ADDEXT:		LAHF
		XOR AL, AL
		MOV CX, 40H
		CLD
	REPNZ	SCASB
		JNZ ADDXT0
		NEG CX
		ADD CX, 3FH
		DEC DI
		MOV BP, DI
		DEC DI
		MOV AL, 2EH
		STD
	REPNZ	SCASB
		JNZ ADDXT2
		SAHF
		JNC ADDXT0
		MOV BP, DI
		INC BP
ADDXT2:		MOV DI, BP
		CLD
		SAHF
		JC ADDXT1
		STOSB
		MOV CL, [SI]
		XOR CH, CH
		INC SI
	REPZ	MOVSB
ADDXT1:		XOR AL, AL
		STOSB
ADDXT0:		RET
