Terabyte

A terabyte is a unit of measurement in computers of approximately one million million (American trillion) bytes.

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

1. 1,099,511,627,776 bytes - 1024 times 1024 times 1024 times 1024, or 2⁴⁰. This is 1024 times a gigabyte. This is the definition used in computer science and computer programming
2. 1,000,000,000,000 bytes - or 10 ¹².

A typical video store contains about 8 terabytes of video. The books in the largest library in the world, the U.S. Library of Congress, contain about 20 terabytes of text.

A petabyte is 1024 times an terabyte.

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 tebibyte (TiB), and meaning (2) is called by the IEC a terabyte. This naming convention has not, as of 2003, been widely adopted.

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