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Why use bitwise OR / AND

Former Member

I have been programming for over an year now. I still don't get why bitwise OR and AND operators are used. They seem to return random numbers.

What mathematical purpose do they have?

Parents

  • It can seem this way if your looking at the values as decimal or hex

     

    These operations are a binary operation so it works on ones and zeroes

     

    For example the decimal number 15 is 0F in hex or 00001111 in binary

     

    If I and 16 with 4 I will get 4, why well consider the binary value

     

    0000 1111 <-- 16

     

    0000 0100 <-- 4

     

    Only where the ones align will you have a 1 left in the answer, therefor you get 00000100 or 4

     

    It can appear random if your looking at the number in decimal

     

    Now the opersit is more confusing

     

    Given

     

    01010011 <-- 83 anded  with

     

    10010101 <-- 149 results in

     

    00010001 <-- 17

     

    Looking at this in decimal would be really confusing but looking at it in binary it makes perfect sense. So again only where the ones match are you left with a one. With the OR operator it wirks that you get a one where ever there is a one on either or both sides (But no carry)

     

    So

     

    10101010 OR

     

    01010101 =

     

    11111111

     

     

     

    Then again

     

    11110000 OR

     

    00000000 =

     

    11110000

     

    Hope that clarifies the issue

     

    Also the binary notation has values like this

     

    128, 64, 32, 16, 8, 4, 2, 1 and to get to the decimal just add up where each bit has a one aligned with it

Reply

  • It can seem this way if your looking at the values as decimal or hex

     

    These operations are a binary operation so it works on ones and zeroes

     

    For example the decimal number 15 is 0F in hex or 00001111 in binary

     

    If I and 16 with 4 I will get 4, why well consider the binary value

     

    0000 1111 <-- 16

     

    0000 0100 <-- 4

     

    Only where the ones align will you have a 1 left in the answer, therefor you get 00000100 or 4

     

    It can appear random if your looking at the number in decimal

     

    Now the opersit is more confusing

     

    Given

     

    01010011 <-- 83 anded  with

     

    10010101 <-- 149 results in

     

    00010001 <-- 17

     

    Looking at this in decimal would be really confusing but looking at it in binary it makes perfect sense. So again only where the ones match are you left with a one. With the OR operator it wirks that you get a one where ever there is a one on either or both sides (But no carry)

     

    So

     

    10101010 OR

     

    01010101 =

     

    11111111

     

     

     

    Then again

     

    11110000 OR

     

    00000000 =

     

    11110000

     

    Hope that clarifies the issue

     

    Also the binary notation has values like this

     

    128, 64, 32, 16, 8, 4, 2, 1 and to get to the decimal just add up where each bit has a one aligned with it

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