diff --git a/source/digits_hits/detector/src/G4SDManager.cc b/source/digits_hits/detector/src/G4SDManager.cc
index d13b209db..12dc9fb7c 100644
--- a/source/digits_hits/detector/src/G4SDManager.cc
+++ b/source/digits_hits/detector/src/G4SDManager.cc
@@ -71,7 +71,7 @@ void G4SDManager::AddNewDetector(G4VSensitiveDetector* aSD)
 {
   G4int numberOfCollections = aSD->GetNumberOfCollections();
   G4String pathName         = aSD->GetPathName();
-  if(pathName[0] != '/')
+  if(pathName.at(0) != '/')
     pathName.insert(0, "/");
   if(pathName.back() != '/')
     pathName += "/";
@@ -125,7 +125,7 @@ void G4SDManager::TerminateCurrentEvent(G4HCofThisEvent* HCE)
 void G4SDManager::Activate(G4String dName, G4bool activeFlag)
 {
   G4String pathName = dName;
-  if(pathName[0] != '/')
+  if(pathName.at(0) != '/')
     pathName.insert(0, "/");
   treeTop->Activate(pathName, activeFlag);
 }
@@ -134,7 +134,7 @@ G4VSensitiveDetector* G4SDManager::FindSensitiveDetector(G4String dName,
                                                          G4bool warning)
 {
   G4String pathName = dName;
-  if(pathName[0] != '/')
+  if(pathName.at(0) != '/')
     pathName.insert(0, "/");
   return treeTop->FindSensitiveDetector(pathName, warning);
 }
diff --git a/source/digits_hits/detector/src/G4VSensitiveDetector.cc b/source/digits_hits/detector/src/G4VSensitiveDetector.cc
index 79d8e01b6..49d4330a8 100644
--- a/source/digits_hits/detector/src/G4VSensitiveDetector.cc
+++ b/source/digits_hits/detector/src/G4VSensitiveDetector.cc
@@ -47,7 +47,7 @@ G4VSensitiveDetector::G4VSensitiveDetector(G4String name)
     SensitiveDetectorName.erase(0, sLast + 1);
     thePathName = name;
     thePathName.erase(sLast + 1);
-    if(thePathName[0] != '/')
+    if(thePathName.at(0) != '/')
       thePathName.insert(0, "/");
   }
   fullPathName = thePathName + SensitiveDetectorName;
diff --git a/source/intercoms/src/G4UIbridge.cc b/source/intercoms/src/G4UIbridge.cc
index 575f291c7..1bacd90e2 100644
--- a/source/intercoms/src/G4UIbridge.cc
+++ b/source/intercoms/src/G4UIbridge.cc
@@ -35,7 +35,7 @@ G4UIbridge::G4UIbridge(G4UImanager* localUI, G4String dir)
   : localUImanager(localUI)
 {
   // make sure dirName starts and ends with '/'
-  if(dir[0] == '/')
+  if(dir.at(0) == '/')
   {
     dirName = dir;
   }
diff --git a/source/intercoms/src/G4UIcommand.cc b/source/intercoms/src/G4UIcommand.cc
index 7aeee19b7..116d8acb8 100644
--- a/source/intercoms/src/G4UIcommand.cc
+++ b/source/intercoms/src/G4UIcommand.cc
@@ -165,10 +165,10 @@ G4int G4UIcommand::DoIt(G4String parameterList)
         correctParameters.append(" ");
       }
       aToken = parameterToken();
-      if(aToken.length() > 0 && aToken[0] == '"')
+      if(aToken.length() > 0 && aToken.at(0) == '"')
       {
         while(aToken.back() != '"' ||
-              (aToken.length() == 1 && aToken[0] == '"'))
+              (aToken.length() == 1 && aToken.at(0) == '"'))
         {
           G4String additionalToken = parameterToken();
           if(additionalToken.empty())
@@ -215,7 +215,7 @@ G4int G4UIcommand::DoIt(G4String parameterList)
