This is an assignment I had to do, it is running but as soon as the program tries to output this line "3 is a prime number.", it doesn't work. Could someone please explain what errors I made and how to fix it? This is c++ if you didn't know already.

bool isPrime(int);

// ********************************************

int main()

{

// Declare program variables.

char goAgain;

int numberToTest;

bool numberIsPrime{};

// Loop as many times as the user would like

do {

// Prompt the user to enter a number and read their answer

do {

cout << "What positive whole number would you like to test to see if it is prime: ";

cin >> numberToTest;

} while (numberToTest <= 0);// the number to test must be greater than 0

// TODO: Call function to determine if the user's number is a prime

// Pass one argument representing the number to be tested

// Assign the returned value to the correct variable

// numberIsPrime = isPrime(numberToTest);

// Display output

if (numberIsPrime)

cout << numberToTest << " is a prime number." << endl;

else

cout << numberToTest << " is NOT a prime number." << endl;

cout << endl;

// Ask the user if they want to test another number and read their answer

cout << "Do you want to test another number (y/n): ";

cin >> goAgain;

} while (tolower(goAgain) == 'y');// Repeat until the user answers something other than Y or y.

cout << "End program - ";

return 0;

}

// Define/Implement function HERE

bool isPrime(int a)

{

int i, counter = 0;

for (i = 2; i < a, i++;)

{

if (a % i == 0)

counter++;

}

if (counter == 0)

return true;

else

return false;

}

/* Sample Output

What positive whole number would you like to test to see if it is prime: -10

What positive whole number would you like to test to see if it is prime: 0

What positive whole number would you like to test to see if it is prime: 3

3 is a prime number.

Do you want to test another number (y/n): y

What positive whole number would you like to test to see if it is prime: 4

4 is NOT a prime number.

Do you want to test another number (y/n): y

What positive whole number would you like to test to see if it is prime: 5

5 is a prime number.

Do you want to test another number (y/n): y

What positive whole number would you like to test to see if it is prime: 67

67 is a prime number.

Do you want to test another number (y/n): n

End program - Press any key to continue . . .

*/