Switch Statment Programming Errors

[rayryan2011]

#include<iostream>
using namespace std;
int main()
{
// declare variables
int first;
int second;
int answer;
char operation;

//user input
cout<<"Choose an operation:";
cin>>operation;
operation=toupper(operation);
switch (operation)
{
cout<<"enter the first number"<<"\n\n";
cin>>first;
cout<<"enter the second number"<<"\n\n";
cin>>second;

case "A":
{
answer= first + second;
break;
}
case "M":
{

answer= first * second;
break;
}
case "S":
{
if(first >= second)
answer=first - second;
else
answer=second - first;

}
case "D":
{
if(second>first)
answer=second / first;
else
answer=first/second;

}// end switch
else

cout<<answer<<endl;

}


system("pause");
return 0;
}
These are the errors that im getting please help
Error 1 error C2051: case expression not constant e:\new project\project 4\project 4\project 4\project 4.cpp 22
Error 2 error C2051: case expression not constant e:\new project\project 4\project 4\project 4\project 4.cpp 27
Error 3 error C2051: case expression not constant e:\new project\project 4\project 4\project 4\project 4.cpp 33
Error 4 error C2051: case expression not constant e:\new project\project 4\project 4\project 4\project 4.cpp 41
Error 5 error C2181: illegal else without matching if e:\new project\project 4\project 4\project 4\project 4.cpp 49

[Dy7SLyTq]

code tags. you need to do case 'D', ie with single quotes, you can only have constants (and sometimes function calls) that arent strings in a casetest