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Numbering Scheme
There are many different numbering schemes for assigning nominal numbers to entities. These generally require an agreed set of rules, or a central coordinator. The schemes can be considered to be examples of a primary key of a database management system table, whose table definitions require a database design. In computability theory, the simplest numbering scheme is the assignment of natural numbers to a set of objects such as functions, rational numbers, graphs, or words in some formal language. A numbering can be used to transfer the idea of computability and related concepts, which are originally defined on the natural numbers using computable functions, to these different types of objects. A simple extension is to assign cardinal numbers to physical objects according to the choice of some base of reference and of measurement units for counting or measuring these objects within a given precision. In such case, numbering is a kind of classification, i.e. assigning a numeric p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Primary Key
In the relational model of databases, a primary key is a ''specific choice'' of a ''minimal'' set of attributes (Column (database), columns) that uniquely specify a tuple (Row (database), row) in a Relation (database), relation (Table (database), table). Informally, a primary key is "which attributes identify a record," and in simple cases constitute a single attribute: a unique ID. More formally, a primary key is a choice of candidate key (a minimal superkey); any other candidate key is an alternate key. A primary key may consist of real-world observables, in which case it is called a ''natural key'', while an attribute created to function as a key and not used for identification outside the database is called a ''surrogate key''. For example, for a database of people (of a given nationality), time and location of birth could be a natural key. National identification number is another example of an attribute that may be used as a natural key. History Although mainly used today in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zero-based Numbering
Zero-based numbering is a way of numbering in which the initial element of a sequence is assigned the index 0, rather than the index 1 as is typical in everyday ''non-mathematical'' or ''non-programming'' circumstances. Under zero-based numbering, the initial element is sometimes termed the ''zeroth'' element, rather than the ''first'' element; ''zeroth'' is a coined ordinal number corresponding to the number zero. In some cases, an object or value that does not (originally) belong to a given sequence, but which could be naturally placed before its initial element, may be termed the zeroth element. There is not wide agreement regarding the correctness of using zero as an ordinal (nor regarding the use of the term ''zeroth''), as it creates ambiguity for all subsequent elements of the sequence when lacking context. Numbering sequences starting at 0 is quite common in mathematics notation, in particular in combinatorics, though programming languages for mathematics usuall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
China Telephone Numbering Plan
Telephone numbers in China are organized according to the Chinese Telephone Code Plan. The numerical formats of landlines and mobile phones are different: landlines have area codes, whereas mobile phones do not. In major cities, landline numbers consist of a two-digit area code followed by an eight-digit inner number. In other places, landline numbers consist of a three-digit area code followed by a seven- or eight-digit internal number. The numbers of mobile phones consist of eleven digits. When one landline is used to dial another landline within the same area, it is not necessary to specify the area code. The target number must be prepended between different regions with the trunk prefix, which is 0. Calling a mobile phone from a landline requires the addition of the "0" in front of the mobile phone number if they are not in the same area. Mobile to landline calls requires the "0" and the area code if the landline is not within the same place. Mobile to mobile calls does not ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Australian Telephone Numbering Plan
The Australian telephone numbering plan describes the allocation of phone numbers in Australia. It has changed many times, the most recent major reorganisation by the Australian Communications & Media Authority taking place between 1994 and 1998. Overview For landline telephony, Australia is now geographically divided into four large areas, three of which cover more than one state and/or territory. All local telephone numbers within these four areas are of eight digits, consisting (mainly) of a four digit exchange code plus a four digit number. The national significant number consists of a single digit area code followed by the local eight digit number – a total of nine digits. Within Australia, to access the number of a landline telephone in an area other than that in which the caller is located (including callers using mobile phones), it is first necessary to dial the Australian trunk code of 0 plus the area code, followed by the local number. Thus, the full national ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Argentine Telephone Numbering Plan
In Argentina, area codes are two, three, or four digits long (after the initial zero). Local customer numbers are six to eight figures long. The total number of digits is ten, for example, phone number (11) 1234-5678 for Buenos Aires is made up of a 2-digit area code number and an 8-digit subscriber's number, while (383) 123-4567 would be an example of a Catamarca number. Local dialing Local landline phone numbers in Argentina can have 6, 7 or 8 digits, depending on where they are located: * Most of Greater Buenos Aires uses 8 digits * Second-tier cities use 7 digits * Remaining towns and cities use 6 digits Local numbers usually begin with a 4, although in recent times numbers having 2, 3, 5, 6, or even 7 as the first digit are not uncommon. Thus, for example to call a local number within Buenos Aires, one should dial 1234–5678; within Mar del Plata, 123-4567 and within Villa Carlos Paz, 12–3456. For mobile phone dialing, see the corresponding section below. Recent ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telephone Numbering Plan
