Linux Torvalds in this less than 3 minute video clip gives a great answer to a question about teaching children how to write computer code. He specifically mentions the Raspberry Pi as having the attractive property of being cheap enough to throw away. I've said before that if you persuade kids to try a computer programming course, some number of them will hate it, and will vow never to wrestle with computer software again. But there should be some who will decide this is fascinating and will pursue it further, perhaps making a career out of it.
My conclusion is that an introductory programming course should therefore be short. I like Udacity CS101. It is nominally only 8 weeks at 5 hours of class time per week. It is self-paced and not on a fixed schedule. You may want to see my blog post: Is the Udacity CS101 Course Watered Down?
There are many possible ways to introduce computer programming. For example, you could pick a commercially important programming language, e.g. C or Java, and organize a course around learning that language. Or you could create/select a student language just for the students to get started with the concepts (Scratch, Logo, Basic, CUPL, ...) and teach that. I think Udacity CS101 chose wisely in picking a subset of Python. Python is a clean, powerful, multi-paradigm programming language that does see some real use commercially. Udacity CS101 doesn't visit all aspects of the language, but it does teach enough of it to give a good start at understanding the construction of computer programs. I believe it is much easier to get started in Python than in C or Java and that Python can carry you a lot further than Scratch, Basic or CUPL.
Another approach to introducing computer programming is to pick projects that are particularly attractive to students. Robots and computer games are two oft-mentioned examples. The parts and tools needed for a Robot-centered course call for a substantial investment ($10-$25 thousand per team is a working estimate I've seen on the web) and also requires comparatively large secure space to store the project, parts and tools. Real-time software that interacts with sensors and motors strikes me as more advanced material then a short introductory course should aim to cover. Games keep the work in the virtual world, so there's less need for parts and a workshop space, but interactive software with graphics is again, in my opinion, more advanced material that a short introductory course should aim to cover. Fair enough to stir into an introductory course a bit of foreshadowing to hint at how the material the course is covering can be extended to work in games or robots.
But I haven't any real experience teaching computer programming to students. I've been trying to launch such a course at the local community center here in the New Cassel section of North Hempstead, NY for well more than a year now, but it hasn't gotten off the ground yet. A shameless plug for yet another of my blog posts: Marketing the Importance of Programming Education. The comment thread on that article is, in my opinion, particularly worth reading.
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