$help me solve.  When a control-S is typed at the keyboard, program
$execution is halted (exactly as what happens after ctrl-Numlock) until
$another key is hit.  I am using BIOS call 0x16 to read characters; is there
$any easy way to correct this problem and read a ctrl-S when it is pressed?

   The use of ^S to pause display isn't done by the BIOS, and it isn't done
on keyboard reads.  It is done when you output to the screen using a DOS
call (int 21h, assorted functions).  You can stop this behaviour in one
of two ways:

- write to the screen using only int 10h so that DOS never gets its
  hands on the ^S ... this is icky, though, since you'll have to write
  your own routines for outputting strings if you're not running on an AT
  (although it is faster!)

- use a call to IOCTL to put handle 1 (stdout) into raw mode.  This is
  likely what you want to do.  Here's a code fragment from Duncan, 1st
  edition, pg. 351:

	mov	ax, 4400h	; get current device information
	mov	bx, 1		; std output = handle 1
	int	21h		; transfer to DOS
	mov	dh, 0		; force DH = 0 - req'd
	or	dl, 20h		; set raw mode bit
	mov	ax, 4401h	; set current device information
	int	21h		; transfer to DOS

  Raw mode stops DOS from filtering out such nasties as ^P, ^S, and
^C, and also speeds up output.
-- 
Stephen M. Dunn                               cs4g6ag@maccs.dcss.mcmaster.ca
          <std_disclaimer.h> = "\nI'm only an undergraduate!!!\n";
****************************************************************************
    "So sorry, I never meant to break your heart ... but you broke mine."