# 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.

To understand this example, you should have the knowledge of following C++ programming topics:

• C++ for Loop
• C++ if, if…else and Nested if…else
• C++ break and continue Statement
• C++ Functions
• Types of User-defined Functions in C++

## Example: Check Prime Number

```#include <iostream>
using namespace std;

int main()
{
int n;

cout << "Enter a positive  integer: ";
cin >> n;

cout << n << " is a prime number.";
else
cout << n << " is not a prime number.";
return 0;
}
{
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