**ISO 80000** or **IEC 80000** is an international standard promulgated jointly by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC).

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.^{[1] }

The standard has 14 parts.^{[2] }

ISO 80000-4:2006 supersedes ISO 31-3.^{[3] } and specifies names and symbols for quantities and units of classical mechanics, and defines these names and symbols. The document is under review.^{[4] }

ISO 80000-5:2007 supersedes ISO 31-4^{[5] } which "gives names, symbols and definitions for quantities and units of thermodynamics". The document is under review.^{[6] }

IEC 80000-6:2008 supersedes ISO 31-5^{[7] } as well as IEC 60027-1, and specifies names and symbols for quantities and units related to electromagnetism, and defines these quantities and units.

ISO 80000-7:2008 supersedes ISO 31-6,^{[8] } 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.^{[9] }

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^{[10] } and is under review.^{[11] } 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:

- period duration (symbol T): duration of one cycle of a periodic phenomenon
- frequency (symbol f): f = 1/T
- logarithmic frequency interval (symbol G): G = lb(f/f)
- angular frequency (symbol ω): ω = 2πf
- wavelength (symbol λ): for a sinusoidal wave and in a direction perpendicular to the wavefront, distance between two successive points where at a given instant the phase ... differs by 2 π
- wavenumber (symbol σ): σ = 1/λ
- angular wavenumber (symbol k): k = ω/c
- density (symbol ρ): ρ = m/V
- static pressure (symbol p): pressure that would exist in the absence of sound waves
- sound pressure (symbol p): difference between instantaneous total pressure and static pressure
- sound particle displacement (symbol
**δ**): instantaneous displacement of a particle in a medium from what would be its position in the absence of sound waves - sound particle velocity (symbol
**v**,**u**):**v**= d**δ**/dt - sound particle acceleration (symbol
**a**):**a**= d**v**/dt - sound volume velocity (symbol q): surface integral of the normal component of the sound particle velocity ... over the cross-section (through which the sound propagates)
- phase speed of sound (symbol c): c = ω/k
- group speed of sound (symbol c): c = dω/dk
- sound energy density (symbol w): time-averaged sound energy in a given volume divided by that volume
- sound power (symbol P, P): through a surface, product of the sound pressure ... and the component of the particle velocity ... at a point on the surface in the direction normal to the surface, integrated over that surface
- sound intensity (symbol i):
**i**= p.**v** - time-averaged sound intensity (symbol I):
- sound exposure (symbol E):
- characteristic impedance of a medium (symbol Z): at a point in a non-dissipative medium and for a plane progressive wave, the quotient of the sound pressure ... by the component of the sound particle velocity ... in the direction of the wave propagation
- acoustic impedance (symbol Z): at a surface, the complex quotient of the average sound pressure ... over that surface by the sound volume flow rate ... through that surface
- mechanical surface impedance (symbol Z): at a surface, the complex quotient of the total force on the surface by the component of the average sound particle velocity ... at the surface in the direction of the force
- sound pressure level (symbol L):
- sound power level (symbol L):
- sound exposure level (symbol L):
- attenuation coefficient (symbol α):
- phase coefficient (symbol β):
- propagation coefficient (symbol γ):
- dissipation factor for sound power (symbol δ, ψ):
- reflection factor for sound power (symbol r):
- transmission factor for sound power (symbol τ):
- absorption factor for sound power (symbol α):
- sound reduction index (symbol R):
- equivalent absorption area of a surface or object (symbol A):
- reverberation time (symbol T):

IEC 80000-13:2008 defines quantities and units used in information science, and specifies names and symbols for these quantities and units.^{[12] } The document was last-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:

- traffic intensity [A]: number of simultaneously busy resources in a particular pool of resources
- traffic offered intensity [A]: traffic intensity ... of the traffic that would have been generated by the users of a pool of resources if their use had not been limited by the size of the pool
- traffic carried intensity [Y]: traffic intensity ... of the traffic served by a particular pool of resources
- mean queue length [L, (Ω)]: time average of queue length
- loss probability [B]: probability for losing a call attempt
- waiting probability [W]: probability for waiting for a resource
- call intensity, calling rate [λ]: number of call attempts over a specified time interval divided by the duration (ISO 80000-3 ...) of this interval
- completed call intensity [μ]: call intensity ... for the call attempts that result in the transmission of an answer signal
- storage capacity, storage size [M]
- equivalent binary storage capacity [M]
- transfer rate [r, (ν)]
- period of data elements [T]
- binary digit rate, bit rate [r, r (ν, ν)]
- period of binary digits, bit period [T, T]
- equivalent binary digit rate, equivalent bit rate [r, (ν)]
- modulation rate, line digit rate [r, u]
- quantizing distortion power [T]
- carrier power [P, C]
- signal energy per binary digit [E, E]
- error probability [P]
- Hamming distance [d]
- clock frequency, clock rate [f]
- decision content [D]
- information content [I(x)]
- entropy [H]
- maximum entropy [H, (H)]
- relative entropy [H]
- redundancy [R]
- relative redundancy [r]
- joint information content [I(x, y)]
- conditional information content [I(x|y)]
- conditional entropy, mean conditional information content, average conditional information content [H(X|Y)]
- equivocation [H(X∣Y)]
- irrelevance [C]
- transinformation content [T(x, y)]
- mean transinformation content [T]
- character mean entropy [H′]
- average information rate [H*]
- character mean transinformation content [T′]
- average transinformation rate [T*]
- channel capacity per character; channel capacity [C′]
- channel time capacity; channel capacity [C*]

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 1024^{1 } (kibi-), 1024^{2 } (mebi-), 1024^{3 } (gibi-), 1024^{4 } (tebi-), 1024^{5 } (pebi-), 1024^{6 } (exbi-), 1024^{7 } (zebi-) and 1024^{8 } (yobi-).

Part | Year | Name | Replaces | Status^{[13] } |
---|---|---|---|---|

ISO 80000-1^{[14] } | 2009 | General | ISO 31-0, IEC 60027-1 and IEC 60027-3 | under review |

ISO 80000-2^{[15] } | 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^{[16] } | 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/IEC 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 1024^{2 } bytes, to distinguish them from their decimal counterparts such as megabyte (MB), for precisely one million (1000^{2 }) 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., 2^{10 } Hz (1024 Hz), is one kibihertz (1 KiHz).

Historically, these binary prefixes were standardized first in a 1999 addendum to IEC 60027-2. The harmonized IEC 80000-13:2008 standard obsoletes 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 is the addition of explicit definitions for some quantities.

- International Vocabulary of Metrology
- International System of Units
- BIPM – publishes freely available information on SI units
- NIST – official U.S. representative for SI; publishes freely available guide to use of SI

- Standards Catalogue TC/12 Quantities and Units
- BSI/ISO Standards
- "ISO 80000-4:2006". International Organization for Standardization. Retrieved 20 July 2013.
- Standards and projects under the direct responsibility of ISO/TC 12 Secretariat
- "ISO 80000-5:2007". International Organization for Standardization. Retrieved 20 July 2013.
- Standards and projects under the direct responsibility of ISO/TC 12 Secretariat
- "IEC 80000-6:2008". International Organization for Standardization. Retrieved 20 July 2013.
- "ISO 80000-7:2008". International Organization for Standardization. Retrieved 21 July 2013.
- Standards and projects under the direct responsibility of ISO/TC 12 Secretariat
- "ISO 80000-8:2007". International Organization for Standardization. Retrieved 21 July 2013.
- Standards and projects under the direct responsibility of ISO/TC 12 Secretariat
- "IEC 80000-13:2008". International Organization for Standardization. Retrieved 21 July 2013.
- Standards and projects under the direct responsibility of ISO/TC 12 Secretariat
- "ISO 80000-1:2009". International Organization for Standardization. Retrieved 20 July 2013.
- "ISO 80000-2:2009". International Organization for Standardization. Retrieved 1 July 2010.
- "ISO 80000-3:2006". International Organization for Standardization. Retrieved 20 July 2013.

