Kinds of Data (Types)

Think about a fruit basket. An apple, a banana, and a grape are all fruit, but they’re different kinds of fruit. In Rust, the values you store also come in different kinds. We call those kinds types. 🔢

The everyday types

Here are the ones you’ll meet most often:

i32 — a whole number, like 10 or -3. (No decimal point.)
f64 — a decimal number, like 3.14 or 0.5.
bool — a true-or-false value: true or false.
char — a single character, like 'A' or '🦀'. (Use single quotes!)

New word A type is the kind of data a value is — a whole number, a decimal, a true/false, a letter, and so on.

What about words?

A piece of text is called a string. You write it inside double quotes, like "hello". There are two flavors you’ll hear about: &str (a quick borrowed bit of text) and String (text you can grow and change). For now, just remember: text goes in double quotes. 📝

fn main() {
    let age: i32 = 10;
    let height: f64 = 1.4;
    let is_fun: bool = true;
    let grade: char = 'A';
    let name: &str = "Ferris";

    println!("Name: {name}");
    println!("Age: {age}");
    println!("Height: {height}");
    println!("Likes coding? {is_fun}");
    println!("Grade: {grade}");
}

The little : i32 after a name tells Rust the type. Most of the time Rust can guess the type on its own, but writing it out makes things extra clear. 🎉

Groups of values: tuples and arrays

Sometimes you want to keep a few values together:

A tuple holds a small mix of different things: (10, "ten", true).
An array holds a list of the same kind of thing: [1, 2, 3].

Think of it like this… A tuple is like a meal deal with a sandwich, a drink, and a side — all different things bundled together. An array is like an egg carton — every slot holds the same kind of thing. 🥚

Try this! Add a line that makes a decimal called let pi: f64 = 3.14; and print it. Press ▶ Run to see your decimal appear!

Quick quiz

Which type would you use for the value true?

Yes! A bool holds a true-or-false value. 👍

You learned… Every value has a type: whole numbers (i32), decimals (f64), true/false (bool), single letters (char), and text (&str / String). Next up: building little machines called functions! ⚙️