Training and Development

My life as a tech teacher, part 5: It's all about control

In a flashback to my early school years, it occurred to me that part of the Scratch coding environment follows the old 'logo' turtle programming method. Many years ago we would write instructions to move a wheeled, pen-equipped device across the classroom floor. Pen up, pen down, rotate left, move forward, etc.

So far I've been teaching the children in a similar way, with pre-programmed instructions rather than direct control of an on-screen sprite. This is an approved method of using Scratch: there's even a 'Pen' section allowing you to leave a line behind your sprite as you instruct it to move around the screen.

But now for the next stage. I asked the class whether they typed instructions into any of the computer games they played at home. Since they're all rather young for Infocom text adventures they said no. We then discussed how computer game input usually results in immediate effect. You press a key or button, or move a mouse or tap the screen, and your character responds instantly.


So I gave them the task of adding immediate control to their sprite. Nothing too complicated; I wanted them to be able to move the sprite left, right, up and down using the arrow keys. This can be achieved in just four separate blocks of two instructions using Scratch, so it wasn't too hard for the children to get to grips with it.

But it taught them two things. First, that control consists of two steps: an input 'event' and an action or consequence of that event. Second, that we can define positions on the screen in terms of X and Y co-ordinates, whereas until now we've been dealing in 'steps' instead.

Actually, three things: each input event and action/consequence are separate items, not dependent on each other. This is a useful concept for programming, getting across the idea of simultaneous event trapping and processing. Not all code is linear.

Just before this week's lesson a reporter and photographer from the regional newspaper arrived at the school, wanting to interview me about the course. This had been arranged by the school principal and I had no time to prepare.

Since I'd just been to the gym and was dosed up on coffee, the reporter received an enthusiastic stream-of-consciousness babble from me about the reasons for wanting to teach the course, the way it was structured, and the abilities of the children to soak up this new information.

I outpaced her shorthand by an order of magnitude, but hopefully she got the gist. I haven't yet seen the finished article but if it gets other techies thinking about sharing their knowledge with the next generation, so much the better.


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Alex Cruickshank

Alex Cruickshank has been writing about technology and business since 1994. He has lived in various far-flung places around the world and is now based in Berlin.  

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