Published Oct 20, 2023
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A variable is a fundamental concept in computer programming. It represents a location in computer memory used to store data temporarily. Whenever there’s a need to store a piece of data for use in a program, a variable is used. This practice ensures code reusability, as variables can replace the same value in multiple locations within the same code.

Data types in Rust

In the Rust programming language, variables are associated with specific data types. These data types determine:

  • The layout and size of the variable in memory.
  • The range of values that can be stored within that memory.
  • The operations that can be conducted on the variable.

Declaring a Variable

In Rust, variable declaration follows a specific syntax pattern. Here’s a basic example:

let number: i32 = 42;

The declaration above uses the name number, with an initial value of 42, and a data type of i32 (a 32-bit signed integer).

Declaring a Mutable Variable

The mut keyword is short for mutable and is used in combination with let to create mutable variables. Mutable variables allow their values to be changed after the initial assignment.

let mut number: f64 = 3.14159;


This example demonstrates variable declaration and mutability in Rust. First, it declares an immutable variable x with an initial value of 5 and a mutable variable y with an initial value of 10.

fn main() {
// Declare an immutable variable named 'x' with an initial value of 5.
let x = 5;
// Declare a mutable variable named 'y' with an initial value of 10.
let mut y = 10;
// Print the values of 'x' and 'y' to the console.
println!("Value of 'x': {}", x);
println!("Value of 'y': {}", y);
// Change the value of 'y'.
y = 20;
// Print the updated value of 'y' to the console.
println!("Updated value of 'y': {}", y);

This example results in the following output:

Value of 'x': 5
Value of 'y': 10
Updated value of 'y': 20

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