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https://en.wikipedia.org/wiki/TDM | TDM may refer to:
TDM, a 2023 Indian Marathi comedy film
TDM (Macau) (), a Macanese radio and television network
The Yamaha TDM, a motorcycle model
Target Disk Mode, a boot mode on certain Macintosh computers
Team deathmatch, a mode of gameplay in video games
Technical death metal, a subgenre of heavy metal music
, a Mozambican telecommunications and Internet service provider
Teresian Daughters of Mary, a Filipino Roman Catholic institute
Text data mining, a process of deriving high-quality information from text
The Difference Machine, an album by English rock band Big Big Train
Therapeutic drug monitoring, a branch of clinical chemistry
Time-division multiplexing, a method of transmitting and receiving independent signals over a common signal path
Toad Data Modeler, a database design tool
Transportation demand management, also traffic demand management or travel demand management
DanTDM, British YouTube personality |
https://en.wikipedia.org/wiki/XNS | XNS or xns may refer to:
Computing
Xerox Network Systems, an early computer networking protocol suite
Extensible Name Service, an XML-based digital identity architecture
Other uses
Kanashi language (ISO 639:xns), a Sino-Tibetan language
Navtech System Support (IATA code: XNS), in the List of airline codes
Christians (XNS), in the List of acronyms: X |
https://en.wikipedia.org/wiki/Creative%20Commons | Creative Commons (CC) is an American non-profit organization and international network devoted to educational access and expanding the range of creative works available for others to build upon legally and to share. The organization has released several copyright licenses, known as Creative Commons licenses, free of charge to the public. These licenses allow authors of creative works to communicate which rights they reserve and which rights they waive for the benefit of recipients or other creators. An easy-to-understand one-page explanation of rights, with associated visual symbols, explains the specifics of each Creative Commons license. Content owners still maintain their copyright, but Creative Commons licenses give standard releases that replace the individual negotiations for specific rights between copyright owner (licensor) and licensee, that are necessary under an "all rights reserved" copyright management.
The organization was founded in 2001 by Lawrence Lessig, Hal Abelson, and Eric Eldred with the support of Center for the Public Domain. The first article in a general interest publication about Creative Commons, written by Hal Plotkin, was published in February 2002. The first set of copyright licenses was released in December 2002. The founding management team that developed the licenses and built the Creative Commons infrastructure as it is known today included Molly Shaffer Van Houweling, Glenn Otis Brown, Neeru Paharia, and Ben Adida.
In 2002, the Open Content Project, a 1998 precursor project by David A. Wiley, announced the Creative Commons as successor project and Wiley joined as CC director. Aaron Swartz played a role in the early stages of Creative Commons, as did Matthew Haughey.
, there were "nearly 2 billion" works licensed under the various Creative Commons licenses. Wikipedia and its sister projects use one of these licenses. According to a 2017 report, Flickr alone hosted over 415 million cc-licensed photos, along with around 49 million works in YouTube, 40 million works in DeviantArt and 37 million works in Wikimedia Commons. The licenses are also used by Stack Exchange, MDN, Internet Archive, Khan Academy, LibreTexts, OpenStax, MIT OpenCourseWare, WikiHow, TED, OpenStreetMap, GeoGebra, Doubtnut, Fandom, Arduino, ccmixter.org, Ninjam, etc., and formerly by Unsplash, Pixabay and Socratic.
Purpose and goal
Creative Commons has been an early participant in the copyleft movement, which seeks to provide alternative solutions to copyright, and has been dubbed "some rights reserved". Creative Commons has been credited with contributing to a re-thinking of the role of the "commons" in the "information age". Their frameworks help individuals and groups distribute content more freely while still protecting themselves and their intellectual property rights legally.
According to its founder Lawrence Lessig, Creative Commons' goal is to counter the dominant and increasingly restrictive permission culture that limits artistic |
https://en.wikipedia.org/wiki/Axiom%20of%20extensionality | In axiomatic set theory and the branches of logic, mathematics, and computer science that use it, the axiom of extensionality, or axiom of extension, is one of the axioms of Zermelo–Fraenkel set theory. It says that sets having the same elements are the same set.
Formal statement
In the formal language of the Zermelo–Fraenkel axioms, the axiom reads:
or in words:
Given any set A and any set B, if for every set X, X is a member of A if and only if X is a member of B, then A is equal to B.
(It is not really essential that X here be a set — but in ZF, everything is. See Ur-elements below for when this is violated.)
The converse, of this axiom follows from the substitution property of equality.
Interpretation
To understand this axiom, note that the clause in parentheses in the symbolic statement above simply states that A and B have precisely the same members.
Thus, what the axiom is really saying is that two sets are equal if and only if they have precisely the same members.
The essence of this is:
A set is determined uniquely by its members.
The axiom of extensionality can be used with any statement of the form
,
where P is any unary predicate that does not mention A, to define a unique set whose members are precisely the sets satisfying the predicate .
We can then introduce a new symbol for ; it's in this way that definitions in ordinary mathematics ultimately work when their statements are reduced to purely set-theoretic terms.
The axiom of extensionality is generally uncontroversial in set-theoretical foundations of mathematics, and it or an equivalent appears in just about any alternative axiomatisation of set theory.
However, it may require modifications for some purposes, as below.
In predicate logic without equality
The axiom given above assumes that equality is a primitive symbol in predicate logic.
Some treatments of axiomatic set theory prefer to do without this, and instead treat the above statement not as an axiom but as a definition of equality.
Then it is necessary to include the usual axioms of equality from predicate logic as axioms about this defined symbol. Most of the axioms of equality still follow from the definition; the remaining one is the substitution property,
and it becomes this axiom that is referred to as the axiom of extensionality in this context.
In set theory with ur-elements
An ur-element is a member of a set that is not itself a set.
In the Zermelo–Fraenkel axioms, there are no ur-elements, but they are included in some alternative axiomatisations of set theory.
Ur-elements can be treated as a different logical type from sets; in this case, makes no sense if is an ur-element, so the axiom of extensionality simply applies only to sets.
Alternatively, in untyped logic, we can require to be false whenever is an ur-element.
In this case, the usual axiom of extensionality would then imply that every ur-element is equal to the empty set.
To avoid this consequence, we can modify the axiom of extensio |
https://en.wikipedia.org/wiki/Axiom%20of%20pairing | In axiomatic set theory and the branches of logic, mathematics, and computer science that use it, the axiom of pairing is one of the axioms of Zermelo–Fraenkel set theory. It was introduced by as a special case of his axiom of elementary sets.
Formal statement
In the formal language of the Zermelo–Fraenkel axioms, the axiom reads:
In words:
Given any object A and any object B, there is a set C such that, given any object D, D is a member of C if and only if D is equal to A or D is equal to B.
Or in simpler words:
Given two objects, there is a set whose members are exactly the two given objects.
Consequences
As noted, what the axiom is saying is that, given two objects A and B, we can find a set C whose members are exactly A and B.
We can use the axiom of extensionality to show that this set C is unique.
We call the set C the pair of A and B, and denote it {A,B}.
Thus the essence of the axiom is:
Any two objects have a pair.
The set {A,A} is abbreviated {A}, called the singleton containing A.
Note that a singleton is a special case of a pair. Being able to construct a singleton is necessary, for example, to show the non-existence of the infinitely descending chains from the Axiom of regularity.
The axiom of pairing also allows for the definition of ordered pairs. For any objects and , the ordered pair is defined by the following:
Note that this definition satisfies the condition
Ordered n-tuples can be defined recursively as follows:
Alternatives
Non-independence
The axiom of pairing is generally considered uncontroversial, and it or an equivalent appears in just about any axiomatization of set theory. Nevertheless, in the standard formulation of the Zermelo–Fraenkel set theory, the axiom of pairing follows from the axiom schema of replacement applied to any given set with two or more elements, and thus it is sometimes omitted. The existence of such a set with two elements, such as { {}, { {} } }, can be deduced either from the axiom of empty set and the axiom of power set or from the axiom of infinity.
In the absence of some of the stronger ZFC axioms, the axiom of pairing can still, without loss, be introduced in weaker forms.
Weaker
In the presence of standard forms of the axiom schema of separation we can replace the axiom of pairing by its weaker version:
.
This weak axiom of pairing implies that any given objects and are members of some set . Using the axiom schema of separation we can construct the set whose members are exactly and .
Another axiom which implies the axiom of pairing in the presence of the axiom of empty set is the axiom of adjunction
.
It differs from the standard one by use of instead of .
Using {} for A and x for B, we get {x} for C. Then use {x} for A and y for B, getting {x,y} for C. One may continue in this fashion to build up any finite set. And this could be used to generate all hereditarily finite sets without using the axiom of union.
Stronger
Together with the axiom of empty set and the |
https://en.wikipedia.org/wiki/Stephen%20Wolfram | Stephen Wolfram ( ; born 29 August 1959) is a British-American computer scientist, physicist, and businessman. He is known for his work in computer science, mathematics, and theoretical physics. In 2012, he was named a fellow of the American Mathematical Society.
As a businessman, he is the founder and CEO of the software company Wolfram Research where he works as chief designer of Mathematica and the Wolfram Alpha answer engine.
Early life
Family
Stephen Wolfram was born in London in 1959 to Hugo and Sybil Wolfram, both German Jewish refugees to the United Kingdom. His maternal grandmother was British psychoanalyst Kate Friedlander.
Wolfram's father, Hugo Wolfram, was a textile manufacturer and served as managing director of the Lurex Company—makers of the fabric Lurex. Wolfram's mother, Sybil Wolfram, was a Fellow and Tutor in Philosophy at Lady Margaret Hall at University of Oxford from 1964 to 1993.
Stephen Wolfram is married to a mathematician. They have four children together.
Education
Wolfram was educated at Eton College, but left prematurely in 1976. As a young child, Wolfram had difficulties learning arithmetic. He entered St. John's College, Oxford, at age 17 and left in 1978 without graduating to attend the California Institute of Technology the following year, where he received a PhD in particle physics in 1980. Wolfram's thesis committee was composed of Richard Feynman, Peter Goldreich, Frank J. Sciulli and Steven Frautschi, and chaired by Richard D. Field.
Early career
Wolfram, at the age of 15, began research in applied quantum field theory and particle physics and published scientific papers in peer-reviewed scientific journals including Nuclear Physics B, Australian Journal of Physics, Nuovo Cimento, and Physical Review D. Working independently, Wolfram published a widely cited paper on heavy quark production at age 18 and nine other papers. Wolfram's work with Geoffrey C. Fox on the theory of the strong interaction is still used in experimental particle physics.
Following his PhD, Wolfram joined the faculty at Caltech and became the youngest recipient of a MacArthur Fellowship in 1981, at age 21.
Later career
Complex systems and cellular automata
In 1983, Wolfram left for the School of Natural Sciences of the Institute for Advanced Study in Princeton. By that time, he was no longer interested in particle physics. Instead, he began pursuing investigations into cellular automata, mainly with computer simulations. He produced a series of papers systematically investigating the class of elementary cellular automata, conceiving the Wolfram code, a naming system for one-dimensional cellular automata, and a classification scheme for the complexity of their behaviour. He conjectured that the Rule 110 cellular automaton might be Turing complete, which a research assistant to Wolfram, Matthew Cook, later proved correct. Wolfram sued Cook and temporarily blocked publication of the work on Rule 110 for allegedly violating a no |
https://en.wikipedia.org/wiki/John%20Goldsmith%20%28linguist%29 | John Anton Goldsmith (born 1951) is the Edward Carson Waller Distinguished Service Professor at the University of Chicago, with appointments in linguistics and computer science.
Biography
Goldsmith obtained his B.A. at Swarthmore College in 1972, and completed his PhD in Linguistics at MIT in 1976, under the linguist Morris Halle. He was on the faculty of the Department of Linguistics at Indiana University before joining the University of Chicago in 1984. He has taught at the LSA Linguistic Institutes and has held visiting appointments at many universities, such as McGill, Harvard, and UCSD. In 2007, Goldsmith was elected as a Fellow of the American Academy of Arts and Sciences.
Research
Goldsmith's research ranges from phonology to computational linguistics. His PhD thesis introduced autosegmental phonology; the idea that phonological phenomena is a collection of parallel tiers with individual segments, each representing certain features of speech. His more recent research focuses on unsupervised learning of linguistic structure (as demonstrated by the Linguistica project, a body of software that tries to automatically analyze the morphology of a language), as well as extending computational linguistics algorithms to bioinformatics.
Books
John A Goldsmith, Bernard Laks, Battle in the Mind Fields, University of Chicago Press, 2018
External links
Goldsmith's homepage
Autosegmental phonology (Goldsmith's doctoral dissertation)
Goldsmith's 2014 lecture at the University of Chicago
References
Linguists from the United States
Phonologists
Living people
Swarthmore College alumni
MIT School of Humanities, Arts, and Social Sciences alumni
University of Chicago faculty
1951 births
Distinguished professors in the United States
Fellows of the Linguistic Society of America |
https://en.wikipedia.org/wiki/Final%20Fantasy%20Tactics | is a 1997 tactical role-playing game developed and published by Square for the PlayStation video game console. Released in Japan in June 1997 and in the United States in January 1998 by Sony Computer Entertainment, it is the first game of the Tactics series within the Final Fantasy franchise, and the first entry set in the fictional world later known as Ivalice. The story follows Ramza Beoulve, a highborn cadet placed in the middle of a military conflict known as The Lion War, where two opposing noble factions are coveting the throne of the kingdom.
Production began in 1995 by Yasumi Matsuno, a newcomer who had created the Ogre Battle series at Quest Corporation. Matsuno's wish was for an accessible tactical game with a storyline focusing on class-based conflict and the rewriting of history. Matsuno acted as director and writer, Final Fantasy creator Hironobu Sakaguchi was producer, and the battles were designed by Hiroyuki Ito. Multiple other staff members were veterans of the Ogre Battle series, including artists Hiroshi Minagawa and Akihiko Yoshida, and composers Hitoshi Sakimoto and Masaharu Iwata.
The game received critical acclaim from gaming magazines and websites and has become a cult classic since its release. It sold about 1.24 million units in Japan during 1997, and over 2.4 million worldwide by August 2011. It has been cited as one of the greatest video games of all time. The world of Ivalice saw the setting for multiple other titles, including other Tactics games and the 2006 mainline entry Final Fantasy XII. An enhanced port of Final Fantasy Tactics, Final Fantasy Tactics: The War of the Lions, was released in 2007 as part of the Ivalice Alliance project.
