A variable is a named storage that a program can manipulate.Simply put, variables help programs store values.Variables in Rust are associated with a specific data type.The data type determines the size and layout of the variable's memory, the range of values that can be stored in that memory, and the set of operations that can be performed on the variable.

Variable naming conventions

• Variable names consist of letters, numbers, and underscore characters

• Must start with a letter or underscore

• Case-sensitive

Syntax

The data type is optional while declaring a variable.

By default, the data type is inferred from the value assigned to the variable.

let variable_name = value;            // no type specified
let variable_name:dataType = value;   //type specified

fn main() {
   let fees = 25_000;
   let salary:f64 = 35_000.00;
   println!("fees is {} and salary is {}",fees,salary);
}

Immutable

Rust에서는 변수는 기본적으로 읽기 전용입니다.
즉, 값이 변수 이름에 바인딩되면 변수의 값을 변경할 수 없습니다.
Rust가 프로그래머가 코드를 작성하고 안전하고 쉬운 동시성을 활용할 수 있도록 하는 많은 방법 중 하나입니다.

fn main() {
   let fees = 25_000;
   println!("fees is {} ",fees);
   fees = 35_000;
   println!("fees changed is {}",fees);
}

Mutable

Variable names can be mutable by appending the mut keyword to them

fn main() {
  let mut fees: i32 = 25_000;
  println!("fees is {} ", fees);
  fees = 35_000;
  println!("fees changed is {}", fees);
}