1. Who benefits from clear, understandable code?

In short, just about everyone benefits.

First, clear code is easier to follow while debugging and, for that matter, is less likely to have as many bugs in the first place, so writing clean code makes your own life easier even in the very short term. (For a case in point, see the discussion surrounding Example 27-2 in Item 27.) Further, when you return to the code a month or ayear later—as you surely will if the code is any good and is actually being used—it's much easier to pick it up again and understand what's going on. Most programmers find keeping full details of code in their heads difficult for even a few weeks, especially after having moved on to other work; after a few months or even a few years, it's too easy to go back to your own code and imagine it was written by a stranger—albeit a stranger who curiously happened to follow your personal coding style.

But enough about selfishness. Let's turn to altruism: Those who have to maintain your code also benefit from clarity and readability. After all, to maintain code well one must first grok the code. "To grok," as coined by Robert Heinlein, means to comprehend deeply and fully; in this case, that includes understanding the internal workings of the code itself, as well as its side effects and interactions with other sub-systems. It is altogether too easy to introduce new errors when changing code one does not fully understand. Code that is clear and understandable is easier to grok, and therefore, fixes to such code become less fragile, less risky, less likely to have un-intended side effects.

Most important, however, your end users benefit from clear and understandable code for all these reasons: Such code is likely to have had fewer initial bugs in the first place, and it's likely to have been maintained more correctly without as many new bugs being introduced.