Sometimes understanding the underlying architecture of a system is critical to being able to
work with that system safely and effectively. The x64 version of Windows is a perfect example of
this.
Windows XP and Windows Server 2003 are both available in 64-bit versions which are designed to run on x64 hardware. These x64 Windows operating systems run 64-bit code natively but can also run 32-bit code through the use of an integrated emulator called Windows on Windows 64 (WOW64).
No big deal, you say. After all, the 32-bit versions of the various Windows operating systems are designed to run both 32-bit and 16-bit code simultaneously. (Technically, it's not truly running simultaneously, but explaining how the multitasking engine handles 16-bit code is for another tip).
The point is that 32-bit versions of Windows have a complicated mechanism in place to allow 32- and 16-bit code to run side by side. Still, the system is designed so that whether you're a systems administrator or a casual user, you don't need to know how these mechanisms work.
But 64-bit versions of Windows are different. From a user's standpoint, 64-bit applications simply run side by side with 32-bit applications; nothing special is going on. But for administrators (and members of the help desk), it's a different story: The 32-bit code must be kept isolated from 64-bit code. This isolation is so important that x64 versions of Windows have two registries, one
Windows XP and Windows Server 2003 are both available in 64-bit versions which are designed to run on x64 hardware. These x64 Windows operating systems run 64-bit code natively but can also run 32-bit code through the use of an integrated emulator called Windows on Windows 64 (WOW64).
No big deal, you say. After all, the 32-bit versions of the various Windows operating systems are designed to run both 32-bit and 16-bit code simultaneously. (Technically, it's not truly running simultaneously, but explaining how the multitasking engine handles 16-bit code is for another tip).
The point is that 32-bit versions of Windows have a complicated mechanism in place to allow 32- and 16-bit code to run side by side. Still, the system is designed so that whether you're a systems administrator or a casual user, you don't need to know how these mechanisms work.
But 64-bit versions of Windows are different. From a user's standpoint, 64-bit applications simply run side by side with 32-bit applications; nothing special is going on. But for administrators (and members of the help desk), it's a different story: The 32-bit code must be kept isolated from 64-bit code. This isolation is so important that x64 versions of Windows have two registries, one
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