ISO 31-0

ISO 31-0 is the introductory part of international standard ISO 31 on quantities and units. It provides guidelines for using physical quantities, quantity and unit symbols, and coherent unit systems, especially the SI. It is intended for use in all fields of science and technology and is augmented by more specialized conventions defined in other parts of the ISO 31 standard. ISO 31-0 was withdrawn on 17 November 2009. It is superseded by ISO 80000-1. Other parts of ISO 31 have also been withdrawn and replaced by parts of ISO 80000.

Scope

ISO 31 covers only physical quantities used for the quantitative description of physical phenomena. It does not cover conventional scales (e.g., Beaufort scale, Richter scale, colour intensity scales), results of conventional tests, currencies, or information content. The presentation here is only a brief summary of some of the detailed guidelines and examples given in the standard.

Quantities and units

Physical quantities can be grouped into mutually comparable categories. For example, length, width, diameter and wavelength are all in the same category, that is they are all quantities of the same kind. One particular example of such a quantity can be chosen as a reference quantity, called the unit, and then all other quantities in the same category can be expressed in terms of this unit, multiplied by a number called the numerical value. For example, if we write

the wavelength is λ = 6.982 × 10−7 m

then "λ" is the symbol for the physical quantity (wavelength), "m" is the symbol for the unit (metre), and "6.982 × 10−7" is the numerical value of the wavelength in metres.

More generally, we can write

A = {A} ⋅ [A]

where A is the symbol for the quantity, {A} symbolizes the numerical value of A, and [A] represents the corresponding unit in which A is expressed here. Both the numerical value and the unit symbol are factors, and their product is the quantity. A quantity itself has no inherent particular numerical value or unit; as with any product, there are many different combinations of numerical value and unit that lead to the same quantity (e.g., A = 300 ⋅ m = 0.3 ⋅ km = ...). This ambiguity makes the {A} and [A] notations useless, unless they are used together.

The value of a quantity is independent of the unit chosen to represent it. It must be distinguished from the numerical value of the quantity that occurs when the quantity is expressed in a particular unit. The above curly-bracket notation could be extended with a unit-symbol index to clarify this dependency, as in {λ} = 6.982 × 10−7 or equivalently {λ} = 698.2. In practice, where it is necessary to refer to the numerical value of a quantity expressed in a particular unit, it is notationally more convenient to simply divide the quantity through that unit, as in

λ/m = 6.982 × 10−7

or equivalently

λ/nm = 698.2.

This is a particularly useful and widely used notation for labelling the axes of graphs or for the headings of table columns, where repeating the unit after each numerical value can be typographically inconvenient.

Typographic conventionsSymbols for quantities
  • Quantities are generally represented by a symbol formed from single letters of the Latin or Greek alphabet.
  • Symbols for quantities are set in italic type, independent of the type used in the rest of the text.
  • If in a text different quantities use the same letter symbol, they can be distinguished via subscripts.
  • A subscript is only set in italic type if it consists of a symbol for a quantity or a variable. Other subscripts are set in upright (roman) type. For example, write V for a "nominal volume" (where "n" is just an abbreviation for the word "nominal"), but write V if n is a running index number.
Names and symbols for units
  • If an internationally standardized symbol exists for a unit, then only that symbol should be used. See the SI articles for the list of standard symbols defined by the International System of Units. Note that the distinction between uppercase and lowercase letters is significant for SI unit symbols. For example, "k" is the prefix kilo and "K" stands for the unit kelvin. The symbols of all SI units named after a person or a place start with an uppercase letter, as do the symbols of all prefixes from mega on upwards. All other symbols are lowercase; the only exception is litre, where both l and L are allowed. However, it is stated that the CIPM will examine whether one of the two may be suppressed.
  • Symbols for units should be printed in an upright (roman) typeface.
Numbers

See Sect. 3.3 of the Standard text.

  • Numbers should be printed in upright (roman) type.
  • ISO 31-0 (after Amendment 2) specifies that "the decimal sign is either the comma on the line or the point on the line". This follows resolution 10[1] of the 22nd CGPM, 2003.[2]
For example, one divided by two (one half) may be written as 0.5 or 0,5.
  • Numbers consisting of long sequences of digits can be made more readable by separating them into groups, preferably groups of three, separated by a small space. For this reason, ISO 31-0 specifies that such groups of digits should never be separated by a comma or point, as these are reserved for use as the decimal sign.
For example, one million (1000000) may be written as 1 000 000.
  • For numbers whose magnitude is less than 1, the decimal sign should be preceded by a zero.
  • The multiplication sign is either a cross or a half-height dot, though the latter should not be used when the dot is the decimal separator.
Expressions
  • Unit symbols follow the numerical value in the expression of a quantity.
  • Numerical value and unit symbol are separated by a space. This rule also applies to the symbol "°C" for degrees Celsius, as in "25 °C". The only exception are the symbols for the units of plane angle degree, minute and second, which follow the numerical value without a space in between (for example "30°").
  • Where quantities are added or subtracted, parenthesis can be used to distribute a unit symbol over several numerical values, as in
T = 25 °C − 3 °C = (25 − 3) °C
P = 100 kW ± 5 kW = (100 ± 5) kW
(but not: 100 ± 5 kW)
d = 12 × (1 ± 10−4) m
  • Products can be written as ab, a b, a⋅b, or a×b. The sign for multiplying numbers is a cross (×) or a half-height dot (⋅). The cross should be used adjacent to numbers if a dot on the line is used as the decimal separator, to avoid confusion between a decimal dot and a multiplication dot.
  • Division can be written as a b {\displaystyle {\frac {a}{b}}} , a/b, or by writing the product of a and b−1, for example a⋅b−1. Numerator or denominator can themselves be products or quotients, but in this case, a solidus (/) should not be followed by a multiplication sign or division sign on the same line, unless parentheses are used to avoid ambiguity.
Mathematical signs and symbols

A comprehensive list of internationally standardized mathematical symbols and notations can be found in ISO 31-11.

