How do I loop a menu driven program that uses a switch case?

Question

I need to ask the user in this way "Do you want to do it again?" and the user will choose Y or N whether they want to compute another set of numbers and go through the program all over again.

#include <iostream>

using namespace std;

int main()
{
    float x, y;
    float Sum, Difference, Product, Quotient;
    char choice;

    cout << "Enter x and y: ";
    cin >> x >> y;
    cout << "MENU" << endl;
    cout << "A: Addition " << endl;
    cout << "B: Subtraction" << endl;
    cout << "C: Multiplication " << endl;
    cout << "D: Division " << endl;
    cout << "E: Exit " << endl;
    cout << "Enter your choice :";
    cin >> choice;
        switch (choice)
        {
        case 'A':
            Sum = x+y;
            cout << x << "+" << y << "=" << Sum <<endl;
            break;
        case 'B':
            Difference = x-y;
            cout << x << "-" << y << "=" << Difference <<endl;
            break;
        case 'C':
            Product = x*y;
            cout << x << "*" << y << "=" << Product <<endl;
            break;
        case 'D':
            Quotient = x/y;
            cout << x << "/" << y << "=" <<  Quotient <<endl;
            break;
        case 'E':
            break;
        default:
            cout << "Invalid input" << endl;
        }
    return 0;
}

Answer 1

It's actually pretty simple. You can use loops as such:

    #include <iostream>

    using namespace std;

    void showChoices();
    int main()
    {
        while (true) // This is a while loop
        {
            system("cls"); // Clear the screen. If you don't want to clear the screen you can remove this line

            float x, y;
            float Sum, Difference, Product, Quotient;
            char choice;

            cout << "Enter x and y: ";
            cin >> x >> y;

            showChoices();
            cin >> choice;
            switch (choice)
            {
            case 'A':
                Sum = x + y;
                cout << x << "+" << y << "=" << Sum << endl;
                break;
            case 'B':
                Difference = x - y;
                cout << x << "-" << y << "=" << Difference << endl;
                break;
            case 'C':
                Product = x - y;
                cout << x << "*" << y << "=" << Product << endl;
                break;
            case 'D':
                Quotient = x - y;
                cout << x << "/" << y << "=" << Quotient << endl;
                break;
            case 'E':
                return 0; // Instead of break, use return here
            default:
                cout << "Invalid input" << endl;
            }
        }
    }

    void showChoices()
    {
        cout << "MENU" << endl;
        cout << "A: Addition " << endl;
        cout << "B: Subtraction" << endl;
        cout << "C: Multiplication " << endl;
        cout << "D: Division " << endl;
        cout << "E: Exit " << endl;
        cout << "Enter your choice :";
    }

Also consider removing the line:

using namespace std

...because it's not considered as a good practice.

Also consider refactoring your code by moving the code inside the loop to a separate function, which returns a boolean something like this:

    #include <iostream>

    using namespace std;

    void showChoices();
    bool askUser();
    int main()
    {
        while (askUser()) { /* Loop */ }
    }

    void showChoices()
    {
        cout << "MENU" << endl;
        cout << "A: Addition " << endl;
        cout << "B: Subtraction" << endl;
        cout << "C: Multiplication " << endl;
        cout << "D: Division " << endl;
        cout << "E: Exit " << endl;
        cout << "Enter your choice :";
    }

    bool askUser()
    {
        system("cls"); // Clear the screen. Can be removed if you don't want to do so.

        float x, y;
        float Sum, Difference, Product, Quotient;
        char choice;

        cout << "Enter x and y: ";
        cin >> x >> y;

        showChoices();
        cin >> choice;
        switch (choice)
        {
        case 'A':
            Sum = x + y;
            cout << x << "+" << y << "=" << Sum << endl;
            break;
        case 'B':
            Difference = x - y;
            cout << x << "-" << y << "=" << Difference << endl;
            break;
        case 'C':
            Product = x - y;
            cout << x << "*" << y << "=" << Product << endl;
            break;
        case 'D':
            Quotient = x - y;
            cout << x << "/" << y << "=" << Quotient << endl;
            break;
        case 'E':
            return false;
        default:
            cout << "Invalid input" << endl;
        }

        return true;
    }

I hope it was useful :).