Dear users , I encountered a question when I dealt the  data of Hits.root. My program is as follows: {   gROOT->Reset( );   Char_t chRoot_File[100];   TChain chain("Hits");   sprintf(chRoot_File,"Hits.root",0);   Int_t           runID;   Int_t           eventID;   Int_t           rsectorID;   Int_t           moduleID;   Int_t           submoduleID;   Int_t           crystalID;   Int_t           layerID;   Char_t          processName[14];   Float_t         edep;   Float_t         posX;   Float_t         posY;   Float_t         posZ;   Int_t           parentID;   Int_t           photonID;   Int_t           primaryID;   Double_t        time;   Float_t         localPosX;   Float_t         localPosY;   Float_t         localPosZ;   Int_t           sourceID;   Float_t         sourcePosX;   Float_t         sourcePosY;   Float_t         sourcePosZ;   Int_t           nCrystalCompton;   Int_t           nCrystalRayleigh;   Int_t           volumeID[10];   Char_t          RayleighVolName[5];   Char_t          comptVolName[5];   Int_t           nPhantomCompton;   Int_t           nPhantomRayleigh;   Int_t           gantryID;   Int_t           trackID;   Float_t         stepLength;   Float_t         rotationAngle;   Float_t         axialPos; //###################################################################################### //#                        Set branch addresses - Chain Hits                           # //######################################################################################   Hits->SetBranchAddress("runID",&runID);   Hits->SetBranchAddress("eventID",&eventID);   Hits->SetBranchAddress("rsectorID",&rsectorID);   Hits->SetBranchAddress("moduleID",&moduleID);   Hits->SetBranchAddress("submoduleID",&submoduleID);   Hits->SetBranchAddress("crystalID",&crystalID);   Hits->SetBranchAddress("layerID",&layerID);   Hits->SetBranchAddress("processName",processName);   Hits->SetBranchAddress("edep",&edep);   Hits->SetBranchAddress("posX",&posX);   Hits->SetBranchAddress("posY",&posY);    Hits->SetBranchAddress("posZ",&posZ);   Hits->setBranchAddress("parentID",&parentID);   Hits->setBranchAddress("photonID",&photonID);   Hits->setBranchAddress("primaryID",&primaryID);   Hits->SetBranchAddress("time",&time);   Hits->SetBranchAddress("localPosX",&localPosX);   Hits->SetBranchAddress("localPosY",&localPosY);   Hits->SetBranchAddress("localPosZ",&localPosZ);   Hits->SetBranchAddress("sourceID",&sourceID);   Hits->SetBranchAddress("sourcePosX",&sourcePosX);   Hits->SetBranchAddress("sourcePosY",&sourcePosY);   Hits->SetBranchAddress("sourcePosZ",&sourcePosZ);   Hits->setBranchAddress("nCrystalCompton",&nCrystalCompton);   Hits->setBranchAddress("nCrystalRayleigh",&nCrystalRayleigh);   Hits->setBranchAddress("volumeID",volumeID);   Hits->setBranchAddress("RayleighVolName",RayleighVolName);   Hits->setBranchAddress("comptVolName",comptVolName);   Hits->setBranchAddress("nPhantomCompton",&nPhantomCompton);   Hits->setBranchAddress("nPhantomRayleigh",&nPhantomRayleigh);   Hits->setBranchAddress("axialPos",&axialPos);   Hits->setBranchAddress("gantryID",&gantryID);   Hits->setBranchAddress("trackID",&trackID);   Hits->setBranchAddress("stepLength",&stepLength);   Hits->setBranchAddress("rotationAngle",&rotationAngle);  /////////////STAT////////      gStyle -> SetStatW(0.28);   gStyle -> SetStatH(0.3);   gStyle -> SetStatColor(41);     gStyle -> SetStatX(1);   gStyle -> SetStatY(1);     gStyle -> SetStatFont(42);   gStyle->SetOptStat(0);   gStyle->SetOptFit(0);   ///////////////////////// ... }   Hits.root is Hits file. When I run this program, I would get the error information:   Error: Can't call TChain::setBranchAddress("parentID",&parentID) in current scope Hits.c:130:   Possible candidates are...   *** Interpreter error recovered ***   The same error information was given for variables: photonID,primaryID,nCrystalCompton,nCrystalRayleigh,   volumeID,RayleighVolName,comptVolName,nPhantomCompton,nPhantomRayleigh,axialPos,gantryID,trackID,stepLength,   rotationAngle.So I can't get these information,especially the primaryID.   When I commented the variables as above,then the error information disappeared.And the other variables such   as runID ,eventID,rsectorID,moduleID and so on can be used successfully.   I don't know why this happened. Can anyone know the reason? Hope your help.Thanks very much.   Best wishes,   Jinxia Guo. --