See also References
  1. "Resolution 10", 22nd General Conference on Weights and Measures, BIPM.
  2. Brief reference to the history, NIST.
Bibliography
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ISO 31-0

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ISO 31-0

ISO 31-0 is the introductory part of international standard ISO 31 on quantities and units. It provides guidelines for using physical quantities, quantity and unit symbols, and coherent unit systems, especially the SI. It is intended for use in all fields of science and technology and is augmented by more specialized conventions defined in other parts of the ISO 31 standard. ISO 31-0 was withdrawn on 17 November 2009. It is superseded by ISO 80000-1. Other parts of ISO 31 have also been withdrawn and replaced by parts of ISO 80000. Scope ISO 31 covers only physical quantities used for the quantitative description of physical phenomena. It does not cover conventional scales (e.g., Beaufort scale, Richter scale, colour intensity scales), results of conventional tests, currencies, or information content. The presentation here is only a brief summary of some of the detailed guidelines and examples given in the standard. Quantities and units Physical quantities can be grouped into mutually comparable categories. ...more...

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ISO 31

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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. 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...

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ISO 31-11

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ISO 31-11

ISO 31-11:1992 was the part of international standard ISO 31 that defines mathematical signs and symbols for use in physical sciences and technology. It was superseded in 2009 by ISO 80000-2.[1] Its definitions include the following:[2] Mathematical logic Sign Example Name Meaning and verbal equivalent Remarks ∧ p ∧ q conjunction sign p and q ∨ p ∨ q disjunction sign p or q (or both) ¬ ¬ p negation sign negation of p; not p; non p ⇒ p ⇒ q implication sign if p then q; p implies q Can also be written as q ⇐ p. Sometimes → is used. ∀ ∀x∈A p(x) (∀x∈A) p(x) universal quantifier for every x belonging to A, the proposition p(x) is true The "∈A" can be dropped where A is clear from context. ∃ ∃x∈A p(x) (∃x∈A) p(x) existential quantifier there exists an x belonging to A for which the proposition p(x) is true The "∈A" can be dropped where A is clear from context. ∃! is used where exactly one x exists for which p(x) is true. Sets Sign Example Meaning and verbal equivalent Remarks ...more...

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ISO 31-5

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ISO 31-5

ISO 31-5 is the part of international standard ISO 31 that defines names and symbols for quantities and units related to electricity and magnetism. It is superseded by ISO 80000-6. Some of its definitions are below, with values taken from NIST values of the constants: Name Symbol Definition Value Speed of light in vacuum c 299 792 458 m s−1 299 792 458 m s−1 Magnetic constant μ 4π × 10−7 N A−2 12.566 370 614... x 10−7 N A−2 Electric constant ε 1 μ 0 c 0 2 {\displaystyle {\begin{matrix}{\frac {1}{\mu _{0}{c_{0}}^{2}}}\end{matrix}}} 8.854 187 817... x 10−12 F m−1 Characteristic impedance of vacuum Z μ c 376.730 313 461...Ω ...more...

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ISO 31-10

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ISO 31-10

ISO 31-10 is the part of international standard ISO 31 that defines names and symbols for quantities and units related to nuclear reactions and ionizing radiations. It gives names and symbols for 70 quantities and units. Where appropriate, conversion factors are also given. Its definitions include: Quantity Unit Remarks Name Symbol Definition Name Symbol Definition ⋮ activity A Expectation value of the number of spontaneous nuclear transitions from a particular energy state occurring in an amount of radionuclide in a small time interval, divided by that time interval becquerel Bq 1 Bq = 1/s The becquerel is a special name for second to the power minus one, to be used as the SI unit of activity.curie: 1 Ci = 3.7×1010 Bq (exactly) ⋮ absorbed dose D For any ionizing radiation, the mean energy imparted to an element of irradiated matter divided by the mass of this element grey Gy 1 Gy = 1 J/kg The grey is a special name for joule per kilogram, to be used as the SI unit for absorbed dose.rad: 1 rad = ...more...

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ISO 31-4

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ISO 31-4

ISO 31-4 is the part of international standard ISO 31 that defines names and symbols for quantities and units related to heat. It is superseded by ISO 80000-5. Its definitions include: Quantity Unit Remarks Name Symbol Name Symbol Definition thermodynamic temperature T, (Θ) kelvin K The kelvin is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water. For practical measurements, the International Temperature Scale of 1990 defines several fixed points and interpolation procedures. Celsius temperature t, φ degree Celsius °C The degree Celsius is a special name for the unit kelvin, for use in stating values of Celsius temperature. t = T − T, where T = 273.15 K linear expansion coefficient α reciprocal kelvin, kelvin to the power negative 1 K−1 α l = 1 l l T {\displaystyle \alpha _{l}={\frac {1}{l}}{\frac {l}{T}}} ... Annex A of ISO 31-4 lists units of heat based on the foot, pound and second and some other units, including the degree Rankine, ...more...

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ISO 31-7

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ISO 31-7

ISO 31-7 is the part of international standard ISO 31 that defines names and symbols for quantities and units related to acoustics. It is superseded by ISO 80000-8. Its definitions include: Quantity Unit Remarks Name Symbol Definition Name Symbol period, periodic time T time of one cycle second s frequency f, ν f = 1/T hertz Hz 1 Hz = 1 s−1 . . . loudness level L L = ln(p/p) where p is the root-mean-square value of the sound pressure of a pure tone of 1 kHz, which is judged by a normal observer under standardized listening conditions as being as loud as the sound under investigation, and where p = 20 µPa phon The loudness level is 1 phon if 20 log(p/p)=1, that is for a pure tone of frequency 1 kHz, 1 phon = 1 dB sound pressure level. This is not a purely physical quantity and unit, as it involves the subjective evaluation by humans. loudness N A normal observer's auditory estimate of the ratio between the strength of the sound considered and that of a reference sound having a loudnes ...more...

