Prime Number Checker

A simple C library for working with prime numbers.

Functions

is_prime(int x)

Checks if a number is prime.

• Returns:
  • 1 if the number is prime
  • 0 if the number is not prime
  • -1 if the number is less than 2

next_prime(int x)

Finds the next prime number starting from the given number.

• Returns: The next prime number greater than or equal to x

Files

• prime.h - Header file with function declarations
• prime.c - Implementation of prime number functions

Usage

Include the header file in your C program:

#include "prime.h"

int main() {
    int num = 10;
    
    if (is_prime(num) == 1) {
        printf("%d is prime\n", num);
    } else {
        printf("%d is not prime\n", num);
    }
    
    printf("Next prime after %d is %d\n", num, next_prime(num));
    
    return 0;
}

Compilation

Compile your program with:

gcc -o program main.c prime.c -lm

Note: The -lm flag is needed to link the math library for the sqrt() function.