How to get and put stream pointers in i/o ?

All i/o streams objects have, at least, one internal stream pointer:ifstream, like istream, has a pointer known as the get pointer that points to the element to be read in the next input operation.ofstream, like ostream, has a pointer known as the put pointer that points to the location where the next element has to be written.Finally, fstream, inherits both, the get and the put pointers, from iostream (which is itself derived from both istream and ostream).These internal stream pointers that point to the reading or writing locations within a stream can be manipulated using the following member functions:tellg() and tellp()These two member functions have no parameters and return a value of the member type pos_type, which is an integer data type representing the current position of the get stream pointer (in the case of tellg) or the put stream pointer (in the case of tellp).seekg() and seekp()These functions allow us to change the position of the get and put stream pointers. Both functions are overloaded with two different prototypes. The first prototype is:seekg ( position );seekp ( position );Using this prototype the stream pointer is changed to the absolute position position (counting from the beginning of the file). The type for this parameter is the same as the one returned by functions tellg and tellp: the member type pos_type, which is an integer value.The other prototype for these functions is:seekg ( offset, direction );seekp ( offset, direction );Using this prototype, the position of the get or put pointer is set to an offset value relative to some specific point determined by the parameter direction. offset is of the member type off_type, which is also an integer type. And direction is of type seekdir, which is an enumerated type (enum) that determines the point from where offset is counted from, and that can take any of the following values:ios::beg	 offset counted from the beginning of the streamios::cur	 offset counted from the current position of the stream                      pointerios::end	  offset counted from the end of the streamThe following example uses the member functions we have just seen to obtain the size of a file:// obtaining file size#include <iostream>#include <fstream>using namespace std;int main () {  long begin,end;  ifstream myfile ("example.txt");  begin = myfile.tellg();  myfile.seekg (0, ios::end);  end = myfile.tellg();  myfile.close();  cout << "size is: " << (end-begin) << " bytes.\n";  return 0;}output : size is: 40 bytes.