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ISO 31-8

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ISO 31-8

ISO 31-8 is the part of international standard ISO 31 that defines names and symbols for quantities and units related to physical chemistry and molecular physics. Quantities and units Quantity Unit Remarks Name Symbol Definition Name Symbol relative atomic mass A Ratio of the average mass per atom of an element to 1/12 of the mass of an atom of the nuclide 12C one 1 Formerly called atomic/molecular weight. Example: A(Cl) = 35.453. Both quantities depend on the nuclidic composition. relative molecular mass M Ratio of the average mass per molecule or specified entity of a substance to 1/12 of the mass of an atom of the nuclide 12C number of molecules or other elementary entities N Number of molecules or other elementary entities in a system one 1 amount of substance n, (ν) mole mol The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kg of 12C. When the mole is used, the elementary entities must be specified and may be atoms, mole ...more...

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ISO 8601

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ISO 8601

ISO 8601 Data elements and interchange formats – Information interchange – Representation of dates and times is an international standard covering the exchange of date- and time-related data. It was issued by the International Organization for Standardization (ISO) and was first published in 1988. The purpose of this standard is to provide an unambiguous and well-defined method of representing dates and times, so as to avoid misinterpretation of numeric representations of dates and times, particularly when data are transferred between countries with different conventions for writing numeric dates and times. In general, ISO 8601 applies to representations and formats of dates in the Gregorian (and potentially proleptic Gregorian) calendar, times based on the 24-hour timekeeping system (including optional time zone information), time intervals and combinations thereof.[1] The standard does not assign any specific meaning to elements of the date/time to be represented; the meaning will depend on the context of ...more...

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ISO/IEC 80000

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ISO/IEC 80000

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] Areas The standard has 14 parts.[2] Mechanics 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] Thermodynamics ISO 80000-5:2007 supersedes ISO 31-4[5] which "gives nam ...more...

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ISO 80000-1

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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.[1] 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. Contents list The standard is divided into the following chapters: Foreword Introduction Scope Normative references Terms and definitions Quantities Dimensions Units Printing rules Annex A (normative) – Terms in names for physical quantities Annex B (normative) – Rounding of numbers Annex C (normative) – Logarithmic quantities and their units Annex D (informative) – International organizations in the field of quantities and units Scope ISO 80000-1 gives "gener ...more...

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ISO 80000-3

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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.[1] It is a part of the group of standards called ISO/IEC 80000, which together form the International System of Quantities. Contents list The standard is divided into the following chapters: Foreword Introduction Scope Normative references Names, symbols and definitions Annex A (informative) Units in the CGS system with special names Annex B (informative) Units based on the foot, pound, second, and some other related units Annex C (informative) Other non-SI units given for information, especially regarding the conversion factors Names, symbols and definitionsSpace and timeSpace ISO 80000-3:2006 assigns names and symbols to quantities and units of space and time, and defines these quantities and units. For example, Units of length, area and volume metre (symbol m): "length of the path travelled by light in vacuum during a time interval of 1/(299 792 458) of a secon ...more...

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ISO 4217

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ISO 4217

An airline ticket showing the price in the ISO 4217 code "EUR" (bottom left) and not the currency sign € Find a currency Enter an ISO 4217 code to find the corresponding currency article   ISO 4217 is a standard first published by International Organization for Standardization in 1978, which delineates currency designators, country codes (alpha and numeric), and references to minor units in three tables: Table A.1 – Current currency & funds code list[1] Table A.2 – Current funds codes[2] Table A.3 – List of codes for historic denominations of currencies & funds[3] The tables, history and ongoing discussion are maintained by SIX Interbank Clearing on behalf of ISO and the Swiss Association for Standardization.[4] The ISO 4217 code list is used in banking and business globally. In many countries the ISO codes for the more common currencies are so well known publicly that exchange rates published in newspapers or posted in banks use only these to delineate the different cur ...more...

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ISO 9000

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ISO 9000

The ISO 9000 family of quality management systems standards is designed to help organizations ensure that they meet the needs of customers and other stakeholders while meeting statutory and regulatory requirements related to a product or service.[1] ISO 9000 deals with the fundamentals of quality management systems,[2] including the seven quality management principles upon which the family of standards is based.[2] [3][4] ISO 9001 deals with the requirements that organizations wishing to meet the standard must fulfil.[5] Third-party certification bodies provide independent confirmation that organizations meet the requirements of ISO 9001. Over one million organizations worldwide[6] are independently certified, making ISO 9001 one of the most widely used management tools in the world today. However, the ISO certification process has been criticized[7][8] as being wasteful and not being useful for all organizations.[9][10] Background ISO 9000 was first published in 1987 by ISO (International Organization for ...more...

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List of International Organization for Standardization standards

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List of International Organization for Standardization standards

This is a list of published[Note 1] International Organization for Standardization (ISO) standards and other deliverables.[Note 2] For a complete and up-to-date list of all the ISO standards, see the ISO catalogue.[1] 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.[2] 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/pr ...more...

