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Bit Test

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This is an old revision of this page, as edited by 50.159.82.22 (talk) at 17:56, 10 December 2013 (The the offset from the least significant bit begins at 0. See Notes section here: http://www.fermimn.gov.it/linux/quarta/x86/bt.htm). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

The BT x86 assembly language instruction stands for Bit Test and was added to the x86 instruction set with the 80386 processor. BT copies a bit from a given register to the carry flag.[1]

Example: copy the third least significant bit from EAX to the carry flag 

BT EAX, 2

BTS (Bit Test and Set) operates the same, but also sets the bit in the register,[2] while BTR (Bit Test and Reset) resets it,[3] and BTC (Bit Test and Complement) flips it.[4]

References

  1. ^ "BT - Bit Test". Retrieved 2011-08-21.
  2. ^ "BTS - Bit Test and Set". Retrieved 2011-08-21.
  3. ^ "BTR - Bit Test and Reset". Retrieved 2011-08-21.
  4. ^ "BTC -- Bit Test and Complement". Retrieved 2012-11-04.
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