.386
CODE SEGMENT USE16
	ASSUME CS:CODE,SS:STACK
	OLD_INT0  DW ?,?;原INT 16H的中断矢量
;新的16号中断代码
NEW16H:
	PUSHF
	CMP AH,0H
	JZ CHULI
	CMP AH,10H
	JZ CHULI
	CALL DWORD PTR CS:OLD_INT0
	JMP EEND
CHULI:
	CALL DWORD PTR CS:OLD_INT0
	CMP AL,'A'
	JZ INCA
	CMP AL,'B'
	JZ DECB
	JMP EEND
EEND:
	IRET
INCA:
	INC AL
	JMP EEND
DECB:
	DEC AL
	JMP EEND
;主程序
BEGIN:
	MOV AX,0
	MOV DS,AX
	MOV AX,3516H
	INT 21H
	MOV OLD_INT0,BX
	MOV OLD_INT0+2,ES
	MOV DX,OFFSET NEW16H
	CLI
	MOV WORD PTR DS:[16H*4],OFFSET NEW16H
	MOV DS:[16H*4+2],CS
	STI
	MOV DX,OFFSET BEGIN+15
	SHR DX,4
	ADD DX,10H
	MOV AL,0
	MOV AH,31H
	INT 21H
CODE ENDS
STACK SEGMENT USE16 STACK
	DB 200 DUP(0)
STACK ENDS
END BEGIN