[plt-scheme] Computers considered harmful

From: Prabhakar Ragde (plragde at uwaterloo.ca)
Date: Wed May 6 16:27:54 EDT 2009

John Clements wrote:

> Likewise, the problem with computers is that they confound the use of
> the models (mathematics, computation) that we already have.

Related, perhaps: sometimes students complain that they have to write 
answers out by hand on exams, and they don't have a computer at hand 
like they do for assignments. I tell them that I'm interested in 
assessing their grasp of the ideas, not in whether they can get all the 
details exactly right. A written answer with a couple of minor but fatal 
flaws would lose a mark or two out of ten, but it might have taken them 
another twenty minutes to an hour to discover the error if they had to.

That said, I've heard of people teaching the first course using 
"hand-marked pseudocode", and that perhaps goes too far, with no 
feedback at all prior to assessment. This is a problem with mathematics 
as well. I find marking O-notation "proofs" painful, because the 
students go wildly wrong, and they don't even realize it.

Perhaps we should restrict the use of computers to an hour a day, or 
allow only a dozen times hitting "Run" before the software forces a 
timeout. Back in high school in the '70's, when we had to run cards 
through a machine to set up a batch job (or, even worse, send them 
offsite and get back printouts), we took a lot more care in crafting 
things. (Well: those who didn't flunked out faster, at any rate.)

I teach models such as HtDP describes because I think they are very 
important. Many students don't get it. Their sole model is "run it and 
see if it works". The problem with that, as I repeatedly explain to 
them, is what if it doesn't? They need some independent way of 
explaining the discrepancy between what they thought they were doing and 
what they actually did. The primacy of the computer encourages them to 
neglect mental models. --PR

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