A variable-width encoding is a type of character encoding scheme in which codes of differing lengths are used to encode a character set (a repertoire of symbols) for representation, usually in a computer . Most common variable-width encodings are multibyte encodings (aka MBCS – multi-byte character set ), which use varying numbers of bytes ( octets ) to encode different characters. (Some authors, notably in Microsoft documentation, use the term multibyte character set, which is a misnomer , because representation size is an attribute of the encoding, not of the character set.)
43-550: VWE may refer to: Variable-width encoding Verden–Walsrode Railway in Germany Van Wyck Expressway in New York City Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title VWE . If an internal link led you here, you may wish to change the link to point directly to
86-447: A change would break compatibility with existing systems and therefore might not be feasible at all. Since the aim of a multibyte encoding system is to minimise changes to existing application software, some characters must retain their pre-existing single-unit codes, even while other characters have multiple units in their codes. The result is that there are three sorts of units in a variable-width encoding: singletons , which consist of
129-542: A document is submitted directly for approval as a draft International Standard (DIS) to the ISO member bodies or as a final draft International Standard (FDIS), if the document was developed by an international standardizing body recognized by the ISO Council. The first step, a proposal of work (New Proposal), is approved at the relevant subcommittee or technical committee (e.g., SC 29 and JTC 1 respectively in
172-442: A long process that commonly starts with the proposal of new work within a committee. Some abbreviations used for marking a standard with its status are: Abbreviations used for amendments are: Other abbreviations are: International Standards are developed by ISO technical committees (TC) and subcommittees (SC) by a process with six steps: The TC/SC may set up working groups (WG) of experts for
215-548: A proposal to form a new global standards body. In October 1946, ISA and UNSCC delegates from 25 countries met in London and agreed to join forces to create the International Organization for Standardization. The organization officially began operations on 23 February 1947. ISO Standards were originally known as ISO Recommendations ( ISO/R ), e.g., " ISO 1 " was issued in 1951 as "ISO/R 1". ISO
258-436: A relatively small number of standards, ISO standards are not available free of charge, but rather for a purchase fee, which has been seen by some as unaffordable for small open-source projects. The process of developing standards within ISO was criticized around 2007 as being too difficult for timely completion of large and complex standards, and some members were failing to respond to ballots, causing problems in completing
301-440: A search for the two-unit sequence DF E0 can yield a false positive in the sequence DE DF E0 E1, which consists of two consecutive two-unit sequences. There is also the danger that a single corrupted or lost unit may render the whole interpretation of a large run of multiunit sequences incorrect. In a variable-width encoding where all three types of units are disjunct, string searching always works without false positives, and (provided
344-417: A single unit, lead units , which come first in a multiunit sequence, and trail units , which come afterwards in a multiunit sequence. Input and display software obviously needs to know about the structure of the multibyte encoding scheme, but other software generally doesn't need to know if a pair of bytes represent two separate characters or just one character. For example, the four character string " I♥NY "
387-508: A variable-width encoding called UTF-1 , in which singletons had the range 00–9F, lead units the range A0–FF and trail units the ranges A0–FF and 21–7E. Because of this bad design, similar to Shift JIS and Big5 in its overlap of values, the inventors of the Plan 9 operating system, the first to implement Unicode throughout, abandoned it and replaced it with a much better designed variable-width encoding for Unicode: UTF-8, in which singletons have
430-637: Is "to develop worldwide Information and Communication Technology (ICT) standards for business and consumer applications." There was previously also a JTC 2 that was created in 2009 for a joint project to establish common terminology for "standardization in the field of energy efficiency and renewable energy sources". It was later disbanded. As of 2022 , there are 167 national members representing ISO in their country, with each country having only one member. ISO has three membership categories, Participating members are called "P" members, as opposed to observing members, who are called "O" members. ISO