Gameplay
Final Fantasy Tactics is a tactical role-playing game in which players follow the story of protagonist Ramza Beoulve. The game features two modes of play: battles and the world map. Battles take place on three-dimensional, isometric fields. Characters move on a battlefield composed of square tiles; movement and action ranges are determined by the character's statistics and job class. The battlefield also factors in elements such as terrain and weather to determine strategic advantages and disadvantages during clashes. Battles are turn-based; a unit may act when its Charge Time (CT) reaches 100 and increased once every CT unit (a measure of time in battles) by an amount equal to the unit's speed statistic. During battle, whenever a unit performs an action successfully, it gains experience points (EXP) and job points (JP). Actions can include magical attacks, physical attacks, or using an item. Hit points (HP) of enemy units are also visible to the player (except in the case of certain bosses), allowing the player to know how much damage they still have to inflict on a particular unit.
In the world map, the player moves on predefined paths connecting the towns and battle points. When the character icon is over a town, a menu can be opened with several options: "Bar" for |
https://en.wikipedia.org/wiki/Desktop%20computer | A desktop computer (often abbreviated desktop) is a personal computer designed for regular use at a stationary location on or near a desk (as opposed to a portable computer) due to its size and power requirements. The most common configuration has a case that houses the power supply, motherboard (a printed circuit board with a microprocessor as the central processing unit, memory, bus, certain peripherals and other electronic components), disk storage (usually one or more hard disk drives, solid state drives, optical disc drives, and in early models a floppy disk drive); a keyboard and mouse for input; and a monitor, speakers, and, often, a printer for output. The case may be oriented horizontally or vertically and placed either underneath, beside, or on top of a desk.
Personal computers with their cases oriented vertically are referred to as towers. As the majority of cases offered since the mid-1990s are in this form factor, the term desktop (or pizza box, for compact models) has been retronymically used to refer to modern cases offered in the traditional horizontal orientation.
History
Origins
Prior to the widespread use of microprocessors, a computer that could fit on a desk was considered remarkably small; the type of computers most commonly used were minicomputers, which, despite the name, were rather large and were "mini" only compared to the so-called "big iron". Early computers, and later the general purpose high throughput «mainframes», took up the space of a whole room. Minicomputers, on the contrary, generally fit into one or a few refrigerator-sized racks, or, for the few smaller ones, built into a fairly large desk, not put on top of it.
It was not until the 1970s when fully programmable computers appeared that could fit entirely on top of a desk. 1970 saw the introduction of the Datapoint 2200, a "smart" computer terminal complete with keyboard and monitor, was designed to connect with a mainframe computer but that did not stop owners from using its built-in computational abilities as a stand-alone desktop computer. The HP 9800 series, which started out as programmable calculators in 1971 but was programmable in BASIC by 1972, used a smaller version of a minicomputer design based on ROM memory and had small one-line LED alphanumeric displays and displayed graphics with a plotter. The Wang 2200 of 1973 had a full-size cathode-ray tube (CRT) and cassette tape storage. The IBM 5100 in 1975 had a small CRT display and could be programmed in BASIC and APL. These were generally expensive specialized computers sold for business or scientific uses.
Growth and development
Apple II, TRS-80 and Commodore PET were first generation personal home computers launched in 1977, which were aimed at the consumer market – rather than businessmen or computer hobbyists. Byte magazine referred to these three as the "1977 Trinity" of personal computing. Throughout the 1980s and 1990s, desktop computers became the predominant type, the most popular be |
https://en.wikipedia.org/wiki/Final%20Fantasy%20II | is a fantasy role-playing video game developed and published by Square in 1988 for the Family Computer as the second installment of the Final Fantasy series. The game has received numerous enhanced remakes for the WonderSwan Color, the PlayStation, the Game Boy Advance, the PlayStation Portable, iOS, Android and Windows. As neither this game nor Final Fantasy III were initially released outside Japan, Final Fantasy IV was originally released in North America as Final Fantasy II, so as not to confuse players. Following enhanced versions for iOS and Android in 2010 and 2012 respectively, the game was re-released again as part of the 2021 Final Fantasy Pixel Remaster series.
The game's story centers on four youths whose parents were killed during an army invasion by the empire of Palamecia, who are using hellspawn to conquer the world. Three of the four main characters join a rebellion against the empire, embarking on missions to gain new magic and weapons, destroy enemy superweapons, and rescue leading members of the resistance. The Game Boy Advance remake adds a bonus story after the game is completed.
Final Fantasy II introduced many elements that would later become staples of the Final Fantasy franchise, including chocobos and the recurring character Cid. It also eliminated the traditional experience point leveling system of the previous and later games in the series, instead introducing an activity-based progression system where the characters' statistics increase according to how they are used or acquired. Despite being advertised as a sequel to Final Fantasy, the game includes no characters and locations from the first game. Final Fantasy II received little attention from non-Japanese reviewers at its initial release, though its remakes have garnered favorable reviews.
Gameplay
Final Fantasy II features gameplay similar to that of its predecessor, Final Fantasy. The player can freely roam an overworld containing several towns and dungeons. A menu-based system allows the player to outfit each character with equipment and up to two—often disposable—items for battle. Magic spells are assigned to the character from the item menu, and certain spells, such as "Cure", spelled "Kearu" (IPA: [kéərɯ]) in the Japanese versions, can be used outside of battle. The player can also save their progress on the overworld. Weapons, armor, items, and magic spells can be purchased at shops, and townspeople provide useful information for the player's progression through the game. One new feature is the "Word Memory" system: when in conversation with non-player characters (NPCs), the player can "ask" about and "memorize" special keywords or phrases, which can later be repeated to other NPCs to gain more information or unlock new actions. Similarly, there exist a handful of special items that can be shown to NPCs during conversation or used on certain objects, which have the same effect. Characters and monsters are no longer separated into separate windows in the |
https://en.wikipedia.org/wiki/Network%20address%20translation | Network address translation (NAT) is a method of mapping an IP address space into another by modifying network address information in the IP header of packets while they are in transit across a traffic routing device. The technique was originally used to bypass the need to assign a new address to every host when a network was moved, or when the upstream Internet service provider was replaced, but could not route the network's address space. It has become a popular and essential tool in conserving global address space in the face of IPv4 address exhaustion. One Internet-routable IP address of a NAT gateway can be used for an entire private network.
As network address translation modifies the IP address information in packets, NAT implementations may vary in their specific behavior in various addressing cases and their effect on network traffic. The specifics of NAT behavior are not commonly documented by vendors of equipment containing NAT implementations.
Basic NAT
The simplest type of NAT provides a one-to-one translation of IP addresses (RFC 1631). RFC 2663 refers to this type of NAT as basic NAT; it is also called a one-to-one NAT. In this type of NAT, only the IP addresses, IP header checksum, and any higher-level checksums that include the IP address are changed. Basic NAT can be used to interconnect two IP networks that have incompatible addressing.
One-to-many NAT
The majority of network address translators map multiple private hosts to one publicly exposed IP address.
Here is a typical configuration:
A local network uses one of the designated private IP address subnets (RFC 1918).
The network has a router having both a private and a public address. The private address is used by the router for communicating with other devices in the private local network. The public address (typically assigned by an Internet service provider) is used by the router for communicating with the rest of the Internet.
As traffic passes from the network to the Internet, the router translates the source address in each packet from a private address to the router's own public address. The router tracks basic data about each active connection (particularly the destination address and port). When the router receives inbound traffic from the Internet, it uses the connection tracking data it stored during the outbound phase to determine to which private address (if any) it should forward the reply.
All IP packets have a source IP address and a destination IP address. Typically, packets passing from the private network to the public network will have their source address modified, while packets passing from the public network back to the private network will have their destination address modified. To avoid ambiguity in how replies are translated, further modifications to the packets are required. The vast bulk of Internet traffic uses Transmission Control Protocol (TCP) or User Datagram Protocol (UDP). For these protocols, the port numbers are changed so t |
https://en.wikipedia.org/wiki/Key%20%28cryptography%29 | A key in cryptography is a piece of information, usually a string of numbers or letters that are stored in a file, which, when processed through a cryptographic algorithm, can encode or decode cryptographic data. Based on the used method, the key can be different sizes and varieties, but in all cases, the strength of the encryption relies on the security of the key being maintained. A key's security strength is dependent on its algorithm, the size of the key, the generation of the key, and the process of key exchange.
Scope
The key is what is used to encrypt data from plaintext to ciphertext. There are different methods for utilizing keys and encryption.
Symmetric cryptography
Symmetric cryptography refers to the practice of the same key being used for both encryption and decryption.
Asymmetric cryptography
Asymmetric cryptography has separate keys for encrypting and decrypting. These keys are known as the public and private keys, respectively.
Purpose
Since the key protects the confidentiality and integrity of the system, it is important to be kept secret from unauthorized parties. With public key cryptography, only the private key must be kept secret, but with symmetric cryptography, it is important to maintain the confidentiality of the key. Kerckhoff's principle states that the entire security of the cryptographic system relies on the secrecy of the key.
Key sizes
Key size is the number of bits in the key defined by the algorithm. This size defines the upper bound of the cryptographic algorithm's security. The larger the key size, the longer it will take before the key is compromised by a brute force attack. Since perfect secrecy is not feasible for key algorithms, researches are now more focused on computational security.
In the past, keys were required to be a minimum of 40 bits in length, however, as technology advanced, these keys were being broken quicker and quicker. As a response, restrictions on symmetric keys were enhanced to be greater in size.
Currently, 2048 bit RSA is commonly used, which is sufficient for current systems. However, current key sizes would all be cracked quickly with a powerful quantum computer.
“The keys used in public key cryptography have some mathematical structure. For example, public keys used in the RSA system are the product of two prime numbers. Thus public key systems require longer key lengths than symmetric systems for an equivalent level of security. 3072 bits is the suggested key length for systems based on factoring and integer discrete logarithms which aim to have security equivalent to a 128 bit symmetric cipher.”
Key generation
To prevent a key from being guessed, keys need to be generated randomly and contain sufficient entropy. The problem of how to safely generate random keys is difficult and has been addressed in many ways by various cryptographic systems. A key can directly be generated by using the output of a Random Bit Generator (RBG), a system that generates a sequence o |
https://en.wikipedia.org/wiki/Symmetric-key%20algorithm | Symmetric-key algorithms are algorithms for cryptography that use the same cryptographic keys for both the encryption of plaintext and the decryption of ciphertext. The keys may be identical, or there may be a simple transformation to go between the two keys. The keys, in practice, represent a shared secret between two or more parties that can be used to maintain a private information link. The requirement that both parties have access to the secret key is one of the main drawbacks of symmetric-key encryption, in comparison to public-key encryption (also known as asymmetric-key encryption). However, symmetric-key encryption algorithms are usually better for bulk encryption. With exception of the one-time pad they have a smaller key size, which means less storage space and faster transmission. Due to this, asymmetric-key encryption is often used to exchange the secret key for symmetric-key encryption.
Types
Symmetric-key encryption can use either stream ciphers or block ciphers.
Stream ciphers encrypt the digits (typically bytes), or letters (in substitution ciphers) of a message one at a time. An example is ChaCha20. Substitution ciphers are well-known ciphers, but can be easily decrypted using a frequency table.
Block ciphers take a number of bits and encrypt them in a single unit, padding the plaintext to achieve a multiple of the block size. The Advanced Encryption Standard (AES) algorithm, approved by NIST in December 2001, uses 128-bit blocks.
Implementations
Examples of popular symmetric-key algorithms include Twofish, Serpent, AES (Rijndael), Camellia, Salsa20, ChaCha20, Blowfish, CAST5, Kuznyechik, RC4, DES, 3DES, Skipjack, Safer, and IDEA.
Use as a cryptographic primitive
Symmetric ciphers are commonly used to achieve other cryptographic primitives than just encryption.
Encrypting a message does not guarantee that it will remain unchanged while encrypted. Hence, often a message authentication code is added to a ciphertext to ensure that changes to the ciphertext will be noted by the receiver. Message authentication codes can be constructed from an AEAD cipher (e.g. AES-GCM).
However, symmetric ciphers cannot be used for non-repudiation purposes except by involving additional parties. See the ISO/IEC 13888-2 standard.
Another application is to build hash functions from block ciphers. See one-way compression function for descriptions of several such methods.
Construction of symmetric ciphers
Many modern block ciphers are based on a construction proposed by Horst Feistel. Feistel's construction makes it possible to build invertible functions from other functions that are themselves not invertible.
Security of symmetric ciphers
Symmetric ciphers have historically been susceptible to known-plaintext attacks, chosen-plaintext attacks, differential cryptanalysis and linear cryptanalysis. Careful construction of the functions for each round can greatly reduce the chances of a successful attack. It is also possible to increase th |
https://en.wikipedia.org/wiki/File%20Allocation%20Table | File Allocation Table (FAT) is a file system developed for personal computers and was the default filesystem for MS-DOS and Windows 9x operating systems. Originally developed in 1977 for use on floppy disks, it was adapted for use on hard disks and other devices. The increase in disk drives capacity required three major variants: FAT12, FAT16 and FAT32. FAT was replaced with NTFS as the default file system on Microsoft operating systems starting with Windows XP. Nevertheless, FAT continues to be used on flash and other solid-state memory cards and modules (including USB flash drives), many portable and embedded devices because of its compatibility and ease of implementation.
Uses
Historical
FAT was also used on hard disks throughout the DOS and Windows 9x eras. Microsoft introduced NTFS with the Windows NT platform in 1993, but FAT remained the standard for the home user until the introduction of Windows XP in 2001. Windows Me was the final version of Windows to use FAT as its default file system.
For floppy disks, FAT has been standardized as ECMA-107 and ISO/IEC 9293:1994 (superseding ISO 9293:1987). These standards cover FAT12 and FAT16 with only short 8.3 filename support; long filenames with VFAT were partially patented. While FAT12 is used on floppy disks, FAT16 and FAT32 are typically found on the larger media.
Modern
FAT is used internally for the EFI system partition in the boot stage of EFI-compliant computers. Hidden FAT filesystems are also used in the UEFI boot partition on modern PCs.
