Objectives for this topic

By the end of this topic, you should be able to:

describe the von Neumann Fetch-Decode-Execute cycle;
trace through an assembly language program;
describe the accumulator and its use.

You might also be able to:

discuss the differences between high-level and low-level languages.

Introduction

John von Neumann brought many advances to the field of computing. With the developments of the combined memory model there came a need to formalise the way a program runs. This is known as the Fetch-Decode-Execute cycle; by following the FDE cycle, you can trace an assembly language program to identify the results.

Along with the development of the method, a number of special purpose memory modules called registers were designed and integrated into the cycle. One of the most important of these is the accumulator – you will be introduced to the use of the accumulator in this topic.

Working through your coursebook

Read pages 18—20 in your Computing Stage 9 book.

Read the Learn box on page 18.
Read the abstraction and algorithmic thinking box; consider how this topic relates to abstraction.
Make sure that you understand the keywords described on page 19. Add them to your cram.com flashcards.
Complete the Practise task on pages 18-20. You can access the worksheet here:

DOWNLOAD - Introducing the fetch decode execute cycle

Read pages 21-25 in your Computing Stage 9 book.
Read the Learn box on pages 21-22.
Read the Computational Thinking box on page 23.
Make sure that you understand the keyword described on page 23. Add it to your cram.com flashcards.
Complete the Practise task on pages 23-25. You will need the link below:

ACCESS - Little Man Computer (peterhigginson.co.uk)

Review

Reflect upon the pages you have just covered. In your notes, summarise:

what you have learnt;
what you already knew;
what surprised you;
what you are curious to know more about.

Support activity for this topic

Watch this video of a more in-depth look at the cycle:

Extension activity for this topic

Watch this video to learn a little more about the LMC: