What can you do to a legacy codebase that will have the greatest impact on improving the quality?

Question

As you work in a legacy codebase what will have the greatest impact over time that will improve the quality of the codebase?

• Remove unused code
• Remove dup

Answer 1

Good documentation. As someone who has to maintain and extend legacy code, that is the number one problem. It's difficult, if not downright dangerous to change code you don't understand. Even if you're lucky enough to be handed documented code, how sure are you that the documentation is right? That it covers all of the implicit knowledge of the original author? That it speaks to all of the "tricks" and edge cases?

Good documentation is what allows those other than the original author to understand, fix, and extend even bad code. I'll take hacked yet well-documented code that I can understand over perfect yet inscrutable code any day of the week.