// This program demonstrates the tellg function.
#include <iostream>
#include <fstream>
using namespace std;

int main()
{
   long offset;    // To hold an offset amount
   long numBytes;  // To hold the file size
   char ch;        // To hold a character
   char again;     // To hold Y or N
   
   // Open the file for input.
   fstream file("letters.txt", ios::in);

   // Determine the number of bytes in the file.
   file.seekg(0L, ios::end);
   numBytes = file.tellg();
   cout << "The file has " << numBytes << " bytes.\n";

   // Go back to the beginning of the file.
   file.seekg(0L, ios::beg);

   // Let the user move around within the file.
   do
   {
      // Display the current read position.
      cout << "Currently at position " << file.tellg() << endl;

      // Get a byte number from the user.
      cout << "Enter an offset from the beginning of the file: ";
      cin >> offset;

      // Move the read position to that byte, read the
      // character there, and display it.
      if (offset >= numBytes)    // Past the end of the file?
         cout << "Cannot read past the end of the file.\n";
      else
      {
         file.seekg(offset, ios::beg);
         file.get(ch);
         cout << "Character read: " << ch << endl;
      }

      // Does the user want to try this again?
      cout << "Do it again? ";
      cin >> again;
    } while (again == 'Y' || again == 'y');

   // Close the file.
    file.close();
   return 0;
}