Some Simple Logic Gates
The operators used most often are AND
and OR. The AND
operation says if and only if all
inputs are on, the output will be on. The output will be off if any of
the inputs are off. The OR operation
says if any input is on, the output
will be on. It's easy to see all of the combinations by using what are
called truth tables, illustrated
below. At the bottom of each table is shown the schematic symbol found
in circuit diagrams.
| AND
(all high = high, else low) |
| Input 1 |
Input 2 |
Output |
| 0 |
0 |
0 |
| 0 |
1 |
0 |
| 1 |
0 |
0 |
| 1 |
1 |
1 |
|
|
|
| OR
(any high = high, else low) |
| Input 1 |
Input 2 |
Output |
| 0 |
0 |
0 |
| 0 |
1 |
1 |
| 1 |
0 |
1 |
| 1 |
1 |
1 |
|
|
|
Another one, the inverter or NOT
operation, says that the output will be opposite in state to the input.
It obviously has only one input and one output.
| NOT
(inverter) |
| Input = 1 |
Output = 0 |
| Input = 0 |
Output = 1 |
 |
|