dict.org

The DICT Development Group


Search for:
Search type:
Database:

Database copyright information
Server information


1 definition found
 for SI prefix
From The Free On-line Dictionary of Computing (30 December 2018) :

  SI prefix
  
      The standard metric prefixes used in the
     Système International d'Unités (SI) conventions for
     scientific measurement.
  
     Here are the SI magnifying prefixes, along with the
     corresponding binary interpretations in common use:
  
      prefix abr decimal  binary
  
      yocto-     1000^-8
      zepto-     1000^-7
      atto-      1000^-6
      femto-  f  1000^-5
      pico-   p  1000^-4
      nano-   n  1000^-3
      micro-  *  1000^-2          * Abbreviation: Greek mu
      milli-  m  1000^-1
  
      kilo- 	 k  1000^1  1024^1 = 2^10 = 1,024
      mega- 	 M  1000^2  1024^2 = 2^20 = 1,048,576
      giga- 	 G  1000^3  1024^3 = 2^30 = 1,073,741,824
      tera- 	 T  1000^4  1024^4 = 2^40 = 1,099,511,627,776
      peta- 	    1000^5  1024^5 = 2^50 = 1,125,899,906,842,624
      exa-  	    1000^6  1024^6 = 2^60 = 1,152,921,504,606,846,976
      zetta-     1000^7  1024^7 = 2^70 = 1,180,591,620,717,411,303,424
      yotta-     1000^8  1024^8 = 2^80 = 1,208,925,819,614,629,174,706,176
  
     "Femto" and "atto" derive not from Greek but from Danish.
  
     The abbreviated forms of these prefixes are common in
     electronics and physics.
  
     When used with bytes of storage, these prefixes usually denote
     multiplication by powers of 1024 = 2^10 (K, M, G and T are
     common in computing).  Thus "MB" stands for megabytes (2^20
     bytes).  This common practice goes against the edicts of the
     BIPM who deprecate the use of these prefixes for powers of
     two.  The formal SI prefix for 1000 is lower case "k"; some,
     including this dictionary, use this strictly, reserving upper
     case "K" for multiplication by 1024 (KB is thus "kilobytes").
  
     Also, in data transfer rates the prefixes stand for powers of
     ten so, for example, 28.8 kb/s means 28,800 bits per second.
  
     The unit is often dropped so one may talk of "a 40K salary"
     (40000 dollars) or "2 meg of disk space" (2*2^20 bytes).
  
     The accepted pronunciation of the initial G of "giga-" is
     hard, /gi'ga/.
  
     Confusing 1000 and 1024 (or other powers of 2 and 10 close in
     magnitude) - for example, describing a memory in units of 500K
     or 524K instead of 512K - is a sure sign of the marketroid.
     For example, 3.5" microfloppies are often described as
     storing "1.44 MB".  In fact, this is completely specious.  The
     correct size is 1440 KB = 1440 * 1024 = 1474560 bytes.  Alas,
     this point is probably lost on the world forever.
  
     In 1993, hacker Morgan Burke proposed, to general approval on
     Usenet, the following additional prefixes: groucho (10^-30),
     harpo (10^-27), harpi (10^27), grouchi (10^30).  This would
     leave the prefixes zeppo-, gummo-, and chico- available for
     future expansion.  Sadly, there is little immediate prospect
     that Mr. Burke's eminently sensible proposal will be ratified.
  
     (2009-09-01)
  

Contact=webmaster@dict.org Specification=RFC 2229