Switch statements inside while loop C++

Question

Trying to write a program that calculates the Volume, Surface Area, or "Girth" of a box. I want to be able to enter a letter for each subject and after it calculates that subject,then enter a letter for the next subject. The program also want to end when a Q is typed. I believe my math is right but this program is not working for me. It compiles fine but the Volume wont calculate at all, though the other two subjects will. I also get three lines of answers, and when I enter a second letter for a second value, the program runs crazy. Any and all help is much appreciated. Thanks for your time.

include <iostream>
include <iomanip>

using namespace std;

const char SENTINEL = 'Q';//found this suggestion online to quit a program

int main ()
{

char V, A, G, inputChar;
float length, width, depth, totalV, totalA, totalG;

cout<<"Enter character V for Volume, character A for Surface Area,\n";
cout<<"character G or Girth plus Depth or Q to quit\n"<<endl;
cin>>inputChar;// pick letter
while (inputChar!=SENTINEL)// if not Q then check the if-ele statments
{
      switch (inputChar)
      case 'V':
      {
                cout<<"Enter Length, Width, and Depth for Volume\n";
                cin>>length, width, depth;
                totalV=length*width*depth;//math for volume
                cout<<"The Volume = "<<totalV<<endl;
                break;
      }
      case 'A':
      {
               cout<<"Enter Length, Width, and Depth for Surface Area\n";
               cin>>length, width, depth;
               totalA=2*length*width+2*width*depth+2*length*depth;//math for area
               cout<<"The Surface Area = "<<totalA<<endl;
               break;
      }
      case 'G':
      {
               cout<<"Enter Length, Width, and Depth for Girth\n";
               cin>>length, width, depth;
               totalG=2*(length+width)+depth;//math for girth
               cout<<"The Girth = "<<totalG<<endl;
               break;
      }          
}
      system ("pause");
      return 0;
}

Answer 1

Write

while ( cin >> inputChar && inputChar != SENTINEL )
{
//... 

instead of

cin>>inputChar;// pick letter
while (inputChar!=SENTINEL)// 

Also you could write

auto prompt = []
{
    cout << "\nEnter character V for Volume, character A for Surface Area,\n";
    cout << "character G or Girth plus Depth or Q to quit\n"<<endl;
};

while ( prompt(), cin >> inputChar && inputChar != SENTINEL )
{
//... 

Or

auto prompt = []
{
    cout << "\nEnter character V for Volume, character A for Surface Area,\n";
    cout << "character G or Girth plus Depth or Q to quit\n"<<endl;
};

prompt();
while ( cin >> inputChar && inputChar != SENTINEL )
{
    switch (inputChar)
    {
    case 'V':
    {
    //...
    }

    //...
    }

    prompt();
}

Answer 2

Just add cin>>inputChar; at the end of while loop. Thats it. Just compile after that & run. You will get expected output. :-)

-Jayesh

Answer 3

You need to prompt the user for data again, inside the while loop:

do
{
    cout << "Enter character 'V' for Volume, character 'A' for Surface Area,\n";
    cout << "character 'G' for Girth plus Depth or 'Q' to quit\n"<<endl;
    //Right here before the switch statement
    cin >> inputChar;
    switch (inputChar)
    {
        //I also recommend stacking your cases, for lower case and upper case support:
        case 'V':
        case 'v':
        {
            //
        }
        case 'A':
        case 'a':
        {
            //
        }
        case 'G':
        case 'g':
        {
            //
        }
        //Add a default case if they're not any of the above letters
        default:
        {
            cout << inputChar << " is not valid input!";
        }
    }
} while (inputChar != SENTINEL);

Answer 4

Adding to Elliot's answer, I found some improvements in your program without which I don't think it would compile. Like '#' in include statements and wrong switch block. Even for inputting more than one value we need cascading >> but not commas.

Here is a code that would compile:

#include <iostream>
#include <iomanip>

using namespace std;

const char SENTINEL = 'Q';//found this suggestion online to quit a program

int main ()
{

char V, A, G, inputChar;
float length, width, depth, totalV, totalA, totalG;

cout<<"Enter character V for Volume, character A for Surface Area,\n";
cout<<"character G or Girth plus Depth or Q to quit\n"<<endl;
cin>>inputChar;// pick letter

while (inputChar!=SENTINEL)// if not Q then check the if-ele statments
{
      switch (inputChar)
      {
         case 'V':

                cout<<"Enter Length, Width, and Depth for Volume\n";
                cin>>length>>width>>depth;
                totalV=length*width*depth;//math for volume
                cout<<"The Volume = "<<totalV<<endl;
                break;

         case 'A':

               cout<<"Enter Length, Width, and Depth for Surface Area\n";
               cin>>length>>width>>depth;
               totalA=2*length*width+2*width*depth+2*length*depth;//math for area
               cout<<"The Surface Area = "<<totalA<<endl;
               break;

         case 'G':

               cout<<"Enter Length, Width, and Depth for Girth\n";
               cin>>length>>width>>depth;
               totalG=2*(length+width)+depth;//math for girth
               cout<<"The Girth = "<<totalG<<endl;
               break;
      }

   cout<<"Enter character V for Volume, character A for Surface Area,\n";
   cout<<"character G or Girth plus Depth or Q to quit\n"<<endl;
   cin>>inputChar;// pick letter          
}
      return 0;
}

Answer 5

You never update your inputChar. At the end of your while loop read another char,

  cin>>inputChar;
}
system ("pause");

Otherwise, it will enter a tight loop (probably with high cpu usage) when the char doesn't match your switch cases or sentinel.