How can I determine whether a process is 32 or 64 bit?

Question

Given a Windows process handle, how can I determine, using C++ code, whether the process is 32 bit or 64 bit?

Answer 1

If you have a process handle, use IsWow64Process().

If IsWow64Process() reports true, the process is 32-bit running on a 64-bit OS.

If IsWow64Process() reports false (or does not exist in kernel32.dll), then the process is either 32-bit running on a 32-bit OS, or is 64-bit running on a 64-bit OS. To know if the OS itself is 32-bit or 64-bit, use GetNativeSystemInfo() (or GetSystemInfo() if GetNativeSystemInfo() is not available in kernel32.dll).