FAT is still used in drives expected to be used by multiple operating systems, such as in shared Windows, Linux and DOS environments. Microsoft Windows additionally comes with a pre-installed tool to convert a FAT file system into NTFS directly without the need to rewrite all files, though this cannot be reversed easily. The FAT file system is used in removable media such as floppy disks, super-floppies, memory and flash memory cards or USB flash drives. FAT is supported by portable devices such as PDAs, digital cameras, camcorders, media players, and mobile phones.
The DCF file system adopted by almost all digital cameras since 1998 defines a logical file system with 8.3 filenames and makes the use of either FAT12, FAT16, FAT32 or exFAT mandatory for its physical layer for compatibility.
Technical details
The file system uses an index table stored on the device to identify chains of data storage areas associated with a file, the File Allocation Table (FAT). The FAT is statically allocated at the time of formatting. The table is a linked list of entries for each cluster, a contiguous area of disk storage. Each entry contains either the number of the next cluster in the file, or else a marker indicating the end of the file, unused disk space, or special reserved areas of the disk. The root directory of the disk contains the number of the first cluster of each file in that directory. The operating system can then traverse the FAT, looking u |
https://en.wikipedia.org/wiki/Darwin%20%28operating%20system%29 | Darwin is the core Unix operating system of macOS (previously OS X and Mac OS X), iOS, watchOS, tvOS, iPadOS, visionOS, and bridgeOS. It previously existed as an independent open-source operating system, first released by Apple Inc. in 2000. It is composed of code derived from NeXTSTEP, BSD, Mach, and other free software projects' code, as well as code developed by Apple.
Darwin is mostly POSIX-compatible, but has never, by itself, been certified as compatible with any version of POSIX. Starting with Leopard, macOS has been certified as compatible with the Single UNIX Specification version 3 (SUSv3).
History
The heritage of Darwin began with Unix derivatives supplemented by aspects of NeXT's NeXTSTEP operating system (later, since version 4.0, known as OPENSTEP), first released in 1989. After Apple bought NeXT in 1996, it announced it would base its next operating system on OPENSTEP. This was developed into Rhapsody in 1997, Mac OS X Server 1.0 in 1999, Mac OS X Public Beta in 2000, and Mac OS X 10.0 in 2001.
In 1999, Apple announced it would release the source code for the Mach 2.5 microkernel, BSD Unix 4.4 OS, and the Apache Web server components of Mac OS X Server. At the time, interim CEO Steve Jobs alluded to British naturalist Charles Darwin by announcing "because it's about evolution". In 2000, the core operating system components of Mac OS X were released as open-source software under the Apple Public Source License (APSL) as Darwin; the higher-level components, such as the Cocoa and Carbon frameworks, remained closed-source.
Up to Darwin 8.0.1, released in April 2005, Apple released a binary installer (as an ISO image) after each major Mac OS X release that allowed one to install Darwin on PowerPC and Intel x86 systems as a standalone operating system. Minor updates were released as packages that were installed separately. Darwin is now only available as source code. As of January 2023, Apple no longer mentions Darwin by name on its Open Source website and only publishes an incomplete collection of open-source projects relating to macOS and iOS.
Design
Kernel
The kernel of Darwin is XNU, a hybrid kernel which uses OSFMK 7.3 (Open Software Foundation Mach Kernel) from the OSF, various elements of FreeBSD (including the process model, network stack, and virtual file system), and an object-oriented device driver API called I/O Kit. The hybrid kernel design provides the flexibility of a microkernel and the performance of a monolithic kernel.
Hardware and software support
The last bootable full release of Darwin supported 32-bit and 64-bit Apple PowerPC systems and 32-bit Intel PCs.
Darwin currently includes support for the 64-bit x86-64 variant of the Intel x86 processors used in Intel-based Macs and the 64-bit ARM processors used in the iPhone 5S and later, the 6th generation iPod Touch, the 5th generation iPad and later, the iPad Air family, the iPad Mini 2 and later, the iPad Pro family, the fourth generation and later Apple TVs |
https://en.wikipedia.org/wiki/OpenStep | OpenStep is a defunct object-oriented application programming interface (API) specification for a legacy object-oriented operating system, with the basic goal of offering a NeXTSTEP-like environment on non-NeXTSTEP operating systems. OpenStep was principally developed by NeXT with Sun Microsystems, to allow advanced application development on Sun's operating systems, specifically Solaris. NeXT produced a version of OpenStep for its own Mach-based Unix, stylized as OPENSTEP, as well as a version for Windows NT. The software libraries that shipped with OPENSTEP are a superset of the original OpenStep specification, including many features from the original NeXTSTEP.
History
Workstations from Sun Microsystems were originally programmed at a relatively low-level making calls directly to the underlying Unix operating system and the SunView window system toolkit, and to libraries built atop those interfaces. This led to complex programming even for simple projects. An attempt to address this with an object oriented programming model was made in the mid-1980s with Sun's NeWS windowing system, but the combination of a complex application programming interface (API) and generally poor performance led to little real-world use and the system was eventually abandoned.
Sun then began looking for other options. Taligent was considered to be a competitor in the operating system and object markets, and Microsoft's Cairo was at least a consideration, even without any product releases from either. Taligent's theoretical newness was often compared to NeXT's older but mature and commercially established platform. Sun held exploratory meetings with Taligent before deciding upon building out its object application framework OpenStep in partnership with NeXT as a "preemptive move against Taligent and Cairo". Bud Tribble, a founding designer of the Macintosh and of NeXTStep, was now SunSoft's Vice President of Object Products to lead this decision. The 1993 partnership included a $10 million investment from Sun into NeXT. The deal was described as "the first unadulterated piece of good news in the NeXT community in the last four years".
The basic concept was to take a cut-down version of the NeXTSTEP operating system's object layers and adapt them to run on Sun's Solaris operating system, more specifically, Solaris on SPARC-based hardware. Most of the OpenStep effort was to strip away those portions of NeXTSTEP that depended on Mach or NeXT-specific hardware being present. This resulted in a smaller system that consisted primarily of Display PostScript, the Objective-C runtime and compilers, and the majority of the NeXTSTEP Objective-C libraries. Not included was the basic operating system, or the lower-level display system.
Steve Jobs said "We are ahead today, but the race is far from over. ... [In 1996,] Cairo will be very close behind, and Taligent will be very far behind." Sun's CEO Scott McNealy said, "We have no insurance policy. We have made a firm one-compan |
https://en.wikipedia.org/wiki/Liberty%20BASIC | Liberty BASIC (LB) is a commercial computer programming language and integrated development environment (IDE). It has an interpreter, developed in Smalltalk, which recognizes its own dialect of the BASIC programming language. It runs on 16- and 32-bit Windows and OS/2.
Background
Liberty BASIC was written by Carl "Gunner" Gundel and published in its first release by his company, Shoptalk Systems, in 1991. It has progressed steadily since then. to the software, version 4.5.1, was in June 2018.
Though Liberty BASIC has its share of limitations in its design for advanced programming, it provides an introductory integrated development environment, IDE, for moderate to advanced users of Windows and OS/2. Dynamic-link libraries (DLLs) are available. In its current version, it runs only on Microsoft Windows, and under Wine on Linux. Alpha testing of Liberty BASIC v5.0 is underway with versions that run on Microsoft Windows, Mac OS X, Linux and on the Raspberry Pi as well.
Liberty BASIC does not compile to native code. Instead it compiles the code written in the IDE to an encrypted file with the extension TKN. This file is then executed by an EXE file that carries the same file name, although this may change with the release of version 5.
Features
A visual development tool called FreeForm, written in Liberty BASIC and greatly extended by the Liberty BASIC community over the years
Source level debugger
calling of DLLs and application programming interfaces (APIs)
Color graphics capability
Can create games with sprite animation, sound, music, and joystick control
An add-on package called Assist with many new features, such as a code formatter, source code versioning, a performance profiler, an easy-to-use code difference browser, and an improved package and deployment system
Distinguishing features
Liberty BASIC allows for procedural programming in a style similar to DOS BASICs that run in console mode, using a default "main window" that displays formatted text and accepts user input. It also supports event-driven programming based on a graphical user interface (GUI), using several types of windows that may contain the standard controls such as buttons, menus, textboxes, etc.
A central idea in creating Liberty BASIC was to model the handling of windows after the syntax for file handling. For example, (from the Liberty BASIC Help File):
"The OPEN command opens communication with a device, which can be a disk file, a window, a dynamic-link library or a serial communications port."
OPEN device FOR purpose AS #handle {LEN = n}
Once a “device” is open, data and also commands to control that device can be “printed” to it. For each type of device there is a set of commands which can be sent to it in this way. In the more recent versions of LB the word "print" may be dropped from the "print" statement, making the syntax even simpler.
Simplicity has been at the heart of Liberty BASIC from the beginning. This makes it easier to learn but at som |
https://en.wikipedia.org/wiki/Advogato | Advogato was an online community and social networking site dedicated to free software development and created by Raph Levien. In 2007, Steve Rainwater took over maintenance and new development from Raph. In 2016, Rainwater's running instance was shut down and backed up to archive.org.
History
Advogato described itself as "the free software developer's advocate." Advogato was an early pioneer of blogs, formerly known as "online diaries", and one of the earliest social networking websites. Advogato combined the most recent entries from each user's diary together into a single continuous feed called the recentlog, directly inspiring the creation of the Planet aggregator somewhat later.
Several high-profile members of the free software and open source software movements were users of the site, including Richard M. Stallman, Eric Raymond, Alan Cox, Bruce Perens, and Jamie Zawinski.
Because Advogato was the first website to use a robust, attack-resistant trust metric and to release the underlying code for that trust mechanism under a free software license, it has been the basis of numerous research papers on trust metrics and social networking (see the list below for specific examples). Advogato's early adoption of an XML-RPC interface led to its use as an example of how such interfaces could be used by web programmers.
Advogato saw use as a testbed for social networking and semantic web technologies. Tim Berners-Lee, who was an Advogato user himself, included Advogato in a short list of sites notable for their early adoption of the FOAF as a method of exporting user RDF URIs.
Trust metric
The motivating idea for Advogato was to try out in practice Levien's ideas about attack-resistant trust metrics, having users certify each other in a kind of peer review process and use this information to avoid the abuses that plague open community sites. Levien observed that his notion of attack-resistant trust metric was fundamentally very similar to the PageRank algorithm used by Google to rate article interest. In the case of Advogato, the trust metric was designed to include all individuals who could reasonably be considered members of the Free Software and Open Source communities while excluding others.
The implementation of this trust metric was through an Apache module called mod_virgule. mod_virgule is free software, licensed under the GPL and written in C.
Despite the trust metric, posting privileges to the front page of Advogato were gained by controversial individuals, leading some to claim Advogato's trust metric solution was faulty.
Misunderstanding of the purpose of Advogato's trust metric was common, which often led to the assumption that it should exclude specific individuals on the basis that they were known cranks.
See also
Everything2
Kuro5hin
Slashdot
References
Advogato and mod_virgule references
Raph Levien (2004). Attack Resistant Trust Metrics. Early draft of abandoned PhD manuscript.
Raph Levien (2007). Lessons From Advo |
https://en.wikipedia.org/wiki/Cable%20modem | A cable modem is a type of network bridge that provides bi-directional data communication via radio frequency channels on a hybrid fibre-coaxial (HFC), radio frequency over glass (RFoG) and coaxial cable infrastructure. Cable modems are primarily used to deliver broadband Internet access in the form of cable Internet, taking advantage of the high bandwidth of a HFC and RFoG network. They are commonly deployed in the Americas, Asia, Australia, and Europe.
History
MITRE Cablenet
Internet Experiment Note (IEN) 96 (1979) describes an early RF cable modem system. From pages 2 and 3 of IEN 96:
The Cable-Bus System
The MITRE/Washington Cablenet system is based on a technology developed at MITRE/Bedford. Similar cable-bus systems are in operation at a number of government sites, e.g. Walter Reed Army Hospital, and the NASA Johnson Space Center, but these are all standalone, local-only networks.
The system uses standard Community Antenna Television (CATV) coaxial cable and microprocessor based Bus Interface Units (BIUs) to connect subscriber computers and terminals to the cable. ... The cable bus consists of two parallel coaxial cables, one inbound and the other outbound. The inbound cable and outbound cable are connected at one end, the headend, and electrically terminated at their other ends. This architecture takes advantage of the well developed unidirectional CATV components. The topology is dendritic (i.e. branched like a tree).
...
The BIUs contain Radio Frequency (RF) modems which modulate a carrier signal to transmit digital information using 1 MHz of the available bandwidth in the 24 MHz frequency range. The remainder of the 294 MHz bandwidth can be used to carry other communication channels, such as off-the-air TV, FM, closed circuit TV, or a voice telephone system, or, other digital channels. The data rate of our test-bed system is 307.2 kbps.
IEEE 802.3b (10BROAD36)
The IEEE 802 Committee defined 10BROAD36 in 802.3b-1985 as a 10 Mbit/s IEEE 802.3/Ethernet broadband system to run up to over CATV coax network cabling. The word broadband as used in the original IEEE 802.3 specifications implied operation in frequency-division multiplexed (FDM) channel bands as opposed to digital baseband square-waveform modulations (also known as line coding), which begin near zero Hz and theoretically consume infinite frequency bandwidth. (In real-world systems, higher-order signal components become indistinguishable from background noise.) In the market 10BROAD36 equipment was not developed by many vendors nor deployed in many user networks as compared to equipment for IEEE 802.3/Ethernet baseband standards such as 10BASE5 (1983), 10BASE2 (1985), 10BASE-T (1990), etc.
IEEE 802.7
The IEEE 802 Committee also specified a broadband CATV digital networking standard in 1989 with 802.7-1989. However, like 10BROAD36, 802.7-1989 saw little commercial success.
Hybrid networks
Hybrid Networks developed, demonstrated and patented the first high-speed, asymmet |
https://en.wikipedia.org/wiki/File%20Transfer%20Protocol | The File Transfer Protocol (FTP) is a standard communication protocol used for the transfer of computer files from a server to a client on a computer network. FTP is built on a client–server model architecture using separate control and data connections between the client and the server. FTP users may authenticate themselves with a plain-text sign-in protocol, normally in the form of a username and password, but can connect anonymously if the server is configured to allow it. For secure transmission that protects the username and password, and encrypts the content, FTP is often secured with SSL/TLS (FTPS) or replaced with SSH File Transfer Protocol (SFTP).
