MODULE IupTest;
    IMPORT
        Iup := IupLib,
        SYSTEM;
    CONST
        expand = "EXPAND";
    VAR
        ml: Iup.Ihandle;

PROCEDURE [ccall] BtnCB(self: Iup.Ihandle);
BEGIN
    Iup.SetAttribute(ml, "VALUE", "Hello!")     
END BtnCB; 
   
PROCEDURE Main*;
    VAR
        dlg, bt, split: Iup.Ihandle;
        res: INTEGER;
        ih: Iup.Ihandle;
        prev: Iup.Icallback; (* the address of the previous function associated to the action. *)
BEGIN
    res := Iup.Open(NIL, NIL);
   
    bt := Iup.Button("Button", "btn_test");
    Iup.SetAttribute(bt, expand, "YES");
    prev := Iup.SetCallback(bt, "ACTION", SYSTEM.ADR(BtnCB));
   
    ml := Iup.SetAttributes(Iup.MultiLine(NIL), "EXPAND = YES, VISIBLELINES = 5, VISIBLECOLUMNS = 10");
   
    split := Iup.Split(bt, ml);
    Iup.SetAttribute(split, "ORIENTATION", "VERTICAL");
    Iup.SetAttribute(split, "COLOR", "255 20 20");
   
    dlg := Iup.Dialog(Iup.SetAttributes(Iup.Vbox(split, NIL), "MARGIN = 10x10, GAP = 10"));
    Iup.SetAttribute(dlg, "TITLE", "IupSplit Example");
   
    res := Iup.Show(dlg);
    res := Iup.MainLoop();
    Iup.Close();
       
END Main;
       
BEGIN
    Main;
END IupTest.

^Q DevLinker.LinkExe
Simple.exe := IupTest ~