# The psychology of arbitrary limits

NewsGator - which I use to fetch blog posts - today decided to fetch an August third post for me. At least it's from this year.

In it, Larry talks about the volume control of a TV going from 0 to 63. And he discusses a possible reason for it, as do many of his readers.

Which brings me to:

Eric's Law of Arbitrary Limits

If you are designing a piece of tech gear - be it hardware or software - and you need to choose an arbitrary limit or range for something, make sure the limit is either 2^n or 2^n - 1.

The majority of the developers who use your product will convince themselves that you've chosen that limit for some well-thought-out reason, such as the internal data structure of your product, rather than just choosing a number because. They will speculate on why you chose that particular number, and you won't spend your time justifying the limit.

And they will be happy that they understand "the secret" behind why you chose such a strange number...

1. LarryOsterman says:

I LIKE it.

I’ll have to remember that one.

I wonder what they’ll say about Vista’s volume going from 0.0 to 1.0 ðŸ™‚

2. Dave Arkley says:

The Vista volume range 0.0 to 1.0 is great;. 1.0 is both 2^0 and 2^1-1 so a doubly clever number

3. David Levine says:

If the product is derivative of a pre-1970 era then I suggest 8^n – octal notation is so retro….(and still fulfills the 2^n requirement)