Making ‘more blocks’ in Scratch – a great way to promote computational thinking

Last month on the blog I looked at ScratchMaths, an incredibly powerful tool for helping children to visualise abstract mathematical concepts like angles and coordinates, writes Rowan Roberts, London CLC’s computing tutor.

This month I want to delve a bit deeper into Scratch 2 and highlight a brilliant feature that has much to offer and yet I rarely see teachers using it – more blocks.

‘More blocks’ allows you to create your own instruction block, then tell Scratch what should happen when you click on the block. This can be really handy if you have a program which runs the same instruction lots of times but not necessarily consecutively (eg the chorus of a song), so where a repeat block alone won’t do the job. It’s also great for the developing the thinking skill ‘decomposition’; ie breaking things down into smaller parts.

For example, if I asked you to tell Scratch to draw a house your first response might be to program each line and turn within that drawing individually. This would be a time consuming process (you’d need at least 12 blocks) and would also create a program that is very difficult to read.

A better solution might be to first program the sprite to draw a square, and then a triangle, and then put the two scripts together. This is much easier to do when you create ‘more blocks’. It allows you to turn each of these two scripts into what, in programming terms, is know as a procedure. You could then combine the two procedures so that they run one after the other. You could even create a third block called ‘house’ which combines the two, which is known as ‘nesting’.

Procedures are not mentioned in the curriculum for primary but our pupils will need to know about them when they get to key stage 3 and, in my opinion, they can make a whole range of programming techniques and concepts way easier to understand. Programs are much easier to read and if they are broken down into simple, readable parts, and this makes them must easier to debug if they go wrong.

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