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Question ? What is a Kibit ? Or why does my OS show me less space than the manufacturer of the Disk ?   [
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 Of course everyone knows that 1 Kilobyte equals to 1.024 bytes. Well - this is wrong !

A kibibit (a contraction of kilo binary digit) is a unit of information or computer storage, abbreviated Kibit, or sometimes Kib. (Note that the abbreviation is capitalized, while kbit is not.)

1 kibibit = 210 bits = 1,024 bits
1 kibibit = 27 bytes = 128 bytes

The kibibit is closely related to the kilobit, which can either be a synonym for kibibit, or refer to 103 bits = 1,000 bits, depending on context.
The National Institute of Science and Technologies notes that

it is important to recognize that the new prefixes for binary multiples are not part of the International System of Units (SI), the modern metric system.

It should also be noted that they are not in general use among professional software and electrical engineers, who generally use decimal prefixes when referring to binary quantities.

In short - we need to make the difference between the Metric Prefix system - this one handles the comon Kilo naming convention, and the Binary prefix systems - which is the real definition for binary formats as found on harddisks.

The following table shows you the comon namings and sizes

Metric (Symbol)Std. SI Binary (Symbol)Value
kilobit (kb) 103 bit kibibit (Kibit) 210 bit
megabit (Mb) 106 bit mebibit (Mibit) 220 bit
gigabit (Gb) 109 bit gibibit (Gibit) 230 bit
terabit (Tb) 1012 bit tebibit (Tibit) 240 bit
petabit (Pb) 1015 bit pebibit (Pibit) 250 bit
exabit (Eb) 1018 bit exbibit (Eibit) 260 bit
zettabit (Zb) 1021 bit zebibit (Zibit) 270 bit
yottabit (Yb) 1024 bit yobibit (Yibit) 280 bit

BTW - same also applies to the Byte fraction

Metric (Symbol)Std. SI Binary (Symbol)Value
kilobyte (kb) 103 byte kibibyte (Kibyte) 210 byte
megabyte (Mb) 106 byte mebibyte (Mibyte) 220 byte
gigabyte (Gb) 109 byte gibibyte (Gibyte) 230 byte
terabyte (Tb) 1012 byte tebibyte (Tibyte) 240 byte
petabyte (Pb) 1015 byte pebibyte (Pibyte) 250 byte
exabyte (Eb) 1018 byte exbibyte (Eibyte) 260 byte
zettabyte (Zb) 1021 byte zebibyte (Zibyte) 270 byte
yottabyte (Yb) 1024 byte yobibyte (Yibyte) 280 byte

By looking at these 2 previous tables - you might ask yourself - but what is the difference. Well - really only if you handle Bytes or Bits. This is the main differenciator.
So - what does this mean for us ? Check for yourself with some examples:

MediaMetric SystemBinary System
100GB Harddisk100 Gigabyte93,1 Gibibyte
DVD Rom 54,7 Gigabyte4,37 Gibibyte
CD Rom 700 Megabyte700 Mebibyte
1 GB Ram1,074 Gigabyte1 Gibibyte
USB Stick 8GB8 Gigabyte7,45 Gibibyte
DSL 2000 2,0 Megabit1,91 Mebibit
Memory Interface 256Bit 256 Bit256 Bit
Memory Interface 1.024Bit 1,024 Kilobit1 Kibibit

Entered by smurphy on Tuesday, 09 October 2007 @ 14:21:38  
Nothing Specific - META Questions, # Hits: 54950
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