📦 variable — Rust Variables

In Rust, variables are used to store data for later use in your program. They are declared using the let keyword.

By default, Rust variables are immutable — meaning once a value is assigned, it cannot be changed. If you want to change the value of a variable later, you must explicitly make it mutable by adding mut before the variable name.

fn main() {
    let x = 5;//immutable variable
    println!("x is: {}", x);
}

🔎 Line-by-line breakdown:

  • let creates a new variable.

  • x is the variable name.

  • 5 is the integer value assigned.

  • println! is a macro that prints text to the console.

💡 If you're not sure what a macro is, don’t worry! For now, just remember that println! is used to display text in the console.

You might be wondering about the {} inside the string:
This is a placeholder. It gets replaced by the value of x when printed. So the line:

#![allow(unused)]
fn main() {
println!("x is: {}", x);
}

will output:

#![allow(unused)]
fn main() {
x is: 5
}