Unregistered
October 16th, 2001, 16:53
How to revers the statement 'AND'
ex. AND EDI,7F in this case edi=1398C and the answer =C
How to get EDI if i have C and 7F ??
Fake51
October 16th, 2001, 18:38
You don't
Fake
Unregistered
October 16th, 2001, 18:43
'AND' is not completely reversible, because it loses some information. only the bits that were '1' in the known operand are recoverable, while the information the bits that were 0 are lost.
Example
0110 ox6 and
1101 oxD
-------------
0100 ox4
if you know the result, ox4 and one of the operands, oxD, you know that the other operand has the binary form 01?1, which reduces the universe of choice quite a bit: either 0101 or 0111
But if the operand you know is 0000, the other operand cand be any thing, from 0000 to 1111. I am using 4 bit numbers for sake of clarity in this example.
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