data representation gcse computer science

Data Representation: Storing Images

Introduction to image data.

• An image consists of a collection of pixels , each with their own coordinates and colour.
• Each pixel in an image is represented by a binary code, which will determine the colour and intensity of that pixel.
• The more pixels an image has, the higher the resolution – a high-resolution image conveys more visual information than low-resolution images, but at a higher data cost.

Bitmap Images

• Bitmap images , also known as raster images, are composed of pixels in a grid.
• Each pixel is represented by colour depth , the number of bits used to store colour data for each pixel. More bits provide a wider range of possible colours.
• Common bitmap image formats include .jpeg , .png , and .bmp .
• Bitmap images can lose quality when zoomed in or resized due to the fixed number of pixels.

Vector Images

• Vector images are not composed of pixels. Instead, they use mathematical formulas to draw lines and curves that make up the image.
• This means that vector images can be resized without any loss in quality, unlike bitmap images.
• Common vector image formats include .svg and .ai .

Efficiency in Storing Images

• Various methods are used to reduce the amount of data needed to store image data.
• Lossy compression reduces file size by throwing away less significant data. Once lost, this data cannot be recovered, which can cause loss of quality.
• Lossless compression reduces file size without losing data, preserving the original quality of the image. However, this method does not reduce file size as drastically as lossy compression.
• Images are also optimised by changing the image size , reducing the resolution or altering the colour depth .

File Formats and Metadata

• Different file formats use different methods of compression, resulting in variations in file size and image quality.
• Metadata about an image (such as its dimensions, colour depth, or the date it was created) is also stored in the file.

Colour Depth and Quality

• Colour depth refers to the number of bits used to represent the color of each pixel in an image. The greater the colour depth, the more colours can be represented.
• 1 bit colour depth can represent 2 different colours (usually black and white), while 24 bit colour depth can represent around 16.7 million colours.
• Increasing the colour depth results in higher quality images, but also increases file size.

Data Representation

Lesson Presentations

Exam Style Questions

Binary Numbers

Binary Numbers (2)

Compression

Quizlet - Data Representation

• Skip to main content
• Skip to footer
• Accessibility statement and help

GCSE – Data representations

Curriculum KS4 Unit

This unit allows learners to gain the understanding and skills required for the data representation sections of the GCSE computer science exam. First, learners look at binary and hexadecimal numbering systems, how they work, and how to convert between bases. Then, learners explore different coding systems and find out how text, images, and sound are represented in computers. All lessons include worksheets to allow learners to explore each topic through practical application.

Updated: 10 Feb 2023

Learning graph

Updated: 21 Feb 2023

Summative assessment

What is representation?

Number bases

Binary addition

Binary subtraction

Binary shifts

Signed binary integers

Hexadecimal

Representing text

Unicode and file size calculation

Representing bitmap images

Bitmap file size calculation

Representing sound

Sound file size calculation

Measurements of storage

Lossy and lossless compression

Run length encoding

Huffman coding

Enjoyed teaching these lessons? Found a mistake?

Fill in a short form to give feedback on these resources.

This website works best with JavaScript switched on. Please enable JavaScript

• Centre Services
• Associate Extranet
• All About Maths

GCSE Computer Science

• Specification
• Planning resources
• Teaching resources
• Assessment resources
• Introduction
• Specification at a glance

Subject content

• Scheme of assessment
• Programming skills
• General administration

This subject content should be taught within a range of realistic contexts based around the major themes in the specification. To gain the most from the specification, a number of the sections will benefit from being taught holistically. For example, algorithms could be taught alongside programming techniques as there is a close relationship between them.

The specification content in Sections 3.1–3.8 is presented in a two-column format. The left hand column contains the specification content that all students must cover and that is assessed in the written papers. The right hand column exemplifies the additional information that teachers will require to ensure that their students study the topic in an appropriate depth and, where appropriate, gives teachers the parameters in which the subject will be assessed.

