Objective:

Write a C++ program to calculate the factorial of a number using a while loop.

Task:

1. Write a program that prompts the user to enter a number.
2. The program should calculate the factorial of that number using a while loop and display the result.

Code:

#include <iostream>
using namespace std;

int main() {
    int num, factorial = 1;

    cout << "Enter a number: ";
    cin >> num;

    if (num < 0) {
        cout << "Factorial is not defined for negative numbers." << endl;
    } else {
        int i = 1;
        while (i <= num) {
            factorial *= i;
            i++;
        }

        cout << "The factorial of " << num << " is: " << factorial << endl;
    }

    return 0;
}

Explanation:

This program prompts the user to enter a number (num).
It checks if the number is negative. If negative, it outputs that the factorial is not defined for negative numbers.
It uses a while loop to calculate the factorial of the number by multiplying the factorial variable with numbers from 1 to num.
The result is displayed using the cout statement.

Expected Output:

Enter a number: 5
The factorial of 5 is: 120