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how does 16 bit register works ?


kb432

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what is moving something to cl or ax or dl ? 

what does it mean ? i know it's 16 bit register. Can anyone give me an example so i understand better ? 

Thanks 

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EAX is a 32bit register, but you can still access the last 16 bits (compatibility etc)

EAX is the full 32-bit value
AX is the lower 16-bits
AL is the lower 8 bits
AH is the bits 8 through 15 (zero-based)

e.g.

EAX   BADC0DE5

AX               0DE5

AH               0D

AL                   E5

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mrexodia

Watch out with RAX, it doesn't work in the same way as subregisters for EAX. If you do "mov eax,12345678" in x64, you will get "RAX = 12345678 & 0xFFFFFFFF", effectively clearing the upper part of RAX.

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CodeExplorer

CodeCracker never said that! :D:P

SHR r/m8 = Unsigned divide r/m8 by 2, 1 time.
If EAX = BADC0DE5 and you want BADC
you divide EAX to 2^16 = 65536 ( SHR is divide by power of two).

Edited by CodeCracker (see edit history)
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