1/n

Thread: Managing cognitive load when introducing sub-programs.

Had a great discussion with @httcs.online (PS - ooh nice handle!) about this the other day. Here's my suggested approach.

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11/n Shortcuts

Now you can start to 'reveal' the magic hacks/shortcuts. Call one sub from within another. Use a returned value as an argument for a different sub. Calling from a print or as part of a calculation. Let them create from solid foundations

Fin

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Does adding data to a USB flash drive make it heavier? A great fertile question for data rep & storage lessons. Here's always excellent @fryrsquared.bsky.social with another brilliant explanation. #TeamCompSci #CASchat #CSed #CSscot
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10/n Functions with parameters

Data going in and out of the sub program. Now we can make our calculator useful. I teach to get user input in the main then send the arguments to the subs, which do the calc and return the answer into a variable in the main.

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8/n - Procedures with parameters and arguments

Now introduce data going IN to the sub program. Still super simple examples here (adding two numbers etc).

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7/n - Procedures first (NO parameters yet)

Just procedures first. Let students practice defining, calling and the new flow of a modular program without the extra load of parameters and return values.

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2/n - When to teach

I introduce them just after teaching about decomposition so they fit in with what students have just learned. Up to then I have taught the basic programming skills/structures of output, input, variables, selection & iteration

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3/n - Language

Be super careful about your language. Call them sub-programs/subroutines or whatever fits your curriculum. BUT - procedures and functions are TYPES of sub-program and should be introduced as such.

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5b/n

... they ARE right (for the moment). Explain that you've simplified the subs because you want them to just practice defining and calling. This does seem overly complex, but makes the a MUCH better CS thinker & programmer with bigger tasks later.

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5a/n - It will seem pointless at first, and that's fine

If you've followed step 4 then some students will probably ask you why they just can't write a sequential program - that's a much simpler way of achieving the same result right?

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4/n - Super simple subs

Your subs shouldn't do anything especially complex (and DEFINITELY no new skills) for a while. Just getting used to defining and calling is plenty for the working memory to be getting on with.

Simple outputs/calculations at first.
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9/n - Functions with no parameters

Next, return values. Hard coded calculations that return the value back to the main program. I teach to ALWAYS assign the return value to a variable (one thing per line) for use in the main program. No parameters yet.

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6/n - One thing per line

Just like with all my teaching, I go the long way round. Make your examples do one 'thing' per line as much as poss - no function calls print statements etc. Reducing the syntactic density of each line really helps new learners.

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