The Kollected Kode Vicious

Kode Vicious - @kode_vicious

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Structuring Success

The problem with software structure is people don't really learn it until they really need it.

Dear KV,

In teaching an algorithms course this semester, I discovered my students had received very little instruction about how to divide their code into functions. So, I spent a weekend trolling various programming handbooks and discovered most of them are silent on this topic. I ended up writing a quick handbook to help my students, but was struck more by the advice gap. We just don't give people guidance!

Guiding Light


Dear Guiding,

Well, luckily, you're in the guidance business! I read over the handbook, and not only do I agree with it, but I think I've given similar advice—although not so nicely—in these columns in the past. I also note that you cite one of my favorite books on the topic of good software engineering, The Practice of Programming by Kernighan and Pike, a classic I read when it came out more than 20 years ago.

I want to look at this problem from another angle, since you've so nicely and concisely gone after the prescriptive advice. I have not taken your class, nor even sought out the syllabus, but as you say that it's an algorithms class, I wonder if that's a part of the challenge. I find that people develop a taste for good program structure—which is what you're arguing for—only after they've either been exposed to it in a well-written system or had the need thrust upon them by the problem they are trying to solve. If the programming guides you consulted are like the ones I've seen, they definitely have that 1980s PROGRAMMING IN BASIC mode of thought, in which the goal wasn't to understand the program so much as it was to type it into your personal computer correctly so you could play the game they were showing you.

In the modern world, this type of programming has been carried over to the Maker-like tutorials, those that blink a light or make an art project out of an Arduino and some string. It is not that these projects are bad (although the ones with sound are ultimately annoying when you're sharing a makerspace), it's that they are not meant to teach good software engineering. And the problem is not limited to the hobbyist world. While many algorithms can be broken down into constituent parts, textbooks do not often treat them that way, preferring, instead, to get the whole concept across in a large block of pseudocode. Good software structure is hard to show in a linear form like a book chapter; it is best when directly experienced.

To that end, I strongly suggest that your first project be one that requires some level of software structure, and this can be done in a few ways. The cruelest, surely, is to give the students such a horrendously complex assignment that the only way to solve it is through proper structure, rather than through the cleverness of the algorithmic design of a single function. The algorithm itself can be trivial, but the requirements for acquiring, processing, and storing the data, along with some nasty reporting requirements, would definitely make your students more aware of why they might want to structure their code. Interacting with the underlying system to get input, store output, and make reports is a straightforward way of ensuring the students want to have structure.

Another possibility, and one that might be a bit less cruel, is to cite the algorithm within some other system that already has structure. Rather than write a sorting algorithm that just takes an input string and produces the sorted string (as we did when I was an undergrad), have the students replace an algorithm in an existing system—for example, one that deals with encryption—where there can be choices of algorithms but the framework is not under their control. The modern world of open-source software should help you here. You can use many different pieces of software, admittedly of highly variable quality, as the frameworks for such homework.

The problem with software structure is people don't really learn it until they really need it, and your homework assignments will have to force them to look closely at how they are solving problems, not only through algorithms but through structure.



George V. Neville-Neil works on networking and operating-system code for fun and profit. He also teaches courses on various subjects related to programming. His areas of interest are computer security, operating systems, networking, time protocols, and the care and feeding of large code bases. He is the author of The Kollected Kode Vicious and coauthor with Marshall Kirk McKusick and Robert N. M. Watson of The Design and Implementation of the FreeBSD Operating System. For nearly 20 years he has been the columnist better known as Kode Vicious. Since 2014, he has been an industrial visitor at the University of Cambridge, where he is involved in several projects relating to computer security. He earned his bachelor's degree in computer science at Northeastern University in Boston, Massachusetts, and is a member of ACM, the Usenix Association, and IEEE. His software not only runs on Earth, but also has been deployed as part of VxWorks in NASA's missions to Mars. He is an avid bicyclist and traveler who currently lives in New York City.

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Originally published in Queue vol. 22, no. 2
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