The New data types were defined by using the typedef or #define statements. This was to allow the transition from 16 bit to 32 bit system. Some of the fresh data types are MSG, WNDCLASSEX, HINSTANCE, PSTR, WPARAM, UINT, LPARAM, LRESULT, HDC and HWND. The significance of the new data types are as follows:
HINSTANCE is a Handle to an illustration that is the program itself.
PSTR is a pointer to the character string, that is, char *.
HWND is a Handle to the window.
MSG is the message structure.
UINT is an unsigned int.
WNDCLASSEX is a window class configuration.
LRESULT is of the type LONG.
HDC is a Handle to the Device Context
When Windows was 16 bit WPARAM was a WORD that was a 16 bit unsigned short integer and LPARAM was LONG that was a 32 bit signed long integer. Therefore only the 'W' & 'L' prefix. In the Windows 95 WPARAM is the UINT and LPARAM is LONG. Both of them are the 32 bit values.