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Information about Gigabyte

This article is about the unit of measurement. For the computer hardware manufacturer, see Gigabyte Technology. For the cartoon character, see ReBoot.
A gigabyte or Gbyte (derived from the SI prefix giga-) is a unit of information or computer storage meaning either 1000³ bytes or 1024³ bytes (1000³ = one billion). The usage of the word "gigabyte" is ambiguous, depending on the context. When referring to RAM sizes and file sizes, it traditionally has a binary definition, of 1024³ bytes. For every other use, it means exactly 1000³ bytes. In order to address this confusion, currently all relevant standards bodies promote the use of the term "gibibyte" for the binary definition.

It is commonly abbreviated GB (not to be confused with Gb, which is used for gigabits).

Definition

 •  • [ e]
Quantities of bytes
SI prefixes Historical use Binary prefixes
Symbol
(name)		 Value  Symbol  Value Symbol
(name)		 Value
kB (kilobyte)10001 = 103KB10241 = 210KiB (kibibyte)210
MB (megabyte)10002 = 106MB10242 = 220MiB (mebibyte)220
GB (gigabyte)10003 = 109GB10243 = 230GiB (gibibyte)230
TB (terabyte)10004 = 1012TB10244 = 240TiB (tebibyte)240
PB (petabyte)10005 = 1015PB10245 = 250PiB (pebibyte)250
EB (exabyte)10006 = 1018EB10246 = 260EiB (exbibyte)260
ZB (zettabyte)10007 = 1021ZB10247 = 270ZiB (zebibyte)270
YB (yottabyte)10008 = 1024YB10248 = 280YiB (yobibyte)280
Legacy Units
Unit Value
KB210 Bytes = 1024 Bytes
MB220 Bytes = 1024 KB
GB230 Bytes = 1024 MB
TB240 Bytes = 1024 GB


There are two slightly different definitions of gigabyte in general use:
  • 1,000,000,000 bytes or 109 bytes is the decimal definition used in telecommunications (such as network speeds) and most computer storage manufacturers (such as hard disks and flash drives). This usage is compatible with SI. Quotes from Seagate: "The storage industry standard is to display capacity in decimal",[1] and, "One gigabyte, or GB, equals one billion bytes when referring to hard drive capacity".[2] Similar quotes are found on the websites of other storage manufacturers.
  • 1,073,741,824 bytes, equal to 1024³, or 230 bytes. This is the definition commonly used for computer memory and file sizes. Since 1999, the IEC recommends that this unit should instead be called a gibibyte (abbreviated GiB). Microsoft uses this definition to display hard drive sizes, as do most other operating systems [3]. Every operating system uses this definition when referring to the size of files. By this definition, there are 1,024 megabytes in a gigabyte.

Gigabytes vs gigabits

In conventional modern usage, a byte is 8 bits. One gigabyte is equivalent to eight gigabits.

Abbreviation No. of megabytes Usage
gigabytesGB (Note: uppercase "B")1000Computer storage (eg 500 GB hard disk)
gigabytesGB (Note: uppercase "B")1024Computer memory (eg 4 GB RAM)
gigabitGb (Note: lowercase "b")125Network throughput (eg 1 Gb/s data transfer rate)

Consumer confusion

As of 2007, most consumer hard drives are defined by their gigabyte-range capacities. The true capacity is usually some number above or below the class designation. Although most manufacturers of hard disks and Flash disks define 1 gigabyte as 1,000,000,000 bytes, the computer operating systems used by most users usually calculate a gigabyte by dividing the bytes (whether it is disk capacity, file size, or system RAM) by 1,073,741,824. This distinction is a cause of confusion, especially for people from a non-technical background, as a hard disk with a manufacturer rated capacity of 400 gigabytes may have its capacity reported by the operating system as only 372 GB, depending on the type of report.

