Page 36 - Touhpad Ai

The following figure shows the circuit symbol and truth table of the NAND gate:
Truth Table of NAND Gate

Input 1 Input 2 Output
0 0 1
0 1 1
1 0 1
1 1 0

Let us understand through an example.
Imagine a security alarm that does NOT go off if both doors in a house are closed (safe). But it does go off if even one door
is open.
Door 1 Closed Door 2 Closed Alarm (Output)

1 (Yes) 1 (Yes) 0 (No Alarm)
1 (Yes) 0 (No) 1 (Alarm ON)
0 (No) 1 (Yes) 1 (Alarm ON)

0 (No) 0 (No) 1 (Alarm ON)
So, the alarm stays OFF only when both doors are closed, and it turns ON in all other cases—just like how a NAND gate
works!

NOR Gate

A NOR gate, also known as negated OR gate, performs an OR operation first and then applies a NOT operation to the
result. The output is 1 (True) only when both inputs are 0. If either or both inputs are 1, the output is 0 (False).

The following figure shows the circuit symbol and truth table of the NOR gate:
Truth Table of NOR Gate
Input 1 Input 2 Output

0 0 1
0 1 0
1 0 0
1 1 0

Let us understand through an example. Suppose you have a mobile that only allows notifications when both Do Not
Disturb and Silent Mode are OFF.

Do Not Disturb ON Silent Mode ON Notifications Allowed (Output)
0 (OFF) 0 (OFF) 1 (Allowed)

1 (ON) 0 (OFF) 0 (Blocked)
0 (OFF) 1 (ON) 0 (Blocked)
1 (ON) 1 (ON) 0 (Blocked)

So, the phone sends notifications only when both settings are OFF, just like a NOR gate gives 1 when both inputs are 0.
XNOR Gate

An XNOR, also known as exclusive NOR, gate performs an XOR operation first and then applies a NOT operation to
the result. The output is 1 (True) if both inputs are the same (0,0 or 1,1). If the inputs are different (0,1 or 1,0), the output
is 0 (False).

34 Touchpad Artificial Intelligence - XI