Great software helps you out when you misunderstand it. If you try to drag a file to a button in the taskbar, Windows pops up a message that says, essentially, “You can’t do that!” but then it goes on to tell you how you can accomplish what you’re obviously trying to do (try it!)

Great software pops up messages that show that the designers have thought about the problem you’re working on, probably more than you have. In FogBugz, for example, if you try to reply to an email message but someone else tries to reply to that same email at the same time, you get a warning and your response is not sent until you can check out what’s going on.

Great software works the way everybody expects it to. What great software has in common is being deeply debugged and the only way to get software that’s deeply debugged is to keep track of your bugs.

A bug tracking database is not just a memory aid or a scheduling tool. It doesn’t make it easier to produce great software, it makes it possible to create great software.

With bug tracking, every idea gets into the system. Every flaw gets into the system. Every tester’s possible misinterpretation of the user interface gets into the system. Every possible improvement that anybody thinks about gets into the system.

Bug tracking software captures the cosmic rays that cause the genetic mutations that make your software evolve into something superior.

And as you constantly evaluate, reprioritize, triage, punt, and assign these flaws, the software evolves, it gets better and better. It learns to deal with more weird situations, more misunderstanding users and more scenarios.

That’s when something magical happens and your software becomes better than just the sum of its features. Suddenly it becomes reliable. Reliable, meaning, it never screws up. It never makes its users angry. It never makes its customers wish they had purchased something else.