There are a series of Greek, Latin, Danish and
Spanish prefixes used for specifying large numbers. The prefixes have different meaning when talking about RAM than
when talking about disk space.
Two Kinds of Gigabytes
Hard disk capacities are measured in decimal gigabytes, in billions of bytes, namely 109 = 1000x1000x1000 = 1,000,000,000
bytes.
106 means 1 followed by 6 zeros, i.e. 1,000,000.
10-6 means 1 in the 6th decimal place, i.e. .000001.
However, Windows measures hard disk capacity using the binary RAM definition.
For measuring RAM, a gigabyte is a little over a billion bytes, or more precisely, 1024 megabytes = 230 bytes
= 1024x1024x1024 bytes = 1,073,741,824 bytes. A byte is approximately one character of information.
Two Kinds of Megabytes
A megabyte on disk is precisely a million, namely 109 =1000x1000x1000 = 1,000,000 bytes. For RAM it is a
little over a million bytes, namely 220 = 1024 × 1024 = 1,048,576
bytes.
SI Prefixes
| SI prefixes |
|---|
| Factor |
Name |
Symbol |
|---|
| 1024 |
yotta |
Y |
| 1021 |
zetta |
Z |
| 1018 |
exa |
E |
| 1015 |
peta |
P |
| 1012 |
tera |
T |
| 109 |
giga |
G |
| 106 |
mega |
M |
| 103 |
kilo |
k |
| 102 |
hecto |
h |
| 101 |
deka |
da |
|
|
| Factor |
Name |
Symbol |
|---|
| 10-1 |
deci |
d |
| 10-2 |
centi |
c |
| 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 |
|
by Roedy Green ©1997-2009 Canadian Mind Products
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