diff --git a/src/fbutton.h b/src/fbutton.h
index d110bfc2..89dd8bed 100644
--- a/src/fbutton.h
+++ b/src/fbutton.h
@@ -31,7 +31,7 @@ class FButton : public FWidget
    friend class FDialog;
 
  public:
-   FButton (FWidget* parent=0);  // constructor
+   explicit FButton (FWidget* parent=0);  // constructor
    FButton (const FString&, FWidget* parent=0);  // constructor
    virtual ~FButton();  // destructor
 
diff --git a/src/fbuttongroup.h b/src/fbuttongroup.h
index a4d6c572..75bf77c1 100644
--- a/src/fbuttongroup.h
+++ b/src/fbuttongroup.h
@@ -38,7 +38,7 @@ class FButtonGroup : public FWidget
    void  drawLabel();
 
  public:
-   FButtonGroup (FWidget* parent=0);  // constructor
+   explicit FButtonGroup (FWidget* parent=0);  // constructor
    FButtonGroup (const FString&, FWidget* parent=0);  // constructor
    virtual ~FButtonGroup();  // destructor
    const char* getClassName() const;
diff --git a/src/fcheckbox.h b/src/fcheckbox.h
index 02bc40aa..1f921ff2 100644
--- a/src/fcheckbox.h
+++ b/src/fcheckbox.h
@@ -23,7 +23,7 @@ class FCheckBox : public FToggleButton
    void drawCheckButton();
 
  public:
-   FCheckBox (FWidget* parent=0);  // constructor
+   explicit FCheckBox (FWidget* parent=0);  // constructor
    FCheckBox (const FString&, FWidget* parent=0);  // constructor
    virtual ~FCheckBox();  // destructor
    const char* getClassName() const;
diff --git a/src/fdialog.h b/src/fdialog.h
index f7bb73f1..974ea43e 100644
--- a/src/fdialog.h
+++ b/src/fdialog.h
@@ -46,7 +46,7 @@ class FDialog : public FWindow
    virtual void onClose (FCloseEvent*);
 
  public:
-   FDialog (FWidget* parent=0);  // constructor
+   explicit FDialog (FWidget* parent=0);  // constructor
    FDialog (const FString&, FWidget* parent=0);  // constructor
    virtual ~FDialog();  // destructor
    virtual const char* getClassName() const;
diff --git a/src/fevent.h b/src/fevent.h
index e2742447..1426ee0b 100644
--- a/src/fevent.h
+++ b/src/fevent.h
@@ -40,7 +40,7 @@
 class FEvent // event base class
 {
  public:
-   FEvent(int);
+   explicit FEvent(int);
   ~FEvent();
    int type() const;
 
@@ -190,7 +190,7 @@ enum FocusTypes
 class FFocusEvent : public FEvent        // focus event
 {
  public:
-   FFocusEvent (int);
+   explicit FFocusEvent (int);
    bool gotFocus()  const;
    bool lostFocus() const;
    FocusTypes getFocusType() const;
@@ -239,7 +239,7 @@ class FAccelEvent : public FEvent    // focus event
 class FResizeEvent : public FEvent    // resize event
 {
  public:
-   FResizeEvent (int);
+   explicit FResizeEvent (int);
    bool isAccepted() const;
    void accept();
    void ignore();
@@ -258,7 +258,7 @@ class FResizeEvent : public FEvent    // resize event
 class FShowEvent : public FEvent    // show event
 {
  public:
-   FShowEvent (int);
+   explicit FShowEvent (int);
 };
 
 #define F_SHOW_EVENT(x)  ((FShowEvent*)x)
@@ -271,7 +271,7 @@ class FShowEvent : public FEvent    // show event
 class FHideEvent : public FEvent    // hide event
 {
  public:
-   FHideEvent (int);
+   explicit FHideEvent (int);
 };
 
