#include <string>
#include "TTree.h"

void tree_str_test_1 () {
  TTree *t  = new TTree("t","tree t");

  char str_1[4], str_2[4];

  t->Branch("str_1",str_1,"str_1/C");
  t->Branch("str_2",str_2,"str_2/C");
  
  strcpy (str_1,"aa1");
  strcpy (str_2,"aa2");
  t->Fill();

  strcpy (str_1,"bb1");
  strcpy (str_2,"bb2");
  t->Fill();

  strcpy (str_1,"aa1");
  strcpy (str_2,"bb2");
  t->Fill();

  t->Scan();
  t->Draw("str_1:str_2","","colz");
}