Bitwise Operations
Prerequisites[edit]
Bitwise Operations[edit]
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[edit]
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
AND[edit]
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
OR[edit]
0101 OR 0011 ———————— = 0111
XOR[edit]
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