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Code:MOV AX, 0 ; AX = 0
MOV AL, 0 ; AL = 0
MOV AH, 0 ; AH = 0
MOV AL, FFh ; AL = FFh
; AX = 00FFh
; AH = 00h
;I understand up to here
INC AX ; AX = AX + 1
; AX = 0100h
; AH = 01h
; AL = 00h
;but not this. I thought that:
; since AL (FFh) + 1 = 100
; and AH (00h) +1 = 01h
; that AH|AL would be 01|100, but it should be 0100h. What am I missing?
It's a little bit confusing, but AX is not an independent register but only the merger of AH and AL.Code:Since AH and AL form the AX register together you have
; start
mov ax, 0
; AX: 00 00h
; AH AL
mov al, 0
mov ah, 0
; those were both redundant, since they are already 0
mov al, FFh
; AX: 00 FFh
; AH AL
inc ax
; AX: 01 00h
; AH AL
; AL cannot hold more than FFh
Has this been resolved?
I think it has, but I never heard from the poster again.