Each message which is sent to a window procedure has two data items which
serve as arguments to that message. The two items are a word-long item,
wParam, and  double-word-long item, lParam. The lParam argument is
ocassionally subdivided into two word-long parameters. These word can be
extracted using the LOWORD(lParam) and the HIWORD(lParam) macros.

 EM_GETHANDLE
 EM_GETLINE
 EM_GETLINECOUNT
 EM_GETMODIFY
 EM_GETSEL
 EM_LIMITTEXT
 EM_LINEFROMCHAR
 EM_LINEINDEX
 EM_LINELENGTH
 EM_LINESCROLL
 EM_REPLACESEL
 EM_SETMODIFY
 EM_SETPASSWORDCHAR
 EM_SETSEL
 EM_UNDO