; By Steve Holzner (from June 11, 1985 issue of PC Magazine)interrupts	segment at 0h	; This is where the disk interrupt	org	13h*4		; holds the address of its service routinedisk_int	label	dwordinterrupts	endsscreen	segment at 0B000h	; A dummy segment to use as the Extrascreen	ends			; Segment so we can write to the displaycode_seg	segment	assume	cs:code_seg	org	0100h		; ORG = 100h to make this a .COM filefirst:	jmp	load_watch	; First time through jump to initialize routine	msg_part_1	db	'Disk error: '	; Here are the error messages	msg_part_2	db	'No response Failed Seek NEC Error   '			db	'Bad CRC SeenDMA Overrun Impos Sector'			db	'No Addr MarkW. ProtectedErr Unknown '	first_position	dw	?		; Position of 1st char on screen	flags		dw	?	screen_seg_offset dw	0		; 0 for mono, 8000h for graphics	old_disk_int	dd	?		; Location of old disk interrupt	ret_addr	label dword		; Used in fooling around with	ret_addr_word	dw 2 dup(?)		;   the stackdisk_watch	proc	far	; The disk interrupt will now come here	assume	cs:code_seg	pushf			; First, call old disk interrupt	call	old_disk_int	pushf			; Save the flags in memory location "FLAGS"	pop	flags		; (cunning name)	jc	error		; If there was an error, carry flag will have	jmp	fin		;  been set by Disk Interrupterror:	push	ax		; AH has the status of the error	push	cx		; Push all used registers for politeness	push	dx	push	di	push	si	push	es	lea	si,msg_part_1	; Always print "Disk Error: " part.	assume	es:screen	; Use screen as extra segment	mov	dx,screen	mov	es,dx	mov	di,screen_seg_offset	; DI will be pointer to screen position	add	di,first_position	; Add to point to desired area on screen	call	write_to_screen		; This writes 12 chars from [SI] to [DI]	mov	dx,80h			; Initialize for later comparisons	mov	cx,7			; Loop seven timese_loop:	cmp	ah,dh			; Are error code and DH the same?	je	e_found			; If yes, Error has been found	add	si,12			; Point to next error message	shr	dh,1			; Divide DH by 2	loop	e_loop			; Keep going until matched  DH = 0	cmp	ah,3			; Error code no even number; 3 perhaps?	je	e_found			; If yes, have found the error	add	si,12			; Err unknown; unknown error returnede_found:call	write_to_screen		; Write the error message to the screen	pop	es		; Restore the registers	pop	si	pop	di	pop	dx	pop	cx	pop	axfin:	pop	ret_addr_word		; Fooling with the stack. We want to	pop	ret_addr_word[2]	; preserve the flags but the old flags	add	sp,2			; are still on the stack. First remove	push	flags			; return address, then flags. Fill flags	popf				; from "FLAGS", return to correct addr.	jmp	ret_addrdisk_watch	endpwrite_to_screen	proc	near	; Puts 12 characters on screen	mov	cx,12		; Loop 12 timesw_loop:	movs	es:byte ptr[di],cs:[si] ; Move to the screen	mov	al,7		; Move screen attribute into screen buffer	mov	es:[di],al	inc	di		; Point to next byte in screen buffer	loop	w_loop		; Keep going until done	retwrite_to_screen	endpload_watch	proc	near	; This procedure initializes everything	assume	ds:interrupts	; The data segment will be the interrupt area	mov	ax,interrupts	mov	ds,ax	mov	ax,disk_int	; Get the old interrupt service routine	mov	old_disk_int,ax	; address and put it into our location	mov	ax,disk_int[2]	; OLD_DISK_INT so we can call it.	mov	old_disk_int[2],ax	mov	disk_int,offset disk_watch  ; Now load the address of DskWatch	mov	disk_int[2],cs		; routine into the disk interrupt	mov	ah,15		; Ask for service 15 of INT 10h	int	10h		; This tells us how display is set up	sub	ah,25		; Move to twenty five places before edge	shl	ah,1		; Mult. by two (char & attribute bytes)	mov	byte ptr first_position,ah	; Set screen cursor	test	al,4		; Is it a monochrome display?	jnz	exit		; Yes - jump out	mov	screen_seg_offset,8000h	; No, set up for graphics displayexit:	mov	dx,offset load_watch	; Set up everything but this program to	int	27h			; stay and attach itself to DOSload_watch	endp	code_seg	ends	end	first	; END "FIRST" so 8088 will go to FIRST first.