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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

  • In low-level programming, you often use an integer to represent a collection of single bit fields, or fields that are only a few bits wide.  The bit-wise operators are useful for checking the values of those fields or changing individual bits.  A good example in GNU/Linux is the "file mode" field that represents permissions as a bit vector, often shown in octal.  For example, "0664" = 110.110.100 means that the file is readable and writable by its owner and its group, but to the world it's read-only.

     

    Data communications protocols often use individual bits and short fields in headers for various control purposes.

     

    Bit-wise AND and OR are often used for device registers, where individual bits may represent the values of GPIO inputs or outputs.

     

    Bit-wise XOR is often used for making linear-feedback shift registers, which may be used as pseudo-random number generators.

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  • In low-level programming, you often use an integer to represent a collection of single bit fields, or fields that are only a few bits wide.  The bit-wise operators are useful for checking the values of those fields or changing individual bits.  A good example in GNU/Linux is the "file mode" field that represents permissions as a bit vector, often shown in octal.  For example, "0664" = 110.110.100 means that the file is readable and writable by its owner and its group, but to the world it's read-only.

     

    Data communications protocols often use individual bits and short fields in headers for various control purposes.

     

    Bit-wise AND and OR are often used for device registers, where individual bits may represent the values of GPIO inputs or outputs.

     

    Bit-wise XOR is often used for making linear-feedback shift registers, which may be used as pseudo-random number generators.

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