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L11: Functions and Blocks

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Overview​

In this lesson, students will learn how to create their own custom programming blocks in MicroBlocks.

Custom blocks allow programmers to:

  • organize code
  • reuse code
  • simplify large programs
  • create cleaner workspaces

In many text-based programming languages, custom blocks are called:

  • functions
  • methods
  • procedures

Students will create a sound frequency sweep program and then convert the long code into a reusable custom block.

They will also learn:

  • how to hide block definitions
  • how to show hidden definitions again
  • how to add arguments (inputs) to custom blocks

Learning Goals​

Students will:

  • create custom blocks
  • organize large programs
  • reuse code
  • hide and show block definitions
  • add arguments to custom blocks
  • understand how functions work in programming

Time Required​

45–60 minutes

Materials​

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

Teacher Notes​

This lesson introduces:

abstraction and reusable code

Students should understand:

  • large programs become difficult to manage
  • custom blocks simplify programs
  • reusable code is an important programming concept

This lesson connects strongly to:

  • loops
  • sounds
  • variables
  • organization

Students are now beginning to think like software developers.

What is a Custom Block?​

MicroBlocks includes many built-in blocks such as:

  • play note
  • repeat
  • display image

These blocks were created by other programmers.

Custom blocks allow:

YOU to create your own blocks.

This makes programs:

  • easier to read
  • easier to reuse
  • easier to understand

Why Use Custom Blocks?​

Without custom blocks:

  • programs become large
  • code gets repeated
  • projects become difficult to manage

Custom blocks help programmers:

  • organize ideas
  • simplify projects
  • reuse behaviors many times

Professional software systems use thousands of functions and reusable blocks.

Step 1 — Create an Electronic Sound​

Students will create an electronic sound using a repeated frequency sweep.

The program:

  • starts at a low frequency
  • increases gradually
  • repeats multiple times

We will use a for loop, which loops with a variable in a range, changing it every step by a specific number. In this case, we are changing i from 500 to 5000 with 50 added in every loop.

start tone frequency will be set to variable i. A small delay is added so we are looping too fast.

Repeat this sweep a few times and you will have a cool electronic sound effect.

Finally, we need to stop the tone.

elec sound

Click on the block to hear the generated sound.

Step 2 — Create a Custom Block​

Open:

  • My Blocks

Add a command block called make sound.

MicroBlocks will now generate a starting point for our block definition.

Move all earlier sweep code inside the new block definition.

Now the entire program becomes:

make sound

instead of many blocks.

Students should immediately notice:

the workspace becomes much cleaner.

make sound

The custom block hides the internal complexity.

Instead of seeing:

  • loops
  • waits
  • tones
  • variables

students now see:

one simple command

This concept is called:

abstraction

Programs become easier to understand by hiding unnecessary details.

Step 3 - Adding an Argument​

Custom blocks can receive inputs called:

arguments

Arguments allow the block to behave differently depending on the value provided.

Students will add:

  • number of sweep repetitions

Go back to the block define and click the small right arrow next to make sound. This will add an argument called foo but you can click on it and rename it to count.

We can now use count. For example, we will drag count argument inside the repeat loop.

make sound argument

where:

  • count becomes an input argument

Students can now call the custom block just like before but this time with a provided count.

The same make sound block now behaves differently depending on the input value.

This makes the custom block:

  • more flexible
  • more reusable
  • more powerful

Understanding Arguments​

Arguments allow programmers to:

  • customize behavior
  • reuse code in different ways
  • avoid creating many similar blocks

Examples in real programs:

  • draw circle size
  • play sound frequency
  • move character speed

Arguments make functions dynamic.

Hiding Block Definitions​

MicroBlocks allows custom block definitions to be hidden.

Right-click on the block definition and select:

Hide Block Definition

The workspace now becomes even cleaner.

This is useful in large projects where:

  • many custom blocks exist
  • definitions take up space
  • programmers want to focus on the main logic

Showing Hidden Definitions Again​

To show the definition again:

  1. Open:My Blocks palette

  2. Find the custom block

  3. Right-click the block

  4. Select:

    Show Block Definition

Students should practice:

  • hiding definitions
  • restoring definitions

This helps manage large projects.

Real-World Connection​

Custom blocks and functions are used in:

  • games
  • apps
  • robots
  • operating systems
  • websites
  • AI systems

Without reusable functions, modern software would be impossible to manage.

Try It​

Can you:

  • create different sweep styles
  • make a custom melody block
  • animate graphics during sounds
  • add more arguments

Troubleshooting​

  • Custom block does not run
    • verify code is inside the block definition
    • Sweep repeats incorrectly
    • check repeat argument value
  • Hidden block cannot be found
    • look under My Blocks
  • Sound behaves strangely
    • verify wait timing and frequencies

Vocabulary​

WordMeaning
Custom BlockUser-created programming block
FunctionReusable section of code
ArgumentInput sent to a block
Reusable CodeCode used multiple times
AbstractionHiding complexity

Wrap-Up Question​

Why are custom blocks useful in large programs?