GCSE · Computer Science · AQA · Spec 8525

AND logic gate

Computer Science · Logic gates

Logic gates — build the truth table

Toggle inputs A and B — watch when the AND gate outputs 1 and compare with OR and XOR.

A	B	AND out
0	0	0
0	1	0
1	0	0
1	1	1

Predict, then check

Read the inputs carefully before committing — AND is strict.

A two-input AND gate has A = 1 and B = 0. Before checking the truth table, what is the output?

How the AND gate processes its inputs

Follow one signal through — notice where a single 0 stops everything.

Signal passed on or blockedA 1 output passes the signal downstream to the next gate or component. A 0 output stops it — the circuit knows the condition was not fully met.

AND vs OR — know the difference

AND gatevsOR gate

This is the most common mix-up in logic gate questions.

Focus

Output rule

AND gate

ALL inputs must be 1

OR gate

AT LEAST ONE input must be 1

The insight

AND is stricter — a single 0 kills the output; OR is more permissive — a single 1 is enough.

Rows outputting 1 (2-input table)

AND gate

1 row only (row 1,1)

OR gate

3 rows (01, 10, 11)

Boolean symbol

AND gate

A · B (dot)

OR gate

A + B (plus)

Real-world analogy

AND gate

Need ticket AND ID to enter

OR gate

Need ticket OR student card to enter

Cross-subject · Exam skill

Command Word Coach

AND logic gate — AQA exam language

CompleteBloom · Apply

01Definition

Fill in every missing cell of a truth table following the gate's rule exactly.

02Mark-band signal

A strong answer covers every input combination and gets every output cell correct.

03Sentence stems

Complete the truth table for the AND gate below.
Complete the truth table to show the output for each combination of inputs.

04Common mistake

Leaving a row out or repeating one — working in binary counting order (00, 01, 10, 11) helps you cover all four.

Exam line: Completing a truth table is a common AND-gate task. Work through the input combinations systematically and remember that only 1 AND 1 gives an output of 1. You may also be asked to write the Boolean expression: AND is written as a dot, so A AND B is A.B

Watch out: The command word is a guide to how much to write: 'State' asks for a fact, while 'Explain' asks for a rule and a reason. Match your answer to the command.

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

Output is 1 only when ALL inputs are 1 — the gatekeeper of Boolean logic.

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