473-466: Is a voluntary organization whose members are recognized authorities on standards, each one representing one country. Members meet annually at a General Assembly to discuss the strategic objectives of ISO. The organization is coordinated by a central secretariat based in Geneva . A council with a rotating membership of 20 member bodies provides guidance and governance, including setting the annual budget of
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#1732793754165516-464: Is abused, ISO should halt the process... ISO is an engineering old boys club and these things are boring so you have to have a lot of passion ... then suddenly you have an investment of a lot of money and lobbying and you get artificial results. The process is not set up to deal with intensive corporate lobbying and so you end up with something being a standard that is not clear. International Workshop Agreements (IWAs) are documents that establish
559-517: Is an abbreviation for "International Standardization Organization" or a similar title in another language, the letters do not officially represent an acronym or initialism . The organization provides this explanation of the name: Because 'International Organization for Standardization' would have different acronyms in different languages (IOS in English, OIN in French), our founders decided to give it
602-521: Is approved as an International Standard (IS) if a two-thirds majority of the P-members of the TC/SC is in favour and not more than one-quarter of the total number of votes cast are negative. After approval, the document is published by the ISO central secretariat , with only minor editorial changes introduced in the publication process before the publication as an International Standard. Except for
645-577: Is encoded in UTF-8 like this (shown as hexadecimal byte values): 49 E2 99 A5 4E 59 . Of the six units in that sequence, 49, 4E, and 59 are singletons (for I, N, and Y ), E2 is a lead unit and 99 and A5 are trail units. The heart symbol is represented by the combination of the lead unit and the two trail units. UTF-8 makes it easy for a program to identify the three sorts of units, since they fall into separate value ranges. Older variable-width encodings are typically not as well-designed, since
688-522: Is funded by a combination of: International standards are the main products of ISO. It also publishes technical reports, technical specifications, publicly available specifications, technical corrigenda (corrections), and guides. International standards Technical reports For example: Technical and publicly available specifications For example: Technical corrigenda ISO guides For example: ISO documents have strict copyright restrictions and ISO charges for most copies. As of 2020 ,
731-425: Is produced, for example, for audio and video coding standards is called a verification model (VM) (previously also called a "simulation and test model"). When a sufficient confidence in the stability of the standard under development is reached, a working draft (WD) is produced. This is in the form of a standard, but is kept internal to working group for revision. When a working draft is sufficiently mature and
774-617: Is restricted. The organization that is known today as ISO began in 1926 as the International Federation of the National Standardizing Associations ( ISA ), which primarily focused on mechanical engineering . The ISA was suspended in 1942 during World War II but, after the war, the ISA was approached by the recently-formed United Nations Standards Coordinating Committee (UNSCC) with
817-655: The International Electrotechnical Commission . It is headquartered in Geneva , Switzerland. The three official languages of ISO are English , French , and Russian . The International Organization for Standardization in French is Organisation internationale de normalisation and in Russian, Международная организация по стандартизации ( Mezhdunarodnaya organizatsiya po standartizatsii ). Although one might think ISO
860-494: The ISO 2022 7-bit encodings were replaced by a set of 8-bit encoding schemes, the Extended Unix Code: EUC-JP, EUC-CN and EUC-KR. Instead of distinguishing between the multiunit sequences and the singletons with escape sequences, which made the encodings stateful, multiunit sequences were marked by having the most significant bit set, that is, being in the range 80–FF (hexadecimal), while the singletons were in
903-694: The ISO Statutes. ISO was founded on 23 February 1947, and (as of July 2024 ) it has published over 25,000 international standards covering almost all aspects of technology and manufacturing. It has over 800 technical committees (TCs) and subcommittees (SCs) to take care of standards development. The organization develops and publishes international standards in technical and nontechnical fields, including everything from manufactured products and technology to food safety, transport, IT, agriculture, and healthcare. More specialized topics like electrical and electronic engineering are instead handled by
