The standard introduces the International System of Quantities (ISQ). It is a style guide for the use of physical quantities and units of measurement, formulas involving them, and their corresponding units, in scientific and educational documents for worldwide use. In most countries, the notations used in mathematics and science textbooks at schools and universities follow closely the guidelines in this standard.
The ISO/IEC 80000 family of standards was completed with the publication of Part 1 in November 2009.
The 80000 standard currently has 14 parts.
ISO 80000-7:2008 supersedes ISO 31-6, and specifies names and symbols to quantities and units for light and other electromagnetic radiation, and defines these quantities and units. The document is under review.
ISO 80000-8:2007 specifies names, symbols for quantities and units of acoustics and provides definitions for these quantities and units. It supersedes ISO 31-7 and is under review. It has a foreword; introduction; scope; normative references; and names, symbols and definitions. The standard includes definitions of sound pressure, sound power and sound exposure, and their corresponding levels: sound pressure level, sound power level and sound exposure level. For example:
IEC 80000-13:2008 defines quantities and units used in information science, and specifies names and symbols for these quantities and units. The current edition was published in 2008, and replaces subclauses 3.8 and 3.9 of IEC 60027-2:2005 and IEC 60027-3. It has a scope; normative references; names, definitions and symbols; and prefixes for binary multiples. Quantities defined in this standard are:
The Standard also includes definitions for units relating to information technology, such as the erlang (symbol E), bit (bit), octet (o), byte (B), baud (Bd), shannon (Sh), hartley (Hart) and the natural unit of information (nat).
Clause 4 of the Standard defines standard binary prefixes used to denote powers of 1024 as 10241 (kibi-), 10242 (mebi-), 10243 (gibi-), 10244 (tebi-), 10245 (pebi-), 10246 (exbi-), 10247 (zebi-) and 10248 (yobi-).
|ISO 80000-1||2009||General||ISO 31-0, IEC 60027-1 and IEC 60027-3||under review|
|ISO 80000-2||2009||Mathematical signs and symbols to be used in the natural sciences and technology||ISO 31-11, IEC 60027-1||under review|
|ISO 80000-3||2006||Space and time||ISO 31-1 and ISO 31-2||under review|
|ISO 80000-9||2008||Physical chemistry and molecular physics||ISO 31-8||under review|
|ISO 80000-10||2009||Atomic and nuclear physics||ISO 31-9 and ISO 31-10||under review|
|ISO 80000-11||2008||Characteristic numbers||ISO 31-12||under review|
|ISO 80000-12||2009||Solid state physics||ISO 31-13||under review|
|IEC 80000-14||2008||Telebiometrics related to human physiology||IEC 60027-7||withdrawn|
Part 1 of ISO 80000 introduces the International System of Quantities and describes its relationship with the International System of Units (SI). Specifically, its introduction states "The system of quantities, including the relations among the quantities used as the basis of the units of the SI, is named the International System of Quantities, denoted 'ISQ', in all languages.", and further clarifies that "ISQ is simply a convenient notation to assign to the essentially infinite and continually evolving and expanding system of quantities and equations on which all of modern science and technology rests".
The standard includes all SI units but is not limited to only SI units. Units that form part of the standard but not the SI include the units of information storage (bit and byte), units of entropy (shannon, natural unit of information and hartley), the erlang (a unit of traffic intensity) and units of level (neper and decibel). The standard includes all SI prefixes as well as the binary prefixes kibi-, mebi-, gibi-, etc., originally introduced by the International Electrotechnical Commission to standardise binary multiples of byte such as mebibyte (MiB), for 10242 bytes, to distinguish them from their decimal counterparts such as megabyte (MB), for precisely one million (10002) bytes. In the standard, the application of the binary prefixes is not limited to units of information storage. For example, a frequency ten octaves above one hertz, i.e., 210 Hz (1024 Hz), is one kibihertz (1 KiHz).
