Is there a Windows API call that will tell me if I'm running on a 64-bit OS?

Question

Is there a Windows API call that will tell me if I'm running on a 64-bit OS? I have some legacy c++ code that makes a call to GetVersionEx to fill in a OSVERSIONINFO structure, but that only tells me (AFAIK) the OS (Vista, V7, etc.), but not the processing architecture. I can hack around this by simply looking for the existence of "C:\Program Files (x86)...", but this seems ugly. I'm sure there must be an API to return this info.

Just out of curiosity, why do you need to know? Is it not something that can't be done if pre-compiler directives? — Rowland Shaw, Oct 29 '09 at 20:48
@Rowland: That cannot be done after a program has been released. Besides, a 64-bit OS is significantly different from a 32-bit at the hardware layers; i.e. a 32-bit driver installer should detect the 'bitness' of the host OS before installing. — Cecil Has a Name, Oct 29 '09 at 20:54
I thought WOW handled the talking to drivers et al - I would assume that installation of said drivers would be done with an installation framework; just curiosity with the the intention of understanding *why* this would need to be done... — Rowland Shaw, Oct 29 '09 at 21:00

score 7 · Accepted Answer · answered Oct 29 '09 at 20:56

7

IsWow64Process might be what you are looking for.

answered Oct 29 '09 at 20:56

Michael

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Just be aware that this function always returns false if run from a 64-bit application (because 64-bit apps aren't running in WoW64 mode). – Powerlord Oct 29 '09 at 21:00
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Absolutely. (Of course, detecting whether the current application is a 64-bit application could be done at compile-time, e.g. via `_M_X64` in msvc) – Michael Oct 29 '09 at 21:09

score 4 · Answer 2 · answered Oct 29 '09 at 20:54

4

GetNativeSystemInfo()

answered Oct 29 '09 at 20:54

Jerry Coffin

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score 1 · Answer 3 · edited May 23 '17 at 12:33

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I found this post that seems to provide a good answer: Detect whether current Windows version is 32 bit or 64 bit

I don't know why it didn't come up when I search Stack Overflow before posting.

Incidentally, the best solution for me is to simply check for the ProgramW6432 environment variable.

edited May 23 '17 at 12:33

Community

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answered Oct 29 '09 at 21:05

Howard Pinsley

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score 0 · Answer 4 · edited May 23 '17 at 12:01

The solution is pretty straight-forward. If you are compiling for 64-bit, you already know that you are running on a 64-bit version of Windows. So you only need to call IsWow64Process when compiling for 32-bit. The following implementation returns true, if it is running on a 64-bit version of Windows:

bool Is64BitPlatform() {
    #if defined(_WIN64)
        return true;  // 64-bit code implies a 64-bit OS
    #elif defined(_WIN32)
        // 32-bit code runs on a 64-bit OS, if IsWow64Process returns TRUE
        BOOL f = FALSE;
        return ::IsWow64Process(GetCurrentProcess(), &f) && f;
    #else
        #error Unexpected platform.
    #endif
}

This answers the question you asked. The answer to the question you should have asked instead was posted in the response by Jerry Coffin already: Simply call GetNativeSystemInfo.

Is there a Windows API call that will tell me if I'm running on a 64-bit OS?

4 Answers4

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