Binary units vs SI units

As a follow-on to my first post, I'll do a quick explanation of the binary vs SI prefix thing I mentioned.

Quick question, is a kilobyte 1000 bytes or 1024 bytes?  Is a gigabyte 1 billion bytes or 1024 * 1024 * 1024 bytes? If you said 1024, you're actually wrong.  That a kibibyte (or gibibyte for the billion version).  Early Operating Systems used a binary approximation of 1000 as 1024 in order to make calculations more efficient, but kilo is a standard term meaning 1000 (kilogram, for example).  They supplanted the term and thus was born the 1024 byte "kilobyte". The industry caught back up at some point and renamed the binary approximations, but there's still a lot of confusion out there because memory manufacturers and a lot of software still refer to the binary approximations with the standard prefixes.  1GB of RAM is actually 1 GiB (gibibyte).  Interestingly, network bandwidth and hard disk capacity don't suffer from this problem.  1Gb of bandwidth is one billion bits.

So when your computer says your 1TB hard drive is really only 850GB or whatever, it's your OS that's wrong.  Quit blaming the marketing departments of hard disk manufacturers because Microsoft can't bother to read a spec.

More info at wikipedia: http://en.wikipedia.org/wiki/Kibibyte