🚀 go-pugleaf

Here is a TSR I wrote some time back that switches the ESC, backspace,
and `/~ keys on an 84-key keyboard.  It works by hooking into the key-
stroke interrupt vector (09h) and modifying the BIOS typeahead buffer
before any other program has a chance to see what was originally put
there by the BIOS' keyboard routine.

I wrote this because I was losing my mind trying to cope with the dif-
ferences between my clone's keyboard at home and my Sun-3/50's keyboard
at school.  With this program (and after rearranging the relevant key
caps at home), the main set of keys are the same on both keyboards.

Load this TSR as early as possible in your AUTOEXEC.BAT file.

This program doesn't use Int 15h function 4Fh, so it should work on any
XT-type machine.  On the other hand, it assumes that each keystroke puts
at most one entry into the typeahead buffer -- so it won't work with an
"extended" keyboard that represents some keys with two buffer entries.

Note that the program needs to look at the status of the "shift" keys in
order to tell how to map the backspace key (~ if shifted, ` if not).  I
was unable to figure out any way to address this issue via the keyboard
remapping facilities of an ANSI console driver; hence this TSR.

I'd welcome any comments on this program.

-- Rich Wales <wales@CS.UCLA.EDU> // UCLA Computer Science Department
   3531 Boelter Hall // Los Angeles, CA 90024-1596 // +1 (213) 825-5683
   "I never lie when I've got sand in my shoes, Commodore."

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begin 644 kb84fix.com
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M8"EU!L<'&P'K'8'Z?BET]('Z"`YU$?8&%P`#=0;'!V`IZP3'!WXI'UI;6,\S
CP([8H20`+J,``:$F`"ZC`@'ZN`0!HR0`C,BC)@#[NED!S2?'
`
end

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

; ======================================================================
;
;	KB84FIX.ASM
;
;	(C) Copyright 1990 Richard B. Wales <wales@CS.UCLA.EDU>
;	May be distributed and used freely, so long as the original
;	source is included in any distribution, no charge (other than
;	a nominal communications or handling charge) is assessed, and
;	this notice is retained intact.
;
;	This TSR hooks into Int 9H and switches the BKSP, ESCAPE, and
;	Tilde/Grave keys on an 84-key keyboard.  It needs to be loaded
;	as early as possible -- before any other TSR's that hook into
;	the Int 9H vector.
;
;	I wrote this program because I wanted the keys on the top row
;	of my home "clone" system to be arranged in the same way as on
;	the Sun 3/50 workstation I use at school.  I pried off the caps
;	for the three keys in question; this TSR intercepts the key-
;	strokes and makes the keys generate the characters on the caps.
;
;	This program should be readily adaptable to other applications
;	that need to swap keys (e.g., a Dvorak keyboard mapper) or
;	otherwise manipulate the BIOS keystroke buffer.  Note, however,
;	that I assume each keystroke will result in at most one entry
;	being placed in the BIOS buffer; hence, this program would have
;	to be modified somewhat to work with an "extended" keyboard.
;
;	Assembled using Microsoft Assembler (MASM) version 5.1.  After
;	assembly and linkage, use EXE2BIN to convert the program into a
;	.COM file.
;
; ======================================================================

; Segment 0000H (interrupt vectors)
INTVECS	segment	at 0000H
	org	24H
int9vec	dw	?		; Interrupt vector 09H
	dw	?
INTVECS	ends

; Segment 0040H (BIOS data area)
BIOSDTA	segment	at 0040H
	org	17H
kbflags	db	?		; Keyboard flags
	org	1CH
buftail	dw	?		; Tail pointer (character buffer)
BIOSDTA	ends

; Shift-key mask for kbflags
SHFTMSK	equ	03H		; look for left and/or right shift key

; Character codes we are interested in changing
ESCAPE	equ	011BH		; escape
BKSP	equ	0E08H		; backspace
GRAVE	equ	2960H		; grave accent
TILDE	equ	297EH		; tilde

; ======================================================================

CODESEG	segment
	assume	cs:CODESEG, ds:BIOSDTA
	org	100H

; Buffer to hold address of original system Int 9H
; (will overlay the "jmp" at the start of the program)
oldint9	label	dword

begin:	jmp	short init	; Will be overlaid by "oldint9" value
	dw	0		; ditto

; New Int 9H handler
newint9	proc	far

	; Save the registers we'll be playing with
	push	ax
	push	bx
	push	dx
	push	ds

	; Establish the BIOS segment register for accessing BIOS data
	mov	ax, seg BIOSDTA
	mov	ds, ax

	; Get the tail pointer to the character buffer
	mov	bx, [buftail]

	; Call the original (BIOS) Int 9H routine first, and
	; let it put a new character into the circular buffer
	pushf
	call	[oldint9]

	; Did the BIOS routine add a character to the buffer?
	; If so, copy it into a register so we can examine it
	cmp	bx, [buftail]
	je	short done
	mov	dx, [bx]

	; Check for the four codes of interest, and switch them around

	; ESCAPE -> BKSP
	cmp	dx, ESCAPE
	jne	short notesc
	mov	[bx], BKSP
	jmp	short done
notesc:

	; (GRAVE or TILDE) -> ESCAPE
	cmp	dx, GRAVE
	jne	short notgrv
makesc:	mov	[bx], ESCAPE
	jmp	short done
notgrv:	cmp	dx, TILDE
	je	short makesc

	; BKSP -> GRAVE (if unshifted) or TILDE (if shifted)
	cmp	dx, BKSP
	jne	short done
	test	byte ptr kbflags, SHFTMSK
	jnz	short shift
	mov	[bx], GRAVE
	jmp	short done
shift:	mov	[bx], TILDE

	; All done.
done:	pop	ds
	pop	dx
	pop	bx
	pop	ax
	iret
newint9	endp

; ======================================================================

; TSR initialization code

init:
	assume	ds:INTVECS

	; Establish a zero segment register for interrupt vector area
	xor	ax, ax
	mov	ds, ax

	; Save the old Int 9H pointer
	mov	ax, [int9vec]
	mov	word ptr oldint9, ax
	mov	ax, [int9vec+2]
	mov	word ptr oldint9[2], ax

	; Hook in the new Int 9H handler
	cli
	mov	ax, offset newint9
	mov	[int9vec], ax
	mov	ax, cs
	mov	[int9vec+2], ax
	sti

	; Exit via a TSR call
	mov	dx, offset init
	int	27H

CODESEG	ends
	end	begin

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

-- Rich Wales <wales@CS.UCLA.EDU> // UCLA Computer Science Department
   3531 Boelter Hall // Los Angeles, CA 90024-1596 // +1 (213) 825-5683
   "Then they hurl heavy objects. . . .  And claw at you. . . ."