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Percentage

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Percentage

A pie chart showing the percentage by web browser visiting Wikimedia sites (April 2009 to 2012) In mathematics, a percentage is a number or ratio expressed as a fraction of 100. It is often denoted using the percent sign, "%", or the abbreviations "pct.", "pct"; sometimes the abbreviation "pc" is also used.[1] A percentage is a dimensionless number (pure number). Examples For example, 45% (read as "forty-five percent") is equal to ​45⁄, 45:100, or 0.45. Percentages are often used to express a proportionate part of a total. (Similarly, one can express a number as a fraction of 1,000 using the term "per mille" or the symbol "‰".) Example 1 If 50% of the total number of students in the class are male, that means that 50 out of every 100 students are male. If there are 500 students, then 250 of them are male. Example 2 An increase of $0.15 on a price of $2.50 is an increase by a fraction of 0.15/2.50 = 0.06. Expressed as a percentage, this is a 6% increase. While many percentage values are between 0 and 10 ...more...

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ISO week date

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ISO week date

The ISO week date system is effectively a leap week calendar system that is part of the ISO 8601 date and time standard issued by the International Organization for Standardization (ISO) since 1988 (last revised in 2004) and, before that, it was defined in ISO (R) 2015 since 1971. It is used (mainly) in government and business for fiscal years, as well as in timekeeping. This was previously known as "Industrial date coding". The system specifies a week year atop the Gregorian calendar by defining a notation for ordinal weeks of the year. The Gregorian leap cycle, which has 97 leap days spread across 400 years, contains a whole number of weeks (20871). In every cycle there are 71 years with an additional 53rd week (corresponding to the Gregorian years that contain 53 Thursdays). An average year is exactly 52.1775 weeks long; months (1/12 year) average at exactly 4.348125 weeks. An ISO week-numbering year (also called ISO year informally) has 52 or 53 full weeks. That is 364 or 371 days instead of the usual 3 ...more...

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ISO 8583

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ISO 8583

ISO 8583 is an international standard for financial transaction card originated interchange messaging. It is the International Organization for Standardization standard for systems that exchange electronic transactions initiated by cardholders using payment cards. ISO 8583 defines a message format and a communication flow so that different systems can exchange these transaction requests and responses. The vast majority of transactions made when a customer uses a card to make a payment in a store (EFTPOS) use ISO 8583 at some point in the communication chain, as do transactions made at ATMs. In particular, both the MasterCard and Visa networks base their authorization communications on the ISO 8583 standard, as do many other institutions and networks. Although ISO 8583 defines a common standard, it is not typically used directly by systems or networks. It defines many standard fields (data elements) which remain the same in all systems or networks, and leaves a few additional fields for passing network-speci ...more...

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C0 and C1 control codes

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C0 and C1 control codes

The C0 and C1 control code or control character sets define control codes for use in text by computer systems that use the ISO/IEC 2022 system of specifying control and graphic characters. Most character encodings, in addition to representing printable characters, also have characters such as these that represent additional information about the text, such as the position of a cursor, an instruction to start a new line, or a message that the text has been received. The C0 set defines codes in the range 00–1F and the C1 set defines codes in the range 80–9F. The default C0 set was originally defined in ISO 646 (ASCII), while the default C1 set was originally defined in ECMA-48 (harmonized later with ISO 6429). While other C0 and C1 sets are available for specialized applications, they are rarely used. Encoding interoperability While the C1 control characters are used in conjunction with the ISO/IEC 8859 series of graphical character sets among others, they are rarely used directly, except on specific platform ...more...

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ISO 216

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ISO 216

ISO 216 specifies international standard (ISO) paper sizes used in most countries in the world today, although not in Canada, the United States, Mexico, or the Dominican Republic. The standard defines the "A" and "B" series of paper sizes, including A4, the most commonly available size. Two supplementary standards, ISO 217 and ISO 269, define related paper sizes; the ISO 269 "C" series is commonly listed alongside the A and B sizes. All ISO 216, ISO 217 and ISO 269 paper sizes (except some envelopes) have the same aspect ratio, √2:1, within rounding to millimetres. This ratio has the unique property that when cut or folded in half widthways, the halves also have the same aspect ratio. Each ISO paper size is one half of the area of the next larger size in the same series. Dimensions of A, B and C Series ISO/DIN paper sizes in millimetres and in inches Size A series formats B series formats C series formats mm inches mm inches mm inches 0 0841 × 1189 33.1 × 46.8 1000 × 1414 39.4 × 55.7 0917 × 1297 36 ...more...

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ISO/IEC 8859-8

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ISO/IEC 8859-8

ISO/IEC 8859-8, Information technology — 8-bit single-byte coded graphic character sets — Part 8: Latin/Hebrew alphabet, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings. ISO/IEC 8859-8:1999 from 1999 represents its second and current revision, preceded by the first edition ISO/IEC 8859-8:1988 in 1988. It is informally referred to as Latin/Hebrew. ISO/IEC 8859-8 covers all the Hebrew letters, but no Hebrew vowel signs. IBM assigned code page 916 to it.[1] ISO-8859-8 is the IANA preferred charset name for this standard when supplemented with the C0 and C1 control codes from ISO/IEC 6429. The text is (usually) in logical order, so bidi processing is required for display. Nominally ISO-8859-8 (code page 28598) is for “visual order”, and ISO-8859-8-I (code page 38598) is for logical order. But usually in practice, and required for HTML and XML documents, ISO-8859-8 also stands for logical order text. There is also ISO-8859-8-E which supposedly requires directionality to be explicitl ...more...

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ISO/IEC 8859

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ISO/IEC 8859

ISO/IEC 8859 is a joint ISO and IEC series of standards for 8-bit character encodings. The series of standards consists of numbered parts, such as ISO/IEC 8859-1, ISO/IEC 8859-2, etc. There are 15 parts, excluding the abandoned ISO/IEC 8859-12. The ISO working group maintaining this series of standards has been disbanded. ISO/IEC 8859 parts 1, 2, 3, and 4 were originally Ecma International standard ECMA-94. Introduction While the bit patterns of the 95 printable ASCII characters are sufficient to exchange information in modern English, most other languages that use Latin alphabets need additional symbols not covered by ASCII. ISO/IEC 8859 sought to remedy this problem by utilizing the eighth bit in an 8-bit byte to allow positions for another 96 printable characters. Early encodings were limited to 7 bits because of restrictions of some data transmission protocols, and partially for historical reasons. However, more characters were needed than could fit in a single 8-bit character encoding, so several mappi ...more...

