im sure i asked that before, but google wont index this site and i cant find it using search.php.


i have 32 bits:

a rd 1


and i want to use all bits like bool variables.


bt [a],0 - bt [a],31 thats testing, bit will copy to CF

and now i want to set [a],0
how?

Since you already know BT, read also about BTS/BTR/BTC.

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All BT/BTC/BTS/BTR put the bit value in the carry flag - this is the "test". There is no single instruction to swap the carry flag and another bit. IIRC, there is a binary math trick to swap bits requiring two instructions, but no branch.

no, that means complement.
com1=0
com0=1

and this subject is still aborded on the board many times.

asmcoder,

How about good old or [a],1?

btx family is good for bit manipulation at an arbitrary bit index (they support register operand as bit index), for fixed bit index test, and, or & xor are somewhat better (proper coding ensures that you won't access word[0xFFFF] in 16-bit RM ), though barely equivalent (btx, you see).

By the way, IA-32 (2003 A.D.) and Intel® 64 (April 2008, maybe 1st ) ASDMs in vol. 2 both insist that with btx you can index 16 bits using only 3 bits (32 bits' indices are correctly stated as 5 bits wide).