int TTree_ReadFile () 
{
  TFile f ( "simplest_tree.root", "RECREATE" );

  TTree* t = new TTree ( "mytree" , "Tree of data for my analysis" );

  Long64_t Nevents = t->ReadFile ( "MyExpData.txt" , "det/I:energy/F:time/F" );

  cout << "The created tree has " << t->GetEntries() << " entries. Printing stats: \n\n";

  t->Print ();

  cout << "\n * Press Enter to scan the tree entries. \n";    cin.ignore(); 

  t->Scan ( "det:energy:time" );

  cout << "\n * Press Enter to draw some data. \n";    cin.ignore(); 

  t->Draw ( "energy:time" , "det>=7" );

  t->Write ();

  return 0;
}