The decimal system that is now universally accepted is based on the fact that each digit to the *left* of the first digit of a decimal number is worth ten times that of the digit immediately to its right. In other words, the digit on the left-hand side of the decimal place, represented by a full stop, is worth one; the digit immediately to its left is worth ten times __more__; and the digit immediately to its right is worth ten times __less__. The same holds true for every digit in any number, from 10 to one googol. Indeed, the amount of digits that can be used is infinite, since, as has already been proven, 1 can always be added to any number, making for some very large numbers - bigger even than a googolplex.

How, then, to represent these huge numbers using shorthand? Fear not, there is a way... Two ways, in fact. The boring way is to use words like hundred, thousand, million, billion, trillion, quadrillion and so forth. Easy to remember, no challenge there. I say 'bah' at them.

### Bah!

Enough of that. The second, somewhat cooler way is to use metric prefixes in front of words. Sure, it makes them sound somewhat irregular, but when the day comes when metric will revolutionise the world, you will be hailed as someone who saw it coming. Mind you, some words have already crept into the language of countries that do not use metric - simple metric terms such as centimetre, and terms associated with computing: bytes, kilobytes, et cetera.

## A list of some more common and less common metric prefixes

Power of 10 Name Numerical Equivalent
24 Yotta 1,000,000,000,000,000,000,000,000 (one heptillion)
21 Zetta 1,000,000,000,000,000,000,000 (one sextillion)
18 Exa 1,000,000,000,000,000,000 (one quinrillion)
15 Peta 1,000,000,000,000,000 (one quadrillion)
12 Tera 1,000,000,000,000 (one trillion)
9 Giga 1,000,000,000 (one billion)
6 Mega 1,000,000 (one million)
4 Myria 10,000 (ten thousand) (not in very common use*)
3 Kilo 1,000 (one thousand)
2 Hecto 100 (one hundred) (not in very common use*)
1 Deca 10 (ten) (not in very common use*)
0 ----- 1 (one)
-1 Deci 0.1 (one tenth) (not in very common use*)
-2 Centi 0.01 (one hundredth) (not in very common use*)
-3 Milli 0.001 (one thousandth)
-6 Micro 0.000001 (one millionth)
-9 Nano 0.000000001 (one billionth)
-12 Pico 0.000000000001 (one trillionth)
-15 Femto 0.000000000000001 (one quadrillionth)
-18 Atto 0.000000000000000001 (one quinrillionth)
-21 Zepto 0.000000000000000000001 (one sextillionth)
-24 Yocto 0.000000000000000000000001 (one heptillionth)

Please to not try to imagine some of the larger or smaller numbers. It shall result in a tera-headache.

These prefixes generally go in front of other metric terms, such as metre and gram to make words such as milligram, centimetre, kilometre. Of course, they can also go in front of other SI units such as joule (commonly kilojoule) and electron volt (commonly mega electron volt). They also have their shorthand symbols, as metre, gram, joule and electron volt have m, g, J and eV respectively. This is how we get not only km, MeV and mA, but also the technological abbreviations kB, MB, GB and above.

Yotta Y
Zetta Z
Exa E
Peta P
Tera T
Giga G
Mega M
Myria my**
Kilo k
Hecto h
Deca D**
Deci d
Centi c
Milli m
Micro μ
Nano n
Pico p
Femto f
Atto a
Zepto z
Yocto y

On a final note, the powers of 10 mentioned above are **not** used for computing in terms of measuring memory. They use powers of 2 instead, skipping a few every so often. For quick reference:

- One byte = one byte
- One kilobyte (kB***) = 1,024 bytes
- One megabyte (MB) = 1,024 kB = 1,048,576 bytes
- One gigabyte (GB) = 1,024 MB = 1,073,741,824 bytes
- One yottabyte (YB) = 1,208,925,819,614,629,174,706,176 bytes. This is, of course, obscenely and unnecessarily large - as large, obscene and unnecessary as a googolplex.

So, how many of E2's nodes - assuming they are an average of 10KB on the Windoze program Notepad - would fit on a 3 exabyte disk? You do the math.

*Where I have marked "Not in very common use", this says exactly that. Technically, ten metres equals one decametre, but for some strange reason, metric-speakers prefer to use "ten metres". However, "centimetre" is a common term. Also note ambiguity in worded terms of billion(th) and above/below. Varying usages of the SI 'billion' have been 'thousand million', and the original SI 'billion', which was originally defined as a 'million million'. The terms laid out above are becoming more and more universal.

**Another technicality: "Deca" is sometimes spelled as "Deka" and has the symbol "da" to prevent ambiguity. Generally, though, if a prefix is capitalised, it is a number larger than one, with the exception of "hecto" (h), "kilo" (k) and "deka" (da). "Myria", however, must be spelt (my) since there are already capital and lowercase m values there.

***...although this abbreviation has become more commonly used as KiB. See binary prefixes for more information.

Main resource: http://lamar.colostate.edu/~hillger/si-prefixes.html (but the tables were my own interpretation)

Onward and... more complicated!