For a system of moderate complexity, there are myriad answers to question (1). A skilled programmer has the intuition to guess the most likely causes. This rang

For a system of moderate complexity, there are myriad answers to question (1). A skilled programmer has the intuition to guess the most likely causes. This ranges from the mundane (e.g. recompile everything from scratch) to the occasional almost magical lucky guess which immediately leads to a solution.