The Cargo Book

Cargo uses conventions for file placement to make it easy to dive into a new Cargo package:

.
├── Cargo.lock
├── Cargo.toml
├── benches
│   └── large-input.rs
├── examples
│   └── simple.rs
├── src
│   ├── bin
│   │   └── another_executable.rs
│   ├── lib.rs
│   └── main.rs
└── tests
    └── some-integration-tests.rs

• Cargo.toml and Cargo.lock are stored in the root of your package (package root).
• Source code goes in the src directory.
• The default library file is src/lib.rs.
• The default executable file is src/main.rs.
• Other executables can be placed in src/bin/*.rs.
• Integration tests go in the tests directory (unit tests go in each file they're testing).
• Examples go in the examples directory.
• Benchmarks go in the benches directory.

These are explained in more detail in the manifest description.