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Decimal separator

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Decimal separator

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. 9995 (meaning, ...more...

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ISO basic Latin alphabet

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ISO basic Latin alphabet

The ISO basic Latin alphabet is a Latin-script alphabet and consists of two sets of 26 letters, codified in[1] various national and international standards and used widely in international communication. The two sets contain the following 26 letters each:[1][2] ISO basic Latin alphabet Uppercase Latin alphabet A B C D E F G H I J K L M N O P Q R S T U V W X Y Z Lowercase Latin alphabet a b c d e f g h i j k l m n o p q r s t u v w x y z History By the 1960s it became apparent to the computer and telecommunications industries in the First World that a non-proprietary method of encoding characters was needed. The International Organization for Standardization (ISO) encapsulated the Latin script in their (ISO/IEC 646) 7-bit character-encoding standard. To achieve widespread acceptance, this encapsulation was based on popular usage. The standard was based on the already published American Standard Code for Information Interchange, better known as ASCII, which included in the character set the 26 × 2 lette ...more...

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ISO/IEC 8859-9

topic

ISO/IEC 8859-9

ISO/IEC 8859-9:1999, Information technology — 8-bit single-byte coded graphic character sets — Part 9: Latin alphabet No. 5, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings, first edition published in 1989. It is informally referred to as Latin-5 or Turkish. It was designed to cover the Turkish language, designed as being of more use than the ISO/IEC 8859-3 encoding. It is identical to ISO/IEC 8859-1 except for these six replacements of Icelandic characters with characters unique to the Turkish alphabet: Position 0xD0 0xDD 0xDE 0xF0 0xFD 0xFE 8859-9 Ğ İ Ş ğ ı ş 8859-1 Ð Ý Þ ð ý þ ISO-8859-9 is the IANA preferred charset name for this standard when supplemented with the C0 and C1 control codes from ISO/IEC 6429. In modern applications Unicode and UTF-8 are preferred. 0.1% of all web pages use ISO-8859-9 in February 2016.[1][2] Microsoft has assigned code page 28599 a.k.a. Windows-28599 to ISO-8859-9 in Windows. IBM has assigned Code page 920 to ISO-8859-9. Codepage lay ...more...

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ISO 6346

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ISO 6346

ISO-code and dimension/load table at several newly washed containers ISO 6346 is an international standard covering the coding, identification and marking of intermodal (shipping) containers used within containerized intermodal freight transport.[1] The standard establishes a visual identification system for every container that includes a unique serial number (with check digit), the owner, a country code, a size, type and equipment category as well as any operational marks. The standard is managed by the International Container Bureau (BIC). Identification System Example of an ISO 6346 compliant container number: BIC code on the end of a shipping container The illustrated example is a code for a container owned by Hapag-Lloyd AG.[2] Owner Code The owner code consists of three capital letters of the Latin alphabet to indicate the owner or principal operator of the container. Such code needs to be registered at the Bureau International des Conteneurs in Paris to ensure uniqueness worldwide. An o ...more...

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Paper size

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Paper size

A size chart illustrating the ISO A series and a comparison with American letter and legal formats. Comparison of some paper and photographic paper sizes close to the A4 size. Many paper size standards conventions have existed at different times and in different countries. Today, the A and B series of ISO 216, which includes the commonly used A4 size, are the international standard used by almost every country. However, in many countries in the Americas as well as in the Philippines, the North American series of paper sizes such as 'Letter' is more prevalent.[1] Paper sizes affect writing paper, stationery, cards, and some printed documents. The international standard for envelopes is the C series of ISO 269. International paper sizes Map of the world showing adoption of ISO A4 (blue) vs. US-Letter (red) The international paper size standard is ISO 216. It is based on the German DIN 476 standard for paper sizes. ISO paper sizes are all based on a single aspect ratio of the square root of 2, or ...more...

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Year zero

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Year zero

Year zero does not exist in the Anno Domini system usually used to number years in the Gregorian calendar and in its predecessor, the Julian calendar. In this system, the year 1 BC is followed by AD 1. However, there is a year zero in astronomical year numbering (where it coincides with the Julian year 1 BC) and in ISO 8601:2004 (where it coincides with the Gregorian year 1 BC) as well as in all Buddhist and Hindu calendars. Historical, astronomical and ISO year numbering systemsHistorians The Anno Domini era was introduced in 525 by Scythian monk Dionysius Exiguus (c. 470–c. 544), who used it to identify the years on his Easter table. He introduced the new era to avoid using the Diocletian era, based on the accession of Roman Emperor Diocletian, as he did not wish to continue the memory of a persecutor of Christians. In the preface to his Easter table, Dionysius stated that the "present year" was "the consulship of Probus Junior [Flavius Anicius Probus Iunior]" which was also 525 years "since the incarnatio ...more...

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MPEG-4

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MPEG-4

MPEG-4 is a method of defining compression of audio and visual (AV) digital data. It was introduced in late 1998 and designated a standard for a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group (MPEG) (ISO/IEC JTC1/SC29/WG11) under the formal standard ISO/IEC 14496 – Coding of audio-visual objects. Uses of MPEG-4 include compression of AV data for web (streaming media) and CD distribution, voice (telephone, videophone) and broadcast television applications. Background MPEG-4 absorbs many of the features of MPEG-1 and MPEG-2 and other related standards, adding new features such as (extended) VRML support for 3D rendering, object-oriented composite files (including audio, video and VRML objects), support for externally specified Digital Rights Management and various types of interactivity. AAC (Advanced Audio Coding) was standardized as an adjunct to MPEG-2 (as Part 7) before MPEG-4 was issued. MPEG-4 is still an evolving standard and is di ...more...

