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L10: Arrays & Lists

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Overview​

In this lesson, students will learn how computers store multiple values using lists (also called arrays in programming).

Instead of storing just one value in a variable, a list can store many values such as:

  • words
  • numbers
  • names
  • game items

Students will use lists to build a simple Charades game, where a random word is selected and displayed.

They will also learn how to use a for loop to go through every item in a list.

Learning Goals​

Students will:

  • understand what a list (array) is
  • create and use lists in MicroBlocks
  • store multiple words in one list
  • use random numbers to pick items
  • build a simple Charades game
  • use a for each item loop to iterate through a list

Time Required​

45–60 minutes

Materials​

  • CincoBit or PixoBit
  • USB cable
  • Computer or Chromebook
  • MicroBlocks

Teacher Notes​

This lesson introduces one of the most important data structures in programming:

Lists

Students should understand:

  • variables store single values
  • lists store multiple values
  • lists are used in games, apps, and real systems
  • random selection is commonly used in games

This lesson also introduces:

  • simple game logic
  • iteration over collections
  • basic randomness

What is a List?​

A list is a collection of items stored together.

Instead of:

  • word1 = “cat”
  • word2 = “dog”
  • word3 = “pizza”

We use one list:

["cat", "dog", "pizza"]

In programming, this is called:

a list

Why Use Lists?​

Lists help programmers:

  • organize data
  • store multiple items
  • simplify code
  • build games and apps

Examples in real life:

  • shopping lists
  • contacts on a phone
  • game inventories
  • playlists in music apps

Step 1 - Create a word List​

Just like how MicroBlocks variables can carry a value or a boolean, they can also carry a list.

The list is created from Data palette and then assigned to a variable.

We will create a new variable called words.

list new

Step 2 - Random Word Selection​

To build a Charades game, we randomly pick a word.

Steps:

  1. Get the length of the list
  2. Generate a random number
  3. Use that number to select a word

Example idea:

  • random number between 1 and list length

Use length of block to check a list length. We now can generate a random number between 1 and the length of the list.

The item block returns one of the items in a list. Giving it 2 will result in item 2 in the list. Lists store items in order.

Example:

PositionWord
1cat
2airplane
3pizza
4robot
5elephant

The position number is called an:

index

Programs use index numbers to access items.

This shows a random word each time. Click the block to run and see the results.

list random say

Step 3 - Charades Game​

When the program runs:

  • a random word appears
  • student acts it out
  • classmates guess it

Press button again to:

  • generate a new word

This creates a simple interactive game.

charades

Step 4 — Using a For Loop

A for each item loop allows us to go through every item in a list.

Example:

for each word in words

This means:

  • take each item one at a time
  • run the code for each item

What the Loop Does

For the list:

["cat", "airplane", "pizza"]

The loop runs like this:

  1. cat
  2. airplane
  3. pizza

Each item is processed one by one.

Step 5 — Display All Words​

Use a loop to:

  • show each word
  • or scroll them on the display
  • or play a sound for each item

Example behavior:

  • “cat”
  • wait
  • “airplane”
  • wait
  • “pizza”

This helps students understand iteration over data.

Understanding Lists in Real Systems​

Lists are used everywhere in computing:

Examples:

  • music playlists
  • contact lists
  • game inventories
  • web search results
  • recommendation systems

Without lists, modern software would be extremely limited.

Try It​

Can you:

  • add more words to the list
  • change the game category
  • make words harder or easier

Real-World Connection​

Lists (arrays) are one of the most important data structures in computing.

They are used in:

  • apps
  • games
  • AI systems
  • databases
  • operating systems

Every modern software system uses lists in some form.

Troubleshooting​

  • Same word keeps appearing
    • verify random range includes full list
  • Words do not display
    • check list format
  • Loop does not run correctly
    • verify list connection in for loop

Vocabulary​

WordMeaning
List (Array)Collection of items
ItemSingle value inside a list
IndexPosition in a list
RandomUnpredictable selection
LoopRepeating structure
IterationGoing through items one by one

Wrap-Up Question​

Why are lists important in games and apps?