A1.2.3

Describe the purpose and use of logic gates

Logic gates are electronic circuits that take one or more binary inputs and produce a single binary output. The basic building blocks of digital circuits…

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Logic gates are electronic circuits that take one or more binary inputs and produce a single binary output.
The basic building blocks of digital circuits and CPUs.

Purpose

Make decisions based on binary conditions.
Perform logical operations on data.
Combine inputs to control outputs in hardware systems.

Used in

CPUs
Memory circuits
Control systems
Alarms and security systems
Automatic doors
Embedded systems

Main logic gates

NOT — reverses the input (1 → 0, 0 → 1).
AND — outputs 1 only if all inputs are 1.
OR — outputs 1 if at least one input is 1.
XOR — outputs 1 if inputs are different.
NAND — opposite of AND.
NOR — opposite of OR.

Flowchart showing two inputs feeding AND, OR, and XOR gates, with one input also feeding a NOT gate. A visual trace of the relationships described in this objective.

Example uses

AND — machine starts only if power is on AND safety guard is closed.
OR — alarm sounds if door sensor OR window sensor is triggered.
NOT — output is on when input is off.
XOR — useful in arithmetic circuits (e.g., half adders).