The Rust Programming Language (Covers Rust 2018)

7MANAGING GROWING PROJECTS WITH PACKAGES, CRATES, AND MODULES

As you write large programs, organizing your code will be important because keeping track of your entire program in your head will become impossible. By grouping related functionality and separating code with distinct features, you’ll clarify where to find code that implements a particular feature and where to go to change how a feature works.

The programs we’ve written so far have been in one module in one file. As a project grows, you can organize code by splitting it into multiple modules and then multiple files. A package can contain multiple binary crates and optionally one library ...