Fiducia TogetherData representation
How text, images and sound become numbers.
Please note: This page explains a word or a process in education. It is general information about the system, the law and the guidance in England — not advice about your child, your school or your exam. If a decision is going against you, get advice from one of the free services we link to before you agree to anything or miss a deadline. If you are revising, check your own exam board's specification: boards word things differently and yours is the one that marks you.
What it is
Everything in a computer is binary. Characters use a character set — ASCII (7 or 8 bits) or Unicode (many more, covering most writing systems). Images are pixels with a colour depth in bits. Sound is sampled at a sample rate with a bit depth.
Where it applies
GCSE and A Level computer science.
How it works
File size follows directly from the numbers: an image is width × height × colour depth; a sound file is sample rate × bit depth × duration × channels.
Higher sample rate and bit depth mean better quality and larger files, which is the trade-off every question is about.
How to use it in your work
Learn the two file-size formulae and always convert bits to bytes at the end by dividing by 8.
For "why is the file large" questions, name the specific factor and its effect.
Unicode versus ASCII: Unicode supports far more characters and uses more bits per character. Say both halves.
Where to get help
Your teacher and your board's specification — the pseudocode and the required language differ between boards. Bitesize covers the concepts; the computer science song runs the topics.
Revise this with a song
These are ours. We write revision songs because a lot of people remember a tune when they cannot remember a page, and because revising out loud in the kitchen beats staring at a highlighter.
- The Computer Science Song The GCSE computer science topics, set to music.
Where to read more
Last reviewed 2026-08-28 by Fiducia Together · Next review due 2027-08-28
Please note: This page explains a word or a process in education. It is general information about the system, the law and the guidance in England — not advice about your child, your school or your exam. If a decision is going against you, get advice from one of the free services we link to before you agree to anything or miss a deadline. If you are revising, check your own exam board's specification: boards word things differently and yours is the one that marks you.