Modular Arithmetic Basics in DSA C - Build from Scratch

Modular Arithmetic Basics

📖 Scenario: You are working on a simple calculator that needs to handle modular arithmetic operations. Modular arithmetic means working with remainders after division by a fixed number called the modulus.For example, if the modulus is 5, then 7 mod 5 is 2 because 7 divided by 5 leaves a remainder of 2.

🎯 Goal: Build a small program that calculates the remainder of numbers when divided by a given modulus. You will create a list of numbers, set the modulus, compute the remainders, and then print the results.

📋 What You'll Learn

Create an array of integers with exact values

Create an integer variable for the modulus

Use a loop to compute the remainder of each number when divided by the modulus

Print the remainders in order separated by spaces

💡 Why This Matters

🌍 Real World

Modular arithmetic is used in computer science for hashing, cryptography, and cyclic operations like clock arithmetic.

💼 Career

Understanding modular arithmetic helps in programming tasks involving cycles, encryption, and algorithms that require remainder calculations.

1

Create the array of numbers

Create an integer array called numbers with these exact values: 12, 25, 7, 30, 18.

DSA C

# Your code here

Hint

Use curly braces to list the numbers inside the array.

2

Set the modulus value

Create an integer variable called modulus and set it to 5.

DSA C

int numbers[] = {12, 25, 7, 30, 18};
# Your code here

Hint

Just create a normal integer variable and assign 5 to it.

3

Calculate remainders using modular arithmetic

Use a for loop with variable i from 0 to 4 to calculate the remainder of each element in numbers when divided by modulus. Store each remainder back into the numbers array at the same index.

DSA C

int numbers[] = {12, 25, 7, 30, 18};
int modulus = 5;
// Your code here

Hint

Use the % operator to get the remainder.

4

Print the remainders

Use a for loop with variable i from 0 to 4 to print each element of numbers followed by a space. Then print a newline character.

DSA C

int numbers[] = {12, 25, 7, 30, 18};
int modulus = 5;
for (int i = 0; i < 5; i++) {
    numbers[i] = numbers[i] % modulus;
}
// Your code here

Hint

Use printf("%d ", numbers[i]) inside the loop and printf("\n") after the loop.