add ax, dx;    ---> ax = ax+dx

adc ax, dx;    ---->ax = ax+dx+carry(進位)

sub ax, dx;  ----> ax = ax - dx

sbb ax, dx; ------> ax = ax - dx - carry

assume cs:code, ds:data, ss:stack

data segment
	db 128 dup(0)
data ends

stack segment
	db 128 dup(0)
stack ends

code segment
	start:	mov dx, stack
		mov ss, dx
		mov sp, 128

		mov ax, 0FFFFH
		mov dx, 1000H

		add ax, 0FFFFH
		adc dx,0
	

		mov ax, 4C00H
		int 21H

code ends

end start