🔄📚Intermediate

Check Prime Number By Creating Function

Function to check prime

This program demonstrates how to create a reusable function to check if a number is prime. Functions make code modular and reusable.

Program Code

prime_function.c

1#include <stdio.h>
2#include <stdbool.h>
3
4// Function to check if a number is prime
5bool isPrime(int num) {
6    if (num <= 1) return false;
7    if (num <= 3) return true;
8    if (num % 2 == 0 || num % 3 == 0) return false;
9    
10    for (int i = 5; i * i <= num; i += 6) {
11        if (num % i == 0 || num % (i + 2) == 0)
12            return false;
13    }
14    return true;
15}
16
17int main() {
18    int num;
19    
20    printf("Enter a number: ");
21    scanf("%d", &num);
22    
23    if (isPrime(num)) {
24        printf("%d is Prime\n", num);
25    } else {
26        printf("%d is Not Prime\n", num);
27    }
28    
29    return 0;
30}