This definition is used in all contexts of science (especially data science), engineering, business, and many areas of computing, including storage capacities of hard drives, solid state drives, and tapes, as well as data transmission speeds. The term is also used in some fields of computer science and information technology to denote 1073741824 (10243 or 230) bytes, however, particularly for sizes of RAM. Thus, some usage of gigabyte has been ambiguous. To resolve this difficulty, IEC 80000-13 clarifies that a gigabyte (GB) is 109 bytes and specifies the term gibibyte (GiB) to denote 230 bytes. These differences are still readily seen, for example, when a 400GB drive's capacity is displayed by Microsoft Windows as 372GB instead of 372GiB. Analogously, a memory module that is labeled as having the size "1GB" has one gibibyte (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, the United 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]
Definition
The term gigabyte 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 byte multiples 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.
The binary definition uses powers of the base 2, as does the architectural principle of binarycomputers.
This usage is widely promulgated by some operating systems, such as Microsoft Windows in reference to computer memory (e.g., RAM). This definition is synonymous with the unambiguous unit gibibyte.
Consumer confusion
Since the first disk drive, the IBM 350, disk drive manufacturers expressed hard drive capacities using decimal prefixes. With the advent of gigabyte-range drive capacities, manufacturers labelled many consumer hard drive, solid state drive and USB 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 as 1000000000bytes, which is displayed on the packaging. Some operating systems such as Mac OS X[8] and Ubuntu,[9] and Debian[10] express hard drive capacity or file size using decimal multipliers, while others such as Microsoft Windows report size using binary multipliers. This discrepancy causes confusion, as a disk with an advertised capacity of, for example, 400 GB (meaning 400000000000bytes, equal to 372 GiB) might be reported by the operating system as "372 GB".
For RAM, the JEDEC memory standards use IEEE 100 nomenclature which quote the gigabyte as 1073741824bytes (230 bytes).[11]
The difference between units based on decimal and binary prefixes increases as a semi-logarithmic (linear-log) function—for example, the decimal kilobyte value is nearly 98% of the kibibyte, a megabyte is under 96% of a mebibyte, and a gigabyte is just over 93% of a gibibyte value. This means that a 300GB (279GiB) hard disk might be indicated variously as "300 GB", "279GB" or "279 GiB", depending on the operating system. As storage sizes increase and larger units are used, these differences become more pronounced.
US lawsuits
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 favor 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 manufacturer Western 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]
Other contexts
Because of their physical design, the capacity of modern computer random access memory devices, such as DIMM modules, is always a multiple of a power of 1024. It is thus convenient to use prefixes denoting powers of 1024, known as binary prefixes, in describing them. For example, a memory capacity of 1073741824bytes (10243 B) is conveniently expressed as 1GiB rather than as 1.074GB. The former specification is, however, often quoted as "1GB" 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, like storage hardware size, data transfer rates, clock speeds, operations per second, etc., do not depend on an inherent base, and are usually presented in decimal units. For example, the manufacturer of a "300GB" hard drive is claiming a capacity of 300000000000bytes, not 300×10243 (which would be 322122547200) bytes.
Examples of gigabyte-sized storage
One hour of SDTV video at 2.2Mbit/s is approximately 1GB.
Seven minutes of HDTV video at 19.39Mbit/s is approximately 1GB.
114 minutes of uncompressed CD-quality audio at 1.4Mbit/s is approximately 1GB.
This article uses material from the Wikipedia article Gigabyte, and is written by contributors.
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