The first FTP client applications were command-line programs developed before operating systems had graphical user interfaces, and are still shipped with most Windows, Unix, and Linux operating systems. Many dedicated FTP clients and automation utilities have since been developed for desktops, servers, mobile devices, and hardware, and FTP has been incorporated into productivity applications such as HTML editors and file managers.
An FTP client used to be commonly integrated in web browsers, where file servers are browsed with the URI prefix "ftp://". In 2021, FTP support was dropped by Google Chrome and Firefox, two major web browser vendors, due to it being superseded by the more secure SFTP and FTPS; although neither of them have implemented the newer protocols.
History of FTP servers
The original specification for the File Transfer Protocol was written by Abhay Bhushan and published as on 16 April 1971. Until 1980, FTP ran on NCP, the predecessor of TCP/IP. The protocol was later replaced by a TCP/IP version, (June 1980) and (October 1985), the current specification. Several proposed standards amend , for example (February 1994) enables Firewall-Friendly FTP (passive mode), (June 1997) proposes security extensions, (September 1998) adds support for IPv6 and defines a new type of passive mode.
Protocol overview
Communication and data transfer
FTP may run in active or passive mode, which determines how the data connection is established. (This sense of "mode" is different from that of the MODE command in the FTP protocol.)
In active mode, the client starts listening for incoming data connections from the server on port M. It sends the FTP command PORT M to inform the server on which port it is listening. The server then initiates a data channel to the client from its port 20, the FTP server data port.
In situations where the client is behind a firewall and unable to accept incoming TCP connections, passive mode may be used. In this mode, the client uses the control connection to send a PASV command to the server and then receives a server IP address and server port number from the server, which the client then uses to open a data connection from an arbitrary client port to the server IP address and server port number received.
Both modes were updated in September 1998 to suppor |
https://en.wikipedia.org/wiki/RFC | RFC may refer to:
Computing
Request for Comments, a memorandum on Internet standards
Request for change, change management
Remote Function Call, in SAP computer systems
Rhye's and Fall of Civilization, a modification for Sid Meier's Civilization IV
Science and technology
Regenerative fuel cell
Replication factor C, a protein complex
Radio frequency choke, a type of choke
Organisations
Governmental
Reconstruction Finance Corporation of the US government, 1932-1957
Royal Flying Corps, precursor to the UK Royal Air Force
River Forecast Center of the US National Weather Service
Non-profit
Rosenberg Fund for Children, a charity
Sports
Randers FC, a Danish professional football club
Rangers F.C., a Scottish professional football club
Ratchaburi F.C., a Thai association football club
Reading F.C., an English professional football club
Richmond F.C., an English rugby union club
Richmond Football Club, a team in the AFL, the top-level Australian rules football league
Romulus F.C., an English semi-professional football club
See also |
https://en.wikipedia.org/wiki/Befunge | Befunge is a two-dimensional stack-based, reflective, esoteric programming language. It differs from conventional languages in that programs are arranged on a two-dimensional grid. "Arrow" instructions direct the control flow to the left, right, up or down, and loops are constructed by sending the control flow in a cycle. It has been described as "a cross between Forth and Lemmings".
Befunge was created by Chris Pressey in 1993 for the Amiga. The language was designed to be as hard to compile as possible, featuring self-modifying code and a multi-dimensional playfield. Despite this, several compilers have been written for the language. The original Befunge-93 specification limited programs to an 80x25 grid, and while not Turing-complete, subsequent extensions like Funge-98 expanded the concept to achieve Turing completeness.
The name "Befunge" originated from a typing error in an online discussion. While it was designed to be difficult to compile, compilers such as bef2c and Betty have managed to implement the language using various techniques. Befunge programs are characterized by their use of arrows to change control flow, and they can produce outputs like random number sequences or classic "Hello, World!" messages.
History
The language was originally created by Chris Pressey in 1993 for the Amiga, as an attempt to devise a language which is as hard to compile as possible. Note that the p command allows for self-modifying code. Nevertheless, a number of compilers have subsequently been written. A number of extensions to the original "Befunge-93" specification also exist, most notably Funge-98, which extends the concept to an arbitrary number of dimensions and can be multithreaded, with multiple instruction pointers operating simultaneously on the same space. Befunge-extensions and variants are called Fungeoids or just Funges.
The Befunge-93 specification restricts each valid program to a grid of 80 instructions horizontally by 25 instructions vertically. Program execution which exceeds these limits "wraps around" to a corresponding point on the other side of the grid; a Befunge program is in this manner topologically equivalent to a torus. Since a Befunge-93 program can only have a single stack and its storage array is bounded, the Befunge-93 language is not Turing-complete (however, it has been shown that Befunge-93 is Turing Complete with unbounded stack word size). The later Funge-98 specification provides Turing completeness by removing the size restrictions on the program; rather than wrapping around at a fixed limit, the movement of a Funge-98 instruction pointer follows a model dubbed "Lahey-space" after its originator, Chris Lahey. In this model, the grid behaves like a torus of finite size with respect to wrapping, while still allowing itself to be extended indefinitely.
Etymology
The word Befunge is derived from a typing error in an online discussion, where the word 'before' was intended.
Compilation
As stated, the design goal |
https://en.wikipedia.org/wiki/Esoteric%20programming%20language | An esoteric programming language (sometimes shortened to esolang) is a programming language designed to test the boundaries of computer programming language design, as a proof of concept, as software art, as a hacking interface to another language (particularly functional programming or procedural programming languages), or as a joke. The use of the word esoteric distinguishes them from languages that working developers use to write software. The creators of most esolangs do not intend them to be used for mainstream programming, although some esoteric features, such as visuospatial syntax, have inspired practical applications in the arts. Such languages are often popular among hackers and hobbyists.
Usability is rarely a goal for designers of esoteric programming languages; often their design leads to quite the opposite. Their usual aim is to remove or replace conventional language features while still maintaining a language that is Turing-complete, or even one for which the computational class is unknown.
History
The earliest, and still the canonical example of an esoteric programming language, is INTERCAL, designed in 1972 by Don Woods and James M. Lyon, who said that their intention was to create a programming language unlike any with which they were familiar. It parodied elements of established programming languages of the day such as Fortran, COBOL and assembly language.
For many years, INTERCAL was represented only by paper copies of the INTERCAL manual. Its revival in 1990 as an implementation in C under Unix stimulated a wave of interest in the intentional design of esoteric computer languages.
In 1993, Wouter van Oortmerssen created FALSE, a small stack-oriented programming language with syntax designed to make the code inherently obfuscated, confusing and unreadable. Its compiler is only 1024 bytes in size. This inspired Urban Müller to create an even smaller language, the now-infamous Brainfuck, which consists of only eight recognized characters. Along with Chris Pressey's Befunge (like FALSE, but with a two-dimensional instruction pointer), Brainfuck is now one of the best-supported esoteric programming languages, with canonical examples of minimal Turing tarpits and needlessly obfuscated language features. Brainfuck is related to the P′′ family of Turing machines.
Common features
While esoteric programming languages differ in many ways, there are some common traits that characterize many languages, such as parody, minimalism, and the goal of making programming difficult. Many esoteric programming languages, such as brainfuck, and similar, use single characters as commands, however, it isn't uncommon for languages to read line by line like conventional programming languages.
Unique data representations
Conventional imperative programming languages typically allow data to be stored in variables, but esoteric languages may utilize different methods of storing and accessing data. Languages like Brainfuck and Malbolge only permit |
https://en.wikipedia.org/wiki/APNIC | APNIC (the Asia Pacific Network Information Centre) is the regional Internet address registry (RIR) for the Asia-Pacific region. It is one of the world's five RIRs and is part of the Number Resource Organization (NRO).
APNIC provides numbers resource allocation and registration services that support the global operation of the internet. It is a nonprofit, membership-based organization whose members include Internet service providers, telecommunication providers, data centers, universities, banks, national Internet registries, and similar organizations that have their own networks.
Functions
APNIC's main functions are:
Allocating IPv4 and IPv6 address space, and autonomous system numbers
Maintaining the public APNIC Whois Database for the Asia Pacific region,
Reverse DNS delegations
Training in technical skills
Representing the interests of the Asia Pacific Internet community on the global stage
APNIC manages Internet number resources according to policies developed through an open process of consultation and consensus called the Policy Development Process (PDP).
APNIC PDP
APNIC's policies are developed by the membership and the broader Internet community. The forums for policy development are the face-to-face Open Policy Meetings, which are held twice each year, and the public mailing list discussions of the Special Internet Groups.
APNIC's open PDP also invites stakeholders interested in Internet number resources from around the world (but mostly the Asia Pacific) to participate. These include representatives from governments, regulators, educators, media, the technical community, civil society, and other not-for-profit organizations.
APNIC's PDP is:
Open
Anyone can propose policies.
Everyone can discuss policy proposals.
Transparent
APNIC publicly documents all policy discussions and decisions.
Bottom-up
The community drives policy development.
Structure
Elections are held at each APNIC Annual General Meeting (AGM), which is conducted during the APNIC Member Meeting (AMM) in February. Voting takes place both on-site at these meetings and prior to the meeting via online voting.
APNIC Executive Council
Each APNIC Executive Council (EC) member serves as an individual, not as a representative of any other party or Member. Therefore, they must act at all times in the best interests of APNIC. The APNIC EC meets face-to-face at four regularly scheduled meetings per year.
APNIC Secretariat
The APNIC Secretariat operates to serve its Members and the Asia Pacific Internet community stakeholders.
Its activities are designed to help the APNIC community achieve APNIC's objectives. The Secretariat (APNIC's staff) carries out the day-to-day work. The Secretariat is structured in five divisions: Services, Technical, Business, Communications, and Learning & Development. These divisions encompass all APNIC activities, including that of acting as a central source of information for Members.
Core services
Internet number resource de |
https://en.wikipedia.org/wiki/Morris%20worm | The Morris worm or Internet worm of November 2, 1988, is one of the oldest computer worms distributed via the Internet, and the first to gain significant mainstream media attention. It resulted in the first felony conviction in the US under the 1986 Computer Fraud and Abuse Act. It was written by a graduate student at Cornell University, Robert Tappan Morris, and launched on 8:30 pm November 2, 1988, from the Massachusetts Institute of Technology network.
Architecture
A friend of Morris said that he created the worm simply to see if it could be done, and was released from the Massachusetts Institute of Technology (MIT) in the hope of suggesting that its creator studied there, instead of Cornell. Morris later became a tenured professor at MIT in 2006. The worm's creator Robert Tappan Morris is the son of cryptographer Robert Morris, who worked at the NSA at the time.
The worm exploited several vulnerabilities of targeted systems, including:
A hole in the debug mode of the Unix sendmail program
A buffer overflow or overrun hole in the finger network service
The transitive trust enabled by people setting up network logins with no password requirements via remote execution (rexec) with Remote Shell (rsh), termed rexec/rsh
The worm exploited weak passwords. Morris's exploits became generally obsolete due to decommissioning rsh (normally disabled on untrusted networks), fixes to sendmail and finger, widespread network filtering, and improved awareness of weak passwords.
Though Morris said that he did not intend for the worm to be actively destructive, instead seeking to merely highlight the weaknesses present in many networks of the time, a consequence of Morris's coding resulted in the worm being more damaging and spreadable than originally planned. It was initially programmed to check each computer to determine if the infection was already present, but Morris believed that some system administrators might counter this by instructing the computer to report a false positive. Instead, he programmed the worm to copy itself 14% of the time, regardless of the status of infection on the computer. This resulted in a computer potentially being infected multiple times, with each additional infection slowing the machine down to unusability. This had the same effect as a fork bomb, and crashed the computer several times.
The main body of the worm can only infect DEC VAX machines running 4BSD, alongside Sun-3 systems. A portable C "grappling hook" component of the worm was used to download the main body parts, and the grappling hook runs on other systems, loading them down and making them peripheral victims.
Replication rate
Morris's coding instructing the worm to replicate itself regardless of a computer's reported infection status, transformed the worm from a potentially harmless intellectual and computing exercise into a viral denial-of-service attack. Morris's inclusion of the rate of copy within the worm was inspired by Michael Rabin's mantra of |
https://en.wikipedia.org/wiki/Terminal%20emulator | A terminal emulator, or terminal application, is a computer program that emulates a video terminal within some other display architecture. Though typically synonymous with a shell or text terminal, the term terminal covers all remote terminals, including graphical interfaces. A terminal emulator inside a graphical user interface is often called a terminal window.
A terminal window allows the user access to a text terminal and all its applications such as command-line interfaces (CLI) and text user interface (TUI) applications. These may be running either on the same machine or on a different one via telnet, ssh, dial-up, or over a direct serial connection. On Unix-like operating systems, it is common to have one or more terminal windows connected to the local machine.
Terminals usually support a set of escape sequences for controlling color, cursor position, etc. Examples include the family of terminal control sequence standards known as ECMA-48, ANSI X3.64 or ISO/IEC 6429.
History
Computer terminals
Emulators
Local echo
Terminal emulators may implement a local echo function, which may erroneously be named "half-duplex", or still slightly incorrectly "echoplex" (which is formally an error detection mechanism rather than an input display option).
Line-at-a-time mode/Local editing
Terminal emulators may implement local editing, also known as "line-at-a-time mode". This is also mistakenly referred to as "half-duplex". In this mode, the terminal emulator only sends complete lines of input to the host system. The user enters and edits a line, but it is held locally within the terminal emulator as it is being edited. It is not transmitted until the user signals its completion, usually with the key on the keyboard or a "send" button of some sort in the user interface. At that point, the entire line is transmitted. Line-at-a-time mode implies local echo, since otherwise the user will not be able to see the line as it is being edited and constructed. However, line-at-a-time mode is independent of echo mode and does not require local echo. When entering a password, for example, line-at-a-time entry with local editing is possible, but local echo is turned off (otherwise the password would be displayed).
The complexities of line-at-a-time mode are exemplified by the line-at-a-time mode option in the telnet protocol. To implement it correctly, the Network Virtual Terminal implementation provided by the terminal emulator program must be capable of recognizing and properly dealing with "interrupt" and "abort" events that arrive in the middle of locally editing a line.
