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A gigabyte (symbol GB) is a unit of measurement in computers of one thousand million bytes (the same as one billion bytes in the short scale usage). However, because computers work on the binary system, rather than a gigabyte being 103 megabytes (1000 MBs), a gigabyte is actually 210 megabytes (1024 MBs).
Because of differences in definition between the standard SI implementation of prefixes and the computer implementations, the exact number in common practice could be either of the following:
- 1,000,000,000 bytes or 109 bytes is the definition used by telecommunications engineers and some storage manufacturers. This is consistent with the SI prefix "giga-".
- 1,073,741,824 bytes, equal to 10243, or 230. This is the definition most often used in computer science, computer programming, and almost all computer operating systems. It has been suggested that this measure can be abbreviated as GiB (gibibyte) to avoid ambiguity, as defined in IEC 60027-2.
See integral data type.
Likewise, a terabyte is either equal to 1024 gigabytes or to 1000 gigabytes depending on the usages.
Thus, to convert metric gigabytes into binary gigabytes (for example a 100GB drive contains 93GiB when installed), follow this formula:
- <math>\frac{y \cdot 10^9}{2^{30}}<math>
where <math>y<math> is size of drive in metric gigabytes
Gigabytes in use
As of 2004, most consumer hard drives are measured in gigabyte-range capacities. Per-gigabyte costs are 0.50-0.80 USD.
In speech, gigabyte is often abbreviated to gig, as in "This is a ten-gig hard drive". The initial G in giga- is usually pronounced hard as in geek, not soft as in giant.
A gigabit, which should not be confused with gigabyte, is 1/8th of a gigabyte and is mainly used to describe bandwidth, e.g. 2 gigabit/s is the speed of current Fibre Channel interfaces.
Unicode has a symbol for Gigabyte: (㎇).
Distinction between 1000 and 1024 megabytes
Main article: Binary prefix
To clarify the distinction between decimal and binary prefixes, the International Electrotechnical Commission (IEC), a standards body, in 1997 proposed short unions of the International System of Units (SI) prefixes with the word "binary". Thus meaning (2) would be called a gibibyte (GiB). This naming convention has not yet been widely accepted.
Origin of prefix
The prefix "giga" comes from the Greek word γίγας (gigas) meaning "giant", and was chosen because 109 can be described as a "gigantic" number.
See also
External links
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