Solved Why did they name it "System32" in 64-bit Vista?

[Cytherian]

Back in the early days of Windows 3.11, it was a 16 bit operating system. As part of it's structure, system files were located in an aptly named "System" folder off the "Windows" root. Later on as processors became more advanced and capable of addressing 32 bits, Windows NT was developed. Implicitly, its system folder was named "System32". In order to extend compatibility with Windows 3.11, a System32 folder was added so that "System" and "System32" co-existed together.

When 64-bit processing became possible, Microsoft was faced with a dilemma. Should they now start naming the new system folder "System64" and leave "System32" around for backward compatibility? The trouble was legacy. By this time, Windows development policies and guidelines did not prohibit programs from directly referencing System32. Also, if a software engineer developed a program for 32-bit and then provided a 64-bit version, they'd have to be careful about changing the System32 reference. In the end, Microsoft just didn't want to take chances.


To make matters more complicated, Microsoft also introduced another folder called "Winsxs" (Windows Side-by(x)-Side assemblies) which allows multiple versions of a system file to co-exist, under 32 bit and 64 bit. That's because some programs may be written to work with an older version of a system file and be incompatible with a later one. In the past, installing the program would replace the system file. Now Windows makes sure that multiple versions can co-exist, depending upon what program needs them. How does Windows know which version is needed for a given program? There is a manifest file that provides a guide to the library of files available for the redirector.

Two different naming conventions are used under Winsxs: "amd64_microsoft-windows" and "x86_microsoft-windows". "amd64" was chosen because AMD was the first CPU company to create a 64 bit processor. And because 32 bit was started on the old Intel 8086 architecture, x86 was chosen. Thus, dynamic file redirection is used to access one system file or the other, depending upon which type of program is running (32 bit or 64 bit).

I'm not totally sure how System32 and Winsxs work together. I believe System32 is the "default" system files, with Winsxs as the alternate when required. If I'm wrong, someone please correct me.

Next, there's also the folder SysWow64. This is essential the System for Windows on Windows, providing the ability for 32 bit programs to make function calls to the native 64 bit system. This is the 2nd time Microsoft has done this. In Windows 95/98, there was a SysWow32, so that 16 bit programs could make function calls to the native 32 bit system.


Ultimately, it would have probably been better for Microsoft to never change the name of "System", leaving it as the default for whatever version of the operating system is installed. Then, for legacy system versions there would be a number system (e.g. Sys16 for 16 bit, Sys32 for 32 bit). Thus, the developer would never have to worry about hard coded references to System, and then Windows would handle redirection accordingly. But, we aren't privy to Microsoft's internal decisions. There was probably a good reason why the naming convention was chosen as-is, which is just unfortunately a bit mystifying to the uninitiated.


For more information about the Windows x64 system, I suggest reading the Sepago blog on Windows x64.

 

[tom982]

Nice post Gary! Another thing to add is the mystery of the Sysnative folder. Here, try it out for yourself and see if you can work it out:

Open a command prompt Window, and run this command:

echo test > %systemroot%\system32\a.txt

Then close that command prompt window and run these two command prompts:

C:\Windows\system32\cmd.exe
C:\Windows\SysWow64\cmd.exe

Then put the Windows side by side, so you can see both and run the following command in each:

type C:\Windows\sysnative\a.txt

Any idea as to why that's happening? No Googling

Tom

 

[Cytherian]

Thanks, Tom. It's of course from a pseudo-layman's perspective (I'm software technical, but have long ago dropped my Windows SDK programming skills). I figured some folks might find it useful.

Curious, I hadn't heard of "Sysnative" before. Interesting how the command prompt needs to be executed from the 32 bit libraries in order to see the file via Sysnative. Looks like some kind of secretive redirection for 32 bit, as SysWow64 allows access while System32 does not. What's the intended purpose?

 

[tom982]

Wow, I never knew you were a programmer! You learn something new every day

In x64 installations, when x86 software tries to access C:\Windows\system32, it is automatically redirected to C:\Windows\SysWow64 because of reasons outlined in your post above. If things actually need to access the x64 components (to perform replacements etc.) then instead, the filepath should be C:\Windows\sysnative and Windows will recognise this as a special case and not perform the redirection

Edit: See here for more info: http://msdn.microsoft.com/en-gb/library/windows/desktop/aa384187(v=vs.85).aspx

32-bit applications can access the native system directory by substituting %windir%\Sysnative for %windir%\System32. WOW64 recognizes Sysnative as a special alias used to indicate that the file system should not redirect the access. This mechanism is flexible and easy to use, therefore, it is the recommended mechanism to bypass file system redirection. Note that 64-bit applications cannot use the Sysnative alias as it is a virtual directory not a real one.

 

[Cytherian]

Consequently, I ended up discovering Sysnative.com and spied you as a member there. How is that forum relative to ones like VF and SF?

Thanks for link reference. Good example of the purpose; makes a lot of sense to me. It's also encouraging to see how much Vista and W7 have in common under the hood.

 

[tom982]

Consequently, I ended up discovering Sysnative.com and spied you as a member there. How is that forum relative to ones like VF and SF?

Thanks for link reference. Good example of the purpose; makes a lot of sense to me. It's also encouraging to see how much Vista and W7 have in common under the hood.

I can't go into much detail I'm afraid as I might wake up tomorrow to a ban for promoting a competitors website, but I think (well I hope!) I'm okay to say that it's more BSOD and Windows Update orientated than VF and SF But VF and SF are much bigger and there are always threads around here if you want one.

Yeah, they're very similar Take Vista, add a few features, make loads of cosmetic changes and you have Windows 7 - they didn't really change much at all.

Tom