Exabyte

Because of irregularities in definition and usage of the kilobyte, the exact number could be any one of the following:

1. 1,152,921,504,606,846,976 bytes - 1024 times 1024 times 1024 times 1024 times 1024 times 1024, or 2⁶⁰. This is 1024 times a petabyte. This is the definition used in computer science and computer programming
2. 1,000,000,000,000,000,000 bytes - or 10 ¹⁸.

A zettabyte is 1024 times an exabyte.

As of 2003 exabytes of data are almost never encountered in a practical context. For example the total amount of printed material in the world is estimated to be around a fifth of an exabyte. Exabytes may also appear to be encountered if a computer's file system is corrupt and displaying incorrect file sizes.

To clarify the meaning (1) above, the International Electrotechnical Commission (IEC), a standards body, in 1998 defined new prefixes by combining the International System of Units (SI) prefixes with the word "binary." Thus meaning (1) is called by the IEC a exbibyte (EiB), and meaning (2) is called by the IEC an exabyte. This naming convention has not, as of 2003, been widely adopted.

External Links:

• http://www.quinion.com/words/turnsofphrase/tp-kib1.htm
• http://www.nist.gov/public_affairs/techbeat/tb9903.htm

Exabyte is also the name used for a brand of digital tape cartridges from NCR Corporation. Of course no-one has yet made a cartridge capable of holding a true exabyte.