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Null
Null may refer to: Science, technology, and mathematics Astronomy *Nuller, an optical tool using interferometry to block certain sources of light Computing *Null (SQL) (or NULL), a special marker and keyword in SQL indicating that a data value does not exist, is not known, or is missing. *Null character, the zero-valued ASCII character, also designated by , often used as a terminator, separator or filler. This symbol has no visual representation. *Null device, a virtual file that discards data written to it, on Unix systems /dev/null *Null pointer or reference (sometimes written NULL, nil, or None), an object pointer (or reference) not currently set to point (or refer) to a valid object Mathematics *Null (mathematics), a zero value in several branches of mathematics Physics *Null (physics), a point in a field where the field quantity is zero *Null (radio), a concept in electromagnetism Arts and media *The Null Corporation, an imprint of the band Nine Inch Nails *Null (Intronaut ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Null Pointer
In computing, a null pointer (sometimes shortened to nullptr or null) or null reference is a value saved for indicating that the Pointer (computer programming), pointer or reference (computer science), reference does not refer to a valid Object (computer science), object. Programs routinely use null pointers to represent conditions such as the end of a List (computing), list of unknown length or the failure to perform some action; this use of null pointers can be compared to nullable types and to the ''Nothing'' value in an option type. A null pointer should not be confused with an uninitialized variable, uninitialized pointer: a null pointer is guaranteed to compare unequal to any pointer that points to a valid object. However, in general, most languages do not offer such guarantee for uninitialized pointers. It might compare equal to other, valid pointers; or it might compare equal to null pointers. It might do both at different times; or the comparison might be undefined behavio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Null (SQL)
In SQL, null or NULL is a special marker used to indicate that a data value does not exist in the database. Introduced by the creator of the Relational model, relational database model, E. F. Codd, SQL null serves to fulfill the requirement that all ''true relational database management systems (Relational database#RDBMS, RDBMS)'' support a representation of "missing information and inapplicable information". Codd also introduced the use of the lowercase Greek omega (ω) symbol to represent null in database theory. In SQL, NULL is a List of SQL reserved words, reserved word used to identify this marker. A null should not be confused with a value of 0. A null indicates a lack of a value, which is not the same as a zero value. For example, consider the question "How many books does Adam own?" The answer may be "zero" (we ''know'' that he owns ''none'') or "null" (we ''do not know'' how many he owns). In a database table, the Column (database), column reporting this answer would ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Null Character
The null character is a control character with the value zero. Many character sets include a code point for a null character including Unicode (Universal Coded Character Set), ASCII (ISO/IEC 646), Baudot, ITA2 codes, the C0 control code, and EBCDIC. In modern character sets, the null character has a code point value of zero which is generally translated to a single code unit with a zero value. For instance, in UTF-8, it is a single, zero byte. However, in Modified UTF-8 the null character is encoded as two bytes : . This allows the byte with the value of zero, which is not used for any character, to be used as a string terminator. Originally, its meaning was like NOP when sent to a printer or a terminal, it had no effect (although some terminals incorrectly displayed it as space). When electromechanical teleprinters were used as computer output devices, one or more null characters were sent at the end of each printed line to allow time for the mechanism to return to the fir ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Null (mathematics)
In mathematics, the word null (from meaning "zero", which is from meaning "none") is often associated with the concept of zero, or with the concept of nothing. It is used in varying contexts from "having zero members in a set" (e.g., null set) to "having a value of zero" (e.g., null vector). In a vector space, the null vector is the neutral element of vector addition; depending on the context, a null vector may also be a vector mapped to some ''null'' by a function under consideration (such as a quadratic form coming with the vector space, see null vector, a linear mapping given as matrix product or dot product, a seminorm in a Minkowski space, etc.). In set theory, the empty set, that is, the set with zero elements, denoted "" or "∅", may also be called null set. In measure theory, a null set is a (possibly nonempty) set with zero measure. A null space of a mapping is the part of the domain that is mapped into the null element of the image (the inverse image of the null e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Null Device
In some operating systems, the null device is a device file that discards all data written to it but reports that the write operation succeeded. This device is called /dev/null on Unix and Unix-like systems, NUL: (see TOPS-20) or NUL on CP/M and DOS (internally \DEV\NUL), nul on OS/2 and newer Windows systems (internally \Device\Null on Windows NT), NIL: on Amiga operating systems, and NL: on OpenVMS. In Windows Powershell, the equivalent is $null. It provides no data to any process that reads from it, yielding EOF immediately. In IBM operating systems DOS/360 and successors and also in OS/360 and successors such files would be assigned in JCL to DD DUMMY. In programmer jargon, especially Unix jargon, it may also be called the bit bucket or black hole. History is described as an empty regular file in Version 4 Unix. The Version 5 Unix manual describes a device with modern semantics. Usage The null device is typically used for disposing of unwanted output streams of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Null (physics)
