C++ Program to Check Prime Number By Creating a Function

You will learn to check whether a number entered by the user is prime or not by passing it to a user-defined function.

Example: Check Prime Number

#include <iostream>
using namespace std;

int checkPrimeNumber(int);

int main()
{
  int n;

  cout << "Enter a positive  integer: ";
  cin >> n;
  
  if(checkPrimeNumber(n) == 0)
    cout << n << " is a prime number.";
  else
    cout << n << " is not a prime number.";
  return 0;
}
int checkPrimeNumber(int n)
{
  bool flag = false;

  for(int i = 2; i <= n/2; ++i)
  {
      if(n%i == 0)
      {
          flag = true;
          break;
      }
  }
  return flag;
}

Output

Enter a positive  integer: 23
23 is a prime number.

In this example, the number entered by the user is passed to the checkPrimeNumber() function.

This function returns true if the number passed to the function is a prime number, and returns false if the number passed is not a prime number.

Finally, the appropriate message is printed from the main() function