Recently, some discussions came up about 32 bit vs. 64 bit implementations of operating systems.

While I was composing a message about this topic, I realized that I did not know if there was a correct term for the number of bits supported by an operating system.

For example, various versions of Solaris and Linux have 32bit and 64bit releases. Is the distinction "architecture"? In my experience, that has referred to chip types (Intel vs. PPC). Is it a "release"? Typically, I think of a release as a version number a consistent feature set, that might run on different architectures.

Maybe it is just "architecture", after all, even though a chip family might have used several different bit sizes over time, the chips themselves are different when you jump from 32bit to 64bit.

3 Answers 3


I would use architecture.

Releases are just the specific versions of the software (or in this case entire Operating System) package.

Also, looking at the chip families, marketing will tie them together more than the technical aspects for any jump between 32bit and 64bit chips.

  • Architecture is as good a term as I've heard. However word size of the OS doesn't neccesarily eqate to wordsize of the processor computation. some of the high end power PC proces use 64 bit OS but do 128 bit math (and of course there is the ubiquitous 32 bit OS on 64 bit proc)
    – Jim B
    Jan 17, 2010 at 17:05

There is no definitive term but architecture is as good as any. By the way, it's word size, not bit size. Bit size is by definition fixed at one bit, whereas words can be any power of two. Although the smallest practical CPU I've seen is four bits.

  • 3
    Awww, you almost had a +1, but word size doesn't have to be a power of two; think of all those old mainframes with 36 bit words...
    – womble
    Jan 17, 2010 at 9:48
  • And I used a PDP8 with a word size of 12 bits. Ah! The good old days.
    – pavium
    Jan 17, 2010 at 11:07
  • You're right womble. Let me clarify and justify that by saying that the power of two applies to all commercially produced and viable monolithic CPUs. Jan 17, 2010 at 21:34
  • 1
    @womble: I think Power of Two is accurate. 2^36 is a power of two.
    – bahamat
    Sep 2, 2012 at 9:42
  • @bahamat: I have no idea what you mean. 36 isn't a power of two, though, and there are a number of computers which have a 36 bit word size.
    – womble
    Sep 20, 2012 at 1:15

The Solaris 10 documentation uses the phrase: "instruction set architecture".

The command for Solaris is to use:

# isainfo -b

If I have time, I will try to add examples for other operating systems.

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