{

TFile *f1 = new TFile("HLT_PTMultiplicity208.root");
TDirectory *d1=(TDirectory*)f1->Get("demo");

TFile *f2 = new TFile("HLTminBias208.root");
TDirectory *d2=(TDirectory*)f2->Get("demo");


TIter next(d1->GetListOfKeys());
TKey *key;
int Hist_num=0;

while ((key = (TKey*)next())) {  
    TClass *cl = gROOT->GetClass(key->GetClassName());
    if (!cl->InheritsFrom("TH1") && !cl->InheritsFrom("TH2")) continue;
     TH1 *h1 = (TH1*)key->ReadObj();
     char *H_name = h1->GetName();

     TH1 *h2=(TH1*)d2->Get(H_name);

TCanvas *c=new TCanvas();
c->Divide(3,1);

	TH1 hd = h1->Clone()-(*h2);
	c->cd(1);
	hd.Draw();

TH1 hf=(*h1)/(*h2);
c->cd(2);
hf.Draw();

TH1 hr= ((*h1)-(*h2))/(*h2);
c->cd(3);
hr.Draw();

}

}