First Project

Cargo makes Rust development easy.

Create a project

cargo new hello_rust

f This creates:

hello_rust/
 ├── Cargo.toml
 └── src/
     └── main.rs

Understand the Files

Cargo.toml (Project configuration)

[package]
name = "hello_rust"
version = "0.1.0"
edition = "2021"

[dependencies]

• name → project name
• version → project version
• dependencies → external libraries

src/main.rs (Main program)

fn main() {
    println!("Hello, Rust!");
}

Running the Program

Inside the project folder:

cd hello_rust
cargo run

Output:

Hello, Rust!

Your first Rust program is running!

Explanation of the Example Code

fn main() {
    let name = "Rust";
    println!("Hello, {}!", name);
}

Code	Meaning
fn	Defines a function
main()	Program entry point
let	Declares a variable
"Rust"	String literal
{}	Placeholder for formatting
println!	Macro to print text to the console
!	Indicates a macro (not a normal function)

Building Without Running

To compile only:

cargo build

To build an optimized version:

cargo build --release

Compiled files go to:

target/
 ├── debug/
 └── release/

Adding a Dependency Example

Let’s add a dependency to show Cargo’s power.

Step 1: Edit Cargo.toml

[dependencies]
rand = "0.8"

Step 2: Use it in code

use rand::Rng;
fn main() {
    let number = rand::thread_rng().gen_range(1..=10);
    println!("Random number: {}", number);
}

Step 3: Run

cargo run

Cargo will:

• Download rand
• Compile it with rustc
• Link it automatically

Useful Cargo Commands

Command	Purpose
cargo new	Create new project
cargo run	Build + run
cargo build	Compile
cargo check	Check errors (fast)
cargo test	Run tests
cargo update	Update dependencies