These binary prefixes were standardized first in a 1999 addendum to IEC 60027-2. The harmonized IEC 80000-13:2008 standard cancels and replaces subclauses 3.8 and 3.9 of IEC 60027-2:2005, which had defined the prefixes for binary multiples. The only significant change in IEC 80000-13 is the addition of explicit definitions for some quantities.
A binary prefix is a unit prefix for multiples of units in data processing, data transmission, and digital information, notably the bit and the byte, to indicate multiplication by a power of 2.
The computer industry has historically used the units kilobyte, megabyte, and gigabyte, and the corresponding symbols KB, MB, and GB, in at least two slightly different measurement systems. In citations of main memory (RAM) capacity, gigabyte customarily means 1073741824 bytes. As this is a power of 1024, and 1024 is a power of two (210), this usage is referred to as a binary measurement.
In most other contexts, the industry uses the multipliers kilo, mega, giga, etc., in a manner consistent with their meaning in the International System of Units (SI), namely as powers of 1000. For example, a 500 gigabyte hard disk holds 500000000000 bytes, and a 1 Gbit/s (gigabit per second) Ethernet connection transfers data at 1000000000 bit/s. In contrast with the binary prefix usage, this use is described as a decimal prefix, as 1000 is a power of 10 (103).
The use of the same unit prefixes with two different meanings has caused confusion. Starting around 1998, the International Electrotechnical Commission (IEC) and several other standards and trade organizations addressed the ambiguity by publishing standards and recommendations for a set of binary prefixes that refer exclusively to powers of 1024. Accordingly, the US National Institute of Standards and Technology (NIST) requires that SI prefixes only be used in the decimal sense: kilobyte and megabyte denote one thousand bytes and one million bytes respectively (consistent with SI), while new terms such as kibibyte, mebibyte and gibibyte, having the symbols KiB, MiB, and GiB, denote 1024 bytes, 1048576 bytes, and 1073741824 bytes, respectively. In 2008, the IEC prefixes were incorporated into the international standard system of units used alongside the International System of Quantities (see ISO/IEC 80000).Giga-
Giga ( or ) is a unit prefix in the metric system denoting a factor of a (short-form) billion (109 or 1000000000). It has the symbol G.
Giga is derived from the Greek word γίγας, meaning "giant". 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 following prefixes to abbreviations for the names of units should be used: G giga 109×".When referring to information units in computing, such as gigabyte, giga may sometimes mean 1073741824 (230), although such use is inconsistent, contrary to standards and has been discouraged by the standards organizations. The inconsistency is that gigabit is never (or very rarely) used with the binary interpretation of the prefix, while gigabyte is sometimes used this way. The binary prefix gibi has been adopted for 230, while reserving giga exclusively for the metric definition.IEC 60027
IEC 60027 (formerly IEC 27) is a technical international standard for letter symbols published by the International Electrotechnical Commission, comprising the following parts:
IEC 60027-1: General
IEC 60027-2: Telecommunications and electronics
IEC 60027-3: Logarithmic and related quantities, and their units
IEC 60027-4: Symbols for quantities to be used for rotating electrical machines
IEC 60027-6: Control technology
IEC 60027-7: Physiological quantities and unitsA closely related international standard on quantities and units is ISO 31. The ISO 31 and IEC 60027 Standards are being revised by the two standardization organizations in collaboration. The revised harmonized standard is known as ISO/IEC 80000, Quantities and units. It supersedes both ISO 31 and part of IEC 60027.IEC TC 25
IEC Technical Committee 25 was established in 1935. It is one of the technical committees of the International Electrotechnical Commission (IEC).
Its title is "Quantities and units, and their letter symbols". It merged with TC 24 and as a committee with "horizontal" responsibilities (i.e. covering matters of a wide-ranging nature and applicable by many “vertical” or product-oriented committees), it is in charge of all questions concerning the SI.
Among other standards it is responsible for parts 6, 13, 14, 15 of ISO/IEC 80000.ISO 1000
International standard ISO 1000 (SI units and recommendations for the use of their multiples and of certain other units, International Organization for Standardization, 1992) is the ISO standard describing the International System of Units (SI).
