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; Install a custom Interrupt 1b (Ctrl-Break exception) handler

;

; Public domain by Bob Stout

;

; Requires MASM 5.1 or later or equivalent

;

; Assemble with: MASM /Mx /z ...

; TASM /jMASM /mx /z ...

% .MODEL memodel,C ;Add model support via command

;line macros, e.g.

;MASM /Dmemodel=LARGE

.DATA?

_origvec dd ?

.DATA

public cbrcvd

cbrcvd dw 0

.CODE

;

; This is our actual ISR

;

myint1b:

mov ax,-1

mov cbrcvd,ax

iret

;

; Call this to install our ISR

;

ins1b PROC USES AX BX DS ES

mov ax,351bh ;get old vector...

int 21h

mov word PTR _origvec,bx

mov word PTR _origvec+2,es ;...and save it

push cs ;get myint1b segment in DS

pop ds

mov dx, OFFSET myint1b ;install myint1b in int 1bh

mov ax,251bh

int 21h

ret

ins1b ENDP

;

; Call this to uninstall our ISR

;

redo1b PROC USES AX BX DS

mov dx, word PTR _origvec ;restore original vector

mov ds, word PTR _origvec+2

mov ax,251bh

int 21h

ret

redo1b ENDP

end