Giga-

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Short description: Metric prefix


Giga (/ˈɡɪɡə/ or /ˈdʒɪɡə/) is a unit prefix in the metric system denoting a factor of a short-scale billion or long-scale milliard (109 or 1,000,000,000). It has the symbol G.

Giga is derived from the Greek word γίγας (gígas), meaning "giant". The Oxford English Dictionary reports the earliest written use of giga in this sense to be in the Reports of the IUPAC 14th Conférence Internationale de Chimie in 1947: "The following prefixes to abbreviations for the names of units should be used: G giga 109×."[1]

When referring to information units in computing, such as gigabyte, giga may sometimes mean 1073741824 (230); this causes ambiguity. Standards organizations discourage this and use giga- to refer to 109 in this context too.[2][3][non-primary source needed] Gigabit is only rarely used with the binary interpretation of the prefix. The binary prefix gibi has been adopted for 230, while reserving giga exclusively for the metric definition.

Pronunciation

In English, the prefix giga can be pronounced /ˈɡɪɡə/ (a hard g as in giggle), or /ˈdʒɪɡə/ (a soft g as in gigantic, which shares giga's Ancient Greek root).[4]

A prominent example of this latter pronunciation is found in the pronunciation of gigawatts in the 1985 film 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 (evidently "Anto-logie") by the German humorous poet Christian Morgenstern that appeared in the third (1908) edition of his Galgenlieder (Gallows Songs).[5][6] This suggests that a hard German [ɡ] was originally intended as the pronunciation. Self was unable to ascertain when the /dʒ/ (soft g) pronunciation came into occasional use, but claimed that as of 1995 it had returned to /ɡ/ (hard g).[7][8]

In 1998, a poll by the phonetician John C. Wells found that 84% of Britons preferred the pronunciation of gigabyte starting with /ɡɪ/ (as in gig), 9% with /dʒɪ/ (as in jig), 6% with /ɡaɪ/ (guy), and 1% with /dʒaɪ/ (as in giant).[9]

Common usage

  • gigahertz—clock rate of a CPU, for instance, 3 GHz = 3000000000Hz
  • gigabit—bandwidth of a network link, for instance, 1 Gbit/s = 1000000000bit/s.
  • gigabyte—for instance, for hard disk capacity, 120 GB = 120000000000bytes;
  • gigayear or gigaannum—one billion (109) years, sometimes abbreviated Gyr, but the preferred usage is Ga or, for years ago, GA.[citation needed]
Prefix Base 10 Decimal English word Adoption[nb 1]
Name Symbol Short scale Long scale
yotta Y  1024 1000000000000000000000000  septillion  quadrillion 1991
zetta Z  1021 1000000000000000000000  sextillion  trilliard 1991
exa E  1018 1000000000000000000  quintillion  trillion 1975
peta P  1015 1000000000000000  quadrillion  billiard 1975
tera T  1012 1000000000000  trillion  billion 1960
giga G  109 1000000000  billion  milliard 1960
mega M  106 1000000  million 1873
kilo k  103 1000  thousand 1795
hecto h  102 100  hundred 1795
deca da  101 10  ten 1795
 100 1  one –
deci d  10−1 0.1  tenth 1795
centi c  10−2 0.01  hundredth 1795
milli m  10−3 0.001  thousandth 1795
micro μ  10−6 0.000001  millionth 1873
nano n  10−9 0.000000001  billionth  milliardth 1960
pico p  10−12 0.000000000001  trillionth  billionth 1960
femto f  10−15 0.000000000000001  quadrillionth  billiardth 1964
atto a  10−18 0.000000000000000001  quintillionth  trillionth 1964
zepto z  10−21 0.000000000000000000001  sextillionth  trilliardth 1991
yocto y  10−24  0.000000000000000000000001  septillionth  quadrillionth 1991
  1. ↑ Prefixes adopted before 1960 already existed before SI. 1873 was the introduction of the CGS system.

Binary prefix

See also

References

  1. ↑ "giga-, comb. form". October 2011. http://www.oed.com/view/Entry/78201. 
  2. ↑ "§3.1 SI prefixes" (in fr, en). The International System of Units (SI) (8th ed.). Paris: STEDI Media. 2006. pp. 127. ISBN 92-822-2213-6. http://www1.bipm.org/utils/common/pdf/si_brochure_8.pdf. Retrieved 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." 
  3. ↑ NIST Guide for the Use of the International System of Units (Appendix D. ref 5)
  4. ↑ "SI prefixes and their etymologies". https://usma.org/si-prefixes-and-their-etymologies. 
  5. ↑ (in de) Galgenlieder nebst dem 'Gingganz'. Illustrated by Karl Walser (22 ed.). Berlin, Germany: Bruno Cassirer. 1917. p. 52. "[First four lines:] Im Anfang lebte, wie bekannt, / als größter Säuger der Gig-ant. / Wobei gig eine Zahl ist, die / es nicht mehr gibt, - so groß war sie!"  [These lines are the only appearance of gig in the book. Gigant is German for "giant"; cf. "gigantic".]
  6. ↑ Gallows Songs: Christian Morgenstern's "Galgenlieder", Bilingual Edition: A Selection. University of California Press. 1963. pp. 24–25. ISBN 9780520008847. https://books.google.com/books?id=bPLXx5DYnT8C&pg=PA24. Retrieved 20 February 2016. "[Translation:] Of yore, on earth was dominant / the biggest mammal: the Gig-ant. / ("Gig" is a numeral so vast, / it's been extinct for ages past.)" 
  7. ↑ "Technically speaking". Spectrum (IEEE): 18. October 1994. 
  8. ↑ "Technically speaking". Spectrum (IEEE): 16. April 1995. 
  9. ↑ Wells, J. C. (1998). LPD pronunciation preference poll 1998.

External links

he:תחיליות במערכת היחידות הבינלאומית#גיגה



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