Q2. Check if a number is a prime number

## Q2. Check if a number is a prime number using a function

### Note on booleans in C++

boolean variables can be declared using the bool keyword
For example,

```bool bPrime = true;
```

Read the following code carefully to understand how to use booleans in C++

### Solution

```/* primetester.cpp */

#include <iostream>
using namespace std;

//function prototype declaration
bool isPrime(int number);

int main() {
int num = 0;

cout << "Enter a number:";   //display prompt to the user
cin >> num;                  //read the number from the keyboard

bool bPrime = isPrime(num);  //call the isPrime function
cout << "bPrime:" << bPrime << endl; //if false print 0 - if true prints 1

if(bPrime == true)              //print whether the number is prime or not
cout << num << " is a prime number" << endl;
else
cout << num << " is not a prime number" << endl;

system("pause"); //this stops the output window from closing automatically
}

bool isPrime(int number) {
bool bPrime = true; //assume that the number is prime

//now test if the number is actually a prime number
for (int i = 2 ; i < number ; i++) {
if (number % i == 0) {
//number is not prime - set bPrime to false
bPrime = false;
//and come out of the loop using break
break;
}
}

return bPrime;
}
```
page revision: 1, last edited: 09 Sep 2009 10:08
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