Thread: Input Error

Okay I made a prog its for temperature conversion its still not developed yet and Im having problems

heres the code

Code:

/* Software Name = Temperature Converter Calculator...
Made by Manzoor Ahmed.*/
// Program that helps converting Temperature degrees.
// Formulas obtained from wikipedia.org.

#include <cstdlib>
#include <cctype>
#include <iostream>

using namespace std;

int CelFunc() ;

void CnvrtTemp()
{
    char Cnvrt_Temp_Option ;


	     cout << "\n==================== Convert Temperature =======================" << endl ;
     do
      {
	     cout << "\n\n[C] Celsius Converter" << endl ;
	     cout << "[F] Fahrenheit Converter" << endl ;
	     cout << "[K] Kelvin Converter" << endl ;
	     cout << "[R] Rankine Converter" << endl ;
	     cout << "[M] Back to Main Menu." << endl ;
	


	     cout << "\n(Characters enclosed by the square brackets are the options.)" << endl ;
	
	     cout << "\nEnter your option: " ;
	     cin >> Cnvrt_Temp_Option ;

	     if ( Cnvrt_Temp_Option == 67 || Cnvrt_Temp_Option == 99 ) // 67 == C      99 == c
		    {
		     CelFunc();
		    }

		    // 70 = F  and 102 = f
	     if ( Cnvrt_Temp_Option == 70 || Cnvrt_Temp_Option == 102 )
		    {
		     cout << "FahrFunc()" << endl ;
		    }
	
	     if ( Cnvrt_Temp_Option == 75 || Cnvrt_Temp_Option == 107 )
		    {
		     cout << "KelFunc()" << endl;
		    }

	     if ( Cnvrt_Temp_Option == 82 || Cnvrt_Temp_Option == 114 )
		    {
		     cout << "RankFunc()" << endl ;
		    }
	   } while (!( Cnvrt_Temp_Option == 77 || Cnvrt_Temp_Option == 109 )); // 77 == M and 109 == m
}

int main()
{
          char Main_Menu_Option;
                            // program name output
          cout << "################################################################################";
          cout << "#                                                                              #";
          cout << "#                                                                              #";
          cout << "#                                                                              #";
          cout << "#                       Temperature Converter Calculator                       #";
          cout << "#                                                                              #";
          cout << "#                                                                              #";
          cout << "#                                                                              #";
          cout << "#                                                                              #";
          cout << "################################################################################\n\n";


          do
            {                      // Main Menu

          cout << "\n================================ Main Menu =====================================\n\n\n";
                     // Menu
          cout << "[C] Convert Temperature" << endl ;
          cout << "[H] Help" << endl ;
          cout << "[E] Exit" << endl ;

          cout << "\n(Characters enclosed by the square brackets are the options.)\n" << endl ;



               cout << "\nEnter your option : ";
               cin >> Main_Menu_Option ;

               // Following I have used ASCII numbers to check the input from user
               // whether the input is correct or not
               // 67 = C,  99 = c, 72 = H, 104 = h, 69 = E, 101 = e .
               if (!( Main_Menu_Option == 67 || Main_Menu_Option == 99 || Main_Menu_Option == 72 || Main_Menu_Option == 104 || Main_Menu_Option == 69 || Main_Menu_Option == 101 ))
               {
                  cout << "\nWrong option entered\n";
               }
                //  67 == C,  99 == c, 72 == H, 104 == h, 69 == E, 101 == e .



                if ( Main_Menu_Option == 67 || Main_Menu_Option == 99) // 67 == C , 99 == c.
                   {
                    CnvrtTemp();
                   }
				
				if ( Main_Menu_Option == 69 || Main_Menu_Option == 104 )
					{
						cout << "Help section is under construction.\n";
					}	


           } while (!( Main_Menu_Option == 69 || Main_Menu_Option == 101 ));
          system ("pause");
          return 0;
}

int CelFunc()
	{	char again;
		cout << "\n=============================== Celsius Converter ==============================\n\n" ;		
		
		
		do {
		cout << "Enter °C (Celsius) degree to convert :";
		long double cTemp2Conv; 
		cin >> cTemp2Conv;
		
			if (isdigit(cTemp2Conv)) {
				
				
				long double cFahrenheit = (cTemp2Conv * 1.8) + 32;
				long double cKelvin = cTemp2Conv + 273.15;
				long double cRankine = (cTemp2Conv + 273.15) * 1.8;
				
				
				cout << "\nAnswer: " << cTemp2Conv << " Celsius in Fahnrenheit scale = " << cFahrenheit;
				cout << "\nAnswer: " << cTemp2Conv << " Celsius in Kelvin scale = " << cKelvin; 
				cout << "\nAnswer: " << cTemp2Conv << " Celsius in Rankine scale = " << cRankine;
				cout << "\n\n";
			}
			else {
				cout << "\nINVALID INPUT !";
				cout << "\nPlease enter numerical values.\n";
			}			
			cout << "\nDo you want to convert temperature again ?";
			cout << "\nEnter Y for yes, N for no.";
			cout << "\nEntering wrong option other than Y/N will result in getting back to \nConvert Temprature menu.";
			cout << "\n[y]/[n]:";
			cin >> again;
				
		} while (again == 'y'|| again == 'Y');
	}

the problem is when you go to Celsius Converter and there input alphabets then the programs start looping infinitely

I tried cin.good() and isdigit() for checking the input but both gave me same results

any help is really appreciated

thanks