As the storage capacity and cost of computer hard drives continue to improve, it just amazes me how many bytes you can store for a reasonable cost. For example, you can purchase an external 1 terabyte drive for less than $150….which is probably a good thing, since downloading a few videos and your daily email will fill that up in no time.
This got me thinking about how megabyte and gigabyte have made it into everyday language. Even Grandma knows that you want lots of gigabytes in your hard drive. Expect terabyte to make it into dinner conversation shortly. These prefixes that help us handle humongoid numbers come from the International System of Units (SI).
When I first started out messing around with electronics as a kid, I had to get used to these units. Back then it was mostly kilohertz and megahertz, along with kilohm and megohm. Not too bad. Capacitance was in microfarads and picofarads. (There was this strange usage of micro-microfarad, which I eventually figured out was the same as picofarad.) I didn’t know a tera from a giga.
There are twenty SI prefixes listed on the NIST web page, including:
| 1024 | yotta | Y |
| 1021 | zetta | Z |
| 1018 | exa | E |
| 1015 | peta | P |
| 1012 | tera | T |
| 109 | giga | G |
| 106 | mega | M |
| 103 | kilo | k |
When we get to 1000 terabytes, that will equal a petabyte. I don’t think I’ve ever used peta to refer to any numerical value, and certainly not exa, zetta and yotta. I kind of like the sound of yotta, as I can hear myself saying “there’s a yotta bytes on that 5 yottabyte hard drive.”
On the low end, we some other prefixes to deal with:
| 10-3 | milli | m |
| 10-6 | micro | µ |
| 10-9 | nano | n |
| 10-12 | pico | p |
| 10-15 | femto | f |
| 10-18 | atto | a |
| 10-21 | zepto | z |
| 10-24 | yocto | y |
I have often used the prefixes up to femto and might have said atto once or twice in my career, but never zepto or yocto. Isn’t zepto the name of one of the Marx brothers? 🙂 I’ve noticed that nano has worked its way into dinner conversation, via terminology such as nanotechnology. I’ve even heard a few non-technical people say something like “that will last about a nanosecond.”
It seems that things are getting more numerous (bytes on hard drives) and smaller (width of a transistor element) at the same time. This stretches out the dynamic range that we end up dealing with, and not just related to technical fields.
We just seem to have a lot of stuff.
73, Bob K0NR
I’ve been seeing petabyte for a while now, because I’ve worked in storage systems; these days we’re even starting to see exabytes creeping into that field.
A few months back, I wrote a blog article on alternative energy that, amongst other things, discussed US energy production and consumption. The total annual electrical generation of the US is perhaps best expressed best in exajoules (it was about 14.4 EJ in 2007), although I used petajoules in my article in order to avoid decimal points.
It’s certaingly interesting that the computing industry has been more successful at teaching understanding of the metric prefixes than decades of instruction in school math and science classes.
Then again, there’s the minor issue that a gigabyte is actually 1,073,741,824 bytes, but a gigameter is 1,000,000,000 meters, because the metric system is base ten, but computers are fundamentally base 2. Oh, what a tangled web we weave…
Kelly, thanks for the comments. I noticed that NIST lists a different set of prefixes to deal with the decimal versus binary problem. See http://physics.nist.gov/cuu/Units/binary.html
one gibibyte 1 GiB = 2^30 B = 1 073 741 824 B
one gigabyte 1 GB = 10^9 B = 1 000 000 000 B
However, I don’t think I’ve ever seen these in use.
Heck, its only an error of 73.7 MBytes…hardly worth counting 🙂
73, Bob K0NR
The error of 73.7 MB I think really is worth counting. With 500GB to 1TB disks being sold, the difference between 500GB and the 500GiB people expect starts to become significant.