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From: chiang@iris.ucdavis.edu (Tom Chiang)
Newsgroups: comp.os.msdos.programmer
Subject: TSR PROGRAMMING PROBLEM
Summary: WHAT'S WRONG WITH THIS CODE?
Message-ID: <8256@ucdavis.ucdavis.edu>
Date: 29 Jan 91 10:37:20 GMT
References: <1991Jan24.210122.5363@usenet@scion.CS.ORST.EDU> <1991Jan26.195955.12946@ugle.unit.no> <1991Jan26.220820.7855@uwasa.fi>
Sender: usenet@ucdavis.ucdavis.edu
Reply-To: chiang@iris.ucdavis.edu (Tom Chiang)
Organization: U.C. Davis - Department of Electrical Engineering and Computer Science
Lines: 72


following below is asm code for a tsr with a few lines added by me...
the tsr basically intercepts int 16 and changes the case of the
letter Y whenever it it is typed....now, i added code to send the 
letter z to printer every time this int occured...but my system
crashes from those new
lines...any help would be appreciated


PAGE 64,132
cseg	segment
		assume	cs:cseg,ds:cseg
		org	100H
TSR		proc far

	jmp	initialize

old_keyboard_io	dd	0

new_keyboard_io		proc far
	assume	cs:cseg,ds:cseg
	sti
	cmp	ah,0
	je	ki0
	assume	ds:nothing
	jmp	old_keyboard_io
ki0:
	pushf
	assume	ds:nothing
	call	old_keyboard_io

	cmp	al,'y'
	jne	ki1
	mov	al,'Y'
	jmp	kidone
ki1:
	cmp	al,'Y'
	jne	kidone
	mov	al,'y'
kidone:
	push dx ----- 
	push ax     | 
	mov dl,'z'  |
	mov ah,5H   | ----- these are the instructions i added
	int 21H     |
	pop ax      |
	pop dx ------
	iret
new_keyboard_io		endp

initialize:
	assume	cs:cseg,ds:cseg
	mov	bx,cs
	mov	ds,bx

	mov	al,16H
	mov	ah,35H
	int	21H
	mov si,offset old_keyboard_io
	mov [si],bx
	mov [si+2],es
	mov	dx,offset new_keyboard_io
	mov	al,16H
	mov	ah,25H
	int	21H

	mov	dx,offset initialize
	int	27H
TSR	endp

cseg	ends
end		TSR