Why Repeatedly Repeating Code is Bad Programming Practice

After a discussion with a friend about the recent eclipse, the subject of the apocalyptic end of the world came up. I was reminded of Y2K, and decided that it may be worth some research, as I was too young at the time to really understand what was truly going on. As a student of computer science, perhaps it would provide me with some important examples of things not to do in my own coding. On a blog post written by Steve Rowe for Microsoft Developer, he shares what he learned from an instructor about the true cause of the Y2K scare, a lack of implementation of the DRY, or the Don’t Repeat Yourself principle. Y2K was caused not by mistakenly representing a four-digit year with too few digits, but by making this error over and over throughout and across multiple files. Unless absolutely necessary, code with identical or near-identical functionality should not be duplicated. Following the DRY principle makes maintaining and repairing code easier and simpler; it is important that those striving to become excellent programmers follow this principle.

While my mistakes are not going to cause the same devastation as the mistakes of the developers that caused the Y2K scare (yet), they have certainly caused me a great deal of frustration while programming for assignments or personal projects. On more than one occasion, I’ve found myself repeatedly trying to remedy a certain piece of code, only to find out later that the error was caused by similar code that was implemented elsewhere. It was this duplicated code that was actually responsible for the error, not the unused or irrelevant piece that I had been wasting time attempting to correct. My failure to follow (or even be aware of) the DRY principle, which I was unfamiliar with before looking over the syllabus for Software Construction, Design and Architecture has resulted in countless hours of wasted time and energy. Any programmer, no matter how good he or she may think they are, could always stand to improve. Not only will following the DRY principle allow your code to be more easily understood by others, it will make writing documentation and performing any maintenance much simpler. Steve Rowe makes an interesting comment before closing his post, stating that, if duplicating code is deemed necessary, “It might not be a bad idea to put a comment in the code to let future maintainers know that there’s similar code elsewhere that they should fix.” If we all attempt to better follow DRY and Rowe’s advice, maybe we can avoid future Y2K-esque scares.