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#1732793754165946-473: The PC ( DOS and Microsoft Windows platforms), two encodings became established for Japanese and Traditional Chinese in which all of singletons, lead units and trail units overlapped: Shift-JIS and Big5 respectively. In Shift-JIS, lead units had the range 81–9F and E0–FC, trail units had the range 40–7E and 80–FC, and singletons had the range 21–7E and A1–DF. In Big5, lead units had the range A1–FE, trail units had
989-491: The case of MPEG, the Moving Picture Experts Group ). A working group (WG) of experts is typically set up by the subcommittee for the preparation of a working draft (e.g., MPEG is a collection of seven working groups as of 2023). When the scope of a new work is sufficiently clarified, some of the working groups may make an open request for proposals—known as a "call for proposals". The first document that
1032-418: The central secretariat. The technical management board is responsible for more than 250 technical committees , who develop the ISO standards. ISO has a joint technical committee (JTC) with the International Electrotechnical Commission (IEC) to develop standards relating to information technology (IT). Known as JTC 1 and entitled "Information technology", it was created in 1987 and its mission
1075-421: The confidence people have in the standards setting process", and alleged that ISO did not carry out its responsibility. He also said that Microsoft had intensely lobbied many countries that traditionally had not participated in ISO and stacked technical committees with Microsoft employees, solution providers, and resellers sympathetic to Office Open XML: When you have a process built on trust and when that trust
1118-467: The decoder is well written) the corruption or loss of one unit corrupts only one character. The first use of multibyte encodings was for the encoding of Chinese, Japanese and Korean, which have large character sets well in excess of 256 characters. At first the encoding was constrained to the limit of 7 bits. The ISO-2022-JP, ISO-2022-CN and ISO-2022-KR encodings used the range 21–7E (hexadecimal) for both lead units and trail units, and marked them off from
1161-413: The document, the draft is then approved for submission as a Final Draft International Standard (FDIS) if a two-thirds majority of the P-members of the TC/SC are in favour and if not more than one-quarter of the total number of votes cast are negative. ISO will then hold a ballot among the national bodies where no technical changes are allowed (a yes/no final approval ballot), within a period of two months. It
1204-762: The intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=VWE&oldid=1105771864 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Variable-width encoding Early variable-width encodings using less than a byte per character were sometimes used to pack English text into fewer bytes in adventure games for early microcomputers . However disks (which unlike tapes allowed random access allowing text to be loaded on demand), increases in computer memory and general purpose compression algorithms have rendered such tricks largely obsolete. Multibyte encodings are usually
1247-721: The necessary steps within the prescribed time limits. In some cases, alternative processes have been used to develop standards outside of ISO and then submit them for its approval. A more rapid "fast-track" approval procedure was used in ISO/IEC JTC 1 for the standardization of Office Open XML (OOXML, ISO/IEC 29500, approved in April 2008), and another rapid alternative "publicly available specification" (PAS) process had been used by OASIS to obtain approval of OpenDocument as an ISO/IEC standard (ISO/IEC 26300, approved in May 2006). As
1290-619: The networks and creating the Internet: Commercialization, privatization, broader access leads to the modern Internet: Examples of Internet services: The International Organization for Standardization ( ISO / ˈ aɪ s oʊ / ) is an independent, non-governmental , international standard development organization composed of representatives from the national standards organizations of member countries. Membership requirements are given in Article 3 of
1333-492: The next stage, called the "enquiry stage". After a consensus to proceed is established, the subcommittee will produce a draft international standard (DIS), and the text is submitted to national bodies for voting and comment within a period of five months. A document in the DIS stage is available to the public for purchase and may be referred to with its ISO DIS reference number. Following consideration of any comments and revision of
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1376-812: The original Unicode (1.x) without breaking compatibility with the 16-bit encoding. In UTF-16, singletons have the range 0000–D7FF (55,296 code points) and E000–FFFF (8192 code points, 63,488 in total), lead units the range D800–DBFF (1024 code points) and trail units the range DC00–DFFF (1024 code points, 2048 in total). The lead and trail units, called high surrogates and low surrogates , respectively, in Unicode terminology, map 1024×1024 or 1,048,576 supplementary characters, making 1,112,064 (63,488 BMP code points + 1,048,576 code points represented by high and low surrogate pairs) encodable code points, or scalar values in Unicode parlance (surrogates are not encodable). ISO Early research and development: Merging
