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getsysteminfo (kernel32)
Retrieves information about the current system

C# Signature:

[DllImport("kernel32.dll", SetLastError=false)]

public static extern void GetSystemInfo(out SYSTEM_INFO Info);

User-Defined Types:

    public enum ProcessorArchitecture
        X86 = 0,
        X64 = 9,
        @Arm = -1,
        Itanium = 6,
        Unknown = 0xFFFF,

    public struct SystemInfo
        public ProcessorArchitecture ProcessorArchitecture; // WORD
        public uint PageSize; // DWORD
        public IntPtr MinimumApplicationAddress; // (long)void*
        public IntPtr MaximumApplicationAddress; // (long)void*
        public IntPtr ActiveProcessorMask; // DWORD*
        public uint NumberOfProcessors; // DWORD (WTF)
        public uint ProcessorType; // DWORD
        public uint AllocationGranularity; // DWORD
        public ushort ProcessorLevel; // WORD
        public ushort ProcessorRevision; // WORD

Alternative C# structure[s]:

    [StructLayout( LayoutKind.Explicit )]
    public struct SYSTEM_INFO_UNION
        [FieldOffset( 0 )]
        public UInt32 OemId;
        [FieldOffset( 0 )]
        public UInt16 ProcessorArchitecture;
        [FieldOffset( 2 )]
        public UInt16 Reserved;

    [StructLayout( LayoutKind.Sequential, Pack = 1 )]
    public struct SYSTEM_INFO
        public SYSTEM_INFO_UNION CpuInfo;
        public UInt32 PageSize;
        public UInt32 MinimumApplicationAddress;
        public UInt32 MaximumApplicationAddress;
        public UInt32 ActiveProcessorMask;
        public UInt32 NumberOfProcessors;
        public UInt32 ProcessorType;
        public UInt32 AllocationGranularity;
        public UInt16 ProcessorLevel;
        public UInt16 ProcessorRevision;

Alternative Managed API:

To determine whether the OS or Process is x64, using .NET 4, see System.Environment (Is64BitProcess, Is64BitOperatingSystem);

Sample Code:

    void Test()
        NativeMethods.GetSystemInfo(out info);


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