#include <iostream>
#include <string>
#include <cctype>
using namespace std;
 
int main()
{
	char numIn[15];
	int num[15];
	char values[17] = "0123456789ABCDEF"; // array used for table lookup
	int ob, nb, i;
 
	cout << "Enter the the number you want to convert: ";
	cin >> numIn;
 
	// convert string to upper case *note* i'm using _strupr_s because vc '08 likes to give me a nasty deprication warning
	_strupr_s(numIn);
 
	cout << "\n Enter the original base: ";
	cin >> ob;
 
	// range checking
	if(ob < 2 || ob > 16)
	{
		cout << "Bases are 2-16. Please re-enter:" << endl;
		cin >> ob;
	}
 
	cout << "\n Enter the new base: ";
	cin >> nb;
 
	// range checking
	if(nb < 2 || nb > 16)
	{
		cout << "Bases are 2-16. Please re-enter:" << endl;
		cin >> nb;
	}
 
	// convert the char array to string
	string s;
	s = numIn;
	cout << "\nAfter converting the char array, the string is: " << s << endl;
 
	// find the string length for the loop
	int length = strlen(numIn);
	cout << "\nThe length of the string is: " << length << endl;
 
	// loop through each subscript of the input
	for(i=0; i < length; i++)
	{
		cout << num[i] << " ";
 
		// check to see if it's a letter or number
		if(isdigit(numIn[i]) == true)
		{
		num[i] = numIn[i] - 48;
		}
		else 
		{
		num[i] = numIn[i] - 55;
		}
	}
 
	// reverse the string for later use
	cout << "\nAfter reversing the string, the string is: ";
      for(i = length - 1; i >= 0; i--)
      {
     cout << numIn[i];
	  }
	  cout << endl;
 
	return 0;
}

 if(isdigit(numIn[i]) == true)

== true

char digit = 'J';
if (digit >= 71 && digit <= 90)
     cout << "Illegal digit";