 #define F_HIDE_EVENT(x)  ((FHideEvent*)x)
@@ -284,7 +284,7 @@ class FHideEvent : public FEvent    // hide event
 class FCloseEvent : public FEvent   // close event
 {
  public:
-   FCloseEvent(int);
+   explicit FCloseEvent(int);
    bool isAccepted() const;
    void accept();
    void ignore();
diff --git a/src/ffiledialog.h b/src/ffiledialog.h
index ee4fbd37..6a8b48c0 100644
--- a/src/ffiledialog.h
+++ b/src/ffiledialog.h
@@ -83,7 +83,7 @@ class FFileDialog : public FDialog
    void adjustSize();
 
  public:
-   FFileDialog (FWidget* parent=0);
+   explicit FFileDialog (FWidget* parent=0);
    FFileDialog (const FString&,
                 const FString&,
                 DialogType type = FFileDialog::Open,
diff --git a/src/flabel.h b/src/flabel.h
index 616cb1c7..8004683b 100644
--- a/src/flabel.h
+++ b/src/flabel.h
@@ -39,7 +39,7 @@ class FLabel : public FWidget
    void  draw();
 
  public:
-   FLabel (FWidget* parent=0);  // constructor
+   explicit FLabel (FWidget* parent=0);  // constructor
    FLabel (const FString&, FWidget* parent=0);  // constructor
    virtual ~FLabel();  // destructor
    const char* getClassName() const;
diff --git a/src/flineedit.h b/src/flineedit.h
index 9f07130d..ef4f7e26 100644
--- a/src/flineedit.h
+++ b/src/flineedit.h
@@ -56,7 +56,7 @@ class FLineEdit : public FWidget
    void adjustSize();
 
  public:
-   FLineEdit (FWidget* parent=0);  // constructor
+   explicit FLineEdit (FWidget* parent=0);  // constructor
    FLineEdit (const FString&, FWidget* parent=0);  // constructor
    virtual ~FLineEdit();  // destructor
    const char* getClassName() const;
diff --git a/src/flistbox.h b/src/flistbox.h
index 16e6209d..39b887f0 100644
--- a/src/flistbox.h
+++ b/src/flistbox.h
@@ -25,9 +25,9 @@ class FListBoxItem
    bool selected;
  public:
    FListBoxItem ();
-   FListBoxItem (FString&);
-   FListBoxItem (const std::string&);
-   FListBoxItem (const char*);
+   explicit FListBoxItem (FString&);
+   explicit FListBoxItem (const std::string&);
+   explicit FListBoxItem (const char*);
    virtual ~FListBoxItem();
    virtual FString getText() const;
  protected:
@@ -111,7 +111,7 @@ class FListBox : public FWidget
    void adjustSize();
 
  public:
-   FListBox (FWidget* parent=0);  // constructor
+   explicit FListBox (FWidget* parent=0);  // constructor
   ~FListBox();  // destructor
    const char* getClassName() const;
 
diff --git a/src/fmessagebox.h b/src/fmessagebox.h
index c643827c..7440a949 100644
--- a/src/fmessagebox.h
+++ b/src/fmessagebox.h
@@ -58,7 +58,7 @@ class FMessageBox : public FDialog
    void cb_processClick (FWidget*, void*);
 
  public:
-   FMessageBox (FWidget* parent=0);
+   explicit FMessageBox (FWidget* parent=0);
    FMessageBox (const FString&, const FString&,
                 int, int, int,
                 FWidget* parent=0);
diff --git a/src/fobject.h b/src/fobject.h
index a3cde427..4fc262b7 100644
--- a/src/fobject.h
+++ b/src/fobject.h
@@ -58,7 +58,7 @@ class FObject
    friend class FApplication;
 
  public:
-   FObject (FObject* parent=0);
+   explicit FObject (FObject* parent=0);
    virtual ~FObject();
    virtual const char* getClassName() const;
 
diff --git a/src/foptimove.h b/src/foptimove.h
index 9cb15dac..f9586507 100644
--- a/src/foptimove.h
+++ b/src/foptimove.h
@@ -78,7 +78,7 @@ class FOptiMove
    bool isWideMove (int, int, int, int);
 
  public:
-   FOptiMove(int baud=0);  // constructor
+   explicit FOptiMove(int baud=0);  // constructor
   ~FOptiMove();            // destructor
 
    void setBaudRate (int);
diff --git a/src/fprogressbar.h b/src/fprogressbar.h
index 841d5c45..5d04877e 100644
--- a/src/fprogressbar.h
+++ b/src/fprogressbar.h
@@ -29,7 +29,7 @@ class FProgressbar : public FWidget
    virtual void draw();
 
  public:
-   FProgressbar(FWidget* parent=0);  // constructor
+   explicit FProgressbar(FWidget* parent=0);  // constructor
    virtual ~FProgressbar();
    const char* getClassName() const;
 
