If every program worked the first time you tried it, that would be the complete development cycle: write the program, compile the source code, link the program, and run it. Unfortunately, almost every program, no matter how trivial, can and will have errors, or bugs, in it. Some bugs will cause the compile to fail, some will cause the link to fail, and some will only show up when you run the program.
Whatever the type of bug you find, you must fix it, and that involves editing your source code, recompiling, relinking, and then rerunning the program. This cycle is represented in Figure 1.3, which diagrams the steps in the development cycle.