A bitwise operation operates on one or more bit patterns at the level of their individual bits. It is a fast, simple action supported by the ALU (Arithmetic Logic Unit) and is used to manipulate values for comparisons and calculations. The normal operation is simply applied bit by bit.
NOT 0111 ———————— = 1000
NOT 0111 = 1000
when considering only a four-bit word, but in the case of an eight-bit word the correct answer would be:
= 1111 1000
As such, it's usually best to left-pad the operand with zeroes before proceeding. For example,
NOT 0000 0111 = 1111 1000
The AND operation is useful for masking bits that are not interesting and then checking to see if a particular bit is set.
0101 AND 0011 ———————— = 0001
0101 OR 0011 ———————— = 0111
The XOR operation is useful for inverting selected bits:
0101 XOR 0011 ———————— = 0110
Because of this property, XOR is sometimes used to clear a register (to zero) by XOR’ing it with itself. In some cases this can be much faster than explicitly loading the value of 0.
1010 XOR 1010 ———————— = 0000
- M1015-10 Complete Merlin Mission Manager Mission M1015-10.
|Knowledge and skills||§10.326|
|Topic areas||Boolean algebra|
|Classroom time||10 minutes|
|Study time||1 hour60 minutes <br />|
|Acquired knowledge||understand the use of bitwise operations with common Boolean operators|
|Acquired skill||demonstrate proficiency in using bitwise operations with common Boolean operators|