- BIPM SI Brochure
- ISO TC12 standards – Quantities, units, symbols, conversion factors
- NIST Special Publication 330 – The International System of Units
- NIST Special Publication 811 – Guide for the Use of the International System of Units

ISO 80000 or IEC 80000 is an international standard promulgated jointly by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). 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. Areas The standard has 14 parts. Mechanics ISO 80000-4:2006 supersedes ISO 31-3 . and specifies names and symbols for quantities and units of classical mechanics, and defines these names and symbols. The document is under review. Thermodynamics ISO 80000-5:2007 supersedes ISO 31-4 which "gives names, symbols and d ...more...

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 . Contents list The Standard is divided into the following chapters: Foreword Introduction Scope Normative references Variables, functions, and operators Mathematical logic Sets Standard number sets and intervals Miscellaneous signs and symbols Elementary geometry Operations Combinatorics Functions Exponential and logarithmic functions Circular and hyperbolic functions Complex numbers Matrices Coordinate systems Scalars, vectors, and tensors Transforms Special functions Annex A (normative) - Clarification of the symbols used Bibliography Symbols for variables and constants Clause 3 specifies that variables such as x and y , and functions in ge ...more...

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 . Parts The standard comes in 14 parts: ISO 31-0 : General principles ISO 31-1 : Space and time (replaced by ISO/IEC 80000 -3:2007) ISO 31-2 : Periodic and related phenomena (replaced by ISO/IEC 80000 -3:2007) ISO 31-3 : Mechanics (replaced by ISO/IEC 80000 -4:2006) ISO 31-4 : Heat (replaced by ISO/IEC 80000 -5) ISO 31-5 : Electricity and magnetism (replaced by ISO/IEC 80000 -6) ISO 31-6 : Light and related electromagnetic radiations (replaced by ISO/IEC 80000 -7) ISO 31-7 : Acoustics (replaced by ISO/IEC 80000 -8:2007) ISO 31-8 : Physical chemistry and molecular physics (replaced by ISO/IEC 80000 -9) ISO 31-9 : Atomic and nuclear physics (replaced by ISO/IEC 80000 -10) ISO 31-10 : Nuclear reactions and ionizing radiations ...more...

This is a list of published International Organization for Standardization (ISO) standards and other deliverables. For a complete and up-to-date list of all the ISO standards, see the ISO catalogue. The standards are protected by copyright and most of them must be purchased. However, about 300 of the standards produced by ISO and IEC 's Joint Technical Committee 1 ( JTC1 ) have been made freely and publicly available. ISO 1 – ISO 99 ISO 1 :2016 Geometrical product specifications (GPS) - Standard reference temperature for the specification of geometrical and dimensional properties ISO 2 :1973 Textiles – Designation of the direction of twist in yarns and related products ISO 3 :1973 Preferred numbers – Series of preferred numbers ISO 4 :1997 Information and documentation – Rules for the abbreviation of title words and titles of publications ISO 5 Photography and graphic technology – Density measurements ISO 6 :1993 Photography – Black-and-white pictorial still camera negative film/process systems – Determinati ...more...

IEC 60027 (formerly IEC 27 ) is the International Electrotechnical Commission 's standard on Letter symbols to be used in electrical technology. It consists of several 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 units A 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 60027-2 IEC 60027-2 Amendment 2, as published in January 1999, was the first international standard defining the binary prefixes , as proposed by International Electrotechnical Commission (IEC) since 1996 ( kibi- (Ki), mebi- (Mi), ...more...

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 1 073 741 824 bytes. As this is a power of 1024, and 1024 is a power of two (2 ), 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 500 000 000 000 bytes, and a 1 Gbit/s (gigabit per second) Ethernet connection transfers data at 1 000 000 000 bit/s. In contrast with the binary prefix usage, this use is described as a decimal p ...more...

IEC 61346 is an electrotechnical standard titled "Industrial systems, Installations and Equipment and Industrial Products — Structuring Principles and Reference Designations". It sets voluntary standards on how to structure systems and generate reference designations. Contents Part 1: Basic rules (IEC 61346-1:1996) Part 2: Classification of objects and codes for classes (IEC 61346-2:2000) Part 3: Application guidelines (IEC/TR 61346-3:2001) Part 4: Discussion of concepts (IEC 61346-4:1998) IEC standards have numbers in the range 60000–79999 while the numbers of older IEC standards were converted in 1997 by adding 60000. Thus the IEC 61346-1 was published as IEC 1346-1. Future standards Future developments of the standards on reference designations will be made in cooperation between the IEC and the ISO and published as IEC 81346 . (Standards developed in cooperation between IEC and ISO are assigned numbers in the 80000 series) Current situation (12-Nov-2010) IEC 61346 has been WITHDRAWN. It is replaced by IEC ...more...

