## Numbers

We will be using US format numbers throughout this document, as they
are what is generally used in the external documentation that this is
based upon. Commas represent thousands, millions, billions,
etc. Periods represent decimal numbers.

One Thousand (10^{3} or 10^3 or ten to the power of three) = 1,000

One Million (10^{6} or 10^6) = 1,000,000

One Tenth (1/10) = 0.1

One Quarter (1/4) = 0.25

## File Size

In computer terminology the basic unit of data is the bit. It is
either a 1 or a 0, and enough bits put together can represent any
data in the computer.

Everything is represented in terms of bits, which are
either 0 or 1, so if you have two bits there are 2^{2} (2^2 or two to the power
of
two) possible combinations: 00, 01, 10, 11. Three bits is 2^{3}
with possible combinations: 000, 001, 010, 011, 100, 101, 110,
111. Four bits has 2^{4} possible combinations, Eight bits has 2^{8}
and on up. This is called "binary notation" where there are only
two digits (0 and 1) as opposed to decimal noation which has ten digits
(0, 1, 2, 3, 4, 5, 6, 7, 8, 9).

A byte is a collection of bits, 8 bits to be precise (00000000,
00000001, 01110101, and 11111111 are some of the 256 possible
combinations). This is the
standard unit that will be used to say how much space a piece of data
takes up. (e.g. that text file is 300 Bytes large, that picture is 2
million bytes, etc)

Because computers can use HUGE numbers of bytes for different
things, we have a set of prefixes that we use to talk about groups of
bytes:

1 Byte (B)

100 Bytes (B)

1,000 Bytes = 1 Kilo Byte (KB)

1,000,000 Bytes = 1,000 KB = 1 Mega Byte (MB)

1,000,000,000 Bytes = 1,000 MB = 1 Giga Byte (GB)

1,000,000,000,000 Bytes = 1,000 GB = 1 Tera Byte (TB)

1,000,000,000,000,000 Bytes = 1,000 TB = 1 Peta Byte (PB)

It is important to note, when you are referring to the computers
Hard Disk (HD), Random Access Memory (RAM), or Network Connection, all
the numbers are stored and displayed by the computer are in binary
format, not decimal format. This includes the size of
files. It just so
happens a KB, that is 2^{10}, is approximately equal to 1,000 in decimal
notation (actually it is
1024) and a MB, 2^{20} is
approximately equal to 1,000,000 (actually 1,048,576). Although for
our human heads, its generally easy to think in the simple powers of
ten, just remember that these are not exact!

For more info see: http://en.wikipedia.org/wiki/File_size
and http://en.wikipedia.org/wiki/Byte