No magic numbers!
Or rather, no magic numbers in the code proper.
On the projects I've worked on, I've developed a huge aversion to "magic numbers", i.e., hardcoded values that "just make the code work" or hard coded limits to the code. You can't ALWAYS avoid the basic REASON for the hard coded number (a 64K limit due to a two byte index field is still a 64K limit, after all), but it's good to at least TRY.
So I always define any such number as a constant, and put it in either a header file or constants file, the program headers themselves, a default configuration file, or in the actual configuration files. Yet even with the mantra, on code I've written in the last two years, I'll occassionally come across someplace where a magic number that got inserted "just to test" before being properly broken out got left in.
It's maddening, because a full 30% of all bugs come from magic numbers, in my experience, where the wrong number is being used. That 64K number I mentioned for example.... was that 0-64K-1 or 1-64K for the allowable range? It makes a difference when you put the magic number as 65535 or 65536; one might give you a rare, difficult to find exception violation or out of bounds error, for example, even though most of the time (since you're being consistent in using it!) the code works correctly.....
