Exorcise and bicycle orr… #

Now that you have started thinking about the individual bits that make up the data that you work with on a daily basis, there are a couple of operations that allow you to do this easily.

AND operation #

AND allows you to create a value that displays where both bits are set.

The syntax is:

    and     Rd, Rn, op2 @ Rd = destination, Rn = first value  

BIC operation #

The BIC performs an AND on a value and the bitwise NOT of the second value.

The syntax is:

    bic     Rd, Rn, op2 @ Rd = destination, Rn = first value   

ORR operation #

This is a fairly easy operation that works as a logical OR. If either bit is set, then the resulting bit set will have the bit set.

    orr     Rd, Rn, op2 @ Rd = destination, Rn = first value   

EOR operation #

I try not to write in first person much, but this is my favorite operation. The exclusive or or XOR has some cool properties. This will set a bit if only one bit of the pair is set.

This is used in many different places in computing checksums, cryptography, random number generators, uniqueness detection…