Chris Bardon

Rant-a gigabyte is NOT 10^9 bytes!

I realized the other day that there's a fundamental problem with the computer indistry, and that's that there's a major difference between what's implemented at the hardware level, and what people seem to want to see. I just got a DVD burner a few weeks ago, and went to burn a backup disc of my hard drive. I set up a directory with 4.7 Gb of files, only to discover that the "4.7 Gb dvd" only held 4.7x10^9 bytes of data (as opposed to the approximately 5 046 586 572 bytes that ARE in a Gb).

When I stopped to think about it though, it made perfect sense. My "120 Gb" hard drive only formatted to 111 Gb. I remember that with smaller drives I used to think that this had something to do with OS overhead and cluster sizes, but now I realize that it's just that 120*10^9 bytes is being marketed as 120 Gb.

For those who don't know, a byte is 8 bits (ones and zeroes). There are 1024 (2*10) bytes in a kilobyte, 1024 kilobytes in a megabyte, and 1024 megabytes in a gigabyte. If you make the assumption that there are 1000 kilobytes in a megabyte for example, there's not all that much error. As you move up in orders of magnitude though, you can see the error becoming much more pronounced.

I guess my point is-in a world where people have no problem with 12 inches in a foot and 5 thousand and something-odd feet in a mile, why can't there be 1024 kilobytes in a megabyte? What would the harm be in selling 4.5 Gb DVD-Rs, or 111 Gb hard drives?

Actually, the most upsetting thing about this to me is just how long it took me to realize what was going on. Never really noticed it that much on CDRs. In retrospect I can see the problem, but I can't believe that I missed it at the time...

Joe Hsu

n/m.

Tom Jr

This can be confusing and frustrating when pushing the limits of storage media.

The 1024 = 'K' thing stems from a 10 bit sequence of bits. If you specifiy an address having 10 bits, you can have 1024 locations, since 2^10 = 1024. Similarly, 2^20 = 1 meg, and 2^30 = 1 gig. It all comes from the fact that computers use a base 2 (1 and 0) system. The use of 'K' or 'Kilo' prefix is an approximation, but an accepted one in the computer world.

However...

Technically, Kilo = 1000x, Mega = 1,000,000x and Giga = 1,000,000,000x, so the marketing people who sell storage devices can get away with overrating their claims. They aren't lying, but it is deceiving.

I get around it by not pushing my storage limits, especially with CD's. I've heard that data integrity can be reduced at the edjes of a CD. I can't back it up. It's just something I heard.

DaveF