Lecture 37 - Check Given Number Prime or Not

To check whether a given number is prime or not, you can write a C++ program that takes an integer input from the user and checks for its divisibility by any numbers other than 1 and itself. A prime number is a positive integer greater than 1 that has no positive divisors other than 1 and itself.

Here's a C++ program to check if a given number is prime or not:

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#include <iostream> bool isPrime(int number) {    if (number <= 1) {        return false;    }    for (int i = 2; i * i <= number; i++) {        if (number % i == 0) {            return false;        }    }    return true; } int main() {    int number;    std::cout << "Enter a positive integer: ";    std::cin >> number;    if (isPrime(number)) {        std::cout << number << " is a prime number." << std::endl;    } else {        std::cout << number << " is not a prime number." << std::endl;    }    return 0; }

Example output:

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Enter a positive integer: 7 7 is a prime number.

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Enter a positive integer: 10 10 is not a prime number.

In the program, we define a separate function isPrime that takes an integer as an argument and returns a boolean value. This function checks whether the number is prime or not by iterating from 2 up to the square root of the number. If the number is divisible by any value in this range, it returns false; otherwise, it returns true. We handle the special cases of numbers less than or equal to 1, as they are not considered prime.

Feel free to run this program with different positive integers to check if they are prime or not.