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C++

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C++

C++ ( "see plus plus") is a general-purpose programming language. It has imperative, object-oriented and generic programming features, while also providing facilities for low-level memory manipulation. It was designed with a bias toward system programming and embedded, resource-constrained and large systems, with performance, efficiency and flexibility of use as its design highlights.[6] C++ has also been found useful in many other contexts, with key strengths being software infrastructure and resource-constrained applications,[6] including desktop applications, servers (e.g. e-commerce, web search or SQL servers), and performance-critical applications (e.g. telephone switches or space probes).[7] C++ is a compiled language, with implementations of it available on many platforms. Many vendors provide C++ compilers, including the Free Software Foundation, Microsoft, Intel, and IBM. C++ is standardized by the International Organization for Standardization (ISO), with the latest standard version ratified and p ...more...

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ISO/IEC 42010

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ISO/IEC 42010

ISO/IEC/IEEE 42010 Systems and software engineering — Architecture description is an international standard for architecture descriptions of systems and software. Overview ISO/IEC/IEEE 42010:2011 defines requirements on the description of system, software and enterprise architectures. It aims to standardise the practice of architecture description by defining standard terms, presenting a conceptual foundation for expressing, communicating and reviewing architectures and specifying requirements that apply to architecture descriptions, architecture frameworks and architecture description languages. Following its predecessor, IEEE Std 1471, the standard makes a strict distinction between Architectures and Architecture Descriptions. The description of ISO/IEC/IEEE 42010 in this article is based upon the standard published in 2011.[1] Terminology ISO/IEC 42010 defines a number of terms: architecting: process of conceiving, defining, expressing, documenting, communicating, certifying proper implementation of ...more...

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ISO/IEC 8859-3

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ISO/IEC 8859-3

ISO/IEC 8859-3:1999, Information technology — 8-bit single-byte coded graphic character sets — Part 3: Latin alphabet No. 3, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings, first edition published in 1988. It is informally referred to as Latin-3 or South European. It was designed to cover Turkish, Maltese and Esperanto, though the introduction of ISO/IEC 8859-9 superseded it for Turkish. The encoding remains popular with users of Esperanto, though use is waning as application support for Unicode becomes more common. ISO-8859-3 is the IANA preferred charset name for this standard when supplemented with the C0 and C1 control codes from ISO/IEC 6429. Microsoft has assigned code page 28593 a.k.a. Windows-28593 to ISO-8859-3 in Windows. IBM has assigned code page 913 to ISO 8859-3. Codepage layout Legend:   Alphabetic   Control character   Numeric digit   Punctuation   Extended punctuation   Graphic character   International   Undefined ISO/IEC 8859-3 _0 _1 _2 ...more...

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Film speed

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Film speed

Film speed is the measure of a photographic film's sensitivity to light, determined by sensitometry and measured on various numerical scales, the most recent being the ISO system. A closely related ISO system is used to describe the relationship between exposure and output image lightness in digital cameras. Relatively insensitive film, with a correspondingly lower speed index, requires more exposure to light to produce the same image density as a more sensitive film, and is thus commonly termed a slow film. Highly sensitive films are correspondingly termed fast films. In both digital and film photography, the reduction of exposure corresponding to use of higher sensitivities generally leads to reduced image quality (via coarser film grain or higher image noise of other types). In short, the higher the sensitivity, the grainier the image will be. Ultimately sensitivity is limited by the quantum efficiency of the film or sensor. This film container denotes its speed as ISO 100/21°, including both arithme ...more...

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Percent sign

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Percent sign

The percent (per cent) sign (%) is the symbol used to indicate a percentage, a number or ratio as a fraction of 100. Related signs include the permille (per thousand) sign ‰ and the permyriad (per ten thousand) sign ‱ (also known as a basis point), which indicate that a number is divided by one thousand or ten thousand respectively. Higher proportions use parts-per notation. Correct styleSpacing English style guides prescribe writing the number and percent sign without any space between.[1][2][3][4][5][6][7] However, the International System of Units and ISO 31-0 standard prescribe a space between the number and percent sign,[8][9][10] in line with the general practice of using a non-breaking space between a numerical value and its corresponding unit of measurement. Other languages have other rules for spacing in front of the percent sign: In Czech, the percent sign is spaced with a non-breaking space if the number is used as a noun,[11] whereas no space is inserted if the number is used as an adjective ( ...more...

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International Bank Account Number

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International Bank Account Number

A typical British bank statement header (from a fictitious bank), showing the location of the account's IBAN The International Bank Account Number (IBAN) is an internationally agreed system of identifying bank accounts across national borders to facilitate the communication and processing of cross border transactions with a reduced risk of transcription errors. It was originally adopted by the European Committee for Banking Standards (ECBS), and later as an international standard under ISO 13616:1997. The current standard is ISO 13616:2007, which indicates SWIFT as the formal registrar. Initially developed to facilitate payments within the European Union, it has been implemented by most European countries and numerous countries in the other parts of the world, mainly in the Middle East and in the Caribbean. As of February 2016, 69 countries were using the IBAN numbering system.[1] The IBAN consists of up to 34 alphanumeric characters comprising: a country code; two check digits; and a number that includes ...more...

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Italic type

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Italic type

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.[1][2] 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".[3] 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...