             for(G4int ii = 0; ii < i_thParameter; ++ii)
             {
               parVal = cvSt();
-              if(parVal[0] == '"')
+              if(parVal.at(0) == '"')
               {
                 while(parVal.back() != '"')
                 {
@@ -230,7 +230,7 @@ G4int G4UIcommand::DoIt(G4String parameterList)
               }
             }
             G4String aCVToken = cvSt();
-            if(aCVToken[0] == '"')
+            if(aCVToken.at(0) == '"')
             {
               while(aCVToken.back() != '"')
               {
@@ -1593,7 +1593,7 @@ G4int G4UIcommand::G4UIpGetc()
 {  // emulation of getc()
   G4int length = rangeString.length();
   if(bp < length)
-    return rangeString[bp++];
+    return rangeString.at(bp++);
   else
     return EOF;
 }
@@ -1603,14 +1603,14 @@ G4int G4UIcommand::G4UIpUngetc(G4int c)
 {  // emulation of ungetc()
   if(c < 0)
     return -1;
-  if(bp > 0 && c == rangeString[bp - 1])
+  if(bp > 0 && c == rangeString.at(bp - 1))
   {
     --bp;
   }
   else
   {
     G4cerr << "G4UIpUngetc() failed." << G4endl;
-    G4cerr << "bp=" << bp << " c=" << c << " pR(bp-1)=" << rangeString[bp - 1]
+    G4cerr << "bp=" << bp << " c=" << c << " pR(bp-1)=" << rangeString.at(bp - 1)
            << G4endl;
     paramERR = 1;
     return -1;
diff --git a/source/intercoms/src/G4UIcommandTree.cc b/source/intercoms/src/G4UIcommandTree.cc
index c7902fee5..5e23b9f8c 100644
--- a/source/intercoms/src/G4UIcommandTree.cc
+++ b/source/intercoms/src/G4UIcommandTree.cc
@@ -516,7 +516,7 @@ G4String G4UIcommandTree::CreateFileName(const char* pName)
   G4int idxs;
   while((idxs = fn.find("/")) != G4int(std::string::npos))
   {
-    fn[idxs] = '_';
+    fn.at(idxs) = '_';
   }
   fn += ".html";
   return fn;
@@ -529,7 +529,7 @@ G4String G4UIcommandTree::ModStr(const char* strS)
   G4String str = strS;
   for(G4int i = 0; i < G4int(str.length()); ++i)
   {
-    char c = str[i];
+      char c = str.at(i);
     switch(c)
     {
       case '<':
diff --git a/source/intercoms/src/G4UIcontrolMessenger.cc b/source/intercoms/src/G4UIcontrolMessenger.cc
index 369d8db4d..2fd1f3e98 100644
--- a/source/intercoms/src/G4UIcontrolMessenger.cc
+++ b/source/intercoms/src/G4UIcontrolMessenger.cc
@@ -592,7 +592,7 @@ void G4UIcontrolMessenger::SetNewValue(G4UIcommand* command, G4String newValue)
       c1 += " ";
       c1 += ca;
     }
-    if(c1[0] == '"')
+    if(c1[(size_t)0] == '"')
     {
       G4String strippedValue;
       if(c1.back() == '"')
@@ -715,7 +715,7 @@ void G4UIcontrolMessenger::SetNewValue(G4UIcommand* command, G4String newValue)
       c1 += " ";
       c1 += ca;
     }
-    if(c1[0] == '"')
+    if(c1[(size_t)0] == '"')
     {
       G4String strippedValue;
       if(c1.back() == '"')
diff --git a/source/intercoms/src/G4UImanager.cc b/source/intercoms/src/G4UImanager.cc
index 494c3d715..bed42f47b 100644
--- a/source/intercoms/src/G4UImanager.cc
+++ b/source/intercoms/src/G4UImanager.cc
@@ -377,7 +377,7 @@ void G4UImanager::ForeachS(const char* valueList)
   }
 
