How can I determine if my computer/operating system is 64-bit?

Windows If you are using Windows 7, click Start -> Control Panel -> System and Security -> System. The System type: line will give you the Operating System type:

Windows Vista users should click Start -> Control Panel -> System and Maintenance -> System. The System type: line will give you the Operating System type:

If you are using Windows XP, click Start -> Run and type dxdiag. If a Windows dialog box is displayed asking if you want to verify your drivers, you can safely click No and continue. When the program has finished loading, you should see something similar to one of the following images:

The Operating System line, refers to Windows x64 or 64-bit edition. The last image above specifies the processor Itanium, which is a 64-bit processor.

Mac

Select About this Mac from the Apple menu. The text below Mac OS X will give the operating system version, and the Processor line will give you the processor type.

Mac OS X 10.5 (or greater) is a 64-bit operating system. Intel Core 2 Duo, Intel Xeon, and PowerPC G5 are 64-bit processors. However, 64-bit Stata for Mac is available only for 64-bit Intel-based Macs.
All currently shipping Macs have a 64-bit processor and a 64-bit operating system.

Unix (IBM-AIX, Sun Solaris)

• IBM-AIX
  
  The getconf command will return the configuration of your machine. Since you are looking only for the kernel parameters, you should type
  
  
  [cph@anna ~]$ getconf -a | grep KERN
  KERNEL_BITMODE: 64
  
  If that fails or does not return a result, try the file command.
  
  
  [cph@anna ~]$ file /usr/lib/boot/unix*
  /usr/lib/boot/unix: 64-bit XCOFF executable or object module not stripped
  /usr/lib/boot/unix_64: 64-bit XCOFF executable or object module not stripped
  /usr/lib/boot/unix_mp: executable (RISC System/6000) or object module not stripped
  /usr/lib/boot/unix_up: executable (RISC System/6000) or object module not stripped
  
  
  [cph@ozona ~]$ file /usr/lib/boot/unix*
  /usr/lib/boot/unix: symbolic link to /usr/lib/boot/unix_up.
  /usr/lib/boot/unix_kdb: executable (RISC System/6000) or object module not stripped
  /usr/lib/boot/unix_up: executable (RISC System/6000) or object module not stripped
  
  We can see that 'anna' is a 64-bit capable platform, and 'ozona' is only 32-bit.
• Sun Solaris
  
  Sun's platforms transitioned to 64-bit over a period of time, making identifying the platform for 64-bit compliance tricky. Sun has stated:
  
  
  Sun has implemented its 64-bit operating system in phases. The Solaris 2.5 Operating Environment provided support for increased precision with 64-bit math and also included support for 64-bit asynchronous I/O. The Solaris 2.6 Operating Environment added support for large datasets with large (1 Terabyte) filesystems while allowing co-existence of 32-bit and 64-bit files. Beginning with the Solaris 7 Operating Environment, Sun introduced support for large virtual address spaces with a full 64-bit operating system. Sun began shipping 64-bit hardware in 1995. By phasing in operating system support for 64-bits Sun has provided 64-bit features as the market has demanded them while guaranteeing compatibility for existing 32-bit applications.
  
  To determine what kind of binaries your Solaris machine can run, try the following:
  
  
  eden:/home/cph: isainfo -v
  64-bit sparcv9 applications
  32-bit sparc applications
  
  You can see that this Solaris machine is capable of running 32-bit as well as 64-bit applications. If isainfo fails, running a 64-bit application on your Sun will generally not be possible, unless of course isainfo is not in your path or has not been installed. You can also use the uname command to glean more information:
  
  
  eden:/home/cph: uname -a
  SunOS eden 5.8 Generic_108528-05 sun4u sparc SUNW,Ultra-5_10
  
  
  lagrange:/usr/users/cph: uname -a
  SunOS lagrange 5.5.1 Generic_103640-29 sun4u sparc SUNW,Ultra-1
  
  
  SunOS/Solaris versions map to the following:

  SunOS	SOLARIS
  5.3	2.3
  5.4	2.4
  5.5	2.5
  5.5.1	2.5.1
  5.6	2.6
  5.7 or greater is 64-bit compliant	2.7 or greater is 64-bit compliant

  
  While all UltraSparc processors are capable of 64-bit computing, the OS release level may be the limiting factor. In the above excerpt, 'eden' (SunOS 5.8) is a fully compliant 64-bit platform, and 'lagrange' (SunOS 5.5.1) is a 64-bit UltraSparc limited to 32-bit computing.

Linux

Linux users should type the uname command. Depending on the platform, you may see

[cph@gaylord ~]$ uname -a
Linux gaylord.stata.com 2.6.11-1.27_FC3 #1 Tue May 17 20:24:57 EDT 2005 x86_64 x86_64 x86_64 GNU/Linux

[cph@caddo ~]$ uname -a
Linux caddo.stata.com 2.6.9-5.0.5.EL #1 SMP Fri Apr 8 14:20:58 EDT 2005 ia64 ia64 ia64 GNU/Linux

[cph@tango ~]$ uname -a
Linux tango.stata.com 2.6.10-1.771_FC2smp #1 SMP Mon Mar 28 01:10:51 EST 2005 i686 i686 i386 GNU/Linux

In the above listing, 'gaylord' (x86_64 GNU/Linux) and 'caddo' (ia64 GNU/Linux) are 64-bit compliant. 'tango' (i386 GNU/Linux) is only a 32-bit platform.