diff --git a/clipboard.cpp b/clipboard.cpp
index 0888d0e..0ade846 100644
--- a/clipboard.cpp
+++ b/clipboard.cpp
@@ -240,7 +240,7 @@ void GraphicsWindow::MenuClipboard(int id) {
     }
 }
 
-bool TextWindow::EditControlDoneForPaste(char *s) {
+bool TextWindow::EditControlDoneForPaste(const char *s) {
     Expr *e;
     switch(edit.meaning) {
         case EDIT_PASTE_TIMES_REPEATED: {
diff --git a/confscreen.cpp b/confscreen.cpp
index 433a12c..869c089 100644
--- a/confscreen.cpp
+++ b/confscreen.cpp
@@ -300,7 +300,7 @@ void TextWindow::ShowConfiguration(void) {
     Printf(false, " %Ft   version  %E%s", glGetString(GL_VERSION));
 }
 
-bool TextWindow::EditControlDoneForConfiguration(char *s) {
+bool TextWindow::EditControlDoneForConfiguration(const char *s) {
     switch(edit.meaning) {
         case EDIT_LIGHT_INTENSITY:
             SS.lightIntensity[edit.i] = min(1, max(0, atof(s)));
diff --git a/expr.cpp b/expr.cpp
index 6e56f4f..1db17bd 100644
--- a/expr.cpp
+++ b/expr.cpp
@@ -714,7 +714,7 @@ void Expr::Parse(void) {
     PopOperator(); // discard the ALL_RESOLVED marker
 }
 
-void Expr::Lex(char *in) {
+void Expr::Lex(const char *in) {
     while(*in) {
         if(UnparsedCnt >= MAX_UNPARSED) throw "too long";
 
@@ -771,7 +771,7 @@ void Expr::Lex(char *in) {
     }
 }
 
-Expr *Expr::From(char *in, bool popUpError) {
+Expr *Expr::From(const char *in, bool popUpError) {
     UnparsedCnt = 0;
     UnparsedP = 0;
     OperandsP = 0;
diff --git a/expr.h b/expr.h
index 642bc97..fa9da83 100644
--- a/expr.h
+++ b/expr.h
@@ -113,8 +113,8 @@ public:
     Expr *DeepCopyWithParamsAsPointers(IdList<Param,hParam> *firstTry,
         IdList<Param,hParam> *thenTry);
 
-    static Expr *From(char *in, bool popUpError);
-    static void  Lex(char *in);
+    static Expr *From(const char *in, bool popUpError);
+    static void  Lex(const char *in);
     static Expr *Next(void);
     static void  Consume(void);
 
diff --git a/mouse.cpp b/mouse.cpp
index ed7fbd5..753b3d6 100644
--- a/mouse.cpp
+++ b/mouse.cpp
@@ -1161,7 +1161,7 @@ void GraphicsWindow::MouseLeftDoubleClick(double mx, double my) {
     }
 }
 
-void GraphicsWindow::EditControlDone(char *s) {
+void GraphicsWindow::EditControlDone(const char *s) {
     HideGraphicsEditControl();
     Constraint *c = SK.GetConstraint(constraintBeingEdited);
 
diff --git a/style.cpp b/style.cpp
index f1d33c3..a3754be 100644
--- a/style.cpp
+++ b/style.cpp
@@ -643,7 +643,7 @@ void TextWindow::ScreenChangeStyleYesNo(int link, DWORD v) {
     InvalidateGraphics();
 }
 
-bool TextWindow::EditControlDoneForStyles(char *str) {
+bool TextWindow::EditControlDoneForStyles(const char *str) {
     Style *s;
     switch(edit.meaning) {
         case EDIT_STYLE_TEXT_HEIGHT:
diff --git a/textscreens.cpp b/textscreens.cpp
index a4cd760..6093f8c 100644
--- a/textscreens.cpp
+++ b/textscreens.cpp
@@ -611,7 +611,7 @@ void TextWindow::ShowTangentArc(void) {
 //-----------------------------------------------------------------------------
 // The edit control is visible, and the user just pressed enter.
 //-----------------------------------------------------------------------------
-void TextWindow::EditControlDone(char *s) {
+void TextWindow::EditControlDone(const char *s) {
     edit.showAgain = false;
 
     switch(edit.meaning) {
diff --git a/ui.h b/ui.h
index b29767d..b601836 100644
--- a/ui.h
+++ b/ui.h
@@ -317,11 +317,11 @@ public:
     static void ScreenChangeViewOrigin(int link, DWORD v);
     static void ScreenChangeViewProjection(int link, DWORD v);
 
-    bool EditControlDoneForStyles(char *s);
-    bool EditControlDoneForConfiguration(char *s);
-    bool EditControlDoneForPaste(char *s);
-    bool EditControlDoneForView(char *s);
-    void EditControlDone(char *s);
+    bool EditControlDoneForStyles(const char *s);
+    bool EditControlDoneForConfiguration(const char *s);
+    bool EditControlDoneForPaste(const char *s);
+    bool EditControlDoneForView(const char *s);
+    void EditControlDone(const char *s);
 };
 
 class GraphicsWindow {
@@ -679,7 +679,7 @@ public:
     void MouseScroll(double x, double y, int delta);
     void MouseLeave(void);
     bool KeyDown(int c);
-    void EditControlDone(char *s);
+    void EditControlDone(const char *s);
 
     SDWORD lastSpaceNavigatorTime;
     hGroup lastSpaceNavigatorGroup;
diff --git a/view.cpp b/view.cpp
index 58d96c2..58b355e 100644
--- a/view.cpp
+++ b/view.cpp
@@ -63,7 +63,7 @@ void TextWindow::ScreenChangeViewProjection(int link, DWORD v) {
     SS.TW.ShowEditControl(24, 10, buf);
 }
 
-bool TextWindow::EditControlDoneForView(char *s) {
+bool TextWindow::EditControlDoneForView(const char *s) {
     switch(edit.meaning) {
         case EDIT_VIEW_SCALE: {
             Expr *e = Expr::From(s, true);