   G4String aliasValue = c1;
-  if(aliasValue[0] == '"')
+  if(aliasValue.at(0) == '"')
   {
     G4String strippedValue;
     if(aliasValue.back() == '"')
@@ -737,7 +737,7 @@ void G4UImanager::SetAlias(const char* aliasLine)
   G4int i             = aLine.find(" ");
   G4String aliasName  = aLine.substr(0, i);
   G4String aliasValue = aLine.substr(i + 1, aLine.length() - (i + 1));
-  if(aliasValue[0] == '"')
+  if(aliasValue.at(0) == '"')
   {
     G4String strippedValue;
     if(aliasValue.back() == '"')
diff --git a/source/intercoms/src/G4UIparameter.cc b/source/intercoms/src/G4UIparameter.cc
index 738eaca12..261c02430 100644
--- a/source/intercoms/src/G4UIparameter.cc
+++ b/source/intercoms/src/G4UIparameter.cc
@@ -1057,7 +1057,7 @@ G4int G4UIparameter::G4UIpGetc()
 {  // emulation of getc()
   G4int length = parameterRange.length();
   if(bp < length)
-    return parameterRange[bp++];
+    return parameterRange.at(bp++);
   else
     return EOF;
 }
@@ -1067,7 +1067,7 @@ G4int G4UIparameter::G4UIpUngetc(G4int c)
 {  // emulation of ungetc()
   if(c < 0)
     return -1;
-  if(bp > 0 && c == parameterRange[bp - 1])
+  if(bp > 0 && c == parameterRange.at(bp - 1))
   {
     --bp;
   }
@@ -1075,7 +1075,7 @@ G4int G4UIparameter::G4UIpUngetc(G4int c)
   {
     G4cerr << "G4UIpUngetc() failed." << G4endl;
     G4cerr << "bp=" << bp << " c=" << c
-           << " pR(bp-1)=" << parameterRange[bp - 1] << G4endl;
+           << " pR(bp-1)=" << parameterRange.at(bp - 1) << G4endl;
     paramERR = 1;
     return -1;
   }
diff --git a/source/interfaces/basic/src/G4UIArrayString.cc b/source/interfaces/basic/src/G4UIArrayString.cc
index 509444c2f..bd7c32aa6 100644
--- a/source/interfaces/basic/src/G4UIArrayString.cc
+++ b/source/interfaces/basic/src/G4UIArrayString.cc
@@ -68,7 +68,7 @@ G4UIArrayString::G4UIArrayString(const G4String& stream)
       stringArray[i]= astream.substr(indx, jc-indx);
     }
     for(G4int j=1; jc+j< G4int(astream.length()); j++ ) { // skip continuing spaces
-      if(astream[jc+j]==' ') jc++;
+      if(astream.at(jc+j)==' ') jc++;
       else break;
     }
     indx= jc+1;
diff --git a/source/interfaces/basic/src/G4UIExecutive.cc b/source/interfaces/basic/src/G4UIExecutive.cc
index 549ab7406..0ac7c85b3 100644
--- a/source/interfaces/basic/src/G4UIExecutive.cc
+++ b/source/interfaces/basic/src/G4UIExecutive.cc
@@ -219,7 +219,7 @@ void G4UIExecutive::SelectSessionByFile(const G4String& appname)
     if( fsession.eof()) break;
     fsession.getline(linebuf, BUFSIZE);
     G4String aline = G4StrUtil::strip_copy(linebuf);
-    if ( aline[0] == '#' ) continue;
+    if ( aline.at(0) == '#' ) continue;
     if ( aline == "" ) continue;
     if ( iline == 1 )
       default_session = aline;
diff --git a/source/interfaces/basic/src/G4UIQt.cc b/source/interfaces/basic/src/G4UIQt.cc
index 9f2dcdf09..aa987f7b1 100644
--- a/source/interfaces/basic/src/G4UIQt.cc
+++ b/source/interfaces/basic/src/G4UIQt.cc
@@ -2392,10 +2392,10 @@ void G4UIQt::AddButton (
        cmd.substr(0,3) != "cd " &&
        cmd != "help" &&
        cmd.substr(0,5) != "help " &&
-       cmd[0] != '?' &&
+       cmd.at(0) != '?' &&
        cmd != "hist" &&
        cmd != "history" &&
-       cmd[0] != '!' &&
+       cmd.at(0) != '!' &&
        cmd != "exit" &&
        cmd != "cont" &&
        cmd != "continue"){
diff --git a/source/interfaces/basic/src/G4UIterminal.cc b/source/interfaces/basic/src/G4UIterminal.cc
index 98805b63e..ac78aab56 100644
--- a/source/interfaces/basic/src/G4UIterminal.cc
+++ b/source/interfaces/basic/src/G4UIterminal.cc
@@ -219,7 +219,7 @@ G4String G4UIterminal::GetCommand(const char* msg)
   if( nC.length() == 0 ) {
     newCommand= nullString;
 
