Block-based coding

Learn

What you’ll learn

• How block coding works
• Events, sequences and commands in blocks
• Where block coding is used for robots, and when to move to text

Blocks instead of typing

Block editors let you snap together code pieces that look like puzzle blocks. Their shapes only fit where they make sense, so there are no syntax errors, and you can focus on logic.

Editor	Used with
Microsoft MakeCode	BBC micro:bit and many robot add-ons
LEGO SPIKE App / Education apps	LEGO SPIKE and Computer Science & AI kits
mBlock	Arduino and Makeblock robots
Scratch	Games and stories; same ideas

Key ideas

• Event blocks start code: “on start”, “forever”, “on button A pressed”.
• Command blocks do things: “show icon”, “set motor speed”, “wait 1 second”.
• Control blocks repeat or choose: “repeat 4 times”, “if … then … else”.
• Value blocks (round or pointed) hold numbers, sensor readings and true/false.

Moving to text

Blocks and text code express exactly the same ideas. MakeCode can show your blocks as JavaScript or Python, which is a great bridge. When programs get long, text becomes quicker to write and read.

Examples

Example: the same program three ways

Blocks (MakeCode): forever → if light level < 50 then show icon Heart else clear screen

JavaScript (MakeCode text view):

basic.forever(function () {
    if (input.lightLevel() < 50) {
        basic.showIcon(IconNames.Heart)
    } else {
        basic.clearScreen()
    }
})

Python (MakeCode):

def on_forever():
    if input.light_level() < 50:
        basic.show_icon(IconNames.HEART)
    else:
        basic.clear_screen()
basic.forever(on_forever)

Practice

Try it in MakeCode

This is Microsoft’s MakeCode for the BBC micro:bit, with a virtual micro:bit on the left. Start a new project and build with blocks; the simulator runs as you edit.

MakeCode for micro:bit (blocks)Open full screen ↗

Start simulator

Runs on Microsoft MakeCode, free, no account needed.

Name badgeEasy

On start, scroll your name across the LEDs, then show a smiley.

Button counterMedium

Make a variable count. Button A adds 1 and shows the number; button B resets it to 0.

Peek at the textHard

Build the light-level heart program in blocks, then switch to JavaScript view. Change the threshold in the text and switch back: did the blocks update? Yes. Blocks and text are two views of the same program, which is why blocks are a good bridge to text coding.

Quick check

1. Why do block editors prevent syntax errors?

Blocks only fit where they make senseThey use AIThey don’t prevent themThey are slower

2. Which block starts code when something happens?

Command blockEvent blockValue blockComment

3. Blocks and text code can express…

Different ideasThe same ideasOnly motor commandsOnly maths

Check my answers