calculating dimensions of a cirlce

Hi,
My menu driven program that repeatedly calculates and prints the diameter of, circumference or area of circle, given the radius,
is not doing what I want it to do...
Can code doc / code friend point out how to make it work?
Thanks

Code:

---

#include<iostream>
using std::cout;
using std::cin;
using std::endl;
#include <iomanip>
using std::setprecision;

int main()
{
        double Diameter, Area, Circumference, radius;
        char D=0, A=0, C=0, X=0, input=0;


        cout << "Please pick an option: " << endl
                  << "Calculate the diameter of the circle:  'D' " << endl
                << "Calculate the area of the circle:      'A' " << endl
                << "Calculate the circumference:                'C' " << endl
                << "Exit the program:                                        'X' " << endl;
                        cin >> ( D || A || C || X )
        cout << setprecision ( 2 )
       
        {
        if ( input == D ){
                        cout << "Enter the lenght of the radius: " << endl;
                        cin >> radius;
                        Diameter = 2* radius ;
                cout << " The diameter of circle with radius " << radius << "is " << Diameter << endl;
        }       
                if ( input == A )
                {                cout << "Enter the lenght of the radius: " << endl;
                        cin >> radius;
                        Area = 3.14 * radius * radius ;
                cout << " The area of cirlce with radius " << radius << "is" << Area << endl;
                }
                if ( input == C)
                {        cout << "Enter the lenght of radius: " << endl;
                        cin >> radius;
                        Circumference = 2 * 3.14 * radius ;
                        cout << "The circumference of the circle with radius " << radius << "is " << Circumference << endl;
                }
                if ( input == X)
                        cout << "Good bye" << endl;
        }
                return 0;

}

---

Please use code tags next time.

It looks like your main problem is this:

Code:

---

cin >> ( D || A || C || X );

---

That line should be:

Code:

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cin >>input;

---

Also, you may want to look into switch statements. For example:

Code:

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switch( input ) //Make some decisions based on input
{
        case 'D': //Synonymous with "If input is == 'D' "
                //Diameter calculations
        break;
       
        case 'A':
                //Area calculations
        break;
       
        case 'C':
                //Circumference
        break;
       
        case 'X':
                //Leave
        break;
       
        default:
                //Unexpected input, problem
}

---

Note how I put character literals in single quotes ( eg 'D', not D ). There are some other logical problems with that code but I think that's enough for you to absorb.

I'm not sure if you cut and paste incorrectly or what, but you also have a nasty habbit of not putting semicolons at the end of a line of code. Also don't forget your code tags.