The difference between units based on SI and binary prefixes increases exponentially — in other words, an SI kilobyte is nearly 98% as much as a kibibyte, but a megabyte is under 96% as much as a mebibyte, and a gigabyte is just over 93% as much as a gibibyte. This means that a 500 GB hard disk drive would appear as "465 GB". As storage sizes get larger and higher units are used, this difference will become more pronounced.

Note that computer memory is addressed in base 2, due to its design, so memory size is always a power of two (or some closely related quantity, for instance 384 MiB = 3×227 bytes). It is thus convenient to work in binary units for RAM. Other computer measurements, like storage hardware size, data transfer rates, clock speeds, operations per second, etc., do not have an inherent base, and are usually presented in decimal units.

As an example, take a hard drive that can store exactly 250109 or 250 billion bytes after formatting. Generally, operating systems calculate disk and file sizes using binary numbers, so this 250 GB drive would be reported as "232.83 GB". The result is that there is a significant discrepancy between what the consumer believes they have purchased and what their operating system says they have.

Some consumers feel short-changed when they discover the difference, and claim that manufacturers of drives and data transfer devices are using the decimal measurements in an intentionally misleading way to inflate their numbers. Several legal disputes have been waged over the confusion. See Binary prefix — Legal disputes.

To further complicate matters, flash memory chips are organized in multiples of 2, but retail flash memory products have available capacities specified by multiples of 10. Removable flash storage products contain file systems that make the devices behave like hard disks instead of RAM, yet it is called 'memory'. In operating systems like Windows Vista, flash memory can indeed be treated like RAM. In operating systems supporting virtual memory, conflicting definitions can even lead to data loss. For example, if an operating system specifies 1 'gigabyte' (230 bytes) virtual memory, but the storage device has 1 gigabyte (109 bytes) available, it can lead to data loss when application is being swapped to this region of non-existent memory.

The basis of the problem is of course that the official definition of the SI units is not well known, and some legal settlements include directions for manufacturers to use clearer info, e.g. by stating a hard disk's size in both GB and GiB. However, JEDEC memory standards still uses the IEEE 100 nomanclatures.

Gigabytes in use

See also

References

External links

Gigabyte Technology

Founded 1986
Headquarters Taiwan

Industry Computer industry
Products Motherboards, graphics cards, notebooks, PDAs
Website www.gigabyte.com.
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Reboot may refer to:
  • Reboot (computer), restarting a computer system
  • Control-Alt-Delete, on PC compatible systems, can be used to reboot the computer

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An SI prefix (also known as a metric prefix) is a name or associated symbol that precedes a unit of measure (or its symbol) to form a decimal multiple or submultiple.
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Giga- (symbol: G) is a prefix in the SI system of units denoting 109, or 1,000,000,000 (1 billion). The Oxford English Dictionary reports the earliest written use of giga- in this sense to be in the Reports of the IUPAC 14th Conference in 1947: "The
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Information is the result of processing, gathering, manipulating and organizing data in a way that adds to the knowledge of the receiver. In other words, it is the context in which data is taken.
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Computer data storage, computer memory, and often casually storage or memory refer to computer components, devices and recording media that retain digital data used for computing for some interval of time.
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byte (pronounced /baɪt/) is a unit of measurement of information storage, most often consisting of eight bits. In many computer architectures it is a unit of memory addressing.
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1,000,000,000 (alternately known as one thousand million and one billion, see below) is the natural number following 999,999,999 and preceding 1,000,000,001.

In scientific notation, it is written as 109.
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gibibyte (a contraction of giga binary byte) is a unit of information or computer storage, abbreviated GiB[1].

1 gibibyte = 230 bytes = 1,073,741,824 bytes = 1,024 mebibytes

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gigabit is a unit of information or computer storage, abbreviated Gbit or sometimes Gb.