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 1024 , therefore: The tebibyte is closely related to the terabyte (TB) , which is defined as 10 bytes = 1 000 000 000 000 bytes . 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 ). One thousand twenty-four tebibytes (1024 TiB) is equal to one pebibyte (1 PiB). See also IEEE 1541 ISO/IEC 80000-13 Orders of magnitude (data) SI prefix References "Prefixes for binary multiples" . NIST. 2007 . Retrieved 10 August 2007 . Storage capacity measurement standards , Seagate Inc. 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 E ...more...

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 . See also List of IEC technical committees External links http://www.iec.ch/tc25 https://web.archive.org/web/20090301164428/http://www.iec.ch/zone/si/si_present.htm 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 n ...more...

IEEE 1541-2002 is a standard issued in 2002 by the Institute of Electrical and Electronics Engineers (IEEE) concerning the use of prefixes for binary multiples of units of measurement related to digital electronics and computing . While the International System of Units (SI) defines multiples based on powers of ten (like k = 10 , M = 10 , etc.), a different definition is sometimes used in computing , based on powers of two (like k = 2 , M = 2 , etc.) This is due to the use of binary addressing for computer memory locations. In the early years of computing, there was no significant error in using the same prefix for either quantity (2 = 1024 and 10 = 1000 are equal, to two significant figures ). Thus, the SI prefixes were borrowed to indicate nearby binary multiples for these computer-related quantities. Meanwhile, manufacturers of storage devices, such as hard disks , traditionally used the standard decimal meanings of the prefixes, and decimal multiples are used for transmission rates and processor clock s ...more...

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 partic ...more...

The byte ( ) is a unit of digital information that most commonly consists of eight bits . Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable unit of memory in many computer architectures . The size of the byte has historically been hardware dependent and no definitive standards existed that mandated the size – byte-sizes from 1 to 48 bits are known to have been used in the past. Early character encoding systems often used six bits , and machines using six-bit and nine-bit bytes were common into the 1960s. These machines most commonly had memory words of 12, 24, 36, 48 or 60 bits, corresponding to two, four, six, eight or 10 six-bit bytes. In this era, bytes in the instruction stream were often referred to as syllables , before the term byte became common. The modern de-facto standard of eight bits, as documented in ISO/IEC 2382-1:1993, is a convenient power of two permitting the values 0 through 255 for o ...more...

This is an incomplete list of DIN standards . The "STATUS" column gives the latest known status of the standard. If a standard has been withdrawn and no replacement specification is listed, either the specification was withdrawn without replacement or a replacement specification could not be identified. DIN stands for " Deutsches Institut für Normung ", meaning "German institute for standardisation". DIN standards that begin with "DIN V" (" Vornorm ", meaning "pre-issue") are the result of standardization work, but because of certain reservations on the content or because of the divergent compared to a standard installation procedure of DIN, they are not yet published standards. DIN 1 to DIN 999 DIN 1 to DIN 99 DIN Title Status DIN replacement Other org replacement DIN 1 Cone Pins, untempered Withdrawn DIN EN 22339 ISO 2339 DIN 3 Standard measurements Withdrawn DIN 5 Technical drawings - Axonometric projections, Isometric projection Withdrawn DIN ISO 5456-1 , DIN ISO 5456-2 , DIN ISO 5456-3 , DIN ISO 5456-4 I ...more...

