prime number logic code example

Example 1: Write a function to check if a number is prime?

#include 
int main() {
    int n, i, flag = 0;
    printf("Enter a positive integer: ");
    scanf("%d", &n);

    for (i = 2; i <= n / 2; ++i) {

        // condition for non-prime
        if (n % i == 0) {
            flag = 1;
            break;
        }
    }

    if (n == 1) {
        printf("1 is neither prime nor composite.");
    }
    else {
        if (flag == 0)
            printf("%d is a prime number.", n);
        else
            printf("%d is not a prime number.", n);
    }

    return 0;
}

Example 2: program to know if a number is prime

#include
using namespace std;
bool Is_Prime(long long x){
	if(x%2==0)return false;
	for(int i=3;i*i<=x;i+=2)
		if(x%i==0)return false;
	return true;
}
int main(){
	long long x;
	cin>>x;
	if(Is_Prime(x))cout<<"Is Prime";
	else cout<<"Is not Prime";
}

Example 3: prime number c

#include 
int main()
{
   int i, num, p = 0;
   printf("Please enter a number: \n");
   scanf("%d", &num);
   for(i=1; i<=num; i++)
   {
      if(num%i==0)
      {
         p++;
      }
   }
   if(p==2)
   {
      printf("Entered number is %d "\
             "and it is a prime number.",num);
   }
   else
   {
      printf("Entered number is %d "\
             "and it is not a prime number.",num);
   }
}