The skills, knowledge and understanding from all of the subject content within the specification will be assumed in all assessments. Both assessments may contain synoptic questions that will require students to use their skills, knowledge and understanding from across the entire specification. For example, whilst the understanding of binary numbers will be directly assessed in paper 2, the underlying knowledge and principles may be indirectly required for questions in paper 1.

For exams from 2022, we will support the following programming languages:

• Python (version 3)

In paper 1 students will be required to design, write, test and refine program code in one of the three languages above. In preparation for paper 1, students should have sufficient practical experience of:

• structuring programs into modular parts with clear documented interfaces to enable them to design appropriate modular structures for solutions
• including authentication and data validation systems/routines within their computer programs
• writing, debugging and testing programs to enable them to develop the skills to articulate how programs work and argue using logical reasoning for the correctness of programs in solving specified problems
• designing and applying test data (normal, boundary and erroneous) to the testing of programs so that they are familiar with these test data types and the purpose of testing
• refining programs in response to testing outcomes.

In preparation for paper 2 students should have sufficient practical experience of  writing and refining SQL.

Students should be given as much opportunity as possible to practise their programming skills in the school or college's chosen language and SQL.

Fundamentals of algorithms

Representing algorithms, efficiency of algorithms, searching algorithms, sorting algorithms, programming.

Students need a theoretical understanding of all the topics in this section for the paper 1 exam even if the programming language(s) taught does not support all of the topics. Exams will always present algorithms using the current version of the AQA pseudo-code. The document can be found on the AQA website.

Students need a practical understanding of all the topics and skills in this section for the paper 1 exam. When they are writing computer programs in an exam they will need to ensure they use meaningful identifier names, use suitable data types and that all logic flow is clearly identifiable to examiners.

Exam questions will explicitly state in what form the response needs to be provided. This will be, for example, pseudo-code, program code or a flowchart, and students must respond as instructed. Where pseudo-code is an accepted method of response, students may present their answers to questions in any suitable format and do not need to use the AQA pseudo-code.

Programming concepts

Arithmetic operations in a programming language, relational operations in a programming language, boolean operations in a programming language, data structures, input/output, string handling operations in a programming language, random number generation in a programming language, structured programming and subroutines (procedures and functions), robust and secure programming, fundamentals of data representation, number bases, converting between number bases, units of information, binary arithmetic, character encoding, representing images, representing sound, data compression, computer systems, hardware and software, boolean logic, software classification, classification of programming languages and translators, systems architecture, fundamentals of computer networks, cyber security, fundamentals of cyber security, cyber security threats.

We've updated the phrases 'white-box penetration test' and 'black-box penetration test' in the 'Additional information' column below.

Social engineering

Malicious code (malware), methods to detect and prevent cyber security threats, relational databases and structured query language (sql), relational databases, structured query language (sql), ethical, legal and environmental impacts of digital technology on wider society, including issues of privacy.

Teach Computer Science

GCSE Computer Science: Data Representation

Teach gcse students about the different types of data in computer systems and how each is used. suitable for use with aqa, cie, edexcel & ocr..

This module covers the different types of data in computer systems and how each is used. Including:

• Binary system
• Hexadecimal system
• Character sets
• File formats and compression

What’s included?

Each module contains:

• An editable PowerPoint lesson presentation
• Editable revision handouts
• A glossary which covers the key terminologies of the module
• Topic mindmaps for visualising the key concepts
• Printable flashcards to help students engage active recall and confidence-based repetition
• A quiz with accompanying answer key to test knowledge and understanding of the module

As a premium member, you get access to the entire library of GCSE Computer science resources. Choose your theory modules to below to start your downloads.

Binary System

Download module 10: binary system.

This download is exclusively for Teach Computer Science subscribers! To download this file, click the button below to signup (it only takes a minute) and you'll be brought right back to this page to start the download!

Hexadecimal System

Download module 11: hexadecimal system, character sets, download module 12: character sets, download module 13: images, download module 14: sounds, file formats and compression, download module 15: file formats and compression.

