Check if Number is Prime in DSA C - Build from Scratch

Check if Number is Prime

📖 Scenario: You are helping a friend who wants to know if a number is prime. A prime number is a number greater than 1 that has no divisors other than 1 and itself.We will write a simple program in C to check if a given number is prime.

🎯 Goal: Build a C program that checks if a number is prime by testing divisibility from 2 up to the number minus one.

📋 What You'll Learn

Create an integer variable called number with the value 29

Create an integer variable called is_prime and set it to 1 (true)

Use a for loop with variable i from 2 to number - 1

Inside the loop, check if number is divisible by i

If divisible, set is_prime to 0 (false) and break the loop

Print "Prime" if is_prime is 1, otherwise print "Not Prime"

💡 Why This Matters

🌍 Real World

Prime numbers are used in cryptography, computer security, and coding theory.

💼 Career

Understanding prime checking helps in algorithm design and problem solving in software development.

1

Create the number variable

Create an integer variable called number and set it to 29.

DSA C

#include 

int main() {
    // Create an integer variable called number and set it to 29
    
    return 0;
}

Hint

Use int number = 29; inside main().

2

Create the is_prime variable

Create an integer variable called is_prime and set it to 1 inside main() after number.

DSA C

#include 

int main() {
    int number = 29;
    // Create an integer variable called is_prime and set it to 1
    
    return 0;
}

Hint

Use int is_prime = 1; to assume the number is prime initially.

3

Check divisibility with a for loop

Use a for loop with variable i from 2 to number - 1. Inside the loop, check if number % i == 0. If yes, set is_prime to 0 and break the loop.

DSA C

#include 

int main() {
    int number = 29;
    int is_prime = 1;
    // Use a for loop from i = 2 to number - 1
    // Check if number is divisible by i
    // If divisible, set is_prime to 0 and break
    
    return 0;
}

Hint

Use for (int i = 2; i < number; i++) and inside check if (number % i == 0).

4

Print if the number is prime or not

Use an if statement to print "Prime" if is_prime is 1, otherwise print "Not Prime".

DSA C

#include 

int main() {
    int number = 29;
    int is_prime = 1;

    for (int i = 2; i < number; i++) {
        if (number % i == 0) {
            is_prime = 0;
            break;
        }
    }

    // Print "Prime" if is_prime is 1, else print "Not Prime"
    
    return 0;
}

Hint

Use if (is_prime == 1) and printf("Prime\n"), else print "Not Prime".