Modulo Operator

Part of the Fundamentals section of Coddy's Swift journey — lesson 17 of 86.

The modulo operator (%) returns the remainder after dividing one number by another. While division tells you how many times a number fits into another, modulo tells you what's left over.

let remainder = 10 % 3  // 1
print(remainder)        // 1

Here, 3 fits into 10 exactly 3 times (which equals 9), leaving a remainder of 1. This operator is incredibly useful for determining if a number is divisible by another — when the remainder is 0, the division is exact.

let evenCheck = 8 % 2   // 0 (8 is even)
let oddCheck = 7 % 2    // 1 (7 is odd)

A common use case is checking whether a number is even or odd. If a number modulo 2 equals 0, it's even; otherwise, it's odd. You'll also find modulo helpful for tasks like cycling through values or wrapping numbers within a range.

Challenge

Easy

Write a function getRemainder that takes two integers dividend and divisor, and returns the remainder when the dividend is divided by the divisor.

Use the modulo operator to calculate what's left over after division.

Parameters:

dividend (Int): The number being divided
divisor (Int): The number to divide by

Returns: The remainder after dividing dividend by divisor (Int)

Cheat sheet

The modulo operator (%) returns the remainder after dividing one number by another:

let remainder = 10 % 3  // 1
print(remainder)        // 1

When the remainder is 0, the division is exact (the number is divisible):

let evenCheck = 8 % 2   // 0 (8 is even)
let oddCheck = 7 % 2    // 1 (7 is odd)

Common use case: checking if a number is even or odd. If number % 2 equals 0, it's even; otherwise, it's odd.

Try it yourself

func getRemainder(dividend: Int, divisor: Int) -> Int {
    // Write code here
}

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Fundamentals

1Introduction

The Language Hello World!Comments

4Operators Part 1

Arithmetic OperatorsModulo OperatorCompound Assignment Recap - Simple Math Comparison Operators

7Basic IO

Print Function String Interpolation ReadLine Input Type Conversion Recap - Till 120 Recap - True or False

10Functions

Declare A Function Parameters And Arguments Return Values Argument Labels Recap - Sigma Function Recap - Validation Function Default Values

13Iterating Over Sequences

Iterating Over Elements The Enumerated Method Iterating Over Strings P1 Iterating Over Strings P2

16Final Challenges

Flat Asterisk Pyramid Pattern Finder What To Buy

2Variables

Let vs Var Type Annotations Numbers String Boolean Naming Conventions Recap - Initialize Variables

5Operators Part 2

Logical Operators Part 1 Logical Operators Part 2 Recap - Simple Logic Logical Operators Part 3 Ternary Operator

8Bill Split Calculator

Welcome Message Getting Input

Calculating Tip And Total

Splitting The Bill

Formatted Output

11FizzBuzz with a Twist

Game Overview The FizzBuzz Function

Looping The Numbers

Adding The Twist

14Arrays Advanced

Array Slicing Part 1 Array Slicing Part 2 Sequence Operators The Contains Method