prime.c

/*
 *  Test if a number is Prime or not. 
 */
#include <stdio.h>

int isPrime(int n) {

    if(n == 0 || n == 1) return 0;

    if(n == 2 || n == 3) return 1;

    int prime = 1, k = 2; 

    while(prime && k * k <= n) {

          prime = (n % k != 0);

          k++;
    }

    return prime;
};

int main() {

    int n;

    printf("n=");
    scanf("%d", &n);

    if(isPrime(n)) printf("%d is Prime Number!\n", n);   
       else printf("Is not prime!\n");  
  
   return(0);
}