The fetch-execute (FE) cycle
Lesson details
Learning outcome
I can describe the steps and functions of components in the fetch-execute (FE) cycle.
Key learning points
- The control unit decodes an instruction and tells other components what to do.
- The accumulator holds any data that is produced.
- Buses carry instructions from one component to another.
Keywords
Bus - used to carry instructions from one component to another
Binary representation - a sequence of 0s and 1s — the machine code of a computer
Accumulator - a register in the CPU that stores the results of calculations
Simulator - a program or system that imitates the behaviour of a real-world process
Common misconception
The CPU decodes and understands the instructions.
The instruction is decoded and then executed. The process only executes the instructions received.
Teacher tip
Demonstrating the FE cycle can be done with students to help understand how data and instructions are passed on, along and off each bus.
Equipment
Pupils will need access to a device that can edit and run simulated assembly language programs. Examples in this lesson use Little Man Computer https://oak.link/lmc
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Which part of the CPU performs mathematical calculations?
Q2.What is the main function of the control unit in the CPU?
Q3.Which of these is NOT a register in the CPU?
Q4.What is the purpose of the buses in von Neumann architecture?
Q5.Which register holds the address of the next instruction to be fetched?
Q6.Put the following steps of the fetch-execute cycle in order:
Assessment exit quiz
6 Questions
Q1.What is the main purpose of the CPU in a computer system?
Q2.Which register stores the address in memory for data or instructions to be accessed?
Q3.Match each CPU component to its description:
Q4.Which component of the von Neumann architecture is responsible for fetching and decoding instructions?
Q5.Which statement best describes what the CPU actually does with instructions?
Q6.Which component holds the data currently being processed by the CPU?
To help you plan your 10 computer science lesson on: The fetch-execute (FE) cycle, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 10 computer science lesson on: The fetch-execute (FE) cycle, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
Our video is a tool for planning, showing how other teachers might teach the lesson, offering helpful tips, modelled explanations and inspiration for your own delivery in the classroom. Plus, you can set it as homework or revision for pupils and keep their learning on track by sharing an online pupil version of this lesson.
Explore more key stage 4 computer science lessons from the Computer Systems unit, dive into the full secondary computer science curriculum, or learn more about lesson planning.