AND gate
Input1 Input2 Output
0 0 0
0 1 0
1 0 0
1 1 1
The OR gate gets its name from the fact that it behaves after the fashion of the logical inclusive "or." The output is "true" if either or both of the inputs are "true." If both inputs are "false," then the output is "false."
OR gate
Input1 Input2 Output
0 0 0
0 1 1
1 0 1
1 1 1
The XOR ( exclusive-OR ) gate acts in the same way as the logical "either/or." The output is "true" if either, but not both, of the inputs are "true." The output is "false" if both inputs are "false" or if both inputs are "true." Another way of looking at this circuit is to observe that the output is 1 if the inputs are different, but 0 if the inputs are the same.
XOR gate
Input1 Input2 Output
0 0 0
0 1 1
1 0 1
1 1 0
A logical inverter , sometimes called a NOT gate to differentiate it from other types of electronic inverter devices, has only one input. It reverses the logic state.
Inverter or NOT gate
Input Output
1 0
0 1
The NAND gate operates as an AND gate followed by a NOT gate. It acts in the manner of the logical operation "and" followed by negation. The output is "false" if both inputs are "true." Otherwise, the output is "true."
NAND gate
Input 1 Input 2 Output
0 0 1
0 1 1
1 0 1
1 1 0
The NOR gate is a combination OR gate followed by an inverter. Its output is "true" if both inputs are "false." Otherwise, the output is "false."
NOR gate
Input 1 Input 2 Output
0 0 1
0 1 0
1 0 0
1 1 0
The XNOR (exclusive-NOR) gate is a combination XOR gate followed by an inverter. Its output is "true" if the inputs are the same, and"false" if the inputs are different.
XNOR gate
Input1 Input2 Output
0 0 1
0 1 0
1 0 0
1 1 1
Using combinations of logic gates, complex operations can be performed. In theory, there is no limit to the number of gates that can be arrayed together in a single device. But in practice, there is a limit to the number of gates that can be packed into a given physical space. Arrays of logic gates are found in digital integrated circuits (ICs). As IC technology advances, the required physical volume for each individual logic gate decreases and digital devices of the same or smaller size become capable of performing ever-more-complicated operations at ever-increasing speeds.