Skip to content
Oak National Academy
Oak National Academy
View my library
0
Teachers
Pupils
New
New
Year 10
AQA

Huffman coding

I can describe and use Huffman coding to create a compressed representation of data.

Download all resources
Share activities with pupils
New
New
Year 10
AQA

Huffman coding

I can describe and use Huffman coding to create a compressed representation of data.

Download all resources
Share activities with pupils

These resources will be removed by end of Summer Term 2025.

Switch to our new teaching resources now - designed by teachers and leading subject experts, and tested in classrooms.

These resources were created for remote use during the pandemic and are not designed for classroom teaching.

View new resources

Lesson details

Key learning points

  1. Huffman coding is a lossless compression technique.
  2. Huffman coding assigns shorter bit sequences to more frequent characters and longer sequences to less frequent ones.
  3. A Huffman tree is used to visually represent the encoding scheme to create compressed data.
  4. A Huffman tree sent alongside compressed data adds overhead and can reduce the overall compression efficiency.

Keywords

  • Huffman tree - a special kind of binary tree used to create short binary codes for data, based on how often each piece of data appears

  • Encoding - to change data into a different format so a computer can store or send it

  • Frequency - how often a piece of data appears in a file

Common misconception

The Huffman tree is the compressed file.

The compressed file is a sequence of bits, and the tree is the representation of the coding system.


To help you plan your year 10 computer science lesson on: Huffman coding, download all teaching resources for free and adapt to suit your pupils' needs...

Break Huffman coding into small, manageable steps and have students practice each one separately. A step-by-step approach reduces cognitive overload, reinforces understanding at each stage, and helps all learners feel successful even with a complex concept like data compression.
Teacher tip

Equipment

Licence

This content is © Oak National Academy Limited (2025), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

Skip lesson video

Loading...

Prior knowledge starter quiz

Download quiz pdf

6 Questions

Q1.
What is the purpose of run length encoding?
Correct answer: to reduce the size of repeating sequences of data
to increase file size
to add redundancy to data
to encrypt data
Q2.
What does redundancy in data refer to?
essential information
encrypted data
random patterns in data
Correct answer: repeated or extra data that isn’t needed
Q3.
Which of the following is a characteristic of lossless compression?
Data is permanently removed.
Correct answer: Data can be perfectly reconstructed.
File size is always reduced.
It works only with images.
Q4.
What type of data is best suited for run length encoding?
randomised data
encrypted data
data with no structure
Correct answer: data with repeating patterns
Q5.
Why might run length encoding not always reduce file size?
It removes all data.
It adds additional data.
Correct answer: It depends on the amount of redundancy in the data.
It works only with text data.
Q6.
What does 'lossless' mean in data compression?
Correct answer: Data is compressed without losing any information.
Data is encrypted.
Data is permanently removed.
Data is randomly altered.

Assessment exit quiz

Download quiz pdf

6 Questions

Q1.
What is Huffman coding?
a method for encrypting data
a way to create random data
a lossy compression technique
Correct answer: a lossless compression technique
Q2.
Match each term with its correct description.
Correct Answer:Huffman tree,a special kind of binary tree used to create short binary codes

a special kind of binary tree used to create short binary codes

Correct Answer:encoding,changing data into a different format

changing data into a different format

Correct Answer:frequency,how often a character appears in data

how often a character appears in data

Correct Answer:lossless,when data is perfectly reconstructed

when data is perfectly reconstructed

Q3.
What does a Huffman tree represent?
the compressed file
Correct answer: the encoding scheme
a sequence of bits
the file size
Q4.
Arrange the steps for creating a Huffman tree in the correct order.
1 - Calculate the frequency of each character.
2 - Build the tree.
3 - Assign bit sequences based on the tree structure.
Q5.
What is the main purpose of Huffman coding?
to increase file size
Correct answer: to compress data efficiently
to encrypt files
to remove all data redundancy
Q6.
Order the following characters based on their bit sequence length in Huffman coding (shortest to longest).
1 - C (frequency: 15)
2 - A (frequency: 10)
3 - B (frequency: 5)
4 - D (frequency: 2)