C++ code

#include <iostream>
using namespace std;

// Function to perform addition
double add(double a, double b) {
    return a + b;
}

// Function to perform subtraction
double subtract(double a, double b) {
    return a - b;
}

// Function to perform multiplication
double multiply(double a, double b) {
    return a * b;
}

// Function to perform division
double divide(double a, double b) {
    if (b != 0) {
        return a / b;
    } else {
        cout << "Error: Division by zero!" << endl;
        return 0;
    }
}

int main() {
    double num1, num2;
    char operation;
    bool running = true;

    while (running) {
        // Display menu
        cout << "Simple Calculator" << endl;
        cout << "Choose an operation:" << endl;
        cout << "+ : Addition" << endl;
        cout << "- : Subtraction" << endl;
        cout << "* : Multiplication" << endl;
        cout << "/ : Division" << endl;
        cout << "q : Quit" << endl;

        // Take user input for operation
        cout << "Enter operation: ";
        cin >> operation;

        // Check if the user wants to quit
        if (operation == 'q') {
            running = false;
            break;
        }

        // Take user input for numbers
        cout << "Enter first number: ";
        cin >> num1;
        cout << "Enter second number: ";
        cin >> num2;

        // Perform the selected operation
        double result;
        switch (operation) {
            case '+':
                result = add(num1, num2);
                cout << "Result: " << result << endl;
                break;
            case '-':
                result = subtract(num1, num2);
                cout << "Result: " << result << endl;
                break;
            case '*':
                result = multiply(num1, num2);
                cout << "Result: " << result << endl;
                break;
            case '/':
                result = divide(num1, num2);
                cout << "Result: " << result << endl;
                break;
            default:
                cout << "Invalid operation!" << endl;
                break;
        }

        // Adding a newline for better readability
        cout << endl;
    }

    cout << "Calculator closed." << endl;
    return 0;
}