Can you expline this program

[simsim]

I found this program in this website, but I didn't understand some functions in it. please, can you expline "what works of each function in this program?"( quickly please...."sorry mu language is broken"

The program as shown:
// isxdigit example (C++)
#include <iostream>
#include <string>
#include <sstream>
#include <locale>
using namespace std;

int main ()
{
locale loc;
string str="ffff";
if ( isxdigit(str[0],loc) )
{
int number;
stringstream(str) >> hex >> number;
cout << "The hexadecimal number " << hex << number;
cout << " is " << dec << number << ".\n";
}
return 0;
}