Synchronous terminals
In asynchronous terminals data can flow in any direction at any time. In synchronous terminals a protocol controls who may send data when. IBM 3270-based terminals used with IBM mainframe computers are an example of synchronous terminals. They operate in an essentially "screen-at-a-time" mode (also known as block mode). Users can make numerous changes to a page, |
https://en.wikipedia.org/wiki/Digital%20media | In mass communication, digital media is any communication media that operate in conjunction with various encoded machine-readable data formats. Digital content can be created, viewed, distributed, modified, listened to, and preserved on a digital electronics device, including digital data storage media (in contrast to analog electronic media) and digital broadcasting. Digital defines as any data represented by a series of digits, and media refers to methods of broadcasting or communicating this information. Together, digital media refers to mediums of digitized information broadcast through a screen and/or a speaker. This also includes text, audio, video, and graphics that are transmitted over the internet for viewing or listening to on the internet.
Digital media platforms, such as YouTube, Vimeo, and Twitch, accounted for viewership rates of 27.9 billion hours in 2020. A contributing factor to its part in what is commonly referred to as the digital revolution can be attributed to the use of interconnectivity.
Examples
Examples of digital media include software, digital images, digital video, video games, web pages and websites, social media, digital data and databases, digital audio such as MP3, electronic documents and electronic books. Digital media often contrasts with print media, such as printed books, newspapers and magazines, and other traditional or analog media, such as photographic film, audio tapes or video tapes.
Digital media has had a significantly broad and complex impact on society and culture. Combined with the Internet and personal computing, digital media has caused disruptive innovation in publishing, journalism, public relations, entertainment, education, commerce and politics. Digital media has also posed new challenges to copyright and intellectual property laws, fostering an open content movement in which content creators voluntarily give up some or all of their legal rights to their work. The ubiquity of digital media and its effects on society suggest that we are at the start of a new era in industrial history, called the Information Age, perhaps leading to a paperless society in which all media are produced and consumed on computers. However, challenges to a digital transition remain, including outdated copyright laws, censorship, the digital divide, and the spectre of a digital dark age, in which older media becomes inaccessible to new or upgraded information systems. Digital media has a significant, wide-ranging and complex impact on society and culture.
Business model
Digital media platforms like YouTube work through a triple-product business model in which platforms provide information and entertainment (infotainment) to the public often at no cost, while simultaneously capturing their attention, and also collecting user data to sell to advertisers. This business model aims to maximize consumer engagement on the platform.
Paid Media
Paid media refers to promotional channels that marketers pay to use, includ |
https://en.wikipedia.org/wiki/Double-precision%20floating-point%20format | Double-precision floating-point format (sometimes called FP64 or float64) is a floating-point number format, usually occupying 64 bits in computer memory; it represents a wide dynamic range of numeric values by using a floating radix point.
Double precision may be chosen when the range or precision of single precision would be insufficient.
In the IEEE 754-2008 standard, the 64-bit base-2 format is officially referred to as binary64; it was called double in IEEE 754-1985. IEEE 754 specifies additional floating-point formats, including 32-bit base-2 single precision and, more recently, base-10 representations (decimal floating point).
One of the first programming languages to provide floating-point data types was Fortran. Before the widespread adoption of IEEE 754-1985, the representation and properties of floating-point data types depended on the computer manufacturer and computer model, and upon decisions made by programming-language implementers. E.g., GW-BASIC's double-precision data type was the 64-bit MBF floating-point format.
IEEE 754 double-precision binary floating-point format: binary64
Double-precision binary floating-point is a commonly used format on PCs, due to its wider range over single-precision floating point, in spite of its performance and bandwidth cost. It is commonly known simply as double. The IEEE 754 standard specifies a binary64 as having:
Sign bit: 1 bit
Exponent: 11 bits
Significand precision: 53 bits (52 explicitly stored)
The sign bit determines the sign of the number (including when this number is zero, which is signed).
The exponent field is an 11-bit unsigned integer from 0 to 2047, in biased form: an exponent value of 1023 represents the actual zero. Exponents range from −1022 to +1023 because exponents of −1023 (all 0s) and +1024 (all 1s) are reserved for special numbers.
The 53-bit significand precision gives from 15 to 17 significant decimal digits precision (2−53 ≈ 1.11 × 10−16). If a decimal string with at most 15 significant digits is converted to the IEEE 754 double-precision format, giving a normal number, and then converted back to a decimal string with the same number of digits, the final result should match the original string. If an IEEE 754 double-precision number is converted to a decimal string with at least 17 significant digits, and then converted back to double-precision representation, the final result must match the original number.
The format is written with the significand having an implicit integer bit of value 1 (except for special data, see the exponent encoding below). With the 52 bits of the fraction (F) significand appearing in the memory format, the total precision is therefore 53 bits (approximately 16 decimal digits, 53 log10(2) ≈ 15.955). The bits are laid out as follows:
The real value assumed by a given 64-bit double-precision datum with a given biased exponent
and a 52-bit fraction is
or
Between 252=4,503,599,627,370,496 and 253=9,007,199,254,740,992 the rep |
https://en.wikipedia.org/wiki/Kruskal%27s%20algorithm | Kruskal's algorithm (also known as Kruskal's method) finds a minimum spanning forest of an undirected edge-weighted graph. If the graph is connected, it finds a minimum spanning tree. (A minimum spanning tree of a connected graph is a subset of the edges that forms a tree that includes every vertex, where the sum of the weights of all the edges in the tree is minimized. For a disconnected graph, a minimum spanning forest is composed of a minimum spanning tree for each connected component.) It is a greedy algorithm in graph theory as in each step it adds the next lowest-weight edge that will not form a cycle to the minimum spanning forest.
This algorithm first appeared in Proceedings of the American Mathematical Society, pp. 48–50 in 1956, and was written by Joseph Kruskal. It was rediscovered by .
Other algorithms for this problem include Prim's algorithm, the reverse-delete algorithm, and Borůvka's algorithm.
Algorithm
create a forest (set of trees) F where each vertex in the graph is a separate tree
create a sorted set S containing all the edges in the graph
while S is nonempty and F is not yet spanning
remove an edge with minimum weight from S
if the removed edge connects two different trees then add it to the forest F, combining two trees into a single tree
At the termination of the algorithm, the forest forms a minimum spanning forest of the graph. If the graph is connected, the forest has a single component and forms a minimum spanning tree.
Pseudocode
The following code is implemented with a disjoint-set data structure. Here, we represent our forest F as a set of edges, and use the disjoint-set data structure to efficiently determine whether two vertices are part of the same tree.
algorithm Kruskal(G) is
F:= ∅
for each v in G.V do
MAKE-SET(v)
for each (u, v) in G.E ordered by weight(u, v), increasing do
if FIND-SET(u) ≠ FIND-SET(v) then
F:= F ∪ {(u, v)} ∪ {(v, u)}
UNION(FIND-SET(u), FIND-SET(v))
return F
Complexity
For a graph with E edges and V vertices, Kruskal's algorithm can be shown to run in O(E log E) time, or equivalently, O(E log V) time, all with simple data structures. These running times are equivalent because:
E is at most and .
Each isolated vertex is a separate component of the minimum spanning forest. If we ignore isolated vertices we obtain V ≤ 2E, so log V is .
We can achieve this bound as follows: first sort the edges by weight using a comparison sort in O(E log E) time; this allows the step "remove an edge with minimum weight from S" to operate in constant time. Next, we use a disjoint-set data structure to keep track of which vertices are in which components. We place each vertex into its own disjoint set, which takes O(V) operations. Finally, in worst case, we need to iterate through all edges, and for each edge we need to do two 'find' operations and possibly one union. Even a simple disjoint-set data structure such as disjoint-set for |
https://en.wikipedia.org/wiki/Ford%E2%80%93Fulkerson%20algorithm | The Ford–Fulkerson method or Ford–Fulkerson algorithm (FFA) is a greedy algorithm that computes the maximum flow in a flow network. It is sometimes called a "method" instead of an "algorithm" as the approach to finding augmenting paths in a residual graph is not fully specified or it is specified in several implementations with different running times. It was published in 1956 by L. R. Ford Jr. and D. R. Fulkerson. The name "Ford–Fulkerson" is often also used for the Edmonds–Karp algorithm, which is a fully defined implementation of the Ford–Fulkerson method.
The idea behind the algorithm is as follows: as long as there is a path from the source (start node) to the sink (end node), with available capacity on all edges in the path, we send flow along one of the paths. Then we find another path, and so on. A path with available capacity is called an augmenting path.
Algorithm
Let be a graph, and for each edge from to , let be the capacity and be the flow. We want to find the maximum flow from the source to the sink . After every step in the algorithm the following is maintained:
{| class="wikitable"
! | Capacity constraints
| || The flow along an edge cannot exceed its capacity.
|-
! | Skew symmetry
| || The net flow from to must be the opposite of the net flow from to (see example).
|-
! | Flow conservation
| || The net flow to a node is zero, except for the source, which "produces" flow, and the sink, which "consumes" flow.
|-
! | Value(f)
| || The flow leaving from must be equal to the flow arriving at .
|-
|}
This means that the flow through the network is a legal flow after each round in the algorithm. We define the residual network to be the network with capacity and no flow. Notice that it can happen that a flow from to is allowed in the residual
network, though disallowed in the original network: if and then .
Inputs Given a Network with flow capacity , a source node , and a sink node
Output Compute a flow from to of maximum value
for all edges
While there is a path from to in , such that for all edges :
Find
For each edge
(Send flow along the path)
(The flow might be "returned" later)
The path in step 2 can be found with, for example, a breadth-first search (BFS) or a depth-first search in . If you use the former, the algorithm is called Edmonds–Karp.
When no more paths in step 2 can be found, will not be able to reach in the residual
network. If is the set of nodes reachable by in the residual network, then the total
capacity in the original network of edges from to the remainder of is on the one hand
equal to the total flow we found from to ,
and on the other hand serves as an upper bound for all such flows.
This proves that the flow we found is maximal. See also Max-flow Min-cut theorem.
If the graph has multiple sources and sinks, we act as follows:
Suppose that and . Add a new source with an edge from to every node , with capacity . And add a new sink with an edge fr |
https://en.wikipedia.org/wiki/Prim%27s%20algorithm | In computer science, Prim's algorithm (also known as Jarník's algorithm) is a greedy algorithm that finds a minimum spanning tree for a weighted undirected graph. This means it finds a subset of the edges that forms a tree that includes every vertex, where the total weight of all the edges in the tree is minimized. The algorithm operates by building this tree one vertex at a time, from an arbitrary starting vertex, at each step adding the cheapest possible connection from the tree to another vertex.
The algorithm was developed in 1930 by Czech mathematician Vojtěch Jarník and later rediscovered and republished by computer scientists Robert C. Prim in 1957 and Edsger W. Dijkstra in 1959. Therefore, it is also sometimes called the Jarník's algorithm, Prim–Jarník algorithm, Prim–Dijkstra algorithm
or the DJP algorithm.
Other well-known algorithms for this problem include Kruskal's algorithm and Borůvka's algorithm. These algorithms find the minimum spanning forest in a possibly disconnected graph; in contrast, the most basic form of Prim's algorithm only finds minimum spanning trees in connected graphs. However, running Prim's algorithm separately for each connected component of the graph, it can also be used to find the minimum spanning forest. In terms of their asymptotic time complexity, these three algorithms are equally fast for sparse graphs, but slower than other more sophisticated algorithms.
However, for graphs that are sufficiently dense, Prim's algorithm can be made to run in linear time, meeting or improving the time bounds for other algorithms.
Description
The algorithm may informally be described as performing the following steps:
In more detail, it may be implemented following the pseudocode below.
As described above, the starting vertex for the algorithm will be chosen arbitrarily, because the first iteration of the main loop of the algorithm will have a set of vertices in Q that all have equal weights, and the algorithm will automatically start a new tree in F when it completes a spanning tree of each connected component of the input graph. The algorithm may be modified to start with any particular vertex s by setting C[s] to be a number smaller than the other values of C (for instance, zero), and it may be modified to only find a single spanning tree rather than an entire spanning forest (matching more closely the informal description) by stopping whenever it encounters another vertex flagged as having no associated edge.
Different variations of the algorithm differ from each other in how the set Q is implemented: as a simple linked list or array of vertices, or as a more complicated priority queue data structure. This choice leads to differences in the time complexity of the algorithm. In general, a priority queue will be quicker at finding the vertex v with minimum cost, but will entail more expensive updates when the value of C[w] changes.
Time complexity
The time complexity of Prim's algorithm depends on the data stru |
https://en.wikipedia.org/wiki/Dictionary%20attack | In cryptanalysis and computer security, a dictionary attack is an attack using a restricted subset of a keyspace to defeat a cipher or authentication mechanism by trying to determine its decryption key or passphrase, sometimes trying thousands or millions of likely possibilities often obtained from lists of past security breaches.
Technique
A dictionary attack is based on trying all the strings in a pre-arranged listing. Such attacks originally used words found in a dictionary (hence the phrase dictionary attack); however, now there are much larger lists available on the open Internet containing hundreds of millions of passwords recovered from past data breaches. There is also cracking software that can use such lists and produce common variations, such as substituting numbers for similar-looking letters. A dictionary attack tries only those possibilities which are deemed most likely to succeed. Dictionary attacks often succeed because many people have a tendency to choose short passwords that are ordinary words or common passwords; or variants obtained, for example, by appending a digit or punctuation character. Dictionary attacks are often successful, since many commonly used password creation techniques are covered by the available lists, combined with cracking software pattern generation. A safer approach is to randomly generate a long password (15 letters or more) or a multiword passphrase, using a password manager program or manually typing a password.
Pre-computed dictionary attack/Rainbow table attack
It is possible to achieve a time–space tradeoff by pre-computing a list of hashes of dictionary words and storing these in a database using the hash as the key. This requires a considerable amount of preparation time, but this allows the actual attack to be executed faster. The storage requirements for the pre-computed tables were once a major cost, but now they are less of an issue because of the low cost of disk storage. Pre-computed dictionary attacks are particularly effective when a large number of passwords are to be cracked. The pre-computed dictionary needs be generated only once, and when it is completed, password hashes can be looked up almost instantly at any time to find the corresponding password. A more refined approach involves the use of rainbow tables, which reduce storage requirements at the cost of slightly longer lookup-times. See LM hash for an example of an authentication system compromised by such an attack.
Pre-computed dictionary attacks, or "rainbow table attacks", can be thwarted by the use of salt, a technique that forces the hash dictionary to be recomputed for each password sought, making precomputation infeasible, provided that the number of possible salt values is large enough.
