Logic Gates
Controlling electricity gives us the ability to make yes and no decisions or true and false. By combining two signals, we can give a single true or false answer, depending on the logic. The flow of electricity is controlled using gates (no, not named after Bill Gates - like a gate).
The simplest gate, this item inverts or reverses the signal. Q=A
Input (A)
Output (Q)
0
1
1
0
Only outputs true if both inputs are true. Q=A⋅B or A×B
A
B
Output (Q)
0
0
0
0
1
0
1
0
0
1
1
1
Any gate with a dot is an inverted gate. Q=A⋅B or A×B
This is the NOT AND gate:
A
B
Output (Q)
0
0
1
0
1
1
1
0
1
1
1
0
One or the other or both! Q=A+B
A
B
Output (Q)
0
0
0
0
1
1
1
0
1
1
1
1
Very simply NOT OR. Q=A+B
A
B
Output (Q)
0
0
1
0
1
0
1
0
0
1
1
0
Exclusive OR meaning only one is true, not both. Q=A⨁B
A
B
Output (Q)
0
0
0
0
1
1
1
0
1
1
1
0
Exclusively NOT OR. If both inputs are the same, output true. Q=A⨁B
A
B
Output (Q)
0
0
1
0
1
0
1
0
0
1
1
1
The two "universal" gates are NOR and NAND - it is said that you can create all the other logic gates with a combination of just these two.
There are tons of videos available about logic gates. If I had to pick a favourite, my current is this one, although she talks incredibly fast and you might need to slow it down or rewind.
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