Example: Mass and Weight Calculator in C++

// Mass and Weight Calculator
#include <iostream> // For input/output operations
#include <iomanip>  // For setting output precision

using namespace std;

int main() {
    // Step 1: Declare variables for mass, weight, and gravitational acceleration
    double mass_kg;
    double weight_newtons;
    const double GRAVITY_EARTH = 9.80665; // Standard gravity on Earth in m/s^2

    // Step 2: Prompt the user to enter their mass
    cout << "Welcome to the Mass and Weight Calculator!" << endl;
    cout << "------------------------------------------" << endl;
    cout << "Please enter your mass in kilograms (kg): ";
    cin >> mass_kg;

    // Step 3: Validate input
    if (mass_kg < 0) {
        cout << "Error: Mass cannot be negative. Please enter a valid mass." << endl;
        return 1; // Indicate an error
    }

    // Step 4: Calculate the weight using the formula W = m * g
    weight_newtons = mass_kg * GRAVITY_EARTH;

    // Step 5: Display the results
    cout << fixed << setprecision(2); // Set output to 2 decimal places
    cout << "\n--- Calculation Results ---" << endl;
    cout << "Your mass is: " << mass_kg << " kg" << endl;
    cout << "Gravitational acceleration (Earth): " << GRAVITY_EARTH << " m/s^2" << endl;
    cout << "Your weight on Earth is: " << weight_newtons << " Newtons (N)" << endl;
    cout << "---------------------------\n" << endl;

    return 0; // Indicate successful execution
}