Most

of us are familiar with the standard International System (SI) prefixes,

such as kilo, mega, milli, and so forth. The prefixes are very handy

and commonly used by engineers and scientists, who speak in terms

of kilometer, megaton, milligrams, kilovolts, nanometers, and picoseconds.

The sexier ones spill over into common language (megastar, megadose)

and product names (e.g., the VTech GigaPhone). As we push the frontiers

of technology and science, formerly exotic prefixes come into vogue.

For example, as disk drive and other storage space has increased

in capacity, the terms megabyte, gigabyte, and even terabyte, have

become increasingly useful and widespread.

If

you are anything like me, you might be curious what other prefixes

are in store for us. It turns out that there are other, more exotic

and extreme SI prefixes on the shelf, ready to be used. Most are

not yet commonly known, but are fascinating to ponder. They are

kind of cool. These extreme prefixes include the division prefixes

atto, zepto, and yocto (I know, I know, sounds like the Marx brothers);

and the multiplier prefixes exa, zetta, and yotta (sounds like the

latest Shirley MacLaine book). The most extreme, and coolest, ones

are the unofficial vendeko (10-33) and vendeka (1033).

Wicked. We now have multi-gigabyte (GB) disk drives; soon, surely,

we will speak of disk drive, or collective network, capacity, in

terms of terabytes, petabytes, even exabytes. I can’t wait

for vendekabytes.

The

current and proposed SI prefixes are found in the table below (drawn

from various sources, including link1,

link2,

link3,

link4):

Prefixes

of the International System (SI)

Divisions

Multiples

factor

prefix

symbol

factor

prefix

symbol

10-1

deci

d

101

deca

da

10-2

centi

c

102

hecto

h

10-3

milli

m

103

kilo

k

10-6

micro

µ

106

mega

M

10-9

nano

n

109

giga

G

10-12

pico

p

1012

tera

T

10-15

femto

f

1015

peta

P

10-18

atto

a

1018

exa

E

10-21

zepto

z

1021

zetta

Z

10-24

yocto

y

1024

yotta

Y

(unofficial)

10-27

xenno

x

1027

xenna

X

10-30

???

w

1030

???

W

10-33

vendeko

v

1033

vendeka

V

10-36

???

u

1036

???

U

As

can be seen, the smaller and lesser-known division prefixes tend

to end in “o”, while the larger and less-known multiplication prefixes

tend to end in “a”. Also, the symbols for the larger multipliers

are capital letters, while those for the division prefixes are small

Roman or greek letters. This

article (p. 3, footnotes * and **) provides an explanation of

the origin of some of the SI and other prefixes. This

article gives some examples of possible uses of some of extreme

prefixes.

While

Googling

for this article, I discovered that the International Electrotechnical

Commission (IEC) has approved a set of prefixes for binary multiples,

which I had never heard of. These are for use in the computer field,

for data processing and data transmission applications. Computer

engineers and programmers typically express numbers in powers of

two because of the use of two-valued bits for computer memory and

logic (each bit can represent a 0 or a 1). A ten-bit memory register,

for example, can store 210 = 1024 different binary numbers

(bit combinations).

As

explained here

(link2),

computer professionals noticed that 210 (1024) was nearly

equal to 1000 and started using the SI prefix “kilo”

to mean 1024, and other SI prefixes to approximate other binary

quantities. This has led to confusion. For example, under the SI

system, megabyte means one million (1,000,000) bytes. Most computer

manufacturers, however, use the term megabyte to mean 220

= 1,048,576 bytes. Similarly, a kilobit usually refers to 210

= 1024 bits instead of 1000 bits.

The

new binary prefixes defined by the IEC are designed to eliminate

this confusion. For example, kibi, instead of kilo, is to be used

for 210 = 1024; and mebi, instead of mega, for 220

= 1,048,576. Thus, megabyte (MB) means 1,000,000 bytes, while mebibyte

(MiB) means 1,048,576 bytes. A tebibyte (TiB) denotes 240

= 1,099,511,627,776 bytes, while a terabyte indicates 1012

= 1,000,000,000,000 (a trillion) bytes. I would tell you what a

gibibyte (GiB) is, but I can’t stop giggling at the name. It remains

to be seen whether these binary prefixes will catch on. While they

are also cool, if a little funny, and seemingly useful, I had never

even heard of them until writing this article.

And

speaking of confusion, it’s also interesting to note that what Americans

call million (106, mega), billion (109, giga),

and trillion (1012, tera), the Brits

refer to as million, milliard, and billion (at least officially,

if not in practice).

Incidentally,

speaking of Googling, the name Google appears to be a variation

of “googol,”

itself an extremely large number (suggesting Google can find information

from a huge number of websites, I suppose). A googol

is 10100, i.e. a 1 followed by 100 zeros. (In official

SI prefix terms, a googol is approximately a yotta squared, squared.)

Even larger is the googolplex, which is equal to 10 to the power

of a googol (10googol); this number is about the same

size as the number of possible games of chess. Even larger

numbers (link2,

link3)

have been defined, such as Skewes’ number, Graham’s number, and

the Moser,

which I won’t even try to describe.

May

I be excused now, please? My brain — which contains

approximately 100

giga-neurons — is full.

January

15, 2001

Stephan

Kinsella [send him mail]

practices patent law in Houston. His website is www.stephankinsella.com.