-  } else if( nC[0] == '#' ) {  
+  } else if( nC.at(0) == '#' ) {
     G4cout << nC << G4endl;
     newCommand= nullString;
 
@@ -249,7 +249,7 @@ G4String G4UIterminal::GetCommand(const char* msg)
     TerminalHelp(nC);
     newCommand= nullString;
 
-  } else if(nC[0] == '?') {   // "show current value of a parameter"
+  } else if(nC.at(0) == '?') {   // "show current value of a parameter"
     ShowCurrent(nC);
     newCommand= nullString;
 
@@ -260,7 +260,7 @@ G4String G4UIterminal::GetCommand(const char* msg)
     }
     newCommand= nullString;
 
-  } else if(nC[0] == '!') {   // "!"
+  } else if(nC.at(0) == '!') {   // "!"
     G4String ss= nC.substr(1, nC.length()-1);
     G4int vl;
     const char* tt= ss;
diff --git a/source/interfaces/basic/src/G4VUIshell.cc b/source/interfaces/basic/src/G4VUIshell.cc
index 9003b7c1a..fa5b50bc3 100644
--- a/source/interfaces/basic/src/G4VUIshell.cc
+++ b/source/interfaces/basic/src/G4VUIshell.cc
@@ -89,17 +89,17 @@ void G4VUIshell::MakePrompt(const char* msg)
 	i++;
         break;
       default:
-	promptString += promptSetting[i];
+	promptString += promptSetting.at(i);
         break;
       }           
     } else {
-      promptString += promptSetting[i];
+      promptString += promptSetting.at(i);
     }
   }
 
   // append last chaacter
   if(i == G4int(promptSetting.length())-1) 
-    promptString += promptSetting[i];
+    promptString += promptSetting.at(i);
 }
 
 
@@ -173,7 +173,7 @@ G4String G4VUIshell::GetAbsCommandDirPath(const G4String& apath) const
         }
       } else if(bpath.substr(indx,jslash-indx) == "."){  // nothing to do
       } else { // add
-        if( !(jslash==indx && bpath[indx]=='/') ) // truncate "////"
+          if (!(jslash == indx && bpath.at(indx) == '/')) // truncate "////"
           absPath+= bpath.substr(indx, jslash-indx+1);
           // better to be check directory existence. (it costs!)
       }
diff --git a/source/interfaces/common/src/G4InteractorMessenger.cc b/source/interfaces/common/src/G4InteractorMessenger.cc
index ae7961127..b99569e8c 100644
--- a/source/interfaces/common/src/G4InteractorMessenger.cc
+++ b/source/interfaces/common/src/G4InteractorMessenger.cc
@@ -217,7 +217,7 @@ G4bool GetValues (
       return false;
     }
     G4String token = tok;
-    if( token[0]=='"' ) {
+    if( token.at(0)=='"' ) {
       while( token.back() != '"' ) {
 	tok = strtok(NULL," ");
 	if( (tok==NULL) || (*tok=='\0')) {
diff --git a/source/interfaces/common/src/G4VBasicShell.cc b/source/interfaces/common/src/G4VBasicShell.cc
index 2112bfac4..c3055e7b2 100644
--- a/source/interfaces/common/src/G4VBasicShell.cc
+++ b/source/interfaces/common/src/G4VBasicShell.cc
@@ -47,7 +47,7 @@ G4VBasicShell::~G4VBasicShell()
 G4String G4VBasicShell::ModifyToFullPathCommand(const char* aCommandLine) const
 {
   G4String rawCommandLine = aCommandLine;
-  if(rawCommandLine.empty()||rawCommandLine[0]=='\0') return rawCommandLine;
+  if(rawCommandLine.empty()||rawCommandLine.at(0)=='\0') return rawCommandLine;
   G4String commandLine = G4StrUtil::strip_copy(rawCommandLine);
   G4String commandString;
   G4String parameterString;
@@ -128,7 +128,7 @@ G4String G4VBasicShell::ModifyPath(const G4String& tempPath) const
   G4String newPath = "";
 