In computing and telecommunications , a unit of information is the capacity of some standard data storage system or communication channel , used to measure the capacities of other systems and channels. In information theory , units of information are also used to measure the entropy of random variables and information contained in messages. The most commonly used units of data storage capacity are the bit , the capacity of a system that has only two states, and the byte (or octet ), which is equivalent to eight bits. Multiples of these units can be formed from these with the SI prefixes (power-of-ten prefixes) or the newer IEC binary prefixes (power-of-two prefixes). Information capacity is considered to be a dimensionless quantity . Primary units Comparison of units of information: bit , trit , nat , ban . Quantity of information is the height of bars. Dark green level is the "Nat" unit. In 1928, Ralph Hartley observed a fundamental storage principle, which was further formalized by Claude Shannon in 1945: ...more...

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. Definition A variable-length sequence of octets, as in Abstract Syntax Notation One (ASN.1), is referred to as an octet string. The international standard IEC 60027-2, chapter 3.8.2, states that a byte is an octet of bits. However, the unit byte has historically been platform -dependent and has represented various storage sizes in the history of computing. Due to the influence of several major computer architectures and product lines, the byte became overwhelmingly associated with eight bits. This meaning of byte is codified in such standards as ISO/IEC 80000-13 . While byte and octet are often used synonymously, those working with certain legacy systems are careful to avoid ambiguity. Octets can be represente ...more...

The decibel (symbol: dB) is a logarithmic unit used to express the ratio of one value of a physical property to another, and may be used to express a change in value (e.g., +1 dB or -1 dB) or an absolute value. In the latter case, it expresses the ratio of a value to a reference value; when used in this way, the decibel symbol should be appended with a suffix that indicates the reference value or some other property. For example, if the reference value is 1 volt , then the suffix is " V " (i.e., "20 dBV"), and if the reference value is one milliwatt , then the suffix is " m " (i.e., "20 dBm"). However, sound pressure level is referenced to the " threshold of hearing " (generally given as 20 micropascals at 1 kHz), and the suffix is " SPL " (i.e., "60 dB SPL"). There are two different scales used when expressing a ratio in decibels depending on the nature of the quantities: field, power, and root-power . When expressing power quantities, the number of decibels is ten times the logarithm to base 10 of the rati ...more...

ISO 37120 Sustainable development of communities -- Indicators for city services and quality of life defines and establishes methodologies for a set of indicators to steer and measure the performance of city services and quality of life. This standard was developed by ISO project committee ISO/TC 268. History The standard was developed by ISO/TC 268, which started work in the year 2012. The first edition of ISO 37120 was published on May 2014. Main requirements of the standard The ISO 37120:2014 adopts the structure in the following breakdown: 1 Scope 2 Normative references 3 Terms and definitions 4 City indicators 5 Economy 6 Education 7 Energy 8 Environment 9 Finance 10 Fire and emergency response 11 Governance 12 Health 13 Recreation 14 Safety 15 Shelter 16 Solid waste 17 Telecommunication and innovation 18 Transportation 19 Urban planning 20 Wastewater 21 Water and sanitation 22 Reporting and record maintenance See also Quality management system List of ISO standards Conformity assessment International O ...more...

ISO 20400 Sustainable procurement -- Guidance provides guidance to organizations, independent of their activity or size, on integrating sustainability within procurement . It is intended for stakeholders involved in, or impacted by, procurement decisions and processes. This standard was developed by ISO project committee ISO/PC 277. History The standard was developed by project committee ISO/PC 277, which started work in the year 2013. The first edition of ISO 20400 was published on 21 April 2017. Main requirements of the standard The ISO 20400:2017 adopts the structure in the following breakdown: 1 Scope 2 Normative references 3 Terms and definitions 4 Understanding the fundamentals 5 Integrating sustainability into the organization's procurement policy and strategy 6 Organizing the procurement function toward sustainability 7 Integrating sustainability into the procurement process See also Quality management system List of ISO standards Conformity assessment International Organization for Standardization ...more...

ISO 13849 is a safety standard which deals with safety-related design principles of employed control systems to establish different safety Performance Levels (PL). It replaced EN 954-1 in December 2011. Part 1 defines the general principles for design. Part 2 describes the validation . References "Safety of machinery -- Safety-related parts of control systems -- Part 1: General principles for design" . ISO . Retrieved 31 October 2013 . "Safety and risk minimization in the operator control of plant machinery" . Plant Engineering. October 21, 2013 . Retrieved 31 October 2013 . ISO 13849 is a safety standard which deals with safety-related design principles of employed control systems to establish different safety Performance Levels (PL). It replaced EN 954-1 in December 2011. Part 1 defines the general principles for design. Part 2 describes the validation . References "Safety of machinery -- Safety-related parts of control systems -- Part 1: General principles for design" . ISO . Retrieved 31 October 2013 . ...more...

