Prefixes for bit and byte
Decimal Value SI 10001 k kilo- 10002 M mega- 10003 G giga- 10004 T tera- 10005 P peta- 10006 E exa- 10007 Z zetta- 10008 Y yotta-	Binary Value FOLDOC IEC 10241 K kilo- Ki kibi- 10242 M mega- Mi mebi- 10243 G giga- Gi gibi- 10244 T tera- Ti tebi- 10245 P peta- Pi pebi- 10246 E exa- Ei exbi- 10247 Z zetta- Zi zebi- 10248 Y yotta- Yi yobi-

A yottabyte (derived from the SI prefix yotta-) is a unit of information or computer storage equal to one septillion (one long scale quadrillion or 10²⁴) bytes. It is commonly abbreviated YB. As of 2008, no computer has yet achieved one yottabyte of storage. In fact, the combined space of all the computer hard drives in the world does not amount to even one zettabyte. According to one study, all the world's computers stored approximately 160 exabytes in 2006, with nearly 1 zettabyte projected by 2010.^[1] When used with byte multiples, the SI prefix may indicate a power of either 1,000 or 1,024, so the exact number may be either:

• 1 septillion, or 1,000,000,000,000,000,000,000,000 bytes — 1000⁸, or 10²⁴, or
• 1,208,925,819,614,629,174,706,176 bytes — 1024⁸, or 2⁸⁰.^{citation needed}

The term "yobibyte", using a binary prefix, has been proposed as an unambiguous reference to the latter value.

References

1. ^ Expanding Digital Universe IDC White Paper (pdf)

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