Explain the role of the CPU and microprocessor
Connect a computer's input, processing and output to the central processing unit and a single-chip microprocessor.
Section 3 · Hardware
Exam scope and assessment notes
This sequence follows Cambridge IGCSE Computer Science 0984, 2026–2028 syllabus Version 4. It covers subject content sections 3.1–3.3 only. The separately published 2029–2031 syllabus is not mapped here. Practice is original, self-checked and does not award an official Cambridge grade. Full timed papers and human subject-teacher review remain outstanding. 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
- No programming language is required. Be comfortable with place value and multiplication; each lesson introduces the computer-science notation it uses.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What does the CPU do with instructions and data?
What you will learn
- Describe the CPU's role in processing instructions and data
- Define a microprocessor
- Connect processing to input and output
The CPU processes instructions and data
The central processing unit (CPU) processes instructions and data supplied to a computer so that results can be produced as output. It coordinates processing by using its internal units, registers and connections to memory and other devices.
Apply and check the rule
A microprocessor is a type of integrated circuit on a single chip that contains a processor. It can be used as the CPU in a computer or embedded device; not every integrated circuit is a complete CPU.
Pause and explain
Which sequence best describes a simple computer task?
Worked example
A laptop receives a key press and displays a character. What role does the CPU play?
Show the worked solution
- The keyboard provides input data.
- The CPU processes the input according to instructions.
- The display presents the result as output.
Answer The CPU processes the key data using instructions so the computer can produce the displayed character.
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.
Define a microprocessor.
Give me a hint
Include its integrated-circuit form and chip location.
Compare my reasoning
- It is a type of integrated circuit.
- It contains a processor on a single chip.
A microprocessor is a processor implemented as an integrated circuit on one chip.
Look for these in your work
- Integrated circuit mentioned
- Single chip mentioned
A smart thermostat reads a temperature and switches a heater. State how the CPU participates.
Give me a hint
Identify the input, processing and output.
Compare my reasoning
- A sensor supplies temperature data.
- The CPU compares/processes the data using instructions.
- An output signal can control the heater actuator.
The CPU processes the sensor reading according to its program and produces a control output for the heater.
Look for these in your work
- Input identified
- Processing linked to instructions
- Output identified
A student says the CPU and a hard disk perform the same role because both hold bits. Explain the difference.
Give me a hint
Distinguish temporary processing from persistent storage.
Compare my reasoning
- The CPU executes instructions and processes data.
- A hard disk provides secondary storage for data retained when power is off.
- Both use binary data, but their functions are different.
The CPU processes instructions and data; the hard disk stores data persistently. Both may involve binary, but they are not interchangeable components.
Look for these in your work
- CPU function stated
- Disk function stated
- Shared data format distinguished from purpose
Common mistakes
- Describing the CPU as long-term storage
- Calling every integrated circuit a microprocessor
What can you explain now?
What is a microprocessor?
Compare with the explanation
A processor implemented as an integrated circuit on a single chip
A microprocessor is a type of single-chip integrated circuit containing a processor.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
What does the CPU do between a computer receiving input and producing output?
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.