What are logical instructions in assembly language?

By: Rajesh P.S.

Logical instructions in assembly language perform bitwise operations and logical comparisons on binary data.

Bitwise AND (and)

Performs a bitwise AND operation between corresponding bits of two operands.

mov eax, 1010b ; EAX = 1010 in binary and eax, 1100b ; EAX = EAX AND 1100 (result: 1000)

Bitwise OR (or)

Performs a bitwise OR operation between corresponding bits of two operands.

mov eax, 1010b ; EAX = 1010 in binary or eax, 1100b ; EAX = EAX OR 1100 (result: 1110)

Bitwise XOR (xor)

Continue Reading...

Performs a bitwise XOR (exclusive OR) operation between corresponding bits of two operands.

mov eax, 1010b ; EAX = 1010 in binary xor eax, 1100b ; EAX = EAX XOR 1100 (result: 0110)

Bitwise NOT (not)

Inverts the bits of the operand, changing 0s to 1s and vice versa.

mov eax, 1010b ; EAX = 1010 in binary not eax ; EAX = NOT 1010 (result: 0101)

Test (test)

Performs a bitwise AND operation for setting flags without changing the operand.

mov eax, 1010b ; EAX = 1010 in binary test eax, 1100b ; Perform AND operation (flags are set based on the result)

Here are some additional examples of how logical instructions can be used in assembly language:

; Check if the value of the register EAX is equal to 10. cmp eax, 10 je equal ; If the value of the register EAX is equal to 10, jump to the label `equal`. ; Check if the value of the register EAX is less than 10. cmp eax, 10 jl less ; If the value of the register EAX is less than 10, jump to the label `less`. ; Set the bit at position 0 in the register EAX. bts eax, 0 ; Clear the bit at position 1 in the register EAX. btr eax, 1 ; Rotate the bits in the register EAX to the left by 1 bit. rol eax, 1

Conclusion

Logical instructions perform bitwise operations like AND, OR, XOR, and NOT, allowing manipulation and comparison of individual bits in binary data. These operations are fundamental for tasks such as masking, setting, clearing specific bits, and logical comparisons in low-level programming.

Next > Data Transfer Instructions in Assembly Language

Related Topics