Dictionary attack software
Cain and Abel
Crack
Aircrack-ng
John the Ripper
L0phtCrack
Metasploit Project
Ophcrack
Cryptool
See also
Brute-force attack
E-mail address harvesting
Intercontinental Dictionary Series, an online linguis |
https://en.wikipedia.org/wiki/Resource%20Description%20Framework | The Resource Description Framework (RDF) is a World Wide Web Consortium (W3C) standard originally designed as a data model for metadata. It has come to be used as a general method for description and exchange of graph data. RDF provides a variety of syntax notations and data serialization formats, with Turtle (Terse RDF Triple Language) currently being the most widely used notation.
RDF is a directed graph composed of triple statements. An RDF graph statement is represented by: 1) a node for the subject, 2) an arc that goes from a subject to an object for the predicate, and 3) a node for the object. Each of the three parts of the statement can be identified by a Uniform Resource Identifier (URI). An object can also be a literal value. This simple, flexible data model has a lot of expressive power to represent complex situations, relationships, and other things of interest, while also being appropriately abstract.
RDF was adopted as a W3C recommendation in 1999. The RDF 1.0 specification was published in 2004, the RDF 1.1 specification in 2014. SPARQL is a standard query language for RDF graphs. RDF Schema (RDFS), Web Ontology Language (OWL) and SHACL (Shapes Constraint Language) are ontology languages that are used to describe RDF data.
Overview
The RDF data model is similar to classical conceptual modeling approaches (such as entity–relationship or class diagrams). It is based on the idea of making statements about resources (in particular web resources) in expressions of the form subject–predicate–object, known as triples. The subject denotes the resource, and the predicate denotes traits or aspects of the resource, and expresses a relationship between the subject and the object.
For example, one way to represent the notion "The sky has the color blue" in RDF is as the triple: a subject denoting "the sky", a predicate denoting "has the color", and an object denoting "blue". Therefore, RDF uses subject instead of object (or entity) in contrast to the typical approach of an entity–attribute–value model in object-oriented design: entity (sky), attribute (color), and value (blue).
RDF is an abstract model with several serialization formats (being essentially specialized file formats). In addition the particular encoding for resources or triples can vary from format to format.
This mechanism for describing resources is a major component in the W3C's Semantic Web activity: an evolutionary stage of the World Wide Web in which automated software can store, exchange, and use machine-readable information distributed throughout the Web, in turn enabling users to deal with the information with greater efficiency and certainty. RDF's simple data model and ability to model disparate, abstract concepts has also led to its increasing use in knowledge management applications unrelated to Semantic Web activity.
A collection of RDF statements intrinsically represents a labeled, directed multigraph. This makes an RDF data model better suited to certain ki |
https://en.wikipedia.org/wiki/EuroWordNet | EuroWordNet is a system of semantic networks for European languages, based on WordNet. Each language develops its own wordnet but they are interconnected with interlingual links stored in the Interlingual Index (ILI).
Unlike the original Princeton WordNet, most of the other wordnets are not freely available.
Languages
The original EuroWordNet project dealt with Dutch, Italian, Spanish, German, French, Czech, and Estonian. These wordnets are now frozen, but wordnets for other languages have been developed to varying degrees.
License
Some examples of EuroWordNet are available for free. Access to the full database, however, is charged. In some cases, OpenThesaurus and BabelNet may serve as a free alternative.
See also
vidby
Babbel
External links
Lexical databases
Computational linguistics
Online dictionaries |
https://en.wikipedia.org/wiki/Text%20corpus | In linguistics and natural language processing, a corpus (: corpora) or text corpus is a dataset, consisting of natively digital and older, digitalized, language resources, either annotated or unannotated.
Annotated, they have been used in corpus linguistics for statistical hypothesis testing, checking occurrences or validating linguistic rules within a specific language territory.
In search technology, a corpus is the collection of documents which is being searched.
Overview
A corpus may contain texts in a single language (monolingual corpus) or text data in multiple languages (multilingual corpus).
In order to make the corpora more useful for doing linguistic research, they are often subjected to a process known as annotation. An example of annotating a corpus is part-of-speech tagging, or POS-tagging, in which information about each word's part of speech (verb, noun, adjective, etc.) is added to the corpus in the form of tags. Another example is indicating the lemma (base) form of each word. When the language of the corpus is not a working language of the researchers who use it, interlinear glossing is used to make the annotation bilingual.
Some corpora have further structured levels of analysis applied. In particular, smaller corpora may be fully parsed. Such corpora are usually called Treebanks or Parsed Corpora. The difficulty of ensuring that the entire corpus is completely and consistently annotated means that these corpora are usually smaller, containing around one to three million words. Other levels of linguistic structured analysis are possible, including annotations for morphology, semantics and pragmatics.
Applications
Corpora are the main knowledge base in corpus linguistics. Other notable areas of application include:
Language technology, natural language processing, computational linguistics
The analysis and processing of various types of corpora are also the subject of much work in computational linguistics, speech recognition and machine translation, where they are often used to create hidden Markov models for part of speech tagging and other purposes. Corpora and frequency lists derived from them are useful for language teaching. Corpora can be considered as a type of foreign language writing aid as the contextualised grammatical knowledge acquired by non-native language users through exposure to authentic texts in corpora allows learners to grasp the manner of sentence formation in the target language, enabling effective writing.
Machine translation
Multilingual corpora that have been specially formatted for side-by-side comparison are called aligned parallel corpora. There are two main types of parallel corpora which contain texts in two languages. In a translation corpus, the texts in one language are translations of texts in the other language. In a comparable corpus, the texts are of the same kind and cover the same content, but they are not translations of each other. To exploit a parallel text, some kin |
https://en.wikipedia.org/wiki/Deep%20Thought | Deep Thought or Deep Thinking may refer to:
Deep Thought (Hitchhiker's Guide to the Galaxy), a fictional computer in The Hitchhiker's Guide to the Galaxy
Deep Thought (chess computer), an IBM-produced chess computer, named after the Hitchhiker's Guide's Deep Thought
Deep Thoughts (album), or The Thought Remains the Same, a 2000 compilation album by bands on Nitro Records
Deep Thoughts by Jack Handey, a segment on Saturday Night Live consisting of one-liner jokes written and orated by Jack Handey
Deep Thinking, a 2017 book by Garry Kasparov and Mig Greengard
See also |
https://en.wikipedia.org/wiki/CYK%20algorithm | In computer science, the Cocke–Younger–Kasami algorithm (alternatively called CYK, or CKY) is a parsing algorithm for context-free grammars published by Itiroo Sakai in 1961. The algorithm is named after some of its rediscoverers: John Cocke, Daniel Younger, Tadao Kasami, and Jacob T. Schwartz. It employs bottom-up parsing and dynamic programming.
The standard version of CYK operates only on context-free grammars given in Chomsky normal form (CNF). However any context-free grammar may be algorithmically transformed into a CNF grammar expressing the same language .
The importance of the CYK algorithm stems from its high efficiency in certain situations. Using big O notation, the worst case running time of CYK is , where is the length of the parsed string and is the size of the CNF grammar . This makes it one of the most efficient parsing algorithms in terms of worst-case asymptotic complexity, although other algorithms exist with better average running time in many practical scenarios.
Standard form
The dynamic programming algorithm requires the context-free grammar to be rendered into Chomsky normal form (CNF), because it tests for possibilities to split the current sequence into two smaller sequences. Any context-free grammar that does not generate the empty string can be represented in CNF using only production rules of the forms , , and where is the start symbol.
Algorithm
As pseudocode
The algorithm in pseudocode is as follows:
let the input be a string I consisting of n characters: a1 ... an.
let the grammar contain r nonterminal symbols R1 ... Rr, with start symbol R1.
let P[n,n,r] be an array of booleans. Initialize all elements of P to false.
let back[n,n,r] be an array of lists of backpointing triples. Initialize all elements of back to the empty list.
for each s = 1 to n
for each unit production Rv → as
set P[1,s,v] = true
for each l = 2 to n -- Length of span
for each s = 1 to n-l+1 -- Start of span
for each p = 1 to l-1 -- Partition of span
for each production Ra → Rb Rc
if P[p,s,b] and P[l-p,s+p,c] then
set P[l,s,a] = true,
append <p,b,c> to back[l,s,a]
if P[n,1,1] is true then
I is member of language
return back -- by retracing the steps through back, one can easily construct all possible parse trees of the string.
else
return "not a member of language"
Probabilistic CYK (for finding the most probable parse)
Allows to recover the most probable parse given the probabilities of all productions.
let the input be a string I consisting of n characters: a1 ... an.
let the grammar contain r nonterminal symbols R1 ... Rr, with start symbol R1.
let P[n,n,r] be an array of real numbers. Initialize all elements of P to zero.
let back[n,n,r] be an array of backpointing triples.
for each s = 1 to n
for each unit production Rv →as
set P[1,s,v] = Pr(Rv →as)
for each l = 2 to n -- Length |
https://en.wikipedia.org/wiki/Real%20data%20type | A real data type is a data type used in a computer program to represent an approximation of a real number.
Because the real numbers are not countable, computers cannot represent them exactly using a finite amount of information.
Most often, a computer will use a rational approximation to a real number.
Rational numbers
The most general data type for a rational number stores the numerator and denominator as integers.
Fixed-point numbers
A fixed-point data type uses the same denominator for all numbers. The denominator is usually a power of two. For example, in a fixed-point system that uses the denominator 65,536 (216), the hexadecimal number 0x12345678 means 0x12345678/65536 or 305419896/65536 or 4660 + 22136/65536 or about 4660.33777.
Floating-point numbers
A floating-point data type is a compromise between the flexibility of a general rational number data type and the speed of fixed-point arithmetic. It uses some of the bits in the data type to specify a power of two for the denominator. See IEEE Standard for Floating-Point Arithmetic.
Decimal numbers
Similar to fixed-point or floating-point data type, but with a denominator that is a power of 10 instead of a power of 2.
Data types |
https://en.wikipedia.org/wiki/Inductive%20logic%20programming | Inductive logic programming (ILP) is a subfield of symbolic artificial intelligence which uses logic programming as a uniform representation for examples, background knowledge and hypotheses. Given an encoding of the known background knowledge and a set of examples represented as a logical database of facts, an ILP system will derive a hypothesised logic program which entails all the positive and none of the negative examples.
Schema: positive examples + negative examples + background knowledge ⇒ hypothesis.
Inductive logic programming is particularly useful in bioinformatics and natural language processing. Gordon Plotkin and Ehud Shapiro laid the initial theoretical foundation for inductive machine learning in a logical setting. Shapiro built their first implementation (Model Inference System) in 1981: a Prolog program that inductively inferred logic programs from positive and negative examples. The first full first-order implementation of inductive logic programming was Theorist in 1986. The term Inductive Logic Programming was first introduced in a paper by Stephen Muggleton in 1991. Muggleton also founded the annual international conference on Inductive Logic Programming, introduced the theoretical ideas of Predicate Invention, Inverse resolution, and Inverse entailment. Muggleton implemented Inverse entailment first in the PROGOL system. The term "inductive" here refers to philosophical (i.e. suggesting a theory to explain observed facts) rather than mathematical (i.e. proving a property for all members of a well-ordered set) induction.
Formal definition
The background knowledge is given as a logic theory , commonly in the form of Horn clauses used in logic programming.
The positive and negative examples are given as a conjunction and of unnegated and negated ground literals, respectively.
A correct hypothesis is a logic proposition satisfying the following requirements.
"Necessity" does not impose a restriction on , but forbids any generation of a hypothesis as long as the positive facts are explainable without it.
"Sufficiency" requires any generated hypothesis to explain all positive examples .
"Weak consistency" forbids generation of any hypothesis that contradicts the background knowledge .
"Strong consistency" also forbids generation of any hypothesis that is inconsistent with the negative examples , given the background knowledge ; it implies "Weak consistency"; if no negative examples are given, both requirements coincide. Džeroski requires only "Sufficiency" (called "Completeness" there) and "Strong consistency".
Example
The following well-known example about learning definitions of family relations uses the abbreviations
, , , , , , , , and .
It starts from the background knowledge (cf. picture)
,
the positive examples
,
and the trivial proposition
to denote the absence of negative examples.
Plotkin's "relative least general generalization (rlgg)" approach to inductive logic programming shall be used to obtain |
https://en.wikipedia.org/wiki/LocalTalk | LocalTalk is a particular implementation of the physical layer of the AppleTalk networking system from Apple Computer.
LocalTalk specifies a system of shielded twisted pair cabling, plugged into self-terminating transceivers, running at a rate of 230.4 kbit/s. CSMA/CA was implemented as a random multiple access method.
Networking was envisioned in the Macintosh during planning, so the Mac was given expensive RS-422 capable serial ports, first on a nine-pin D-connector, then on a Mini-DIN-8 connector. The ports were driven by the Zilog SCC, which could serve as either a standard UART or handle the much more complicated HDLC protocol, which was a packet oriented protocol that incorporated addressing, bit-stuffing, and packet checksumming in hardware. Coupled together with the RS422 electrical connections, this provided a reasonably high-speed data connection.
The 230.4 kbit/s bit rate is the highest in the series of standard serial bit rates (110, 150, 300, 600, 1200, 2400, 4800, 9600, 14400, 19200, 28800, 38400, 57600, 115200, 230400) derived from the 3.6864 MHz clock after the customary divide-by-16. This clock frequency, 3.6864 MHz, was chosen (in part) to support the common asynchronous baud rates up to 38.4 kbit/s using the SCC's internal baud-rate generator. When the SCC's internal PLL was used to lock to the clock embedded in the LocalTalk serial data stream (using its FM0 encoding method) a divide-by-16 setting on the PLL yielded the fastest rate available, namely 230.4 kbit/s.
Originally released as "AppleTalk Personal Network", LocalTalk used shielded twisted-pair cable with 3-pin Mini-DIN connectors. Cables were daisy-chained from transceiver to transceiver. Each transceiver had two 3-pin Mini-DIN ports, and a "pigtail" cable to connect to the Mac's DE-9 serial connector. Later, when the Mac Plus introduced the 8-pin Mini-DIN serial connector, transceivers were updated as well.