1419-411: The preparation of a working drafts. Subcommittees may have several working groups, which may have several Sub Groups (SG). It is possible to omit certain stages, if there is a document with a certain degree of maturity at the start of a standardization project, for example, a standard developed by another organization. ISO/IEC directives also allow the so-called "Fast-track procedure". In this procedure,
1462-435: The range 00–7F alone. The lead units and trail units were in the range A1 to FE (hexadecimal), that is, the same as their range in the ISO 2022 encodings, but with the high bit set to 1. These encodings were reasonably easy to work with provided all your delimiters were ASCII characters and you avoided truncating strings to fixed lengths, but a break in the middle of a multibyte character could still cause major corruption. On
1505-406: The range 00–7F, lead units have the range C0–FD (now actually C2–F4, to avoid overlong sequences and to maintain synchronism with the encoding capacity of UTF-16; see the UTF-8 article), and trail units have the range 80–BF. The lead unit also tells how many trail units follow: one after C2–DF, two after E0–EF and three after F0–F4. UTF-16 was devised to break free of the 65,536-character limit of
1548-532: The range 40–7E and A1–FE, and singletons had the range 21–7E (all values in hexadecimal). This overlap again made processing tricky, though at least most of the symbols had unique byte values (though strangely the backslash does not). The Unicode standard has two variable-width encodings: UTF-8 and UTF-16 (it also has a fixed-width encoding, UTF-32 ). Originally, both the Unicode and ISO 10646 standards were meant to be fixed-width, with Unicode being 16-bit and ISO 10646 being 32-bit. ISO 10646 provided
1591-466: The ranges may overlap. A text processing application that deals with the variable-width encoding must then scan the text from the beginning of all definitive sequences in order to identify the various units and interpret the text correctly. In such encodings, one is liable to encounter false positives when searching for a string in the middle of the text. For example, if the hexadecimal values DE, DF, E0, and E1 can all be either lead units or trail units, then
1634-436: The result of a need to increase the number of characters which can be encoded without breaking backward compatibility with an existing constraint. For example, with one byte (8 bits) per character, one can encode 256 possible characters; in order to encode more than 256 characters, the obvious choice would be to use two or more bytes per encoding unit, two bytes (16 bits) would allow 65,536 possible characters, but such
1677-472: The short form ISO . ISO is derived from the Greek word isos ( ίσος , meaning "equal"). Whatever the country, whatever the language, the short form of our name is always ISO . During the founding meetings of the new organization, however, the Greek word explanation was not invoked, so this meaning may be a false etymology . Both the name ISO and the ISO logo are registered trademarks and their use
1720-462: The singletons by using ISO 2022 escape sequences to switch between single-byte and multibyte mode. A total of 8,836 (94×94) characters could be encoded at first, and further sets of 94×94 characters with switching. The ISO 2022 encoding schemes for CJK are still in use on the Internet. The stateful nature of these encodings and the large overlap make them very awkward to process. On Unix platforms,
1763-509: The subcommittee is satisfied that it has developed an appropriate technical document for the problem being addressed, it becomes a committee draft (CD) and is sent to the P-member national bodies of the SC for the collection of formal comments. Revisions may be made in response to the comments, and successive committee drafts may be produced and circulated until consensus is reached to proceed to
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1806-414: The typical cost of a copy of an ISO standard is about US$ 120 or more (and electronic copies typically have a single-user license, so they cannot be shared among groups of people). Some standards by ISO and its official U.S. representative (and, via the U.S. National Committee, the International Electrotechnical Commission ) are made freely available. A standard published by ISO/IEC is the last stage of
1849-517: Was suggested at the time by Martin Bryan, the outgoing convenor (chairman) of working group 1 (WG1) of ISO/IEC JTC 1/SC 34 , the rules of ISO were eventually tightened so that participating members that fail to respond to votes are demoted to observer status. The computer security entrepreneur and Ubuntu founder, Mark Shuttleworth , was quoted in a ZDNet blog article in 2008 about the process of standardization of OOXML as saying: "I think it de-values
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