How to Debug by Splitting the Problem Space Debugging is fun, because it begins with a mystery. You think it should do something, but instead it does something else. It is not always quite so simple---any examples I can give will be contrived compared to what sometimes happens in practice. Debugging requires creativity and ingenuity. If there is a single key to debugging is to use the divide and conquer technique on the mystery.
How to Debug Using a Log
Logging is the practice of writing a system so that it produces a sequence of informative records, called a log. Printlining is just producing a simple, usually temporary, log. Absolute beginners must understand and use logs because their knowledge of the programming is limited; system architects must understand and use logs because of the complexity of the system.
How to Fix Performance Problems
Most software projects can be made 10 to 100 times faster than they are at the time that they are first released with relatively little effort. Under time-to-market pressure, it is both wise and effective to choose a solution that gets the job done simply and quickly, but less efficiently than some other solution. However, performance is a part of usability, and often it must eventually be considered more carefully.
How to Remove an Error
I've intentionally separated the act of examining a program's execution from the act of fixing an error. But of course, debugging does also mean removing the bug. Ideally you will have perfect understanding of the code and will reach an ‘A-Ha!’ moment where you perfectly see the error and how to fix it. But since your program will often use insufficiently documented systems into which you have no visibility, this is not always possible. In other cases the code is so complicated that your understanding cannot be perfect.
How to Understand Performance Problems
Learning to understand the performance of a running system is unavoidable for the same reason that learning debugging is. Even if you understand perfectly and precisely the cost of the code you write, your code will make calls into other software systems that you have little control over or visibility into. However, in practice performance problems are a little different and a little easier than debugging in general.
Learn to Debug
Debugging is the cornerstone of being a programmer. The first meaning of the verb to debug is to remove errors, but the meaning that really matters is to see into the execution of a program by examining it. A programmer that cannot debug effectively is blind.
To be a good programmer
To be a good programmer is difficult and noble. The hardest part of making real a collective vision of a software project is dealing with one's coworkers and customers. Writing computer programs is important and takes great intelligence and skill. But it is really child's play compared to everything else that a good programmer must do to make a software system that succeeds for both the customer and myriad colleagues for whom she is partially responsible. In this essay I attempt to summarize as concisely as possible those things that I wish someone had explained to me when I was twenty-one.
Debugging is fun, because it begins with a mystery. You think it should do something, but instead