Chapter 17: Crates, Modules, and Packages

In C, large projects are often divided into multiple .c and header files to organize code and share declarations. Although this approach works, it can cause name collisions, obscure dependencies, and leak implementation details through headers. Rust addresses these problems with a more robust, layered system consisting of packages, crates, and modules.

• Packages are the high-level collections of crates, managed by Cargo.
• Crates are individual compilation units—either libraries (.rlib files) or executables.
• Modules provide internal namespaces within a crate, allowing fine-grained control over item visibility.

This chapter dives into Rust’s module system, covering how you group code within crates, package multiple crates into a workspace, and manage everything with Cargo. While we touched on Cargo earlier, a more in-depth look at Rust’s build tool will appear in a later chapter.