Representing sound, images and text digitally
Photos, songs and messages all end up as the same thing inside a computer: streams of binary digits.
Part of your national curriculum
- Data and representation: Understand how sound, images and text can be represented and manipulated in a digital form
Lesson overview
What you'll learn in this lesson
Understand how sound, images and text can be represented and manipulated in a digital form
Key learning points
- • Images as pixels
- • Sound as samples
- • Text as character codes
This lesson at a glance
- 28 minutes
- 17 parts to scroll through
- 3 quick checks
- Marked quiz at the end
- Gentle pace: short sittings with pauses
Words to know
Scroll down — the lesson carries on below
Watch & discover
Part 1 of 17
Visual introductionPicture this
Representing sound, images and text digitally
Photos, songs and messages all end up as the same thing inside a computer: streams of binary digits.
In a nutshell
Understand how sound, images and text can be represented and manipulated in a digital form
Learning cycle
Part 2 of 17
Learning cycle 1 of 2
Part 1 · Images as pixels
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 3 of 17
Learn
Images as pixels
A digital image is a grid of pixels, each stored as numbers for red, green and blue (RGB), often 8 bits each, giving 256 shades per colour and about 16.7 million combinations. A 100x100 pixel image needs 10,000 pixels' worth of data.
Reset break
Part 4 of 17
Pause
That's sitting 1 of 4 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Explore the idea
Part 5 of 17
Learn
Sound as samples
Sound is sampled thousands of times per second; CD audio samples 44,100 times a second (44.1 kHz), storing the wave's height as a number each time. More samples per second, and more bits per sample, capture finer detail but need more storage.
Quick check
Part 6 of 17
Quick check
Part 7 of 17
Reset break
Part 8 of 17
Pause
That's sitting 2 of 4 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Learning cycle
Part 9 of 17
Learning cycle 2 of 2
Part 2 · Text as character codes
A short piece of teaching, then a check to make sure it has landed.
Explore the idea
Part 10 of 17
Learn
Text as character codes
Every character has a number: Unicode assigns 'A' the code 65, and 'a' the code 97. A text file is really just a sequence of these numbers, converted back into letters on screen by the software reading it.
Quick check
Part 11 of 17
Reset break
Part 12 of 17
Pause
That's sitting 3 of 4 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Challenge round
Part 13 of 17
Game · Sort it
Which of these are true?
Drag each card into the right column. Tap a card first if dragging is fiddly.
True
Not true
Challenge round
Part 14 of 17
Game · Fill the gaps
Finish the sentences
Choose the word that belongs in each gap.
A ____ image is a grid of pixels, each stored as numbers for red, green and blue (RGB), often 8 bits each, giving 256 shades per colour and about 16.7 million combinations.
A 100x100 pixel image needs 10,000 ____' worth of data.
Challenge round
Part 15 of 17
Game · Recall cards
What three values usually describe one pixel's colour?
Card 1 of 3
Mastery quiz
Part 16 of 17
Marked quiz
End of lesson quiz: Representing sound, images and text digitally
3 questions, marked with the reasoning shown. No timer.
1. What three values usually describe one pixel's colour?
2. CD audio samples sound how many times per second?
3. What is stored for the character 'A' in a text file?
Lesson round-up
Part 17 of 17
Lesson round-up
Ready when you are
Quiz score
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Best run
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Luna: 0 out of 3 on the practice checks. Only if you feel up to it — one more?
Ask LunaPart 1 of 17 · Watch & discover
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Understand how sound, images and text can be represented and manipulated in a digital form