Tools and Techniques (Score 1)

I do C++ consulting work, so I have to climb the code-base comprehension mountain fairly often. These are the tools and techniques I find most helpful:

• ctags + <a text editor that supports ctags>: The last thing you need when trying to answer the question "what does this function call do" is to be distracted by trying to locate the function.
• A debugger: Being able to set breakpoints and examine the state of the program is a must. Make sure you are fluent in your debugger's capabilities and usage. Setting breakpoints in code sections that you've discovered and then examining the stack to see how you got there is very useful in understanding how things are architected.
• Doxygen: Even on code bases that don't use doxygen-style comments, Doxygen can still generate useful information, especially call graphs and class hierarchies.
• When getting started, ask yourself questions based on the observable behavior of the program. For example, "How does the piece of data I entered here make its way to this output file." Use your tools to find the answer. Repeat until you start to get a feel for how things work.