Use AND and OR gates
Evaluate AND and OR from their input conditions and complete their truth tables.
Exam scope and assessment notes
This original learning sequence follows Topic 10 of Cambridge IGCSE Computer Science 0984, 2026–2028 syllabus Version 4. It covers standard symbols and functions for NOT, AND, OR, NAND, NOR and XOR/EOR, and translation among statements, expressions, circuits and truth tables. NOT has one input; other gates have at most two. Circuit practice is limited to three inputs and one output and keeps the requested design without simplification. Lessons and checks support learning but do not award an official Cambridge grade. Full timed-paper practice, practical programming in an executable workspace and human subject-teacher review remain outstanding; the separate 2029–2031 syllabus is not mapped here. Cambridge states that 0984 has the same 2026–2028 subject content as 0478, with 9–1 grading. In June and November, Cambridge lists 0984 in Administrative zone 3 and for centres in Oman and the UAE. Confirm availability for your centre and exam series with Cambridge International. The separately published 2029–2031 syllabus changes to Python 3 only and removes pseudocode; this 2026–2028 route does not cover those changes.
Before you begin
- Be able to read binary 0 and 1 as the two possible logic values. Each lesson introduces the gate or translation skill it uses.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
When does AND output 1?
What you will learn
- Apply AND to two inputs
- Apply OR to two inputs
- Distinguish both true from at least one true
Core idea
AND returns 1 only when both inputs are 1. OR returns 1 when at least one input is 1, including the case where both are 1. Both gates have two inputs in this course.
In a logic circuit, 1 represents TRUE and 0 represents FALSE. A gate applies a defined rule to its input value or values and produces one binary output.
A reliable method
For each row, test the gate's condition literally. For AND, ask whether both values are 1. For OR, ask whether either value is 1. Enumerate inputs 00, 01, 10, 11 so no case is missed.
Keep the given statement, expression, diagram or table in view while working. Check each row or connection against the rule, and preserve the stated circuit structure; the syllabus does not ask you to simplify it.
Pause and explain
For A=1, B=1, compare AND and OR outputs.
Worked example
Find A AND B and A OR B for rows 00, 01, 10, 11.
Show the worked solution
- For 00, neither condition produces a true result.
- For 01 and 10, only OR is true.
- For 11, both AND and OR are true.
Answer AND: 0,0,0,1. OR: 0,1,1,1.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Complete the AND output for A,B = 00, 01, 10, 11.
Give me a hint
Only the final row has both inputs equal to 1.
Compare my reasoning
- Check each pair for two ones.
- Rows 00, 01 and 10 fail the condition.
- Row 11 satisfies it.
0, 0, 0, 1.
Look for these in your work
- Four rows
- Only 11 outputs 1
A controller opens a gate when button A OR button B is pressed. Give the output for 00, 01, 10, 11.
Give me a hint
One pressed button is enough.
Compare my reasoning
- 00: neither is pressed, output 0.
- 01 and 10 each contain a 1, output 1.
- 11 also satisfies OR, output 1.
0, 1, 1, 1.
Look for these in your work
- None case
- Single-button cases
- Both-button case
A safety system allows a machine to run only if guard G is closed and power P is on. Write an expression and calculate the result for G=1, P=0.
Give me a hint
Both required conditions must hold.
Compare my reasoning
- The condition joins G and P with AND.
- Substitute G=1 and P=0.
- One input is 0, so the AND output is 0.
Run = G AND P; for 1,0 the output is 0.
Look for these in your work
- Requirement translated
- Inputs substituted
- Output justified
Common mistakes
- Reading OR as exactly one true
- Giving AND output 1 when only one input is 1
- Leaving out one input combination
What can you explain now?
For A=1 and B=0, what is A OR B?
Compare with the explanation
1
OR needs at least one input to be 1.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
How does the OR rule differ from the AND rule?
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.