Teach Computing

Revision notes, activities, lesson plans, teaching ideas, and other resources for GCSE, A-Level, and IB Computer Science teachers and students.

What's New

Boolean logic worksheet pack

These three Boolean logic worksheets have exam style questions on logic sta...

Edexcel Computer Science (9-1)

by Ann Weidmann et al Amazon.com | Amazon.co.uk | Book Depository This bo...

Dijkstra's algorithm video

This video is probably the best explanation of Dijkstra's algorithm for IB ...

Input-Process-Output (IPO) Model

The Input-Process-Output model is a simple topic but some students sometime...


A comprehensive review of hexadecimal. The video covers not only how to u...

Subprograms, Local Variables & Structured Programming

Subprograms are known by several different names - methods, functions, proc...

Utility Software and Models

Some students find the difference between operating system software and ut...

Data Structures

This video explains different types of data structures - 1 dimensional ar...

Operating System (OS) - GCSE Computer Science

A detailed overview of operating systems, starting with the general tasks t...

1.4 Processor Fundamentals

Click here for recommended Cambridge A-Level Computer Science textbooks.

1.4.1 CPU architecture

How computers work activity

How Computers Work - Kinesthetic Activity

In this kinesthetic activity students act out the roles of the Arithmetic and Logic Unit (ALU), the CPU, the memory, and the display as they act out how these basic hardware components function by "running" sample programs. This is a great way of introducing the basic concepts before moving on to more advanced machine architecture. You can download the following sheets:

This activity was created by Gary Kacmarcik from cse4k12.org and is licensed under the Creative Commons CC-SA licence.

Updated: 2015-04-25

1.4.2 The fetch-execute cycle

Little Man Computer simulator

Little Man Computer (LMC)

The Little Man Computer (LMC) is a software simulator of a simple computer with a CPU, memory, and a basic instruction set. Students can enter programs in either assembly language or machine code and follow their exceution by watching the change state of the program counter, accumulator, and memory. More advanced versions show animated representations of the address and data lines too. The LMC is a great tool for helping students visualise how code and data are represented in memory and how the fetch-execute cycle works.

There are now many versions of the LMC available. Some of the best include:

Most of these versions of the LMC include instructions but probably the clearest explanation of the instruction set is from Durham University.
Updated: 2015-04-25

1.4.3 The processor’s instruction set

Note: Students also study logic gates in more detail in topic 3.3.1 Logic gates and circuit design

1.4.4 Assembly language

Note: Students also study logic gates in more detail in topic 3.3.1 Logic gates and circuit design