答：下面是一段素数代码：

include

using namespace std;

int main()
{

int n, i; 

cout << "Enter a positive integer: "; 

cin >> n;  

bool isPrime = true;  

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

    if(n % i == 0) {  

        isPrime = false;  

        break;  

    }  

}  

if (isPrime) {     cout << n << " is a prime number";}     else { cout << n << " is not a prime number";}      return 0; }