A variation of LocalTalk called PhoneNET was introduced by Farallon Computing. It used standard unshielded side-by-side telephone wire, with six-position modular connectors (same as the popular RJ11 telephone connectors) connected to a PhoneNET transceiver, instead of the expensive, shielded, twisted-pair cable. In addition to being lower cost, PhoneNET-wired networks were more reliable due to the connections being more difficult to accidentally disconnect. In addition, because it used the "outer" pair of the modular connector, it could travel on many pre-existing phone cables and jacks where just the inner pair was in use for RJ11 telephone service. PhoneNET was also able to use an office's existing phone wire, allowing for entire floors of computers to be easily networked. Farallon introduced a 12-port hub, which made constructing star topology networks of up to 48 devices as easy as adding jacks at the workstations and some jumpers in the phone closet. These factors led to PhoneNET largely supplanting LocalTalk wiring in low-cost networking.
The useful |
https://en.wikipedia.org/wiki/Silk%20Road | The Silk Road () was a network of Eurasian trade routes active from the second century BCE until the mid-15th century. Spanning over 6,400 kilometers (4,000 miles), it played a central role in facilitating economic, cultural, political, and religious interactions between the East and West. The name "Silk Road", first coined in the late 19th century, has fallen into disuse among some modern historians in favor of Silk Routes, on the grounds that it more accurately describes the intricate web of land and sea routes connecting Central, East, South, Southeast, and West Asia, East Africa, and Southern Europe.
The Silk Road derives its name from the highly lucrative trade of silk textiles that were produced almost exclusively in China. The network began with the Han dynasty's expansion into Central Asia around 114 BCE through the missions and explorations of the Chinese imperial envoy Zhang Qian, which brought the region under unified control. The Parthian Empire provided a bridge to East Africa and the Mediterranean. By the early first century CE, Chinese silk was widely sought-after in Rome, Egypt, and Greece. Other lucrative commodities from the East included tea, dyes, perfumes, and porcelain; among Western exports were horses, camels, honey, wine, and gold. Aside from generating substantial wealth for emerging mercantile classes, the proliferation of goods such as paper and gunpowder greatly altered the trajectory of various realms, if not world history.
During its roughly 1,500 years of existence, the Silk Road endured the rise and fall of numerous empires and major events such as the Black Death and the Mongol conquests. As a highly decentralized network, security was sparse. Travelers faced constant threats of banditry and nomadic raiders, and long expanses of inhospitable terrain. Few individuals crossed the entirety of the Silk Road, instead relying on a succession of middlemen based at various stopping points along the way. In addition to goods, the network facilitated an unprecedented exchange of ideas, religions (especially Buddhism), philosophies, and scientific discoveries, many of which were syncretised or reshaped by the societies that encountered them. Likewise, a wide variety of people used the routes. Diseases such as plague also spread along the Silk Road, possibly contributing to the Black Death.
Despite repeatedly surviving many geopolitical changes and disruptions, the Silk Road abruptly lost its importance with the rise of the Ottoman Empire in 1453, which almost immediately severed trade between East and West. This prompted European efforts to seek alternative routes to Eastern riches, thereby ushering the Age of Discovery, European colonialism, and a more intensified process of globalization, which had arguably begun with the Silk Road. In the 21st century, the name "New Silk Road" is used to describe several large infrastructure projects along many of the historic trade routes; among the best known include the Eurasian La |
https://en.wikipedia.org/wiki/Desktop%20publishing | Desktop publishing (DTP) is the creation of documents using page layout software on a personal ("desktop") computer. It was first used almost exclusively for print publications, but now it also assists in the creation of various forms of online content. Desktop publishing software can generate layouts and produce typographic-quality text and images comparable to traditional typography and printing. Desktop publishing is also the main reference for digital typography. This technology allows individuals, businesses, and other organizations to self-publish a wide variety of content, from menus to magazines to books, without the expense of commercial printing.
Desktop publishing often requires the use of a personal computer and WYSIWYG page layout software to create documents for either large-scale publishing or small-scale local multifunction peripheral output and distribution - although non-WYSIWYG systems such as TeX and LaTeX are also used, especially in scientific publishing. Desktop publishing methods provide more control over design, layout, and typography than word processing. However, word processing software has evolved to include most, if not all, capabilities previously available only with professional printing or desktop publishing.
The same DTP skills and software used for common paper and book publishing are sometimes used to create graphics for point of sale displays, presentations, infographics, brochures, business cards, promotional items, trade show exhibits, retail package designs and outdoor signs.
History
Desktop publishing was first developed at Xerox PARC in the 1970s. A contradictory claim states that desktop publishing began in 1983 with a program developed by James Davise at a community newspaper in Philadelphia. The program Type Processor One ran on a PC using a graphics card for a WYSIWYG display and was offered commercially by Best Info in 1984. Desktop typesetting with only limited page makeup facilities arrived in 1978–1979 with the introduction of TeX, and was extended in 1985 with the introduction of LaTeX.
The desktop publishing market took off in 1985 with the introduction in January of the Apple LaserWriter printer. This momentum was kept up with the addition of PageMaker software from Aldus, which rapidly became the standard software application for desktop publishing. With its advanced layout features, PageMaker immediately relegated word processors like Microsoft Word to the composition and editing of purely textual documents. The term "desktop publishing" is attributed to Aldus founder Paul Brainerd, who sought a marketing catchphrase to describe the small size and relative affordability of this suite of products, in contrast to the expensive commercial phototypesetting equipment of the day.
Before the advent of desktop publishing, the only option available to most people for producing typed documents (as opposed to handwritten documents) was a typewriter, which offered only a handful of typefaces (usua |
https://en.wikipedia.org/wiki/Floor%20and%20ceiling%20functions | In mathematics and computer science, the floor function is the function that takes as input a real number , and gives as output the greatest integer less than or equal to , denoted or . Similarly, the ceiling function maps to the least integer greater than or equal to , denoted or .
For example, for floor: , , and for ceiling: , and .
Historically, the floor of has been–and still is–called the integral part or integer part of , often denoted (as well as a variety of other notations). However, the same term, integer part, is also used for truncation towards zero, which differs from the floor function for negative numbers.
For an integer, .
Although and produce graphs that appear exactly alike, they are not the same when the value of x is an exact integer. For example, when =2.0001; . However, if =2, then , while .
Notation
The integral part or integer part of a number ( in the original) was first defined in 1798 by Adrien-Marie Legendre in his proof of the Legendre's formula.
Carl Friedrich Gauss introduced the square bracket notation in his third proof of quadratic reciprocity (1808). This remained the standard in mathematics until Kenneth E. Iverson introduced, in his 1962 book A Programming Language, the names "floor" and "ceiling" and the corresponding notations and . (Iverson used square brackets for a different purpose, the Iverson bracket notation.) Both notations are now used in mathematics, although Iverson's notation will be followed in this article.
In some sources, boldface or double brackets are used for floor, and reversed brackets or for ceiling.
The fractional part is the sawtooth function, denoted by for real and defined by the formula
For all x,
.
These characters are provided in Unicode:
In the LaTeX typesetting system, these symbols can be specified with the and commands in math mode, and extended in size using and as needed.
Some authors define as the round-toward-zero function, so and , and call it the "integer part". This is truncation to zero decimal digits.
Definition and properties
Given real numbers x and y, integers m and n and the set of integers , floor and ceiling may be defined by the equations
Since there is exactly one integer in a half-open interval of length one, for any real number x, there are unique integers m and n satisfying the equation
where and may also be taken as the definition of floor and ceiling.
Equivalences
These formulas can be used to simplify expressions involving floors and ceilings.
In the language of order theory, the floor function is a residuated mapping, that is, part of a Galois connection: it is the upper adjoint of the function that embeds the integers into the reals.
These formulas show how adding an integer to the arguments affects the functions:
The above are never true if is not an integer; however, for every and , the following inequalities hold:
Monotonicity
Both floor and ceiling functions are the monotonically non-d |
https://en.wikipedia.org/wiki/Disassembler | A disassembler is a computer program that translates machine language into assembly language—the inverse operation to that of an assembler. Disassembly, the output of a disassembler, is often formatted for human-readability rather than suitability for input to an assembler, making it principally a reverse-engineering tool. Common uses of disassemblers include analyzing high-level programing language compilers output and their optimizations, recovering source code of a program whose original source was lost, malware analysis, modifying software (such as ROM hacking), and software cracking.
A disassembler differs from a decompiler, which targets a high-level language rather than an assembly language.
Assembly language source code generally permits the use of constants and programmer comments. These are usually removed from the assembled machine code by the assembler. If so, a disassembler operating on the machine code would produce disassembly lacking these constants and comments; the disassembled output becomes more difficult for a human to interpret than the original annotated source code. Some disassemblers provide a built-in code commenting feature where the generated output gets enriched with comments regarding called API functions or parameters of called functions. Some disassemblers make use of the symbolic debugging information present in object files such as ELF. For example, IDA allows the human user to make up mnemonic symbols for values or regions of code in an interactive session: human insight applied to the disassembly process often parallels human creativity in the code writing process.
Challenges
Writing a disassembler which produces code which, when assembled, produces exactly the original binary is possible; however, there are often differences. This poses demands on the expressivity of the assembler. For example, an x86 assembler takes an arbitrary choice between two binary codes for something as simple as MOV AX,BX. If the original code uses the other choice, the original code simply cannot be reproduced at any given point in time. However, even when a fully correct disassembly is produced, problems remain if the program requires modification. For example, the same machine language jump instruction can be generated by assembly code to jump to a specified location (for example, to execute specific code), or to jump a specified number of bytes (for example, to skip over an unwanted branch). A disassembler cannot know what is intended, and may use either syntax to generate a disassembly which reproduces the original binary. However, if a programmer wants to add instructions between the jump instruction and its destination, it is necessary to understand the program's operation to determine whether the jump should be absolute or relative, i.e., whether its destination should remain at a fixed location, or be moved so as to skip both the original and added instructions.
Another challenge is that it is not always possible to iden |
https://en.wikipedia.org/wiki/TI-89%20series | The TI-89 and the TI-89 Titanium are graphing calculators developed by Texas Instruments (TI). They are differentiated from most other TI graphing calculators by their computer algebra system, which allows symbolic manipulation of algebraic expressions—equations can be solved in terms of variables, whereas the TI-83/84 series can only give a numeric result.
TI-89
The TI-89 is a graphing calculator developed by Texas Instruments in 1998. The unit features a 160×100 pixel resolution LCD and a large amount of flash memory, and includes TI's Advanced Mathematics Software. The TI-89 is one of the highest model lines in TI's calculator products, along with the TI-Nspire. In the summer of 2004, the standard TI-89 was replaced by the TI-89 Titanium.
The TI-89 runs on a 32-bit microprocessor, the Motorola 68000, which nominally runs at 10 or 12 MHz, depending on the calculator's hardware version. The calculator has 256 kB of RAM, (190 kB of which are available to the user) and 2 MB of flash memory (700 kB of which is available to the user). The RAM and Flash ROM are used to store expressions, variables, programs, text files, and lists.
The TI-89 is essentially a TI-92 Plus with a limited keyboard and smaller screen. It was created partially in response to the fact that while calculators are allowed on many standardized tests, the TI-92 was not due to the QWERTY layout of its keyboard. Additionally, some people found the TI-92 unwieldy and overly large. The TI-89 is significantly smaller—about the same size as most other graphing calculators. It has a flash ROM, a feature present on the TI-92 Plus but not on the original TI-92.
User features
The major advantage of the TI-89 over other TI calculators is its built-in computer algebra system, or CAS. The calculator can evaluate and simplify algebraic expressions symbolically. For example, entering x^2-4x+4 returns . The answer is "prettyprinted" by default; that is, displayed as it would be written by hand (e.g. the aforementioned rather than x^2-4x+4). The TI-89's abilities include:
Algebraic factoring of expressions, including partial fraction decomposition.
Algebraic simplification; for example, the CAS can combine multiple terms into one fraction by finding a common denominator.
Evaluation of trigonometric expressions to exact values. For example, sin(60°) returns instead of 0.86603.
Solving equations for a certain variable. The CAS can solve for one variable in terms of others; it can also solve systems of equations. For equations such as quadratics where there are multiple solutions, it returns all of them. Equations with infinitely many solutions are solved by introducing arbitrary constants: solve(tan(x+2)=0,x) returns x=2.(90.@n1-1), with the @n1 representing any integer.
Symbolic and numeric differentiation and integration. Derivatives and definite integrals are evaluated exactly when possible, and approximately otherwise.
Calculate greatest common divisor (gcd) and least commo |
https://en.wikipedia.org/wiki/Computer%20algebra%20system | A computer algebra system (CAS) or symbolic algebra system (SAS) is any mathematical software with the ability to manipulate mathematical expressions in a way similar to the traditional manual computations of mathematicians and scientists. The development of the computer algebra systems in the second half of the 20th century is part of the discipline of "computer algebra" or "symbolic computation", which has spurred work in algorithms over mathematical objects such as polynomials.
Computer algebra systems may be divided into two classes: specialized and general-purpose. The specialized ones are devoted to a specific part of mathematics, such as number theory, group theory, or teaching of elementary mathematics.
General-purpose computer algebra systems aim to be useful to a user working in any scientific field that requires manipulation of mathematical expressions. To be useful, a general-purpose computer algebra system must include various features such as:
a user interface allowing a user to enter and display mathematical formulas, typically from a keyboard, menu selections, mouse or stylus.
a programming language and an interpreter (the result of a computation commonly has an unpredictable form and an unpredictable size; therefore user intervention is frequently needed),
a simplifier, which is a rewrite system for simplifying mathematics formulas,
a memory manager, including a garbage collector, needed by the huge size of the intermediate data, which may appear during a computation,
an arbitrary-precision arithmetic, needed by the huge size of the integers that may occur,
a large library of mathematical algorithms and special functions.
The library must not only provide for the needs of the users, but also the needs of the simplifier. For example, the computation of polynomial greatest common divisors is systematically used for the simplification of expressions involving fractions.
This large amount of required computer capabilities explains the small number of general-purpose computer algebra systems. Significant systems include Axiom, GAP, Maxima, Magma, Maple, Mathematica, and SageMath.
History
Computer algebra systems began to appear in the 1960s and evolved out of two quite different sources—the requirements of theoretical physicists and research into artificial intelligence.