An Introduction to A Level Computer Science - residential

CP268 Face to face course

An introduction to A level computer science for those new to teaching the subject or who want to improve their subject knowledge.

View locations and dates.

• York 17 July 10:00—18 July 2024
• York 27 August 10:00—28 August 2024
• York 16 July 10:00—17 July 2025

Begin your journey into the world of teaching A level Computer Science. This two-day residential will help you with the pre-learning required to allow you to teach A level Computer Science. You’ll explore the foundational knowledge needed so that you can help support students develop their programming skills. You’ll explore mathematical content required to deliver the subject; you’ll explore how the mathematical content extends from GCSE.

Programming is a key element of the A Level qualification, you’ll go deep into learning how to use sub programs, such as procedures and functions. You will develop your knowledge on how to use indexing, which will support your ability to use lists and arrays. You may have used external files whilst teaching GCSE computer science, you’ll extend your knowledge of using external files and how these can be combined with data structures. You’ll build confidence and understanding of how to deal with more complex errors, which can then help students with their projects.

Binary and hexadecimal a fundamental within computer science, you’ll explore using sign and magnitude, and two’s complement. You’ll be supported to explain negative numbers to students as well as floating point representation.  

During day 2, you’ll build your knowledge on using assembly language. During this session, you’ll discover the differences between high level code and assembly language. You’ll explore the different mnemonics that exist and how these can be used to write programs.

Across the two days you’ll complete the following courses:

• Introduction to A level programming
• Introduction to Maths in A level Computer Science
• Assembly language in A level Computer Science

Residential information:

This is a residential course at the National STEM Learning Centre, York. Meals and overnight accommodation are included for participants for the duration of the course. Subsidies are also available for teachers from state-funded schools and colleges which can be used towards travel, supply cover, teaching equipment or further local CPD.

If participants wish stay to spend the night before the residential in York, bed and breakfast will be available at the centre’s on-site accommodation at a discounted rate of £45+VAT. Participants can email [email protected] to secure this rate, providing their course booking information and confirming the night(s) they would like to stay.

Who is it for?

This is aimed at teachers who are either new to teaching A Level Computer Science or those who want to upskill themselves in the areas it covers.

Topics covered

How long is this course.

You’ll complete three courses from our A Level offering, totalling approximately 12 hours, split across two days.

How will you learn?

Hands-on experiential learning with the collaborative support of your peers. Expert advice and instruction on the A Level curriculum and the expectations of a computer science teacher, from experienced classroom practitioners.

By the end of this intensive CPD pathway you will be able to:

• Expand your knowledge of using functions and procedures including using functions inside of functions.
• Learn the differences between passing by reference and passing by value and why both approaches exist.
• Develop your knowledge of using indexing alongside using lists and arrays in programming;
• Learn how to handle exceptions that can occur in programs due to the user's inputs;
• Upgrade your knowledge of binary to include representing negative and decimal numbers;
• Learn the rules to convert decimal numbers into floating point and reversing this process;
• Learn the rules of adding and subtracting floating point numbers;
• Learn how to use a range of assembly language commands to create programs for little man computer questions.

This course is part of Teach secondary computing

Teach secondary computing

Our nationally recognised qualification will give you confidence to take your computing teaching to the next level and to apply those skills in the classroom.

Find out more

A level Computer Science subject knowledge

Book this course.

You need to be logged in to start the course.

Login to book this course

Create STEM Learning account

Adapted teaching and effective learning interventions in secondary computing

Develop an evidence-informed approach to education recovery over a sustained period, securing the computing education of young people following a period of great disruption.

Adapting the Teach Computing Curriculum for mixed-year classes - short course

Explore progression within Teach Computing Curriculum and how to use this to adapt it for your own mixed-age setting.

AI in primary computing

Explore how Artificial Intelligence (AI) may be linked to aspects of the primary computing curriculum, supporting creativity, digital literacy, and the use of information technology.