[out] Pointer to the variable where the high-order word of the file size is returned. This parameter can be NULL if the application does not require the high-order word.
[out] Pointer to the variable where the high-order word of the file size is returned. This parameter can be NULL if the application does not require the high-order word.
就是说有的应用程序要求文件大小的高字节的返回值。一般不用这个，直接用NULL代替即可。