    # CStruct Examples
    require 'windows/system_info'
    require 'win32struct'
    include Windows::SystemInfo

    # SYSTEM_INFO in VC6 's SDK
    # typedef struct _SYSTEM_INFO {
    #     union {
    #         DWORD dwOemId;          // Obsolete field...do not use
    #         struct {
    #             WORD wProcessorArchitecture;
    #             WORD wReserved;
    #         };
    #     };
    #     DWORD dwPageSize;
    #     LPVOID lpMinimumApplicationAddress;
    #     LPVOID lpMaximumApplicationAddress;
    #     DWORD dwActiveProcessorMask;
    #     DWORD dwNumberOfProcessors;
    #     DWORD dwProcessorType;
    #     DWORD dwAllocationGranularity;
    #     WORD wProcessorLevel;
    #     WORD wProcessorRevision;
    # } SYSTEM_INFO, *LPSYSTEM_INFO;

    # SYSTEM_INFO in Ruby
    class SYSTEM_INFO < Win32Struct
        union:u do
            DWORD:dwOemId
            struct:x do
                WORD:wProcessorArchitecture
                WORD:wReserved
            end
        end
        DWORD  :dwPageSize
        LPVOID :lpMinimumApplicationAddress
        LPVOID :lpMaximumApplicationAddress
        DWORD  :dwActiveProcessorMask
        DWORD  :dwNumberOfProcessors
        DWORD  :dwProcessorType
        DWORD  :dwAllocationGranularity
        WORD   :wProcessorLevel
        WORD   :wProcessorRevision
    end

    # call GetSystemInfo
    sys_info = SYSTEM_INFO.new
    GetSystemInfo(sys_info.__data__) # __data__ is an alias for method 'data'

    #output
    puts "<System Infomation>"
    puts        "Processor Architecture:#{sys_info.u.x.wProcessorArchitecture}"        # 'u' and 'x' can not be omitted
    puts        "Page Size:#{sys_info.dwPageSize}"
    puts        "Minimum Application Address:0x#{sys_info.lpMinimumApplicationAddress.to_s 16}"
    puts        "Maximum Application Address:0x#{sys_info.lpMaximumApplicationAddress.to_s 16}"
    puts        "Active Processor Mask:#{sys_info.dwActiveProcessorMask}"
    puts        "Number Of Processors:#{sys_info.dwNumberOfProcessors}"
    puts        "Processor Type:#{sys_info.dwProcessorType}"
    puts        "Allocation Granularity:0x#{sys_info.dwAllocationGranularity.to_s 16}"
    puts        "Processor Level:#{sys_info.wProcessorLevel}"
    puts        "Processor Revision:#{sys_info.wProcessorRevision}"