NAND is called universal gate because other logic gates can be realised using NAND gates.
(1) AND gate from NAND gates:
| Inputs |
Output |
| A |
B |
Y = AB |
| 0 |
0 |
0 |
| 0 |
1 |
0 |
| 1 |
0 |
0 |
| 1 |
1 |
1 |
(2) OR gate from NAND gates:
| Inputs |
Output |
| A |
B |
Y = A + B |
| 0 |
0 |
0 |
| 0 |
1 |
1 |
| 1 |
0 |
1 |
| 1 |
1 |
1 |
(3) NOT gate from NAND gate:
| Inputs |
Output |
| A |
\(\bar A\) |
| 0 |
1 |
| 1 |
0 |
(4) XOR gate from NAND gates:
| Inputs |
Output |
| A |
B |
Y |
| 0 |
0 |
0 |
| 0 |
1 |
1 |
| 1 |
0 |
1 |
| 1 |
1 |
0 |
