← ACARA Digital Technologies Years 5–6

Explaining how digital systems use numbers for data

Digital systems turn pictures, colours and text into numbers. Binary uses only 0 and 1, like off and on, and the data type decides what you can do with it.

Part of: ACARA Digital Technologies Years 5–6 — Representing Data with Numbers — Module 48

Understanding Explaining how digital systems use numbers for data in ACARA Digital Technologies Years 5–6

What it does: A row of pixels is written as numbers, with one binary digit for each pixel. The number 5 adds up to 10, but the text "5" is joined to make "55", so the type changes the result. A picture is split into a pixel grid, and each pixel is stored as a number. Binary has just two digits: 0 and 1. The digits 0 to 9 are the everyday number system. A switch has two states. Binary matches this with 0 for off and 1 for on. Each 0 or 1 stands for one pixel. We choose a code, such as 0 for white and 1 for black.

Common mistakes: A black-and-white pixel row uses binary, which has only the digits 0 and 1. The 2 is not a binary digit. It should be row = [0, 1, 1, 0]. A single = stores a value. To compare the bit with 1 you need the double equals ==. It should be if bit == 1:.

Class: _____________________  ·  Name: _____________________  ·  Date: _________

Free printable worksheet with full answer key — or add this module to a class and your students practise it interactively.

🖨 Print worksheet + answer key Add Explaining how digital systems use numbers for data to a class →

This module's key terms are also in a printable crossword (Modules 85–104) and word search (Modules 73–104).

Take this worksheet further — free with Cloodit

Each concept is reinforced from every angle — learned, then applied, then tested.

Learning
Duo
Which sentence explains how a computer stores a picture?
A computer stores a picture as numbers, one for each pixel in the grid.A computer stores a picture as a tiny photo inside the screen.
Matches
Binary uses the digits 0, 1 and 2.
↓
Binary only has two digits, 0 and 1. The digit 2 is not used in binary.
Applying
Meanings
Term
A computer stores a picture as numbers
Meaning
Digital systems turn pictures, colours and text into numbers. Binary uses only 0 and 1, like off and on, and the data type decides what you can do with it.
Practice
A computer stores a picture as numbers.
Testing
Gaps
A computer stores a picture as .
Check Answer
Spots
1row = [0, 1, 2, 0]
2for pixel in row:

Cloodit turns curriculum-aligned coding content into journeys students work through one biome at a time.

The 'Spider' badge — Web Weaver, one of Cloodit's 106 collectible badges
Students earn collectable badges

Over 100 of them, across seven natural biomes.

Study Buddy
Students build a real study resource

Turns their work into revision material ready for Flash Cards and Exam study.

Diamond Dash — one of Cloodit's live, competitive Sprint games
Students lock in with Sprints

Live, competitive practice for the start of the lesson or a teacher-led lesson finisher.

A Cloodit certificate of achievement, ready to personalise and print
Custom printable certificates

Honour your top performers, or encourage a student who's trying hard — ready to print in seconds.

Add to class →

Quick Questions

1. Which sentence explains how a computer stores a picture?
A. A computer stores a picture as numbers, one for each pixel in the grid. ✓
B. A computer stores a picture as a tiny photo inside the screen.
A picture is split into a pixel grid, and each pixel is stored as a number.
2. Which digits does binary use?
A. Only 0 and 1 ✓
B. The digits 0 to 9
Binary has just two digits: 0 and 1. The digits 0 to 9 are the everyday number system.
3. How do we link binary to a light switch?
A. 0 is like on and 1 is like broken
B. 0 is like off and 1 is like on ✓
A switch has two states. Binary matches this with 0 for off and 1 for on.
4. A black-and-white pixel grid is stored using 0s and 1s. What could the 0 and 1 stand for?
A. 0 is a white pixel and 1 is a black pixel ✓
B. 0 is a whole picture and 1 is a sound
Each 0 or 1 stands for one pixel. We choose a code, such as 0 for white and 1 for black.
5. Which sentence about data types is true?
A. The data type does not matter. Every value works the same way.
B. The data type decides what you can do with a value. ✓
You can add numbers, but you can only join text. The type decides which actions make sense.

Match the Pairs

A computer stores a picture as numbers → Digital systems turn pictures into numbers, such as a grid of pixels where each pixel has a number.
Binary uses only 0 and 1 → Binary has two digits, which match off (0) and on (1) like a light switch.
A small pixel grid can store a black-and-white picture, where 0 is a white pixel and 1 is a black pixel. → 0 1 1 0
The data type decides what you can do with a value: numbers can be added, but text is joined together. → 5 + 5 = 10 and "5" + "5" = "55"
Binary uses the digits 0, 1 and 2. → Binary only has two digits, 0 and 1. The digit 2 is not used in binary.
A computer keeps a picture as a photo inside, not as numbers. → A computer does not keep a picture as a photo. It turns the picture into numbers, for example pixel values in a grid.

Key Term

A computer stores a picture as numbers
Digital systems turn pictures, colours and text into numbers. Binary uses only 0 and 1, like off and on, and the data type decides what you can do with it.

Fill in the Blanks

1. A computer stores a picture as numbers.
Hint: Type what digital systems turn pictures and colours into.
2. Binary uses only 0 and 1.
Hint: Type the other binary digit.
3. In binary, 1 means on and 0 means off.
Hint: Type the opposite of on.
4. A picture is a grid of tiny pixels.
Hint: Type the word for the tiny squares that make up an image.
5. The data type decides what you can do with a value.
Hint: Type the two-word term for the kind of data a value is.

Spot the Error

Question 1
A row = [0, 1, 2, 0]
B for pixel in row:
C if pixel == 1:
D print('black')
Line A — A black-and-white pixel row uses binary, which has only the digits 0 and 1. The 2 is not a binary digit. It should be row = [0, 1, 1, 0].
Question 2
A bit = 1
B state = 'off'
C if bit = 1:
D state = 'on'
Line C — A single = stores a value. To compare the bit with 1 you need the double equals ==. It should be if bit == 1:.
Question 3
A colours = ['white', 'black']
B pixel = 2
C print(colours[pixel])
Line B — One bit can only be 0 or 1, so it picks one of two colours. The number 2 does not match any colour in the list. It should be pixel = 0 or pixel = 1.
Question 4
A age = 10
B name = 'Sam'
C print(age + 5)
D print(name - '!')
Line D — Text (a string) can be joined with + but cannot be subtracted. The data type decides what you can do. It should be print(name + '!').
Question 5
A is_on = True
B bit = 0 if is_on else 1
C print(bit)
Line B — Binary links on and off to 1 and 0. On should be 1 and off should be 0, but this line swaps them. It should be bit = 1 if is_on else 0.

Student with a class code? Join your class →