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:

cin >>input;

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

Code:

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.