Logic Gates
Logic gates give an output
depending on the condition of the inputs. Below are the symbols and truth
tables for the common types of logic gates. Note that due to font
limitations the Boolean symbol for XOR expressed here as (+) is actually a +
sign inside a circle.
AND:
A 
B 
Output 

0 
0 
0 
0 
1 
0 
1 
0 
0 
1 
1 
1 
Expression: Output = A.B 
OR:
A 
B 
Output 

0 
0 
0 
0 
1 
1 
1 
0 
1 
1 
1 
1 
Expression: Output = A+B 
XOR:
A 
B 
Output 

0 
0 
0 
0 
1 
1 
1 
0 
1 
1 
1 
0 
Expression: Output = A(+)B 
NOT:
Input 
Output 

0 
1 
1 
0 
Expression: Output =
Input 
NAND:
A 
B 
Output 

0 
0 
1 
0 
1 
1 
1 
0 
1 
1 
1 
0 
Expression: Output =
A.B 
A NOT gate can be formed from a NAND gate by connecting
A and B together.
NOR:
A 
B 
Output 

0 
0 
1 
0 
1 
0 
1 
0 
0 
1 
1 
0 
Expression: Output =
A+B 
A NOT gate can be formed from a NOR gate by connecting A
and B together.
XNOR:
A 
B 
Output 

0 
0 
1 
0 
1 
0 
1 
0 
0 
1 
1 
1 
Expression: Output =
A(+)B 
A NOT gate can be formed from an XNOR gate by connecting
one input to ground.
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