XCHG instruction: load register AX with a 1


In the XCHG instruction, why would be load register AX with a 1 prior to excution of XCHG - is this

- to insure that the "Flag" variable will be set to 1 after the XCHG or

- the XCHG instruction will not work unless a 1 is loaded into AX before executing the XCHG instruction ?


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None of those.

It is to ensure that your local effective address as stored in DX doesn't overload your carry flag.

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Sorry buddy, I am not falling for it this time.


Reply to
Isaac Bosompem

Don't listen to the other guys, they are trying to trick you. You should load EAX with 0x01010101, then the flag will be correctly set to 1 irrespectively of the endian setting.


Reply to
Wilco Dijkstra

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