Boolean algebra or bitwise operations are necessary in low-level programming since it can perform simple calculations by changing the bits of a number. It is commonly used in cryptography's obfuscation and decoding.

NOT

This operation reverses the bits.

Consider the following as an example: NOT AL

If AL equals 1010101b (55h), it becomes 10101010b (AAh).

AND

This operation sets bit to 1 if both are 1s, otherwise it sets bit to 0.

Consider the following as an example: AND AL, AH

If AL equals 10111010b (BAh) and AH equals 11101101b (EDh), AL becomes 10101000b (A8h).

OR

This operation sets bit to 0 if both are 0s, else it sets bit to 1.

Consider the following as an example: OR AL, AH

If AL equals 10111010b (BAh) and AH equals 11101100b (ECh), AL becomes 11111110b (FEh).

XOR

This operation sets bit to 0 if both bits are equal, else it sets bit to 1.

Consider the following as an example: XOR EAX, EAX

XOR-ing the same value will become 0. Thus EAX becomes 0:

XOR AH, AL

If AH were 100010b (22h) and AL were 1101011b (6Bh), AH becomes 1001001b (49h).

SHL/SAL

This operation shifts bits to the left.

Consider the following as an example: SHL AL, 3

If AL were 11011101b (DDh), shifting it to the left by 3 makes AL equal to 11101000b (E8h).

SHR/SAR

This operation shifts bits to the right.

Consider the following as an example: SHR AL, 3

If AL were 11011101b (DDh), shifting it to the right by 3 makes AL equal to 011011b (1Bh).

ROL

This operation rotates bits to the left.

Consider the following as an example: ROL AL, 3

if AL were 11011101b (DDh), rotating it to the left by 3 makes AL equal to 11101110b (EEh).

ROR

This operation rotates bits to the right.

Consider the following as an example: ROR AL, 3

If AL were 11011101b (DDh), rotating it to the right by 3 makes AL equal to 10111011b (BBh).