OS is 64-bit or 32-bit ? , Kernel Compliant ?

Solaris
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# isainfo -v
64-bit sparcv9 applications
32-bit sparc applications

Which Architecture is booted ?
--------------------------------------
# isainfo -kv
64-bit sparcv9 kernel modules

# isalist - display the native instruction sets executable on this platform

# uname -a

UltraSparc processors are capable of 64-bit computing, the OS release level may be the limiting factor
SunOS5.7 or greater is 64-bit compliant
Solaris 2.7 or greater is 64-bit compliant

AIX
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# getconf -a grep KERN

KERNEL_BITMODE: 64


or

# file /usr/lib/boot/unix*

/usr/lib/boot/unix_64


Linux
------

# uname -a

x86_64 x86_64 x86_64 GNU/Linux or ia64 ia64 ia64 GNU/Linux
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Windows
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Start -> Run, and type dxdiag

x64_edition


Mac OS
-------

select About This Mac from the Apple menu

Mac OS X 10.4 offers 64-bit support to console applications