This example uses the WinRegisterUserMsg call to register a user-defined message and define its parameters.

#define INCL_WINMESSAGEMGR
#define INCL_WINTYPES
#include <OS2.H>
#define WM_MY_MESSAGE WM_USER + 11

HAB hab;

WinRegisterUserMessage(hab,
                       WM_MY_MESSAGE,
                       DTYP_BIT16,  /* param1 is a USHORT */
                       RUM_INOUT,   /* param1 is input/output */
                       DTYP_BIT16,  /* param2 is a USHORT */
                       RUM_INOUT,   /* param2 is input/output */
                       DTYP_BIT16); /* reply is a USHORT */