Giga-
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Giga (symbol: G) is a prefix in the SI system of units denoting 109, or 1,000,000,000. The Oxford English Dictionary reports the earliest written use of giga- in this sense to be in the Reports of the IUPAC 14th Conference in 1947: "The following prefixes to abbreviations for the names of units should be used: G giga 109×". Giga comes from the Greek γίγας, meaning 'giant'.
When referring to computing information units, such as gigabit or gigabyte, giga can sometimes mean 1,073,741,824 (230), though such use has been discouraged by various standards organizations.[1][2]. The binary prefix gibi has been suggested for 230, while reserving giga exclusively for 109. See binary prefix.
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[edit] Pronunciation
In English the initial g of giga is often pronounced /ɡ/ (a hard g as in giggle), but may also be pronounced /dʒ/ (a soft g as in its Greek root's meaning, giant).[3]
This latter pronunciation was formalized within the United States in the 1960s and 1980s with the issue by the US National Bureau of Standards of pronunciation guides for the metric prefixes.[4] A prominent example is found in the pronunciation of gigawatts in the 1985 movie Back to the Future.
According to the American writer Kevin Self, a German committee member of the International Electrotechnical Commission proposed giga as a prefix for 109 in the 1920s, drawing on a verse by the humorous poet Christian Morgenstern that appeared in the third (1908) edition of Galgenlieder (Gallows Songs). This suggests that a hard German [ɡ] was originally intended as the pronunciation. Self was unable to ascertain at what point the alternative pronunciation came into occasional use, but as of 1995 it had died out.[5]
[edit] Common usage
- gigabyte—for instance, in hard disk capacity, 120 GB = 120,000,000,000 bytes; in file sizes, 1 GB = 1,073,741,824 bytes (also termed a gibibyte to reduce ambiguity)
- gigahertz—clock rate of a CPU, for instance, 3 GHz = 3,000,000,000 Hz
- gigabit—bandwidth of a network, for instance, 1 Gbit/s = 1,000,000,000 bit/s
- gigayear or gigaannum—one billion (109) years. (sometimes abbreviated Gyr, but the preferred usage is Ga)
| 1000m | 10n | Prefix | Symbol | Since[1] | Short scale | Long scale | Decimal |
|---|---|---|---|---|---|---|---|
| 10008 | 1024 | yotta | Y | 1991 | Septillion | Quadrillion | 1000000000000000000000000 |
| 10007 | 1021 | zetta | Z | 1991 | Sextillion | Trilliard | 1000000000000000000000 |
| 10006 | 1018 | exa | E | 1975 | Quintillion | Trillion | 1000000000000000000 |
| 10005 | 1015 | peta | P | 1975 | Quadrillion | Billiard | 1000000000000000 |
| 10004 | 1012 | tera | T | 1960 | Trillion | Billion | 1000000000000 |
| 10003 | 109 | giga | G | 1960 | Billion | Milliard | 1000000000 |
| 10002 | 106 | mega | M | 1960 | Million | 1 000 000 | |
| 10001 | 103 | kilo | k | 1795 | Thousand | 1000 | |
| 10002⁄3 | 102 | hecto | h | 1795 | Hundred | 100 | |
| 10001⁄3 | 101 | deca | da | 1795 | Ten | 10 | |
| 10000 | 100 | (none) | (none) | NA | One | 1 | |
| 1000−1⁄3 | 10−1 | deci | d | 1795 | Tenth | 0.1 | |
| 1000−2⁄3 | 10−2 | centi | c | 1795 | Hundredth | 0.01 | |
| 1000−1 | 10−3 | milli | m | 1795 | Thousandth | 0.001 | |
| 1000−2 | 10−6 | micro | µ | 1960[2] | Millionth | 0.000001 | |
| 1000−3 | 10−9 | nano | n | 1960 | Billionth | Milliardth | 0.000000001 |
| 1000−4 | 10−12 | pico | p | 1960 | Trillionth | Billionth | 0.000000000001 |
| 1000−5 | 10−15 | femto | f | 1964 | Quadrillionth | Billiardth | 0.000000000000001 |
| 1000−6 | 10−18 | atto | a | 1964 | Quintillionth | Trillionth | 0.000000000000000001 |
| 1000−7 | 10−21 | zepto | z | 1991 | Sextillionth | Trilliardth | 0.000000000000000000001 |
| 1000−8 | 10−24 | yocto | y | 1991 | Septillionth | Quadrillionth | 0.000000000000000000000001 |
[edit] See also
[edit] Notes and references
- ^ "§3.1 SI prefixes" (in French/English) (PDF). The International System of Units (SI) (8th edition ed.). Paris: STEDI Media. 2006. pp. 127. ISBN 92-822-2213-6. http://www1.bipm.org/utils/common/pdf/si_brochure_8.pdf. Retrieved on 2007-02-25. "[Side note:] These SI prefixes refer strictly to powers of 10. They should not be used to indicate powers of 2 (for example, one kilobit represents 1000 bits and not 1024 bits). The IEC has adopted prefixes for binary powers in the international standard IEC 60027-2: 2005, third edition, Letter symbols to be used in electrical technology — Part 2: Telecommunications and electronics. The names and symbols for the prefixes corresponding to 210, 220, 230, 240, 250, and 260 are, respectively: kibi, Ki; mebi, Mi; gibi, Gi; tebi, Ti; pebi, Pi; and exbi, Ei. Thus, for example, one kibibyte would be written: 1 KiB = 210 B = 1024 B, where B denotes a byte. Although these prefixes are not part of the SI, they should be used in the field of information technology to avoid the incorrect usage of the SI prefixes."
- ^ NIST Guide for the Use of the International System of Units (Appendix D. ref 5)
- ^ A Practical Guide to the International System of Units, U.S. Metric Association, Feb 2008
- ^ NBS Special Publication 304 & 304A, revised August 1981, "A Brief History of Measurement Systems"
- ^ Kevin Self, April 1995, "Technically speaking", Spectrum