In physics a null is a point in a Field (physics), field where the field quantity is zero as the result of two or more opposing quantities completely cancelling each other. The field may be Scalar field, scalar, Vector field, vector or Tensor field, tensor in nature. Common situations where nulls arise are in the polar patterns of microphones and antenna (radio), antennae, and nulls caused by Reflection (physics), reflections of Wave, waves. Microphones A common polar pattern for microphones is the cardioid. This has a single direction in which the microphone does not respond to impinging sound waves. Highly directional (shotgun) microphones have more complex polar patterns. These microphones have a large, narrow lobe in the main direction of sound reception but also a smaller lobe in the opposite direction and usually also several other smaller lobes. This pattern is achieved by wave cancellation inside the body of the microphone. Between each of these lobes is a null di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gary Null
Gary Michael Null (born January 6, 1945) is an American talk radio host and author who advocates pseudoscientific alternative medicine and produces a line of questionable dietary supplements. Null is hostile to evidence-based medicine and has accused the medical community of being in a cabal with the pharmaceutical industry to suppress novel treatments for economic gains. He has promoted a range of pseudo-scientific and ineffective alternative treatments, including ones for cancer. He is an HIV/AIDS denialist who believes nutritional deficiencies are the causative agents of ''all'' illnesses, and has accordingly promoted fringe, diet-based treatment regimes for curing AIDS and other illnesses. Null holds strong anti-vaccination views and rejects the scientific consensus on topics such as water fluoridation, genetically modified organisms, and electromagnetic fields. Reactions in the scholarly community to Null's claims have been generally negative, and Null along with his ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuller
A nuller is an optical tool used to block a strong source so that fainter signals near that source can be observed. An example of a nuller is being employed on the Keck Interferometer. This causes the light from a star to destructively Interference (wave propagation), interfere, effectively cancelling the star's image. As a result, the faint light from a ring of dust orbiting the star can then be detected. This project is part of a scientific effort to detect and observe nearby planets. Interferometry ''Nulling interferometry'' is a type of interferometry in which two or more Wiktionary:signal, signals are mixed to produce observational regions in which the incoming signals cancel themselves out. This creates a set of virtual "blind spots" which prevent unwanted signals from those areas from interfering with weaker nearby signals. In 1978 Australian-American astronomer Ronald N. Bracewell suggested using nulling interferometry to search for Extrasolar planet, planets around other ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Christopher Null
Christopher Null (born September 7, 1971) is an American writer, journalist and entrepreneur. A former blogger for Yahoo! Tech, he was the editor of Drinkhacker.com, and the founder and editor-in-chief of Filmcritic.com, which operated from 1995 to 2012. He is also the former magazine editor for '' PC/Computing'' and the founder of Mobile PC magazine. Early life He was born on September 7, 1971, in Houston, Texas. He obtained an MBA at the University of Texas at Austin. Career Null has built a career spanning technology journalism, film criticism, and online publishing. He began his editorial career in technology, serving as Managing Reviews Editor for '' LAN Times'' in the late 1990s before advancing to '' Smart Business'' (formerly ''PC Computing''), where he held roles as Reviews Editor and Executive Editor from 1998 to 2002. Null then became Editor-in-Chief of ''New Architect'' magazine from 2002 to 2003 and led ''Mobile PC'' (later ''Mobile'') magazine as Editor-in-Chief ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Null (radio)
In radio electronics, a null is a direction in an antenna's radiation pattern where the antenna radiates almost no radio waves, so the far field signal strength is a local minimum. Nulls occur because different parts of an antenna radiate radio waves of different phase. In directions at which the antenna radiates equal amplitude radio waves of opposite phase, the radio waves cancel, resulting in little or no radio power being radiated in that direction. In other directions the radio waves from different parts of the antenna are in phase and reinforce, resulting in a maximum signal strength in the radiation pattern, called a lobe. In transmitting antennas designed to provide broad coverage nulls can be a problem, preventing reception in a given area. Null fill in the vertical plane is used to prevent this. Nulling antenna Nulls can also be used to advantage. In a radio receiver the receiver's antenna can be adjusted so the direction of the interference source is located in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ashley Null
John Ashley Null (born 1960 or 1961) is an American theologian and Anglican bishop. As an academic, he is best known for his research on the theology of Thomas Cranmer, particularly Cranmer's doctrines of repentance and scripture, and his influence on the English Reformation. Null's capsule summary of Cranmer's doctrine of anthropology has been widely quoted and is often misattributed directly to Cranmer: "What the heart loves, the will chooses, and the mind justifies." Null also works as a sports chaplain, counseling Olympic and other elite athletes. Ordained in the Episcopal Church, he was canon theologian in the Diocese of Western Kansas but maintained close ties to the Anglican realignment movement as a theological adviser to the Anglican Church in North America's Diocese of the Carolinas. He was also a canon theologian at St. Mark's Pro-Cathedral in Alexandria, Egypt and board chairman of the Alexandria School of Theology, both part of the Anglican Province of Alexandria. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nullification (other)
Nullification may refer to: * Nullification (U.S. Constitution), a legal theory that a state has the right to nullify any federal law deemed unconstitutional with respect to the United States Constitution ** Nullification crisis, the 1832 confrontation between the U.S. government and South Carolina over the latter's attempt to nullify a federal law *** Ordinance of Nullification, declared the Tariffs of 1828 and 1832 null and void within the state borders of South Carolina * Jury nullification Jury nullification, also known as jury equity or as a perverse verdict, is a decision by the jury in a trial, criminal trial resulting in a verdict of Acquittal, not guilty even though they think a defendant has broken the law. The jury's reas ..., a legal term for a jury's ability to deliver a verdict knowingly in contradiction to written law * Nullification (body modification), short for "genital nullification", a member of an extreme body modification subculture See also * Annih ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