1 gigabit = 109 = 1,000,000,000 bits (which is equal to 125 decimal megabytes or 119.
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byte (pronounced /baɪt/) is a unit of measurement of information storage, most often consisting of eight bits. In many computer architectures it is a unit of memory addressing.
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An SI prefix (also known as a metric prefix) is a name or associated symbol that precedes a unit of measure (or its symbol) to form a decimal multiple or submultiple.
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In computing, binary prefixes can be used to quantify large numbers where powers of two are more useful than powers of ten (such as computer memory sizes). Each successive prefix is multiplied by 1024 (210) rather than the 1000 (103
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kilobyte (derived from the SI prefix kilo-, meaning 1,000) is a unit of information or computer storage equal to either 1,000 bytes or 1,024 bytes (210), depending on context.
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kibibyte (a contraction of kilo binary byte) is a unit of information or computer storage, established by the International Electrotechnical Commission in 2000. Its symbol is KiB.
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megabyte or Mbyte is a unit of information or computer storage equal to either 106 (1,000,000) bytes or 220 (1,048,576) bytes, depending on context. In rare cases, it is used to mean 1000×1024 (1,024,000) bytes.
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mebibyte (a contraction of mega binary byte) is a unit of information or computer storage, abbreviated MiB.

1 MiB = 220 bytes = 1,048,576 bytes = 1,024 kibibytes
1 MiB = 1024 (= 210

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gibibyte (a contraction of giga binary byte) is a unit of information or computer storage, abbreviated GiB[1].

1 gibibyte = 230 bytes = 1,073,741,824 bytes = 1,024 mebibytes

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terabyte (derived from the prefix tera- and commonly abbreviated TB) is a measurement term for data storage capacity. The value of a terabyte is based upon a decimal radix (base 10) and is defined as one trillion (short scale) bytes, or 1000 gigabytes.
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tebibyte (a contraction of tera binary byte) is a unit of information or computer storage, abbreviated TiB.

1 tebibyte = 240 bytes = 1,099,511,627,776 bytes = 1,024 gibibytes

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petabyte (derived from the SI prefix peta- ) is a unit of information or computer storage equal to one quadrillion bytes. It is commonly abbreviated PB. When used with byte multiples, the prefix may indicate a power of either 1000 or 1024, so the exact number may be
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pebibyte (a contraction of peta binary byte) is a unit of information or computer storage, abbreviated PiB.

1 pebibyte = 250 bytes = 1,125,899,906,842,624 bytes = 1,024 tebibytes

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exabyte (derived from the SI prefix exa-) is a unit of information or computer storage equal to one quintillion bytes. It is commonly abbreviated EB. When used with byte multiples, the SI prefix may indicate a power of either 1000 or 1024, so the exact number may be
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exbibyte (a contraction of exa binary byte) is a unit of information or computer storage, abbreviated EiB.

1 exbibyte = 260 bytes = 1,152,921,504,606,846,976 bytes = 1,024 pebibytes

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zettabyte (derived from the SI prefix zetta-) is a unit of information or computer storage equal to one sextillion (one long scale trilliard) bytes. It is commonly abbreviated ZB. As of 2007, no computer has one zettabyte of storage.
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zebibyte (a contraction of zetta binary byte) is a unit of information or computer storage, commonly abbreviated ZiB.

1 zebibyte = 270 bytes = 1,180,591,620,717,411,303,424 bytes = 1,024 exbibytes
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yottabyte (derived from the SI prefix yotta-) is a unit of information or computer storage equal to one septillion (one long scale quadrillion or 1024) bytes. It is commonly abbreviated YB. As of 2007, no computer has achieved one yottabyte of storage.
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yobibyte (a contraction of yotta binary byte) is a unit of information or computer storage, commonly abbreviated YiB.

1 yobibyte = 280 bytes = 1,208,925,819,614,629,174,706,176 bytes = 1,024 zebibytes
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Telecommunication is the transmission of signals over a distance for the purpose of communication. In modern times, this process typically involves the sending of electromagnetic waves by electronic transmitters, but in earlier times telecommunication may have involved the use of
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Computer data storage, computer memory, and often casually storage or memory refer to computer components, devices and recording media that retain digital data used for computing for some interval of time.
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