The ISO 1000:1992 standard was withdrawn in 2009, following the publication of ISO/IEC 80000-1.ISO 31
ISO 31 (Quantities and units, International Organization for Standardization, 1992) is a deprecated international standard for the use of physical quantities and units of measurement, and formulas involving them, in scientific and educational documents. It is superseded by ISO/IEC 80000.ISO 80000-1
ISO 80000-1:2009 is a standard describing scientific and mathematical quantities and their units. The standard, whose full name is Quantities and units Part 1: General was developed by the International Organization for Standardization (ISO), superseding ISO 31-0. It provides general information concerning quantities and units and their symbols, especially the International System of Quantities and the International System of Units, and defines these quantities and units. It is a part of a group of standards called ISO/IEC 80000.ISO 80000-2
ISO 80000-2:2009 is a standard describing mathematical signs and symbols developed by the International Organization for Standardization (ISO), superseding ISO 31-11. The Standard, whose full name is Quantities and units — Part 2: Mathematical signs and symbols to be used in the natural sciences and technology, is a part of the group of standards called ISO/IEC 80000.ISO 80000-3
ISO 80000-3:2006 is an ISO standard entitled Quantities and units – Part 3: Space and time, superseding ISO 31-1 and ISO 31-2. It is a part of the group of standards called ISO/IEC 80000, which together form the International System of Quantities.International System of Quantities
The International System of Quantities (ISQ) is a system based on seven base quantities: length, mass, time, electric current, thermodynamic temperature, amount of substance, and luminous intensity. Other quantities such as area, pressure, and electrical resistance are derived from these base quantities by clear, non-contradictory equations. The ISQ defines the quantities that are measured with the SI units and also includes many other quantities in modern science and technology. The ISQ is defined in the international standard ISO/IEC 80000, and was finalised in 2009 with the publication of ISO 80000-1.The 14 parts of ISO/IEC 80000 define quantities used in scientific disciplines such as mechanics (e.g., pressure), light, acoustics (e.g., sound pressure), electromagnetism, information technology (e.g., storage capacity), chemistry, mathematics (e.g., Fourier transform), and physiology.Italic type
In typography, italic type is a cursive font based on a stylized form of calligraphic handwriting. Owing to the influence from calligraphy, italics normally slant slightly to the right. Italics are a way to emphasise key points in a printed text, to identify many types of creative works, or, when quoting a speaker, a way to show which words they stressed. One manual of English usage described italics as "the print equivalent of underlining".The name comes from the fact that calligraphy-inspired typefaces were first designed in Italy, to replace documents traditionally written in a handwriting style called chancery hand. Aldus Manutius and Ludovico Arrighi (both between the 15th and 16th centuries) were the main type designers involved in this process at the time. Different glyph shapes from Roman type are usually used – another influence from calligraphy – and upper-case letters may have swashes, flourishes inspired by ornate calligraphy. An alternative is oblique type, in which the type is slanted but the letterforms do not change shape: this less elaborate approach is used by many sans-serif typefaces.JEDEC memory standards
The JEDEC memory standards are the specifications for semiconductor memory circuits and similar storage devices promulgated by the Joint Electron Device Engineering Council (JEDEC) Solid State Technology Association, a semiconductor trade and engineering standardization organization.
JEDEC Standard 100B.01 specifies common terms, units, and other definitions in use in the semiconductor industry. JESC21-C specifies semiconductor memories from the 256 bit static RAM to the latest DDR3 SDRAM modules. In August 2011, JEDEC announced that its DDR4 standard was expected to be published in mid-2012.Metric prefix
A metric prefix is a unit prefix that precedes a basic unit of measure to indicate a multiple or fraction of the unit. While all metric prefixes in common use today are decadic, historically there have been a number of binary metric prefixes as well. Each prefix has a unique symbol that is prepended to the unit symbol. The prefix kilo-, for example, may be added to gram to indicate multiplication by one thousand: one kilogram is equal to one thousand grams. The prefix milli-, likewise, may be added to metre to indicate division by one thousand; one millimetre is equal to one thousandth of a metre.
