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What are bitwise operators?

Asked 2008-11-09T23:59:26.307
137

I'm someone who writes code just for fun and haven't really delved into it in either an academic or professional setting, so stuff like these bitwise operators really escapes me.

I was reading an article about JavaScript, which apparently supports bitwise operations. I keep seeing this operation mentioned in places, and I've tried reading about to figure out what exactly it is, but I just don't seem to get it at all. So what are they? Clear examples would be great! :D

Just a few more questions - what are some practical applications of bitwise operations? When might you use them?

boolean language-agnostic bitwise-operators boolean-logic
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Bitwise operators are operators that work on a bit at a time.

AND is 1 only if both of its inputs are 1.

OR is 1 if one or more of its inputs are 1.

XOR is 1 only if exactly one of its inputs are 1.

NOT is 1 only if its input are 0.

These can be best described as truth tables. Inputs possibilities are on the top and left, the resultant bit is one of the four (two in the case of NOT since it only has one input) values shown at the intersection of the two inputs.

AND|0 1      OR|0 1
---+----    ---+----
  0|0 0       0|0 1
  1|0 1       1|1 1

XOR|0 1     NOT|0 1
---+----    ---+---
  0|0 1        |1 0
  1|1 0

One example is if you only want the lower 4 bits of an integer, you AND it with 15 (binary 1111) so:

    203: 1100 1011
AND  15: 0000 1111
------------------
 IS  11: 0000 1011
answered 2008-11-10T00:04:28.373

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