Zig Basic Types

A type describes the kind of value that a name holds. Zig has whole-number types, decimal-number types, and a true-or-false type.

Whole-number types hold positive and negative values

i32 values can be negative or positive. A u8 value stays between 0 and 255.

const std = @import("std");

pub fn main() !void {
    const out = std.io.getStdOut().writer();
    const age: i32 = 30;
    const below: i32 = -5;
    const level: u8 = 7;
    try out.print("Age: {d}\n", .{age});
    try out.print("Below: {d}\n", .{below});
    try out.print("Level: {d}\n", .{level});
}

Float types hold decimal numbers

An f64 value can keep a decimal part. A whole float value prints with no decimal part.

const std = @import("std");

pub fn main() !void {
    const out = std.io.getStdOut().writer();
    const pi: f64 = 3.14;
    const whole: f32 = 3.0;
    try out.print("Pi: {d}\n", .{pi});
    try out.print("Whole: {d}\n", .{whole});
}

A bool holds true or false

Each bool name below holds a different one of the two bool values. The prints show both.

const std = @import("std");

pub fn main() !void {
    const out = std.io.getStdOut().writer();
    const ready: bool = true;
    const finished: bool = false;
    try out.print("Ready: {}\n", .{ready});
    try out.print("Finished: {}\n", .{finished});
}

Example

const std = @import("std");

pub fn main() !void {
    const out = std.io.getStdOut().writer();
    const count: i32 = 12;
    const price: f64 = 9.5;
    const code: u8 = 200;
    const in_stock: bool = true;
    try out.print("Count: {d}\n", .{count});
    try out.print("Price: {d}\n", .{price});
    try out.print("Code: {d}\n", .{code});
    try out.print("In stock: {}\n", .{in_stock});
}

Key points

Type: a type says what kind of value a name can hold.
i32: i32 holds whole numbers, both negative and positive.
u8: u8 holds whole numbers from 0 to 255, with no negative values.
f64: f64 holds numbers with a decimal part, such as 3.14.
bool: bool holds one of two values, true or false.
Annotation: writing a type after a name, after a colon, states that name's type.

In this example, count is an i32 and price is an f64, so one holds a whole number and the other holds a decimal number. code is a u8 that holds 200, and in_stock is a bool that holds true.

Note

a value that cannot fit in its type is a compile error in Zig.

Try it Yourself

Edit the code, then press Run.

Running is simulated

const std = @import("std");

pub fn main() !void {
    const out = std.io.getStdOut().writer();
    const count: i32 = 12;
    const price: f64 = 9.5;
    const code: u8 = 200;
    const in_stock: bool = true;
    try out.print("Count: {d}\n", .{count});
    try out.print("Price: {d}\n", .{price});
    try out.print("Code: {d}\n", .{code});
    try out.print("In stock: {}\n", .{in_stock});
}

Exercise

Which type holds the values true and false?

f64 bool u8 i32