case label??

[haxer]

This is my second program in c++ so im kind of new. Ive used the code below but i get quite a few errors. There was one that said "case label does not reduce to an integer constant" and i got no idea what to do. If someone could look at my code and tell me where i went wrong, and tell me if i might recieve more errors later on it would be greatly appreciated. Thanks, Heres the code:

include <iostream>

using namespace std;

int main(void)
{
system ("TITLE Calculator");
char cchar;
double dnumber1;
double dnumber2;
char cdoagain;

do
{
system("CLS");
cout << "Please Enter your First Number" <<endl;
cin >> dnumber1;
cout << endl;
cout << "Please type the operation you would like to use" <<endl;
cout << "+,-,x,/" <<endl;
cin >> cchar;
cout << endl <<"Please Enter the Second Number you would like to use" <<endl;
cin >> dnumber2;

switch (cchar)
{
case "+";  // THIS LINE IS HIGHLIGHTED WITH ERROR SIGN
       cout << dnumber1 << " + " << dnumber2 << " = " << (dnumber1 + dnumber2) <<endl;
       break;


case "-";
       cout << dnumber1 << " - " << dnumber2 << " = " << (dnumber1 - dnumber2) <<endl;
       break;


case "x";
       cout << dnumber1 << " x " << dnumber2 << " = " << (dnumber1 * dnumber2) <<endl;
       break;


case "X";
       cout << dnumber1 << " x " << dnumber2 << " = " << (dnumber1 * dnumber2) <<endl;
       break;


case "*";
       cout << dnumber1 << " * " << dnumber2 << " = " << (dnumber1 * dnumber2) <<endl;
       break;


case "/";
     if (dnumber2 == 0)
     {
cout << "This is an invalid operation" <<endl;
              }

else {
cout << dnumber1 << " / " << dnumber2 << " = " << (dnumber1 / dnumber2) <<endl;
}
break;
default;
cout << "That is an Invalid Operation!" <<endl;
break;

 cout << "Would you like to start again?  (y/n)" <<endl;
 cin >> cdoagain;
  while (cdoagain == "y" || cdoagain == "Y");
 system ("PAUSE");
 return 0;
 }

       }

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[Kurgusov]

you use the " " with string literals as in std::string name = "Bob";

you use the ' ' when dealing with character constants as in char letter = 'a' etc,

the '+' '-' etc are character constants,ie they never change.

I heard over at sourceforge pdCurses forum that using system( 'input command here' ) causes big overhead,
probably better off using the standard cout or c's printf?