Question

Write a function called "isPrime()” that checks if an integer number is prime or not. The function returns integer 1 if the number is prime, or integer 0 if the number is not prime. Write a simple test program in main() to show that the function works properly.in C programming language.

Answer 1

#include <stdio.h>

int isPrime(int n);

int main() {
    int n;
    printf("Enter a number: ");
    scanf("%d", &n);

    if (isPrime(n)) {
        printf("%d is a prime number.\n", n);
    } else {
        printf("%d is not a prime number.\n", n);
    }
    return 0;
}

int isPrime(int n) {
    int i;
    for (i = 2; i < n; ++i) {
        if (n % i == 0) {
            return 0;
        }
    }
    return n > 1;
}