A telephone numbering plan is a type of numbering scheme used in telecommunication to assign telephone number A telephone number is a sequence of digits assigned to a landline telephone subscriber station connected to a telephone line or to a wireless electronic telephony device, such as a radio telephone or a mobile telephone, or to other devices f ...s to subscriber telephones or other telephony endpoints. Telephone numbers are the addresses of participants in a telephone network, reachable by a system of destination code routing. Telephone numbering plans are defined in each of the administrative regions of the public switched telephone network (PSTN) and in private telephone networks. For public numbering systems, geographic location typically plays a role in the sequence of numbers assigned to each telephone subscriber. Many numbering plan administrators subdivide their territory of service into geographic regions designated by a prefix, often called an area code or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
North American Numbering Plan
The North American Numbering Plan (NANP) is a telephone numbering plan for twenty-five regions in twenty countries, primarily in North America and the Caribbean. This group is historically known as World Zone 1 and has the international calling code ''1''. Some North American countries, most notably Mexico, do not participate in the NANP. The NANP was originally devised in the 1940s by the American Telephone and Telegraph Company (AT&T) for the Bell System and the independent telephone operators in North America. The goal was to unify the diverse local numbering plans that had been established in the preceding decades and prepare the continent for direct-dialing of calls by customers without the involvement of telephone operators. AT&T continued to administer the numbering plan until the breakup of the Bell System, when administration was delegated to the North American Numbering Plan Administrator (NANPA), a service that has been procured from the private sector by the Fede ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Country Calling Code
Country calling codes or country dial-in codes are telephone number prefixes for reaching telephone subscribers in the networks of the member countries or regions of the International Telecommunication Union (ITU). The codes are defined by the ITU-T in standards E.123 and E.164. The prefixes enable international direct dialing (IDD) and are also referred to as ''international subscriber dialing'' (ISD) codes. Country codes are a component of the international telephone numbering plan and are necessary only when dialing a telephone number to establish a call to another country. Country codes are dialed before the national telephone number. By convention, international telephone numbers are represented by prefixing the country code with a plus sign (+), which also indicates to the subscriber that the local international call prefix must first be dialed. For example, the international call prefix in all countries of the North American Numbering Plan is 011, while it is 00 in most E ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telephone
A telephone is a telecommunications device that permits two or more users to conduct a conversation when they are too far apart to be easily heard directly. A telephone converts sound, typically and most efficiently the human voice, into electronic signals that are transmitted via cables and other communication channels to another telephone which reproduces the sound to the receiving user. The term is derived from el, τῆλε (''tēle'', ''far'') and φωνή (''phōnē'', ''voice''), together meaning ''distant voice''. A common short form of the term is ''phone'', which came into use early in the telephone's history. In 1876, Alexander Graham Bell was the first to be granted a United States patent for a device that produced clearly intelligible replication of the human voice at a second device. This instrument was further developed by many others, and became rapidly indispensable in business, government, and in households. The essential elements of a telephone are a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Food Additive
Food additives are substances added to food to preserve flavor or enhance taste, appearance, or other sensory qualities. Some additives have been used for centuries as part of an effort to preserve food, for example vinegar (pickling), salt (salting), smoke (smoking), sugar (crystallization), etc. This allows for longer-lasting foods such as bacon, sweets or wines. With the advent of processed foods in the second half of the twentieth century, many additives have been introduced, of both natural and artificial origin. Food additives also include substances that may be introduced to food indirectly (called "indirect additives") in the manufacturing process, through packaging, or during storage or transport. Numbering To regulate these additives and inform consumers, each additive is assigned a unique number called an "E number", which is used in Europe for all approved additives. This numbering scheme has now been adopted and extended by the '' Codex Alimentarius'' Commission to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
E Number
E numbers ("E" stands for "Europe") are codes for substances used as food additives, including those found naturally in many foods such as vitamin C, for use within the European Union (EU) and European Free Trade Association (EFTA). Commonly found on food labels, their safety assessment and approval are the responsibility of the European Food Safety Authority (EFSA). The fact that an additive has an E number implies that its use was at one time permitted in products for sale in the European Single Market; some of these additives are no longer allowed today. Having a single unified list for food additives was first agreed upon in 1962 with food colouring. In 1964, the directives for preservatives were added, in 1970 antioxidants were added, in 1974 emulsifiers, stabilisers, thickeners and gelling agents were added as well. Numbering schemes The numbering scheme follows that of the International Numbering System (INS) as determined by the '' Codex Alimentarius'' committee, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
UN Number
A UN number (United Nations number) is a four-digit number that identifies hazardous materials, and articles (such as explosives, flammable liquids, oxidizers, toxic liquids, etc.) in the framework of international trade and transport. Some hazardous substances have their own UN numbers (e.g. acrylamide has UN 2074), while sometimes groups of chemicals or products with similar properties receive a common UN number (e.g. flammable liquids, not otherwise specified, have UN 1993). A chemical in its solid state may receive a different UN number than the liquid phase if its hazardous properties differ significantly; substances with different levels of purity (or concentration in solution) may also receive different UN numbers. Hazard identifiers Associated with each UN number is a hazard identifier, which encodes the general hazard class and subdivision (and, in the case of explosives, their compatibility group). If a substance poses several dangers, then subsidiary risk identifiers ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