   // temporal full path
-  if( tempPath[0] == '/') newPath = tempPath;
+  if( tempPath.at(0) == '/') newPath = tempPath;
   else newPath = currentDirectory + tempPath;
 
   // body of path...
@@ -240,7 +240,7 @@ void G4VBasicShell::ApplyShellCommand (const G4String& a_string,
 
   G4String command = G4StrUtil::lstrip_copy(a_string);
 
-  if( command[0] == '#' ) {
+  if( command.at(0) == '#' ) {
 
     G4cout << command << G4endl;
 
@@ -261,7 +261,7 @@ void G4VBasicShell::ApplyShellCommand (const G4String& a_string,
 
     TerminalHelp( command );
 
-  } else if( command[0] == '?' ) {
+  } else if( command.at(0) == '?' ) {
 
     ShowCurrent( command );
 
@@ -272,7 +272,7 @@ void G4VBasicShell::ApplyShellCommand (const G4String& a_string,
       G4cout << i << ": " << UI->GetPreviousCommand(i) << G4endl;
     }
 
-  } else if( command[0] == '!' ) {
+  } else if( command.at(0) == '!' ) {
 
     G4String ss = command.substr(1,command.length()-1);
     G4int vl;
diff --git a/source/materials/src/G4MicroElecMaterialStructure.cc b/source/materials/src/G4MicroElecMaterialStructure.cc
index ff032db5f..194d9e2ec 100644
--- a/source/materials/src/G4MicroElecMaterialStructure.cc
+++ b/source/materials/src/G4MicroElecMaterialStructure.cc
@@ -102,7 +102,7 @@ void G4MicroElecMaterialStructure::ReadMaterialFile()
 {
   char *path = std::getenv("G4LEDATA");
   
-  if (materialName[0] == 'G' && materialName[1] == '4') {
+  if (materialName.at(0) == 'G' && materialName.at(1) == '4') {
     //in the case the NIST database is used
     materialName.erase(0, 1);
     materialName.erase(0, 1);
@@ -133,7 +133,7 @@ void G4MicroElecMaterialStructure::ReadMaterialFile()
 	getline(fichier, filler);
 	std::stringstream line(filler);
 	
-	if (filler[0] == '#' || filler.empty()) {continue;}
+	if (filler.at(0) == '#' || filler.empty()) {continue;}
 	
 	line >> varLength;
 	line >> nameParameter;
diff --git a/source/processes/hadronic/models/cascade/cascade/include/G4CascadeParamMessenger.icc b/source/processes/hadronic/models/cascade/cascade/include/G4CascadeParamMessenger.icc
index 416db93e8..6810e0ce8 100644
--- a/source/processes/hadronic/models/cascade/cascade/include/G4CascadeParamMessenger.icc
+++ b/source/processes/hadronic/models/cascade/cascade/include/G4CascadeParamMessenger.icc
@@ -41,7 +41,7 @@ T* G4CascadeParamMessenger::CreateCommand(const G4String& cmd,
 
   // If input name begins with '/', treat as absolute path
   G4String path;
-  if (cmd[0] != '/' && cmdDir) path = cmdDir->GetCommandPath();
+  if (cmd.at(0) != '/' && cmdDir) path = cmdDir->GetCommandPath();
   path += cmd;
 
