This function registers a window class.

#define INCL_WINWINDOWMGR /* Or use INCL_WIN, INCL_PM, Also in COMMON section */
#include <os2.h>

HAB      hab;           /*  Anchor-block handle. */
PSZ      pszClassName;  /*  Window-class name. */
PFNWP    pfnWndProc;    /*  Window-procedure identifier. */
ULONG    flStyle;       /*  Default-window style. */
ULONG    cbWindowData;  /*  Reserved storage. */
BOOL     rc;            /*  Window-class-registration indicator. */

rc = WinRegisterClass(hab, pszClassName, pfnWndProc,
       flStyle, cbWindowData);