Unlocking the Secrets of Prime Numbers with C++

Prerequisites

To fully understand this example, you should have a solid grasp of the following C++ concepts:

• For loops
• If-else statements
• Functions
• User-defined function types

If you’re new to these topics, take a moment to review them before proceeding.

The Quest for Prime Numbers

Imagine being able to determine whether a given number is prime or not. Sounds like a challenge, right? That’s exactly what we’ll tackle in this example.

The user inputs a number, which is then passed to the check_prime() function. This function is the brains behind the operation, returning true if the number is prime and false otherwise.

Unraveling the Mystery of the check_prime() Function

So, how does this function work its magic? Essentially, it takes a number as input and applies a series of tests to determine its primality.

bool check_prime(int num) {
  if (num <= 1) {
    return false;
  }
  for (int i = 2; i * i <= num; i++) {
    if (num % i == 0) {
      return false;
    }
  }
  return true;
}

Want to know the nitty-gritty details? Here’s a step-by-step breakdown:

1. We start by checking if the number is less than or equal to 1, in which case it’s not prime.
2. We then iterate from 2 to the square root of the number, checking if the number is divisible by any of these values.
3. If we find a divisor, we immediately return false, indicating that the number is not prime.
4. If we reach the end of the loop without finding a divisor, we return true, indicating that the number is prime.

The Main Event: Printing the Verdict

Back in the main() function, we receive the verdict from check_prime() and print out a message accordingly.

int main() {
  int num;
  std::cout << "Enter a number: ";
  std::cin >> num;
  if (check_prime(num)) {
    std::cout << "The number is prime!" << std::endl;
  } else {
    std::cout << "The number is not prime." << std::endl;
  }
  return 0;
}

If the number is prime, we celebrate with a triumphant message. Otherwise, we politely inform the user that their number didn’t make the cut.

Putting it All Together

With these components in place, we’ve created a robust program that can accurately identify prime numbers. By harnessing the power of C++ functions and logical operators, we’ve made the complex seem simple.

Now it’s your turn to experiment and push the boundaries of what’s possible!