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Year 5 Coding & Computational Thinking Maths Link

Variables and Data

Learn how computers store and use information using variables -- the same idea as letters in algebra!

What is a Variable?

A variable is like a labelled box that stores information. You give the box a name, and you can put something inside it. You can also change what's inside later!

Variables are Like Labelled Boxes

42
score
"Alex"
name
true
isRaining

In JavaScript, we create a variable using the word let: 

let score = 42;        // A number
let name = "Alex";    // A text string
let isRaining = true; // A boolean (true/false)

Maths Connection: Variables in Algebra

In Maths, you already use variables! When you see:

x + 5 = 12

Here, x is a variable. It stands for the number 7.

In coding, it's exactly the same idea! let x = 7; means "store the number 7 in a box called x." The only difference is that in code, variables can store text and true/false values too, not just numbers.

Types of Data

Variables can store different types of information:

42

Number

Numbers for counting and calculating. Can be whole numbers or decimals.

let age = 10;
"Hi"

String (Text)

Text wrapped in quotation marks. Letters, words, or sentences.

let name = "Alex";
true

Boolean

Only two values: true or false. Like a light switch -- on or off.

let sunny = true;

Try It: Changing a Variable

Variables can change. Watch what happens when we update a score:

let score = 0;          // Start with 0 points
display("Score: " + score); // Shows: Score: 0

score = score + 10;      // Add 10 points
display("Score: " + score); // Shows: Score: 10

score = score + 5;       // Add 5 more points
display("Score: " + score); // Shows: Score: 15

score = score - 3;       // Lose 3 points
display("Score: " + score); // Shows: Score: 12

Try It: Your Name in a Variable

Type your name below to see how string variables work:

let name = "[your name]";
let greeting = "Hello, " + name + "!";
display(greeting);
display("Your name has " + name.length + " letters.");

Key Vocabulary

Variable

A named container that stores a piece of data. The value can be read and changed.

Data Type

The kind of value stored in a variable: number, string, or boolean.

String

Text data wrapped in quotation marks. E.g., "Hello"

Boolean

A value that is either true or false. Named after mathematician George Boole.

Assignment

Using = to put a value into a variable. E.g., score = 10

Input / Output

Input = data going IN to the program. Output = results coming OUT.

Worked Examples

1

What is the final value of total?

let total = 20;
total = total + 15;
total = total - 8;

Step 1: total starts as 20

Step 2: total = 20 + 15 = 35

Step 3: total = 35 - 8 = 27

Answer: The final value of total is 27

2

What data type is each variable?

let temperature = 23.5;
let city = "Sydney";
let isSunny = false;

temperature: Number (23.5 is a decimal number)

city: String ("Sydney" is text in quotes)

isSunny: Boolean (false is a true/false value)

3

What does this code display?

let firstName = "Jo";
let lastName = "Smith";
let fullName = firstName + " " + lastName;
display(fullName);

Step 1: firstName = "Jo"

Step 2: lastName = "Smith"

Step 3: fullName = "Jo" + " " + "Smith" = "Jo Smith"

Answer: It displays "Jo Smith". Joining strings together is called concatenation.

Knowledge Check

Select the correct answer for each question.

Question 1

What is the value of x after this code runs?

let x = 5;
x = x + 3;
x = x * 2;

Question 2

What data type is the value "42" (with quotes)?

Question 3

What does this code display?

let a = 10;
let b = 3;
display(a + b);
display(a - b);

Question 4

Which of these is a valid boolean value?

Question 5

What does this code display?

let colour = "blue";
colour = "red";
display(colour);

Key Concepts Summary

Year 4: Loops Patterns Year 6: Conditionals