The SI base units Symbol Name Quantity A ampere electric current K kelvin temperature s second time m metre length kg kilogram mass cd candela luminous intensity mol mole amount of substance The International System of Units ( SI , abbreviated from the French Système international (d'unités) ) is the modern form of the metric system , and is the most widely used system of measurement . It comprises a coherent system of units of measurement built on seven base units ( ampere , kelvin , second , metre , kilogram , candela , mole ) and a set of twenty decimal prefixes to the unit names and unit symbols that may be used when specifying multiples and fractions of the units. The system also specifies names for 22 derived units for other common physical quantities like lumen, watt, etc. The base units, except for one, are derived from invariant constants of nature, such as the speed of light and triple point of water , which can be readily observed and measured with great accuracy. The kilogram standard of mass is a ...more...

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 ...more...

UTF-8 is a variable width character encoding capable of encoding all 1,112,064 valid code points in Unicode using one to four 8-bit bytes . The encoding is defined by the Unicode standard, and was originally designed by Ken Thompson and Rob Pike . The name is derived from Unicode (or Universal Coded Character Set) Transformation Format – 8-bit. It was designed for backward compatibility with ASCII . Code points with lower numerical values, which tend to occur more frequently, are encoded using fewer bytes. The first 128 characters of Unicode, which correspond one-to-one with ASCII, are encoded using a single octet with the same binary value as ASCII, so that valid ASCII text is valid UTF-8-encoded Unicode as well. Since ASCII bytes do not occur when encoding non-ASCII code points into UTF-8, UTF-8 is safe to use within most programming and document languages that interpret certain ASCII characters in a special way, such as " / " in filenames, " \ " in escape sequences , and "%" in printf . Shows the usag ...more...

In mathematics , the binary logarithm ( log n ) is the power to which the number 2 must be raised to obtain the value n . That is, for any real number x , For example, the binary logarithm of 1 is 0 , the binary logarithm of 2 is 1 , the binary logarithm of 4 is 2 , and the binary logarithm of 32 is 5 . The binary logarithm is the logarithm to the base 2 . The binary logarithm function is the inverse function of the power of two function. As well as log , alternative notations for the binary logarithm include lg , ld , lb (the notation preferred by ISO 31-11 and ISO 80000-2 ), and (with a prior statement that the default base is 2) log . Historically, the first application of binary logarithms was in music theory , by Leonhard Euler : the binary logarithm of a frequency ratio of two musical tones gives the number of octaves by which the tones differ. Binary logarithms can be used to calculate the length of the representation of a number in the binary numeral system , or the number of bits needed to encode ...more...

A Legal Entity Identifier (or LEI ) is a 20-character identifier that identifies distinct legal entities that engage in financial transactions. It is defined by ISO 17442 . Natural persons are not required to have an LEI; they’re eligible to have one issued, however, but only if they act in independent business capacity. The LEI is a global standard, designed to be non-proprietary data that is freely accessible to all. As of October 2017, over 630,000 legal entities from more than 195 countries have now been issued with LEIs. History The LEI system was developed by the G20 , in response to the inability of financial institutions to identify organisations uniquely, so that their financial transactions in different national jurisdictions can be fully tracked. The first LEIs were issued in December 2012. Code structure Structure of LEI codes 1 2 3 4 5 6 7 8 9 ... 18 19 20 LOU- Code Res- erved Entity- Identification Check- sum G.E. Financing GmbH 5493 00 84UKLVMY22DS 16 Jaguar Land Rover Ltd 2138 00 WSGIIZCX ...more...

Ludovico Arrighi 's early "chancery italic" typeface, c. 1527 . At that time italic was only used for the lower case and not for capitals. 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, 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 , flourish ...more...

