Thanks a lot for help. The below is the output of Python (installed on Windows 2008 with python-2.7.2.amd64.msi): Microsoft Windows [版本 6.0.6001] Copyright (c) 2006 Microsoft Corporation. All rights reserved. C:\Users\Administrator>python Python 2.7.2 (default, Jun 12 2011, 14:24:46) [MSC v.1500 64 bit (AMD64)] on win32 Type "help", "copyright", "credits" or "license" for more information. >>> import struct >>> struct.calcsize('P') 8 >>> Regards, Lu, Yuan-Ching/盧元慶 Computer Integrated Manufacturing Department, Manufacturing Operation, TSMC Solid State Lighting Ltd. Tel: 886-3-5636688 Ext: 781-3057 Mobile: 886-938-317596