Why You Should Use Routines...Routinely

As an undergraduate computer science student, I thought that the main reason to create new routines, instead of leaving all the code in one big routine, was to avoid duplicate code. This is undoubtedly the most popular reason for creating a routine, and it’s a good one. Similar code in two routines is a warning sign. David Parnas says that if you use copy and paste while you’re coding, you’re probably committing a design error. Instead of copying code, move it into its own routine. Future modifications will be easier because you will need to modify the code in only one location. The code will be more reliable because you will have only one place in which to be sure that the code is correct. That is one good reason to create a routine, but it hardly makes a complete list.