This definition is used in all contexts of science (especiallydata science),engineering,business, and many areas ofcomputing, including storage capacities ofhard drives,solid-state drives, andtapes, as well asdata transmission speeds. The term is also used in some fields of computer science and information technology to denote1073741824 (10243 or 230) bytes, however, particularly for sizes ofRAM. Thus, some usage ofgigabyte has been ambiguous. To resolve this difficulty,IEC 80000-13 clarifies that agigabyte (GB) is 109 bytes and specifies the termgibibyte (GiB) to denote 230 bytes. These differences are still readily seen, for example, when a 400 GB drive's capacity is displayed byMicrosoft Windows as 372 GB instead of 372 GiB. Analogously, a memory module that is labeled as having the size "1GB" has onegibibyte (1GiB) of storage capacity.
In response to litigation over whether the makers of electronic storage devices must conform to Microsoft Windows' use of a binary definition of "GB" instead of the metric/decimal definition, theUnited States District Court for the Northern District of California rejected that argument, ruling that "the U.S. Congress has deemed the decimal definition of gigabyte to be the 'preferred' one for the purposes of 'U.S. trade and commerce.'"[2][3]
The termgigabyte has a standard definition of 10003 bytes, as well as a discouraged[2] meaning of 10243 bytes. The latter binary usage originated as compromise technical jargon for bytemultiples that needed to be expressed in a power of 2, but lacked a convenient name. As 1024 (210) is approximately 1000 (103), roughly corresponding to SI multiples, it was used for binary multiples as well.
Since the first disk drive, theIBM 350, disk drive manufacturers expressedhard drive capacities using decimal prefixes. With the advent of gigabyte-range drive capacities, manufacturers labelled many consumerhard drive,solid-state drive andUSB flash drive capacities in certain size classes expressed in decimal gigabytes, such as "500 GB". The exact capacity of a given drive model is usually slightly larger than the class designation. Practically all manufacturers of hard disk drives and flash-memory disk devices[5][6] continue to define one gigabyte as1000000000bytes, which is displayed on the packaging. Some operating systems such asMac OS X,[8]iOS,Android,[citation needed]Ubuntu,[9] andDebian[10] express hard drive capacity or file size using decimal multipliers, while others such asMicrosoft Windows (includingWindows Phone) report file size using binary multipliers. This discrepancy causes confusion, as a disk with an advertised capacity of, for example,400 GB (meaning400000000000bytes, equal to 372 GiB) might be reported by the operating system as "372 GB".
ForRAM, theJEDEC memory standards useIEEE 100 nomenclature which quote the gigabyte as1073741824bytes (230 bytes).[11]
The difference between units based on decimal and binary prefixes increases as asemi-logarithmic (linear-log) function—for example, the decimal kilobyte value is nearly 98% of the kibibyte, amegabyte is under 96% of a mebibyte, and a gigabyte is just over 93% of a gibibyte value. This means that a 300 GB (279 GiB) hard disk might be indicated variously as "300 GB", "279 GB" or "279 GiB", depending on the operating system. As storage sizes increase and larger units are used, these differences become more pronounced.
A lawsuit decided in 2019 that arose from alleged breach of contract and other claims over the binary and decimal definitions used for "gigabyte" have ended in favour of the manufacturers, with courts holding that the legal definition of gigabyte or GB is 1 GB = 1,000,000,000 (109) bytes (the decimal definition). Specifically, the courts held that "the U.S. Congress has deemed the decimal definition of gigabyte to be the 'preferred' one for the purposes of 'U.S. trade and commerce' .... The California Legislature has likewise adopted the decimal system for all 'transactions in this state'."[2]
Earlier lawsuits had ended in settlement with no court ruling on the question, such as a lawsuit against drive manufacturerWestern Digital.[12][13] Western Digital settled the challenge and added explicit disclaimers to products that the usable capacity may differ from the advertised capacity.[12]Seagate was sued on similar grounds and also settled.[12][14]
Because of their physical design, the capacity of modern computer random-access memory devices, such asDIMM modules, is always a multiple of a power of 1024. It is thus convenient to use prefixes denoting powers of 1024, known asbinary prefixes, in describing them. For example, a memory capacity of1073741824bytes (10243 B) is conveniently expressed as 1 GiB rather than as 1.074 GB. The former specification is, however, often quoted as "1 GB" when applied to random-access memory.[15]
Software allocates memory in varying degrees of granularity as needed to fulfill data structure requirements and binary multiples are usually not required. Other computer capacities and rates, likestorage hardware size,data transfer rates,clock speeds,operations per second, etc. are usually presented in decimal units. For example, the manufacturer of a "300 GB" hard drive is claiming a capacity of300000000000bytes, not 300 × 10243 (which would be322122547200) bytes.