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MPEG-2

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MPEG-2

MPEG-2 is used in Digital Video Broadcast and DVDs. The MPEG transport stream, TS, and MPEG program stream, PS, are container formats. MPEG-2 (a.k.a. H.222/H.262 as defined by the ITU) is a standard for "the generic coding of moving pictures and associated audio information".[1] It describes a combination of lossy video compression and lossy audio data compression methods, which permit storage and transmission of movies using currently available storage media and transmission bandwidth. While MPEG-2 is not as efficient as newer standards such as H.264/AVC and H.265/HEVC, backwards compatibility with existing hardware and software means it is still widely used, for example in over-the-air digital television broadcasting and in the DVD-Video standard. Main characteristics MPEG-2 is widely used as the format of digital television signals that are broadcast by terrestrial (over-the-air), cable, and direct broadcast satellite TV systems. It also specifies the format of movies and other programs that are distrib ...more...

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Typographical conventions in mathematical formulae

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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 part ...more...

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ISO/IEC 646

topic

ISO/IEC 646

ISO/IEC 646 is the name of a set of ISO standards, described as Information technology — ISO 7-bit coded character set for information interchange and developed in cooperation with ASCII at least since 1964.[1][2] Since its first edition in 1967[3] it has specified a 7-bit character code from which several national standards are derived. ISO/IEC 646 was also ratified by ECMA as ECMA-6. The first version of ECMA-6 had been published in 1965,[4] based on work the ECMA's Technical Committee TC1 had carried out since December 1960.[4] Characters in the ISO/IEC 646 Basic Character Set are invariant characters.[5] Since that portion of ISO/IEC 646, that is the invariant character set shared by all countries, specified only those letters used in the ISO basic Latin alphabet, countries using additional letters needed to create national variants of ISO 646 to be able to use their native scripts. Since transmission and storage of 8-bit codes was not standard at the time, the national characters had to be made to fit ...more...

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Vehicle identification number

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Vehicle identification number

VIN on a Chinese moped VIN on a 1996 Porsche 993 GT2 VIN visible in the windshield VIN is recorded in Vehicle License of China. A vehicle identification number (VIN) is a unique code, including a serial number, used by the automotive industry to identify individual motor vehicles, towed vehicles, motorcycles, scooters and mopeds, as defined in ISO 3779:2009. VINs were first used in 1954 in the United States.[1] From 1954 to 1981, there was no accepted standard for these numbers, so different manufacturers used different formats. In 1981, the National Highway Traffic Safety Administration of the United States standardized the format.[1] It required all on-road vehicles sold to contain a 17-character VIN, which does not include the letters I (i), O (o), and Q (q) (to avoid confusion with numerals 1 and 0). There are vehicle history services in several countries that help potential car owners use VINs to find vehicles that are defective or have been written off. See the Used car article ...more...

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ISO/IEC 8859-11

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ISO/IEC 8859-11

ISO/IEC 8859-11:2001, Information technology — 8-bit single-byte coded graphic character sets — Part 11: Latin/Thai alphabet, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings, first edition published in 2001. It is informally referred to as Latin/Thai. It is nearly identical to the national Thai standard TIS-620 (1990). The sole difference is that ISO/IEC 8859-11 allocates non-breaking space to code 0xA0, while TIS-620 leaves it undefined. (In practice, this small distinction is usually ignored.) ISO-8859-11 is not a main registered IANA charset name despite following the normal pattern for IANA charsets based on the ISO 8859 series. However, it is defined as an alias[1] of the close equivalent TIS-620 (which lacks the non-breaking space), and which can without problems be used for ISO/IEC 8859-11, since the no-break space has a code which was unallocated in TIS-620. Microsoft has assigned code page 28601 a.k.a. Windows-28601 to ISO-8859-11 in Windows.[2] A draft had the Thai le ...more...

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ISO 9660

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ISO 9660

ISO 9660 is a file system for optical disc media. Being published by the International Organization for Standardization (ISO) the file system is considered an international technical standard. Since the specification is available for anybody to purchase,[1] implementations have been written for many operating systems. History ISO 9660 traces its roots to the High Sierra Format file system.[2] High Sierra arranged file information in a dense, sequential layout to minimize nonsequential access by using a hierarchical (eight levels of directories deep) tree file system arrangement, similar to UNIX and FAT. To facilitate cross platform compatibility, it defined a minimal set of common file attributes (directory or ordinary file and time of recording) and name attributes (name, extension, and version), and used a separate system use area where future optional extensions for each file may be specified. High Sierra was adopted in December 1986 (with changes) as an international standard by Ecma International as ...more...

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International Standard Book Number

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International Standard Book Number

The International Standard Book Number (ISBN) is a unique[a][b] numeric commercial book identifier. Publishers purchase ISBNs from an affiliate of the International ISBN Agency.[1] An ISBN is assigned to each edition and variation (except reprintings) of a book. For example, an e-book, a paperback and a hardcover edition of the same book would each have a different ISBN. The ISBN is 13 digits long if assigned on or after 1 January 2007, and 10 digits long if assigned before 2007. The method of assigning an ISBN is nation-based and varies from country to country, often depending on how large the publishing industry is within a country. The initial ISBN configuration of recognition was generated in 1967 based upon the 9-digit Standard Book Numbering (SBN) created in 1966. The 10-digit ISBN format was developed by the International Organization for Standardization (ISO) and was published in 1970 as international standard ISO 2108 (the SBN code can be converted to a ten digit ISBN by prefixing it with a zero). ...more...

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ISO/IEC 7816

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ISO/IEC 7816

ISO/IEC 7816 is an international standard related to electronic identification cards with contacts, especially smart cards, managed jointly by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC). It is edited by the Joint technical committee (JTC) 1 / Sub-Committee (SC) 17, Cards and personal identification.[1] The following describes the different parts of this standard. Note: abstracts and dates, when present, are mere quotations from the ISO website,[2] and are neither guaranteed at the time of edition nor in the future. Parts ISO/IEC 7816-1:2011 Part 1: Cards with contacts—Physical characteristics ISO/IEC 7816-2:2007 Part 2: Cards with contacts—Dimensions and location of the contacts ISO/IEC 7816-3:2006 Part 3: Cards with contacts—Electrical interface and transmission protocols ISO/IEC 7816-4:2013 Part 4: Organization, security and commands for interchange ISO/IEC 7816-5:2004 Part 5: Registration of application providers ISO/IEC ...more...

