Byte by Bite

Just how big is my hard drive?

by Marv Dealy

Note that the measurement given in kilobytes for the size of the hard drive and the amount abbreviated in GB don’t add up, assuming a gigabyte is supposed to be one billion bytes. I’ve talked to several folks about this and no one has been able to give me a reasonable answer, other than “well, maybe it’s hidden stuff on the hard drive, you know, overhead stuff.”

I think the problem is the fact that we assume that the word gigabyte means an actual measurement of one billion bytes, when it’s actually 1,024 megabytes, not 1,000 as you might be led to believe by the decimal connotation of the word. Further, a megabyte isn’t one million bytes, it’s actually 1,048,576 bytes.

What we have here is a rounding error, boys and girls and other faithful readers (now numbering nearly sixty-three I’m told).

Back in the early days of the computers there were probably a total of five people who actually had to know how much a storage device was holding, and they begin measuring and referring to these amounts of data storage in bytes and eventually kilobytes, also known as a KB, kB, Kbyte or kbyte – in any event, what we’d today call a most basic unit of measurement.

Of course, even our lead pencils now come with more storage than early computers, but the point here is that when those five people talked about a kilobyte they knew they all meant a measurement of 1,024 bytes, not a rounded down 1,000 bytes as the word kilo (meaning 1,000) implies to us novices.

When only those five folks were involved in this measurement, it didn’t really matter as they all knew exactly what they were talking about. Now, however, everyone tosses the phrase gigabite around when they’re talking about their iPods, or computers or refrigerators.

Back to the hard drive in the laptop I’m writing this column on – it claims to have a hard drive measured as 40,007,729,152 bytes yet it’s actually reported as being 37.2 GB in size. If a gigabyte were exactly one billion bytes, then I should have a 40 GB drive, based on forty billion plus bytes, right?

However, when you take the rounding into account that those five folks used years ago, and consider that each one of my gigas doesn’t have a billion bytes but actually has 1,073,741,824 bytes (someone else’s math, not mine – see, http://minnesotashopper.com/our-hosting-plans.php), when you divide the number of bytes my hard drive has (40 billion plus) by the actual number of bytes in a giga, you get the 37.2 GB reading that my hard drive properties reports.

The problem we have now is that what was once a sort of jargon measurement among a few professionals got dispersed to the mass media and has now entered the mainstream lexicon, creating confusion such as what we see here.

Some have tried to get the usage of Kb with a leading capital to differentiate the popular usage (1,000 bytes) from the SI usage (1,024 bytes) of kb, although this hasn’t caught on widely – most folks would assume one or the other version was a typo, I suppose.

So just who uses which measurement? RAM is measured based on the binary, or powers of two, as is most software when expressing storage space needed to install. The word “kibibytes” is supposed to be used according to SI standards, but is relatively rare except amongst software where precision is important such as in the Linux kernel or BitTorrent.

The decimal measurement, or 1000 bytes, is often used to measure quantities that aren’t based on powers of two, such as bitrates (used to measure connection speed, transfer rates, digital bandwidth capacity, etc.).

Here again, measurements are divided between binary and decimal, or powers of two compared to powers of ten.

For those still awake at this point in today’s column, you can read even more about this raging controversy at Wikipedia (http://en.wikipedia.org/wiki/Kilobyte). If you’ve got a better theory about where’d the disk space go, now would be the time to raise your hand.

Digitizing Sound – I wrote recently about running signal from your stereo through your UBS port to digitize your older record collection or even those favorite 8-tracks (just try checking that option box on your new vehicle order). Fortunately, common sense rides to rescue as reader Mike Lamasney from Twain Harte writes “I don’t understand the need to record audio through the USB port. Why not just plug in your audio source to the line input on the sound card? I have a shielded cable from my stereo system to my computer and it works just fine. Am I missing something by not using the USB port?”

Mike, I’m assuming here that you have a stereo setup that allows you to pull a signal from the preamp, which would be able to plug directly into your computer’s sound card. Either that, or you’re taking a signal out that is intended to power a speaker and keeping the volume on the stereo low so as not to blow the sound card out of the computer. If you’re using some other setup, please advise.

If you want to try the direct approach, don’t make the cable between your stereo and your computer very long, or you’ll get signal loss. Also, keep the audio cable as far away from power cables as possible to help prevent extra noise being introduced into your music. That said, if you really want to do this right, you’ll have to use a coaxial cable between your stereo and computer, which means you’ll need the correct plugs on each end – may have to get out the soldering iron here. Or, just use one of the USB devices we’ve talked about here previously.