Decimal multiplicative prefixes have been a feature of all forms of the metric system, with six dating back to the system's introduction in the 1790s. Metric prefixes have even been prepended to non-metric units. The SI prefixes are standardized for use in the International System of Units (SI) by the International Bureau of Weights and Measures (BIPM) in resolutions dating from 1960 to 1991. Since 2009, they have formed part of the International System of Quantities.Octet (computing)
The octet is a unit of digital information in computing and telecommunications that consists of eight bits. The term is often used when the term byte might be ambiguous, as the byte has historically been used for storage units of a variety of sizes.
The term octad(e) for eight bits is no longer common.Outline of the metric system
The following outline is provided as an overview of and topical guide to the metric system – various loosely related systems of measurement that trace their origin to the decimal system of measurement introduced in France during the French Revolution.Physical quantity
A physical quantity is a physical property of a material that can be quantified by measurement. A physical quantity can be expressed as the combination of a magnitude expressed by a number – usually a real number – and a unit:
is the magnitude and
is the unit. For example, 1.6749275×10−27 kg (the mass of the neutron), or 299792458 metres per second (the speed of light). The same physical quantity
can be represented equivalently in many unit systems, i.e.
The tebibyte is a multiple of the unit byte for digital information. It is a member of the set of units with binary prefixes defined by the International Electrotechnical Commission (IEC). Its unit symbol is TiB.
The prefix tebi (symbol Ti) represents multiplication by 10244, therefore:
1 tebibyte = 240 bytes = 1099511627776bytes = 1024 gibibytes1024 TiB = 1 pebibyte (PiB)The tebibyte is closely related to the terabyte (TB), which is defined as 1012 bytes = 1000000000000bytes. It follows that one tebibyte (1 TiB) is approximately equal to 1.1 TB.
In some contexts, the terabyte has been used as a synonym for tebibyte. (see Consumer confusion).Thermodynamic potential
A thermodynamic potential (in fact, rather energy than potential) is a scalar quantity used to represent the thermodynamic state of a system. The concept of thermodynamic potentials was introduced by Pierre Duhem in 1886. Josiah Willard Gibbs in his papers used the term fundamental functions. One main thermodynamic potential that has a physical interpretation is the internal energy U. It is the energy of configuration of a given system of conservative forces (that is why it is called potential) and only has meaning with respect to a defined set of references (or data). Expressions for all other thermodynamic energy potentials are derivable via Legendre transforms from an expression for U. In thermodynamics, external forces, such as gravity, are typically disregarded when formulating expressions for potentials. For example, while all the working fluid in a steam engine may have higher energy due to gravity while sitting on top of Mount Everest than it would at the bottom of the Mariana Trench, the gravitational potential energy term in the formula for the internal energy would usually be ignored because changes in gravitational potential within the engine during operation would be negligible. In a large system under even homogeneous external force, like the earth atmosphere under gravity, the intensive parameters () should be studied locally having even in equilibrium different values in different places far from each other (see thermodynamic models of troposphere].Typographical conventions in mathematical formulae
Typographical conventions in mathematical formulae provide uniformity across mathematical texts and help the readers of those texts to grasp new concepts quickly.
Mathematical notation includes letters from various alphabets, as well as special mathematical symbols. Letters in various fonts often have specific, fixed meanings in particular areas of mathematics. A mathematical article or a theorem typically starts from the definitions of the introduced symbols, such as: "Let G = (V, E) be a graph with the vertex set V and edge set E...". Theoretically it is admissible to write "Let X = (a, q) be a graph with the vertex set a and edge set q..."; however, this would decrease readability, since the reader has to consciously memorize these unusual notations in a limited context.
Usage of subscripts and superscripts is also an important convention. In the early days of computers with limited graphical capabilities for text, subscripts and superscripts were represented with the help of additional notation. In particular, n2 could be written as n^2 or n**2 (the latter borrowed from FORTRAN) and n2 could be written as n_2.
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