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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:
| Media | Metric System | Binary System |
|---|
| 100GB Harddisk | 100 Gigabyte | 93,1 Gibibyte |
| DVD Rom 5 | 4,7 Gigabyte | 4,37 Gibibyte |
| CD Rom | 700 Megabyte | 700 Mebibyte |
| 1 GB Ram | 1,074 Gigabyte | 1 Gibibyte |
| USB Stick 8GB | 8 Gigabyte | 7,45 Gibibyte |
| DSL 2000 | 2,0 Megabit | 1,91 Mebibit |
| Memory Interface 256Bit | 256 Bit | 256 Bit |
| Memory Interface 1.024Bit | 1,024 Kilobit | 1 Kibibit |
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Entered by smurphy on Tuesday, 09 October 2007 @ 14:21:38
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