Off topic: nasobky kB

[znouza]

dovolim si replesk:

Once upon a time, computer professionals noticed that 210 was very nearly
equal to 1000 and started using the SI prefix "kilo" to mean 1024. That
worked well enough for a decade or two because everybody who talked
kilobytes knew that the term implied 1024 bytes. But, almost overnight a
much more numerous "everybody" bought computers, and the trade computer
professionals needed to talk to physicists and engineers and even to
ordinary people, most of whom know that a kilometer is 1000 meters and a
kilogram is 1000 grams. 

Then data storage for gigabytes, and even terabytes, became practical, and
the storage devices were not constructed on binary trees, which meant
that, for many practical purposes, binary arithmetic was less convenient
than decimal arithmetic. The result is that today "everybody" does not
"know" what a megabyte is. When discussing computer memory, most
manufacturers use megabyte to mean 220 = 1 048 576 bytes, but the
manufacturers of computer storage devices usually use the term to mean 1
000 000 bytes. Some designers of local area networks have used megabit per
second to mean 1 048 576 bit/s, but all telecommunications engineers use
it to mean 106 bit/s. And if two definitions of the megabyte are not
enough, a third megabyte of 1 024 000 bytes is the megabyte used to format
the familiar 90  mm (3  1/2  inch), "1.44 MB" diskette. The confusion is
real, as is the potential for incompatibility in standards and in
implemented systems

prefix symbol value expanded value  
kibi Ki 2^10                             1 024 
mebi Mi 2^20                         1 048 576 
gibi Gi 2^30                     1 073 741 824 
tebi Ti 2^40                 1 099 511 627 776 
pebi Pi 2^50             1 125 899 906 842 624 
exbi Ei 2^60         1 152 921 504 606 846 976 
zebi Zi 2^70     1 180 591 620 717 411 303 424 
yobi Yi 2^80 1 208 925 819 614 629 174 706 176 
 
Examples and comparisons with SI prefixes 
one kibibit  1 Kibit = 2^10 bit = 1024 bit 
one kilobit  1 kbit = 10^3 bit = 1000 bit 
one mebibyte  1 MiB = 2^20 B = 1 048 576 B 
one megabyte  1 MB = 10^6 B = 1 000 000 B 
one gibibyte  1 GiB = 2^30 B = 1 073 741 824 B 
one gigabyte  1 GB = 10^9 B = 1 000 000 000 B 
 
jeste se muzete mrknout na:
http://eies.njit.edu/~kevin/powers/powers.html

http://www.zdwebopedia.com hlasi:
kilobit:
  1,024 bits for technical purposes, such as data storage. 1,000 for
general purposes. Data transfer rates are measured in kilobits per second,
abbreviated as Kbps, and count a kilo as 1,000 bits. 

megabit:
1) When used to describe data storage, 1,024 kilobits. 
(2) When used to described data transfer rates, it refers to one million
bits. Networks are often measured in megabits per second, abbreviated as
Mbps. 


zajimave, ze;))


On 7 Jun 2000, David Rohleder wrote:

> pajasoft na fonet.cz (Ing. Pavel PaJaSoft Janousek) writes:
> 
> > > Otazka znie ako pocitat nasobky ?
> > > 1 MB = 1024 kB
> > > 1 GB = 1024 MB
> > > 1 TB = 1024 GB
> > > alebo
> > > 1 MB = 1000 kB atd. ?
> > > 
> > > vie niekto 100 % odpoved ?
> > 
> > 	Jedna vec je komerni 'marketing' - tusim, ze prvni kdo prisel s
> > blbosti, ze 1MB = 1000kB byly vyrobci disku...
> > 
> > 1kB = 2^10B
> > 1MB = 2^20B
> > 1GB = 2^30B
> > .
> > .
> > .
> > 
> > 	a nikdy jinak... vse ostatni jsou kecy.
> 
> 
> :-) To je nesmysl.
> 
> Zkratky K, M, ... jsou standardizovane v norme SI jako nasobky
> 1000. Proto 
> 
> 1K = 1000
> 1M = 1 000 000
> 
> atd. 
> 
> proste pouziti techto jednotek na KB, Kb je chyba, bohuzel zazita.
> 
> Proc si myslite, ze KB je 1024 (nejake rozumne vysvetleni)?