A physical quantity is a physical property of a phenomenon , body, or substance, 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 : n u {\textstyle nu} where n {\textstyle n} is the magnitude and u {\textstyle u} is the unit. For example, 1.674 9275 × 10 kg (the mass of the neutron ), or 299 792 458 metres per second (the speed of light ). The same physical quantity x {\textstyle x} can be represented equivalently in many unit systems, i.e. x = n 1 u 1 = n 2 u 2 {\textstyle x=n_{1}u_{1}=n_{2}u_{2}} . Symbols, nomenclature Symbols for quantities should be chosen according to the international recommendations of ISO/IEC 80000 , the IUPAP red book and the IUPAC green book . For example, the recommended symbol for the physical quantity mass is m, and the recommended symbol for the quantity charge is Q. Subscripts and indices Subscripts are used for two reasons, to simply attach a name to t ...more...

A decimal separator is a symbol used to separate the integer part from the fractional part of a number written in decimal form. Different countries officially designate different symbols for the decimal separator. The choice of symbol for the decimal separator also affects the choice of symbol for the thousands separator used in digit grouping, so the latter is also treated in this article. It is often referred to by various other generic names, e.g., decimal mark , decimal marker , or decimal sign , or after the regional representation, e.g., decimal point . When the context is clear, it could also be called just comma (region-specific), or decimal (for ICAO -regulated air traffic control communications). In mathematics the decimal separator is a type of radix point , a term that also applies to number systems with bases other than ten. History In the Middle Ages , before printing, a bar ( ¯ ) over the units digit was used to separate the integral part of a number from its fractional part , e.g. 9 9 95 (mean ...more...

The red curve is the graph of a function f in the Cartesian plane , consisting of all points with coordinates of the form (x, f(x)) . The property of having one output for each input is represented geometrically by the fact that each vertical line (such as the yellow line through the origin) has exactly one crossing point with the curve. In mathematics , a function is a relation between a set of inputs and a set of permissible outputs with the property that each input is related to exactly one output. An example is the function that relates each real number x to its square x . The output of a function f corresponding to an input x is denoted by f(x) (read "f of x"). In this example, if the input is −3, then the output is 9, and we may write f(−3) = 9 . Likewise, if the input is 3, then the output is also 9, and we may write f(3) = 9 . (The same output may be produced by more than one input, but each input gives only one output.) The input variable(s) are sometimes referred to as the argument(s) of the functio ...more...

The flow of sand in an hourglass can be used to measure the passage of time. It also concretely represents the present as being between the past and the future . Time is the indefinite continued progress of existence and events that occur in apparently irreversible succession from the past through the present to the future . Time is a component quantity of various measurements used to sequence events, to compare the duration of events or the intervals between them, and to quantify rates of change of quantities in material reality or in the conscious experience . Time is often referred to as a fourth dimension , along with three spatial dimensions . Time has long been an important subject of study in religion, philosophy, and science, but defining it in a manner applicable to all fields without circularity has consistently eluded scholars. Nevertheless, diverse fields such as business, industry, sports, the sciences, and the performing arts all incorporate some notion of time into their respective ...more...

This article presents a timeline of binary prefixes used to name memory units, in comparison of decimal and binary prefixes for measurement of information and computer storage. Historically, computers have used two different approaches to memory addressing, binary and decimal. Early decimal computers included the ENIAC , UNIVAC 1 , IBM 702 , IBM 705 , IBM 650 , IBM 1400 series , and IBM 1620 . Early binary addressed computers included Zuse Z3 , Colossus , Whirlwind , AN/FSQ-7 , IBM 701 , IBM 704 , IBM 709 , IBM 7030 , IBM 7090 , IBM 7040 , IBM System/360 and DEC PDP series . Decimal systems typically had memory configured in whole decimal multiples, e.g., blocks of 100 and later 1,000. The unit abbreviation 'K' or 'k' if it was used, represented multiplication by 1,000. Binary machine memory had sizes of powers of two or small multiples thereof. In this context, 'K' or 'k' was sometimes used to denote multiples of 1,024 units or just the approximate size, e.g., either '64K' or '65K' for 65,536 (2 ). 1790s 17 ...more...

Javascript Version

Revolvy Server https://www.revolvy.com