diff --git a/src/fradiobutton.h b/src/fradiobutton.h
index 41fec81b..5ec36a86 100644
--- a/src/fradiobutton.h
+++ b/src/fradiobutton.h
@@ -22,7 +22,7 @@ class FRadioButton : public FToggleButton
    void drawRadioButton();
 
  public:
-   FRadioButton (FWidget* parent=0);  // constructor
+   explicit FRadioButton (FWidget* parent=0);  // constructor
    FRadioButton (const FString&, FWidget* parent=0);  // constructor
    virtual ~FRadioButton();  // destructor
    const char* getClassName() const;
diff --git a/src/fscrollbar.h b/src/fscrollbar.h
index 7f22d549..24b12f94 100644
--- a/src/fscrollbar.h
+++ b/src/fscrollbar.h
@@ -59,7 +59,7 @@ class FScrollbar : public FWidget
    void processScroll();
 
  public:
-   FScrollbar(FWidget* parent=0);  // constructor
+   explicit FScrollbar(FWidget* parent=0);  // constructor
    FScrollbar(int o=fc::vertical, FWidget* parent=0);  // constructor
    virtual ~FScrollbar();
    const char* getClassName() const;
diff --git a/src/fstatusbar.h b/src/fstatusbar.h
index 9bb85411..7108f5d1 100644
--- a/src/fstatusbar.h
+++ b/src/fstatusbar.h
@@ -33,7 +33,7 @@ class FStatusKey : public FWidget
    void setStatusbar (FStatusBar*);
 
  public:
-   FStatusKey (FWidget* parent=0);
+   explicit FStatusKey (FWidget* parent=0);
    FStatusKey (int, FString&, FWidget* parent=0);
    FStatusKey (int, const std::string&, FWidget* parent=0);
    FStatusKey (int, const char*, FWidget* parent=0);
@@ -133,7 +133,7 @@ class FStatusBar : public FWindow
    void adjustSize();
 
  public:
-   FStatusBar (FWidget* parent=0);  // constructor
+   explicit FStatusBar (FWidget* parent=0);  // constructor
    virtual ~FStatusBar();  // destructor
    virtual const char* getClassName() const;
 
diff --git a/src/fstring.cpp b/src/fstring.cpp
index 3bba4640..5487d616 100644
--- a/src/fstring.cpp
+++ b/src/fstring.cpp
@@ -753,7 +753,7 @@ const FString operator + (const std::string& s1, const FString& s2)
 //----------------------------------------------------------------------
 const FString operator + (const char* s1, const FString& s2)
 {
-  FString tmp = s1;
+  FString tmp(s1);
   tmp._insert ( tmp.getLength(),
                 uInt(wcslen(s2.wc_str())),
                 s2.wc_str() );
@@ -763,7 +763,7 @@ const FString operator + (const char* s1, const FString& s2)
 //----------------------------------------------------------------------
 const FString operator + (const wchar_t c, const FString& s)
 {
-  FString tmp = c;
+  FString tmp(c);
   tmp._insert (1, uInt(wcslen(s.wc_str())), s.wc_str());
   return (tmp);
 }
@@ -771,7 +771,7 @@ const FString operator + (const wchar_t c, const FString& s)
 //----------------------------------------------------------------------
 const FString operator + (const char c, const FString& s)
 {
-  FString tmp = c;
+  FString tmp(c);
   tmp._insert (1, uInt(wcslen(s.wc_str())), s.wc_str());
   return (tmp);
 }
@@ -1832,7 +1832,7 @@ FString FString::expandTabs (uInt tabstop) const
 {
   uLong end;
   FString instr(this->string);
-  FString outstr = "";
+  FString outstr("");
 
   std::vector<FString> tab_split = instr.split("\t");
   end = tab_split.size();
diff --git a/src/fstring.h b/src/fstring.h
index babcc026..c0c7db45 100644
--- a/src/fstring.h
+++ b/src/fstring.h
@@ -71,8 +71,8 @@ class FString
 
  public:
    FString ();                    // constructor
-   FString (int);                 // constructor
-   FString (uInt);                // constructor
+   explicit FString (int);        // constructor
+   explicit FString (uInt);       // constructor
    FString (int, wchar_t);        // constructor
    FString (uInt, wchar_t);       // constructor
    FString (int, char);           // constructor
@@ -83,7 +83,7 @@ class FString
    FString (const std::string&);  // constructor
    FString (const char*);         // constructor
    FString (const wchar_t);       // constructor
-   FString (const char);          // constructor
+   explicit FString (const char);          // constructor
    virtual ~FString ();  // destructor
 
