Megabyte,Gigabyte,Terabyte-What are they?

Megabytes, Gigabytes, Terabytes...

These terms are usually used in
the world of computing to describe
disk space, or data storage space,
and system memory. For instance,
just a few years ago we were
describing hard drive space using
the term Megabytes. Today,
Gigabytes is the most common
term being used to describe the
size of a hard drive. In the not so
distant future, Terabyte will be a
common term. But what are they?
This is where it gets quite
confusing because there are at
least three accepted definitions of

each term.

According to the IBM Dictionary of
computing, when used to describe
disk storage capacity, a megabyte
is 1,000,000 bytes in decimal
notation. But when the term
megabyte is used for real and
virtual storage, and channel
volume, 2 to the 20th power or
1,048,576 bytes is the appropriate
notation. According to the
Microsoft Press Computer
Dictionary, a megabyte means
either 1,000,000 bytes or 1,048,576
bytes. According to Eric S.
Raymond in The New Hacker's
Dictionary, a megabyte is always
1,048,576 bytes on the argument
that bytes should naturally be
computed in powers of two. So
which definition do most people
conform to?
When referring to a megabyte for
disk storage, the hard drive
manufacturers use the standard
that a megabyte is 1,000,000
bytes. This means that when you
buy an 80 Gigabyte Hard drive you
will get a total of 80,000,000,000
bytes of available storage. This is
where it gets confusing because
Windows uses the 1,048,576 byte
rule so when you look at the
Windows drive properties an 80
Gigabyte drive will report a
capacity of 74.56 Gigabytes and a
250 Gigabyte drive will only yield
232 Gigabytes of available storage
space. Anybody confused yet? With
three accepted definitions, there
will always be some confusion so I
will try to simplify the definitions a

little.
The 1000 can be replaced with
1024 and still be correct using the
other acceptable standards. Both
of these standards are correct
depending on what type of storage
you are referring.
Processor or Virtual Storage Disk Storage
· 1 Bit = Binary Digit
· 8 Bits = 1 Byte
· 1024 Bytes = 1 Kilobyte
· 1024 Kilobytes = 1 Megabyte
· 1024 Megabytes = 1 Gigabyte
· 1024 Gigabytes = 1 Terabyte
· 1024 Terabytes = 1 Petabyte
· 1024 Petabytes = 1 Exabyte
· 1024 Exabytes = 1 Zettabyte
· 1024 Zettabytes = 1 Yottabyte
· 1024 Yottabytes = 1 Brontobyte
· 1024 Brontobytes = 1 Geopbyte

This is based on the IBM
Dictionary of computing method to
describe disk storage - the
simplest.