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Have you seen the My Blocks category in the Scratch Blocks palette?

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When you click on it, no blocks are present until you create one.

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Let's explore how to create a customized block, and when and why you might want to use them.

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Let's say you are creating a Scratch program, and you've written a sequence of steps that performs a particular action.

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That action could be performing a complicated spin move, playing a set of musical notes,

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drawing a shape with the pen tool, performing some complex math, or anything

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else. That stack of blocks is known as a procedure or a routine. Most computer

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programming languages allow you to create a special name for a group of

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commands or lines of code and then call for that sequence to run at any point in

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the main program. In Scratch, we use my blocks. Click on my blocks in the blocks

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palette and then click on make a block. You can give your block any name you

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want, but I'd recommend something descriptive, so you can recall later what this stack of

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blocks does.

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Let's say I want to create a series of blocks that makes my cat sprite spin forward and

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backward.

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I'll call my block Cat Spin.

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Once I click OK, you'll see a new Event Handler block appears on the Scripts area

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that says Define.

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Under this block, I want to add all the code blocks in my procedure.

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For this example, I've added some repeating code that makes the cat whirl and turn forward

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in two complete circles, and then reverse the world, turning in the opposite direction.

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Let's click on this stack and see how it looks.

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Now that I have defined what my custom block does, let's use it in my main program.

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When I want the spin to occur, I'll grab my custom cat spin block,

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now available in the Blocks palette, and place it in my main program.

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In this program that I'm writing, the cat will spin after each background change,

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and say something after the spin.

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Let's see how this looks by clicking the green flag.

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The advantage of writing this procedure separately is that I can use one block to call for a

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whole set of steps to be run each time I need it.

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Creating separate procedures using custom blocks makes the code faster to write and

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read, and easier or quicker to edit.

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If I wasn't using a custom block, this is how the code would look, looking at them side

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by side, which is easier to read.

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And look, if I wanted to change the spin, I only have to edit it in one place, versus

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editing it in multiple places in my long, single code sequence.

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You don't have to use a custom block just for code that will repeat.