Complex software is built in different modules. Those modules have different names in every language -- packages, libraries, etc. -- but modularity is always introduced to help manage the complexity of large projects. One software project may import dozens, or even hundreds, of previously built software modules. What happens when one of those modules changes? If you don't know how those modules fit together, it's a disaster. Which is why we cover build management in the chapter entitled Chapter 5, Building the Code.