   T* theCmd = new T(path.c_str(), this);        // <T> must be G4UIcommand!
diff --git a/source/processes/hadronic/models/cascade/cascade/src/G4CascadeParamMessenger.cc b/source/processes/hadronic/models/cascade/cascade/src/G4CascadeParamMessenger.cc
index 276c58361..74cbfe3d1 100644
--- a/source/processes/hadronic/models/cascade/cascade/src/G4CascadeParamMessenger.cc
+++ b/source/processes/hadronic/models/cascade/cascade/src/G4CascadeParamMessenger.cc
@@ -136,7 +136,7 @@ void G4CascadeParamMessenger::CreateDirectory(const char* path,
 
   // Directory path must be absolute, prepend "/" if ncessary
   G4String fullPath = path;
-  if (fullPath[0] != '/') fullPath.insert(0, "/");
+  if (fullPath.at(0) != '/') fullPath.insert(0, "/");
   if (fullPath.back() != '/') fullPath.append("/");
 
   // See if input path has already been registered
diff --git a/source/visualization/management/src/G4VisCommandsScene.cc b/source/visualization/management/src/G4VisCommandsScene.cc
index 105c9339b..d4e7ef988 100644
--- a/source/visualization/management/src/G4VisCommandsScene.cc
+++ b/source/visualization/management/src/G4VisCommandsScene.cc
@@ -630,7 +630,7 @@ void G4VisCommandSceneNotifyHandlers::SetNewValue (G4UIcommand*,
   std::istringstream is (newValue);
   is >> sceneName >> refresh_flush;
   G4bool flush = false;
-  if (refresh_flush[0] == 'f') flush = true;
+  if (refresh_flush.at(0) == 'f') flush = true;
 
   const G4SceneList& sceneList = fpVisManager -> GetSceneList ();
   G4SceneHandlerList& sceneHandlerList =
diff --git a/source/visualization/management/src/G4VisCommandsSceneAdd.cc b/source/visualization/management/src/G4VisCommandsSceneAdd.cc
index 960d51f59..1660ab2e3 100644
--- a/source/visualization/management/src/G4VisCommandsSceneAdd.cc
+++ b/source/visualization/management/src/G4VisCommandsSceneAdd.cc
@@ -434,9 +434,9 @@ void G4VisCommandSceneAddDate::SetNewValue (G4UIcommand*, G4String newValue)
   is.getline(remainder, NREMAINDER);
   dateString += remainder;
   G4Text::Layout layout = G4Text::right;
-  if (layoutString[0] == 'l') layout = G4Text::left;
-  else if (layoutString[0] == 'c') layout = G4Text::centre;
-  else if (layoutString[0] == 'r') layout = G4Text::right;
+  if (layoutString.at(0) == 'l') layout = G4Text::left;
+  else if (layoutString.at(0) == 'c') layout = G4Text::centre;
+  else if (layoutString.at(0) == 'r') layout = G4Text::right;
 
   Date* date = new Date(fpVisManager, size, x, y, layout, dateString);
   G4VModel* model =
@@ -676,9 +676,9 @@ void G4VisCommandSceneAddEventID::SetNewValue (G4UIcommand*, G4String newValue)
   is >> size >> x >> y >> layoutString;
 
   G4Text::Layout layout = G4Text::right;
-  if (layoutString[0] == 'l') layout = G4Text::left;
-  else if (layoutString[0] == 'c') layout = G4Text::centre;
-  else if (layoutString[0] == 'r') layout = G4Text::right;
+  if (layoutString.at(0) == 'l') layout = G4Text::left;
+  else if (layoutString.at(0) == 'c') layout = G4Text::centre;
+  else if (layoutString.at(0) == 'r') layout = G4Text::right;
 