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Graphical Kernel System

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Graphical Kernel System

The Graphical Kernel System (GKS) was the first ISO standard for low-level computer graphics, introduced in 1977. A draft international standard was circulated for review in September, 1983.[1][2][3] Final ratification of the standard was achieved in 1985.[4][5] GKS provides a set of drawing features for two-dimensional vector graphics suitable for charting and similar duties. The calls are designed to be portable across different programming languages, graphics devices and hardware, so that applications written to use GKS will be readily portable to many platforms and devices. GKS was fairly common on computer workstations in the 1980s and early 1990s.[6] GKS formed the basis of Digital Research's GSX and GEM products; the latter was common on the Atari ST and was occasionally seen on PCs particularly in conjunction with Ventura Publisher. It was little used outside these markets and is essentially obsolete today except insofar as it is the underlying API defining the Computer Graphics Metafile. A descenda ...more...

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ISO/IEC 2022

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ISO/IEC 2022

ISO/IEC 2022 Information technology—Character code structure and extension techniques, is an ISO standard (equivalent to the ECMA standard ECMA-35[1]) specifying a technique for including multiple character sets in a single character encoding system, and a technique for representing these character sets in both 7 and 8 bit systems using the same encoding. Many of the character sets included as ISO/IEC 2022 encodings are 'double byte' encodings where two bytes correspond to a single character. This makes ISO-2022 a variable width encoding. But a specific implementation does not have to implement all of the standard; the conformance level and the supported character sets are defined by the implementation. Introduction Many languages or language families not based on the Latin alphabet such as Greek, Cyrillic, Arabic, or Hebrew have historically been represented on computers with different 8-bit extended ASCII encodings. Written East Asian languages, specifically Chinese, Japanese, and Korean, use far more ...more...

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MPEG-1

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MPEG-1

MPEG-1 is a standard for lossy compression of video and audio. It is designed to compress VHS-quality raw digital video and CD audio down to 1.5 Mbit/s (26:1 and 6:1 compression ratios respectively)[1] without excessive quality loss, making video CDs, digital cable/satellite TV and digital audio broadcasting (DAB) possible.[2][3] Today, MPEG-1 has become the most widely compatible lossy audio/video format in the world, and is used in a large number of products and technologies. Perhaps the best-known part of the MPEG-1 standard is the MP3 audio format it introduced. The MPEG-1 standard is published as ISO/IEC 11172 – Information technology—Coding of moving pictures and associated audio for digital storage media at up to about 1.5 Mbit/s. The standard consists of the following five Parts:[4][5][6][7][8] Systems (storage and synchronization of video, audio, and other data together) Video (compressed video content) Audio (compressed audio content) Conformance testing (testing the correctness of implementa ...more...

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Linux Standard Base

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Linux Standard Base

The LSB logo The Linux Standard Base (LSB) is a joint project by several Linux distributions under the organizational structure of the Linux Foundation to standardize the software system structure, including the filesystem hierarchy used in the Linux operating system. The LSB is based on the POSIX specification, the Single UNIX Specification (SUS), and several other open standards, but extends them in certain areas. According to the LSB: The goal of the LSB is to develop and promote a set of open standards that will increase compatibility among Linux distributions and enable software applications to run on any compliant system even in binary form. In addition, the LSB will help coordinate efforts to recruit software vendors to port and write products for Linux Operating Systems. The LSB compliance may be certified for a product by a certification procedure.[1] The LSB specifies for example: standard libraries, a number of commands and utilities that extend the POSIX standard, the layout of the file sy ...more...

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ISO 9

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ISO 9

The ISO international standard ISO 9 establishes a system for the transliteration into Latin characters of Cyrillic characters constituting the alphabets of many Slavic and non-Slavic languages.[1] The major advantage ISO 9 has over other competing systems is its univocal system of one character for one character equivalents (by the use of diacritics), which faithfully represents the original spelling and allows for reverse transliteration, even if the language is unknown. Earlier versions of the standard, ISO/R 9:1954, ISO/R 9:1968 and ISO 9:1986, were more closely based on the international scholarly system for linguistics (scientific transliteration), but have diverged in favour of unambiguous transliteration over phonemic representation. The edition of 1995 supersedes the edition of 1986.[1] ISO 9:1995, or GOST 7.79 System A [2] The standard features three mapping tables: the first covers contemporary Slavic languages, the second older Slavic orthographies (excluding letters from the first), and the th ...more...

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Parts-per notation

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Parts-per notation

Fluorescein aqueous solutions, diluted from 1–10,000 parts-per-million In science and engineering, the parts-per notation is a set of pseudo-units to describe small values of miscellaneous dimensionless quantities, e.g. mole fraction or mass fraction. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement. Commonly used are ppm (parts-per-million, 10−6), ppb (parts-per-billion, 10−9), ppt (parts-per-trillion, 10−12) and ppq (parts-per-quadrillion, 10−15). This notation is not part of the SI system and its meaning is ambiguous. Overview Parts-per notation is often used describing dilute solutions in chemistry, for instance, the relative abundance of dissolved minerals or pollutants in water. The unit “1 ppm” can be used for a mass fraction if a water-borne pollutant is present at one-millionth of a gram per gram of sample solution. When working with aqueous solutions, it is common to assume that the density of water is 1.00 g/mL. Therefore, it ...more...

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