WS_POPUP WS_CHILD

 WS_POPUP
Pop-up   windows   are   top-level   windows   and   are   connected   to   the   desktop   window 's   child   windows   list.   Applications   usually   use   pop-up   windows   for   dialog   boxes.   The   main   difference   between   pop-up   and   overlapped   windows   is   that   pop-up   windows   need   not   have   captions   and   overlapped   windows   must   have   captions.   When   a   pop-up   window   does   not   have   a   caption,   it   can   be   created   without   a   border.   Pop-up   windows   may   own   other   top-level   windows   or   be   owned   by   other   top-level   windows   or   both.   All   pop-up   windows   have   the   WS_CLIPSIBLINGS   style,   even   if   it   was   not   specified.   Pop-up   windows   must   not   be   created   with   the   CW_USEDEFAULT   value   for   either   the   position   or   the   size   of   the   window.   Pop-up   windows   that   use   CW_USEDEFAULT   will   exist   but   will   have   no   size   or   no   position   or   both.

WS_CHILD
Child   windows   must   have   a   parent   window   and   are   confined   to   the   client   area   of   their   parent.   This   is   the   major   distinction   between   child   windows   and   overlapped   and   pop-up   windows.   Child   window   parents   can   be   top-level   windows   or   other   child   windows.   Child   windows   are   positioned   from   their   parent   window 's   upper-left   corner   and   not   from   the   upper-left   of   the   screen   as   are   top-level   windows.   Child   windows   are   clipped   to   the   client   area   of   their   parent.   Controls   in   a   dialog   box   are   child   windows   whose   parent   is   the   dialog   box.   Child   windows   must   not   be   created   with   the   CW_USEDEFAULT   value   for   either   the   position   or   size   of   the   window.   Child   windows   that   use   CW_USEDEFAULT   will   exist   but   will   have   no   size   or   position   or   both.