   // For End of Event (only for reviewing kept events one by one)
   EventID* eoeEventID
@@ -1656,13 +1656,13 @@ void G4VisCommandSceneAddLogo::SetNewValue (G4UIcommand*, G4String newValue) {
     else if (vp.z() > vp.x() && vp.z() > vp.y()) logoDirection = Z;
     else if (vp.z() < vp.x() && vp.z() < vp.y()) logoDirection = minusZ;
   }
-  else if (direction[0] == 'x') logoDirection = X;
-  else if (direction[0] == 'y') logoDirection = Y;
-  else if (direction[0] == 'z') logoDirection = Z;
-  else if (direction[0] == '-') {
-    if (direction[1] == 'x') logoDirection = minusX;
-    else if (direction[1] == 'y') logoDirection = minusY;
-    else if (direction[1] == 'z') logoDirection = minusZ;
+  else if (direction.at(0) == 'x') logoDirection = X;
+  else if (direction.at(0) == 'y') logoDirection = Y;
+  else if (direction.at(0) == 'z') logoDirection = Z;
+  else if (direction.at(0) == '-') {
+    if (direction.at(0) == 'x') logoDirection = minusX;
+    else if (direction.at(0) == 'y') logoDirection = minusY;
+    else if (direction.at(0) == 'z') logoDirection = minusZ;
   } else {
     if (verbosity >= G4VisManager::errors) {
       G4cerr <<	"ERROR: Unrecogniseed direction: \""
@@ -1975,9 +1975,9 @@ void G4VisCommandSceneAddLogo2D::SetNewValue (G4UIcommand*, G4String newValue)
   std::istringstream is(newValue);
   is >> size >> x >> y >> layoutString;
   G4Text::Layout layout = G4Text::right;
-  if (layoutString[0] == 'l') layout = G4Text::left;
-  else if (layoutString[0] == 'c') layout = G4Text::centre;
-  else if (layoutString[0] == 'r') layout = G4Text::right;
+  if (layoutString.at(0) == 'l') layout = G4Text::left;
+  else if (layoutString.at(0) == 'c') layout = G4Text::centre;
+  else if (layoutString.at(0) == 'r') layout = G4Text::right;
 
   Logo2D* logo2D = new Logo2D(fpVisManager, size, x, y, layout);
   G4VModel* model =
@@ -2265,8 +2265,8 @@ void G4VisCommandSceneAddScale::SetNewValue (G4UIcommand*, G4String newValue) {
   xmid *= unit; ymid *= unit; zmid *= unit;
 
   Scale::Direction scaleDirection (Scale::x);
-  if (direction[0] == 'y') scaleDirection = Scale::y;
-  if (direction[0] == 'z') scaleDirection = Scale::z;
+  if (direction.at(0) == 'y') scaleDirection = Scale::y;
+  if (direction.at(0) == 'z') scaleDirection = Scale::z;
 
   G4VViewer* pViewer = fpVisManager->GetCurrentViewer();
   if (!pViewer) {
diff --git a/source/visualization/management/src/G4VisManager.cc b/source/visualization/management/src/G4VisManager.cc
index 6d881eb14..b2e01edfd 100644
--- a/source/visualization/management/src/G4VisManager.cc
+++ b/source/visualization/management/src/G4VisManager.cc
@@ -2411,13 +2411,13 @@ G4VisManager::Verbosity
 G4VisManager::GetVerbosityValue(const G4String& verbosityString) {
   G4String ss = G4StrUtil::to_lower_copy(verbosityString); 
   Verbosity verbosity;
-  if      (ss[0] == 'q') verbosity = quiet;
-  else if (ss[0] == 's') verbosity = startup;
-  else if (ss[0] == 'e') verbosity = errors;
-  else if (ss[0] == 'w') verbosity = warnings;
-  else if (ss[0] == 'c') verbosity = confirmations;
-  else if (ss[0] == 'p') verbosity = parameters;
-  else if (ss[0] == 'a') verbosity = all;
+  if      (ss.at(0) == 'q') verbosity = quiet;
+  else if (ss.at(0) == 's') verbosity = startup;
+  else if (ss.at(0) == 'e') verbosity = errors;
+  else if (ss.at(0) == 'w') verbosity = warnings;
+  else if (ss.at(0) == 'c') verbosity = confirmations;
+  else if (ss.at(0) == 'p') verbosity = parameters;
+  else if (ss.at(0) == 'a') verbosity = all;
   else {
     G4int intVerbosity;
     std::istringstream is(ss);