ComputingLogic and problem solving25 min★★ difficulty

Boolean logic: AND, OR and NOT

Every decision a computer makes eventually boils down to true or false. Three simple gates — AND, OR and NOT — are enough to build all of it.

Part of your national curriculum

Algorithms and programming: Understand simple Boolean logic and some of its uses in circuits and programming

Lesson overview

What you'll learn in this lesson

Understand simple Boolean logic and some of its uses in circuits and programming

Key learning points

• The three basic gates
• Logic in programming
• Logic in circuits

This lesson at a glance

25 minutes
14 parts to scroll through
3 quick checks
Marked quiz at the end
Gentle pace: short sittings with pauses

Words to know

simplebooleancircuitsprogramming

Scroll down — the lesson carries on below

Part 1 of 14 · Discover7%

Watch & discover

Part 1 of 14

Watch first

Boolean logic: AND, OR and NOT

See how AND, OR and NOT gates let a computer make a decision.

In a nutshell

Understand simple Boolean logic and some of its uses in circuits and programming

Learning cycle

Part 2 of 14

Learning cycle 1 of 2

Part 1 · The three basic gates

A short piece of teaching, then a check to make sure it has landed.

Explore the idea

Part 3 of 14

Learn

The three basic gates

AND is only true when both inputs are true. OR is true when at least one input is true. NOT simply flips a value: true becomes false. A truth table for AND with inputs A and B: 0&0=0, 0&1=0, 1&0=0, 1&1=1 — only the last row is true.

Explore the idea

Part 4 of 14

Learn

Logic in programming

In code, `if raining AND cold: wear coat` only fires when both conditions hold. `if raining OR windy: take umbrella` fires if either is true. Programmers combine these to build precise conditions, such as `age >= 13 AND age <= 18` to spot teenagers.

Quick check

Part 5 of 14

Quick check

What does an AND gate output when both inputs are true?

Reset break

Part 6 of 14

Pause

That's sitting 1 of 2 done

Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.

Stop here for now

Quick check

Part 7 of 14

Quick check

Which condition matches 'if raining OR windy: take umbrella'?

Learning cycle

Part 8 of 14

Learning cycle 2 of 2

Part 2 · Logic in circuits

A short piece of teaching, then a check to make sure it has landed.

Explore the idea

Part 9 of 14

Learn

Logic in circuits

Physical logic gates are tiny electronic circuits inside a chip. An AND gate's output wire only carries current when both input wires do. Millions of these gates wired together let a processor add numbers, compare values and make decisions.

Quick check

Part 10 of 14

Quick check

What does a NOT gate do to a true input?

Challenge round

Part 11 of 14

Game · Sort it

Which of these are true?

Drag each card into the right column. Tap a card first if dragging is fiddly.

True

Not true

Challenge round

Part 12 of 14

Game · Fill the gaps

Finish the sentences

Choose the word that belongs in each gap.

Physical logic gates are tiny electronic ____ inside a chip.

Mastery quiz

Part 13 of 14

Marked quiz

End of lesson quiz: Boolean logic: AND, OR and NOT

3 questions, marked with the reasoning shown. No timer.

1. What does an AND gate output when both inputs are true?
2. Which condition matches 'if raining OR windy: take umbrella'?
3. What does a NOT gate do to a true input?

Lesson round-up

Part 14 of 14

Lesson round-up

Ready when you are

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Do the work

Your written work for this lesson

This is the part you'd do in your book at school. Pick the pieces below, write here or on paper, and photograph anything you draw or work out.

Article

How a supermarket checkout knows the price

When a barcode is scanned, the checkout does not store the price itself. It sends the barcode number to a database and reads back a record: product name, price, whether it needs an age check. The record is the single place the price lives, so changing one row changes every till in the shop at once.

Problems come from bad data, not bad scanners. If two products share a barcode, or a price update reaches the shop overnight but the till holds an old copy in its cache, customers are charged the wrong amount. Shops check this with test transactions: scan a known item, expect a known price, record what actually happened.

Good systems also log every scan. If a customer complains, the log shows exactly which record was used and when.

Written for Good Learning Co.

Reading questions

Write in your own words what the checkout sends and what it receives back.
Explain one way bad data could cause a wrong price, and how logging helps find it.
Design a test table with four tests for a new checkout, with expected and actual results.

Reading and notes
Reading
Read the lesson text again and note the key terms and how each one is used, in your own words — as you would for revision.
Half a page of notes
Extended writing
Writing
Explain a real system that uses this idea — how it works, where it can go wrong, and how you would make it safer or better.
250–350 words
Algorithm on paper
Diagram
Write your steps out as pseudocode or a flowchart before you type anything, then photograph it.
1 flowchart or 10 lines
Code write-up
Writing
Copy your code in, then explain underneath what each part does and what you had to fix.
Code + 5 sentences
Test table
Working out
Make a test table: what you tried, what you expected, what actually happened.
4–6 tests

Write your answer, notes or working here

Saved as you type.

Photos of paper work, diagrams or working outHow many minutes did the written work take?

Part 1 of 14 · Watch & discover

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Understand simple Boolean logic and some of its uses in circuits and programming