    bool isNull() const;
diff --git a/src/ftextview.h b/src/ftextview.h
index a2fb50e3..10194071 100644
--- a/src/ftextview.h
+++ b/src/ftextview.h
@@ -45,7 +45,7 @@ class FTextView : public FWidget
    void adjustSize();
 
  public:
-   FTextView (FWidget* parent=0);  // constructor
+   explicit FTextView (FWidget* parent=0);  // constructor
   ~FTextView();  // destructor
    const char* getClassName() const;
 
diff --git a/src/ftogglebutton.h b/src/ftogglebutton.h
index 17d60102..1d94ef44 100644
--- a/src/ftogglebutton.h
+++ b/src/ftogglebutton.h
@@ -45,7 +45,7 @@ class FToggleButton : public FWidget
    virtual void onKeyPress (FKeyEvent*);
 
  public:
-   FToggleButton (FWidget* parent=0);  // constructor
+   explicit FToggleButton (FWidget* parent=0);  // constructor
    FToggleButton (const FString&, FWidget* parent=0);  // constructor
    virtual ~FToggleButton();  // destructor
    virtual const char* getClassName() const;
diff --git a/src/fwidget.h b/src/fwidget.h
index 9db09f6f..fabe352f 100644
--- a/src/fwidget.h
+++ b/src/fwidget.h
@@ -220,7 +220,7 @@ class FWidget : public FObject, public FTerm
    virtual bool focusPrevChild (void);
 
  public:
-   FWidget (FWidget* parent=0);  // constructor
+   explicit FWidget (FWidget* parent=0);  // constructor
   ~FWidget();  // destructor
 
    const char*      getClassName() const;
diff --git a/src/fwindow.h b/src/fwindow.h
index 9138b91a..c8c715a1 100644
--- a/src/fwindow.h
+++ b/src/fwindow.h
@@ -31,7 +31,7 @@ class FWindow : public FWidget
    virtual void    onWindowLowered (FEvent*);
 
  public:
-   FWindow (FWidget* parent=0);  // constructor
+   explicit FWindow (FWidget* parent=0);  // constructor
   ~FWindow ();  // destructor
 
    const char*     getClassName() const;
diff --git a/test/mandelbrot.cpp b/test/mandelbrot.cpp
index e16a815d..626459f9 100644
--- a/test/mandelbrot.cpp
+++ b/test/mandelbrot.cpp
@@ -17,7 +17,7 @@ class Mandelbrot : public FDialog
    virtual void draw();
 
  public:
-   Mandelbrot (FWidget* parent=0);  // constructor
+   explicit Mandelbrot (FWidget* parent=0);  // constructor
   ~Mandelbrot();  // destructor
    void onAccel (FAccelEvent*);
    void onClose (FCloseEvent*);
diff --git a/test/timer.cpp b/test/timer.cpp
index bf9fb5a3..8d9eb935 100644
--- a/test/timer.cpp
+++ b/test/timer.cpp
@@ -9,7 +9,7 @@
 class timer : public FWidget
 {
  public:
-   timer (FWidget* parent = 0);
+   explicit timer (FWidget* parent = 0);
  protected:
    virtual void draw();
    void onTimer (FTimerEvent*);
diff --git a/test/ui.cpp b/test/ui.cpp
index d39f8a79..f764eb9b 100644
--- a/test/ui.cpp
+++ b/test/ui.cpp
@@ -21,7 +21,7 @@ class ProgressDialog : public FDialog
    FProgressbar* progressBar;
 
  public:
-   ProgressDialog (FWidget* parent=0);  // constructor
+   explicit ProgressDialog (FWidget* parent=0);  // constructor
   ~ProgressDialog();  // destructor
 
    void onShow (FShowEvent*);
@@ -149,7 +149,7 @@ class MyDialog : public FDialog
  private:
    FListBox* myList;
  public:
-   MyDialog (FWidget* parent=0);  // constructor
+   explicit MyDialog (FWidget* parent=0);  // constructor
   ~MyDialog();  // destructor
    void onClose (FCloseEvent*);
    void cb_noFunctionMsg (FWidget*, void*);