Assembly Language Programming 8

Logical Instructions


There are 4 main logical operators :

They operate on the individual bits of a stored number.


NOT

NOT 0 1
  1 0

Example

NOT F0 = NOT 11110000 = 00001111 = 0F


AND

a AND b = 1 if (a=1) AND (b=1)

The Truth Table is as follows :

AND 0 1
0 0 0
1 0 1

Example

6B AND 56

6B = 01101011
56 = 01010110
6B AND 56 = 01000010
  = 42

OR

a OR b = 1 if (a=1) OR (b=1) or both

The Truth Table is as follows :

OR 0 1
0 0 1
1 1 1

Example

6B OR 56

6B = 01101011
56 = 01010110
6B OR 56 = 01111111
  = 7F

XOR

a XOR b = 1 if (a=1) or (b=1) but not both.

The Truth Table is as follows :

AND 0 1
0 0 0
1 0 1

Example

6B XOR 56

6B = 01101011
56 = 01010110
6B XOR 56 = 00111101
  = 3D

Exercises

(All answers are in Hexadecimal)

1 NOT 6B  
2 32 OR AF  
3 3F AND A2  
4 59 XOR CB