A prime example for the first development was the pioneering work conducted by the later Nobel Prize laureate in physics Martinus Veltman, who designed a program for symbolic mathematics, especially high-energy physics, called Schoonschip (Dutch for "clean ship") in 1963. Another early system was FORMAC.
Using Lisp as the programming basis, Carl Engelman created MATHLAB in 1964 at MITRE within an artificial-intelligence research environment. Later MATHLAB was made available to users on PDP-6 and PDP-10 systems running TOPS-10 or TENEX in universities. Today it can still be used on SIMH emulations of the PDP-10. MATHLAB ("mathematical laboratory") should not b |
https://en.wikipedia.org/wiki/Unification%20%28computer%20science%29 | In logic and computer science, unification is an algorithmic process of solving equations between symbolic expressions. For example, using x,y,z as variables, the singleton equation set { cons(x,cons(x,nil)) = cons(2,y) } is a syntactic first-order unification problem that has the substitution { x ↦ 2, y ↦ cons(2,nil) } as its only solution.
A unification algorithm was first discovered by Jacques Herbrand, while a first formal investigation can be attributed to John Alan Robinson, who used first-order syntactical unification as a basic building block of his resolution procedure for first-order logic, a great step forward in automated reasoning technology, as it eliminated one source of combinatorial explosion: searching for instantiation of terms. Today, automated reasoning is still the main application area of unification.
Syntactical first-order unification is used in logic programming and programming language type system implementation, especially in Hindley–Milner based type inference algorithms.
Semantic unification is used in SMT solvers, term rewriting algorithms and cryptographic protocol analysis.
Higher-order unification is used in proof assistants, for example Isabelle and Twelf, and restricted forms of higher-order unification (higher-order pattern unification) are used in some programming language implementations, such as lambdaProlog, as higher-order patterns are expressive, yet their associated unification procedure retains theoretical properties closer to first-order unification.
Formal definition
A unification problem is a finite set of equations to solve, where are in the set of terms or expressions. Depending on which expressions or terms are allowed to occur in an equation set or unification problem, and which expressions are considered equal, several frameworks of unification are distinguished. If higher-order variables, that is, variables representing functions, are allowed in an expression, the process is called higher-order unification, otherwise first-order unification. If a solution is required to make both sides of each equation literally equal, the process is called syntactic or free unification, otherwise semantic or equational unification, or E-unification, or unification modulo theory.
If the right side of each equation is closed (no free variables), the problem is called (pattern) matching. The left side (with variables) of each equation is called the pattern.
Prerequisites
Formally, a unification approach presupposes
An infinite set of variables. For higher-order unification, it is convenient to choose disjoint from the set of lambda-term bound variables.
A set of terms such that . For first-order unification, is usually the set of first-order terms (terms built from variable and function symbols). For higher-order unification consists of first-order terms and lambda terms (terms containing some higher-order variables).
A mapping vars: , assigning to each term the set of free variables occurrin |
https://en.wikipedia.org/wiki/S-expression | In computer programming, an S-expression (or symbolic expression, abbreviated as sexpr or sexp) is an expression in a like-named notation for nested list (tree-structured) data. S-expressions were invented for and popularized by the programming language Lisp, which uses them for source code as well as data.
In the usual parenthesized syntax of Lisp, an S-expression is classically defined as
an atom of the form x, or
an expression of the form (x . y) where x and y are S-expressions.
This definition reflects LISP's representation of a list as a series of "cells", each one an ordered pair. In plain lists, y points to the next cell (if any), thus forming a list. The recursive clause of the definition means that both this representation and the S-expression notation can represent any binary tree. However, the representation can in principle allow circular references, in which case the structure is not a tree at all, but a cyclic graph, and cannot be represented in classical S-expression notation
unless a convention for cross-reference is provided (analogous to SQL foreign keys, SGML/XML IDREFs, etc.). Modern Lisp dialects such as Common Lisp and Scheme provide such syntax via datum labels, with which objects can be marked, which can then recur elsewhere, indicating shared rather than duplicated structure, enabling the reader or printer to detect and thus trigger evaluation or display of cycles without infinitely recursing
#n=(x y . #n#)
The definition of an atom varies per context; in the original definition by John McCarthy, it was assumed that there existed "an infinite set of distinguishable atomic symbols" represented as "strings of capital Latin letters and digits with single embedded blanks" (a subset of character string and numeric literals).
Most modern sexpr notations allow more general quoted strings (for example including punctuation or full Unicode), and use an abbreviated notation to represent lists with more than 2 members, so that
(x y z)
stands for
(x . (y . (z . NIL)))
NIL is the special end-of-list object (alternatively written (), which is the only representation in Scheme).
In the Lisp family of programming languages, S-expressions are used to represent both source code and data. Other uses of S-expressions are in Lisp-derived languages such as DSSSL, and as mark-up in communication protocols like IMAP and John McCarthy's CBCL. It's also used as text representation of WebAssembly. The details of the syntax and supported data types vary in the different languages, but the most common feature among these languages is the use of S-expressions and prefix notation.
Datatypes and syntax
There are many variants of the S-expression format, supporting a variety of different syntaxes for different datatypes. The most widely supported are:
Lists and pairs: (1 () (2 . 3) (4))
Symbols: with-hyphen ?@!$ |a symbol with spaces|
Strings: "Hello, world!"
Integers: -9876543210
Floating-point numbers: -0.0 6.28318 6.022e23
The c |
https://en.wikipedia.org/wiki/Audio%20codec | An audio codec is a device or computer program capable of encoding or decoding a digital data stream (a codec) that encodes or decodes audio. In software, an audio codec is a computer program implementing an algorithm that compresses and decompresses digital audio data according to a given audio file or streaming media audio coding format. The objective of the algorithm is to represent the high-fidelity audio signal with a minimum number of bits while retaining quality. This can effectively reduce the storage space and the bandwidth required for transmission of the stored audio file. Most software codecs are implemented as libraries which interface to one or more multimedia players. Most modern audio compression algorithms are based on modified discrete cosine transform (MDCT) coding and linear predictive coding (LPC).
In hardware, audio codec refers to a single device that encodes analog audio as digital signals and decodes digital back into analog. In other words, it contains both an analog-to-digital converter (ADC) and digital-to-analog converter (DAC) running off the same clock signal. This is used in sound cards that support both audio in and out, for instance. Hardware audio codecs send and receive digital data using buses such as AC-Link, I²S, SPI, I²C, etc. Most commonly the digital data is linear PCM, and this is the only format that most codecs support, but some legacy codecs support other formats such as G.711 for telephony.
See also
Comparison of audio coding formats
List of codecs
List of open-source codecs
Transcoding
Video codec
References
fr:Codec |
https://en.wikipedia.org/wiki/Video%20file%20format | A video file format is a type of file format for storing digital video data on a computer system. Video is almost always stored using lossy compression to reduce the file size.
A video file normally consists of a container (e.g. in the Matroska format) containing visual (video without audio) data in a video coding format (e.g. VP9) alongside audio data in an audio coding format (e.g. Opus). The container can also contain synchronization information, subtitles, and metadata such as title. A standardized (or in some cases de facto standard) video file type such as .webm is a profile specified by a restriction on which container format and which video and audio compression formats are allowed.
The coded video and audio inside a video file container (i.e. not headers, footers, and metadata) is called the essence. A program (or hardware) which can decode compressed video or audio is called a codec; playing or encoding a video file will sometimes require the user to install a codec library corresponding to the type of video and audio coding used in the file.
Good design normally dictates that a file extension enables the user to derive which program will open the file from the file extension. That is the case with some video file formats, such as WebM (.webm), Windows Media Video (.wmv), Flash Video (.flv), and Ogg Video (.ogv), each of which can only contain a few well-defined subtypes of video and audio coding formats, making it relatively easy to know which codec will play the file. In contrast to that, some very general-purpose container types like AVI (.avi) and QuickTime (.mov) can contain video and audio in almost any format, and have file extensions named after the container type, making it very hard for the end user to use the file extension to derive which codec or program to use to play the files.
The free software FFmpeg project's libraries have very wide support for encoding and decoding video file formats. For example, Google uses ffmpeg to support a wide range of upload video formats for YouTube. One widely used media player using the ffmpeg libraries is the free software VLC media player, which can play most video files that end users will encounter.
List of video file formats
See also
Comparison of video container formats
References
Video
Video formats |
https://en.wikipedia.org/wiki/Vertex | Vertex, vertices or vertexes may refer to:
Science and technology
Mathematics and computer science
Vertex (geometry), a point where two or more curves, lines, or edges meet
Vertex (computer graphics), a data structure that describes the position of a point
Vertex (curve), a point of a plane curve where the first derivative of curvature is zero
Vertex (graph theory), the fundamental unit of which graphs are formed
Vertex (topography), in a triangulated irregular network
Vertex of a representation, in finite group theory
Physics
Vertex (physics), the reconstructed location of an individual particle collision
Vertex (optics), a point where the optical axis crosses an optical surface
Vertex function, describing the interaction between a photon and an electron
Biology and anatomy
Vertex (anatomy), the highest point of the head
Vertex (urinary bladder), alternative name of the apex of urinary bladder
Vertex distance, the distance between the surface of the cornea of the eye and a lens situated in front of it
Vertex presentation, a head-first presentation at childbirth
Businesses
Vertex (company), an American business services provider
Vertex Holdings, an investment holding company in Singapore
Vertex Inc, an American tax compliance software and services company
Vertex Pharmaceuticals, an American biotech company
Vertex Railcar, a Chinese-American manufacturer of railroad rolling stock 2014–2018
Vertex Resource Group, a Canadian environmental services company
Other uses
Vertex (album), by Buck 65, 1997
Vertex (band), formed in 1996
Vertex (astrology), the point where the prime vertical intersects the ecliptic
See also
Virtex (disambiguation)
Vortex (disambiguation)
Vertex model, a type of statistical mechanics model
Vertex operator algebra in conformal field theory
External links |
https://en.wikipedia.org/wiki/Edge | Edge or EDGE may refer to:
Technology
Computing
Edge computing, a network load-balancing system
Edge device, an entry point to a computer network
Adobe Edge, a graphical development application
Microsoft Edge, a web browser developed by Microsoft
EdgeHTML, the layout engine previously used in Microsoft Edge
ThinkPad Edge, a Lenovo laptop computer series marketed from 2010
Silhouette edge, in computer graphics, a feature of a 3D body projected onto a 2D plane
Explicit data graph execution, a computer instruction set architecture
Telecommunication(s)
Edge Wireless, an American mobile phone provider
Enhanced Data rates for GSM Evolution, a pre-3G digital mobile phone technology
Motorola Edge, a series of smartphones made by Motorola
Samsung Galaxy Note Edge, a phablet made by Samsung
Samsung Galaxy S7 Edge or Samsung Galaxy S6 Edge, smartphones made by Samsung
Ubuntu Edge, a prototype smartphone made by Canonical
Entertainment
Music
Edge (Daryl Braithwaite album), a 1988 album by Daryl Braithwaite
"Edge", the B-side of the 2008 single "Love the World" by Perfume
"Edge", a 2013 song by Haim from Days Are Gone
Radio and television
93.7 Edge FM, in Bega, New South Wales
Edge FM 102.1, in Wangaratta, Victoria
Edge FM 102.5, in Deniliquin, New South Wales
Edge Radio, in Hobart, Tasmania
Edge TV, a Canadian cable music channel
Edge Media Television, parent company of Irish media company Controversial TV
Video games
Edge (magazine), a UK video games magazine
Edge (video game), a 2008 video game by Mobigame
Edge Games, an American video game company
Edge (Final Fantasy), a character from the game Final Fantasy IV
Edge (Rival Schools), a character from the game Rival Schools
Edge (Suikoden), a character from the game Suikoden III
Organizations
Edge (educational foundation), an organization in the United Kingdom
Edge Church, an assemblies of God megachurch in Adelaide, South Australia
EDGE Foundation, an organization helping female students pursue graduate studies in mathematics
Edge Foundation, Inc., a science and technology think tank
EDGE Group, an advanced military and technology conglomerate based in the United Arab Emirates
People
Surname
Edge (surname)
Other
Morgan Edge, a DC Comics supervillain
Edge (wrestler) (born 1973), ring name of Canadian professional wrestler Adam Copeland
Edgerrin James (born 1978), nicknamed "Edge", American football player
Places
Edge, Cheshire, a former civil parish
Edge, Gloucestershire, a village north of Stroud
Edge, Shropshire, a hamlet near Yockleton
Edge, Texas, a community in the United States
Edge House, a historic home in Groveland, Florida, U.S.
Sports
Edge (cricket), a term used in cricket
Edge rusher, either a defensive end or outside linebacker, positions in American football
St. John's Edge, a Canadian basketball team
West Michigan Edge, an American soccer team
Other
Edge (geometry), a one-dimensional line segment joining two vertices
Edge (graph |
https://en.wikipedia.org/wiki/Pedal | A pedal (from the Latin pes pedis, "foot") is a lever designed to be operated by foot and may refer to:
Computers and other equipment
Footmouse, a foot-operated computer mouse
In medical transcription, a pedal is used to control playback of voice dictations
Geometry
Pedal curve, a curve derived by construction from a given curve
Pedal triangle, a triangle obtained by projecting a point onto the sides of a triangle
Music
Albums
Pedals (Rival Schools album)
Pedals (Speak album)
Other music
Bass drum pedal, a pedal used to play a bass drum while leaving the drummer's hands free to play other drums with drum sticks, hands, etc.
Effects pedal, a pedal used commonly for electric guitars
Pedal keyboard, a musical keyboard operated by the player's feet
Pedal harp, a modern orchestral harp with pedals used to change the tuning of its strings
Pedal point, a type of nonchord tone, usually in the bass
Pedal tone, a fundamental tone played on brass instruments
Piano pedals, typically three pedals used to soften, sustain, or selectively sustain notes played on a piano
Pedal piano, a kind of piano that includes a pedalboard
Player piano, a kind of piano which plays prerecorded music, some designs of which are driven by pedals
Transportation
Bicycle pedal, the part of a bicycle that the rider pushes with their foot to propel the vehicle
Pedalo, a small boat, usually for recreation, propelled by one or more occupants using bicycle style pedals
Automobile pedal, such as the accelerator, brake, and clutch
Pedals (The Nottingham Cycling Campaign), a cycling advocacy group in Nottingham, England
Rudder pedal, to control yaw on an airplane
Other uses
Pedal bin, a container with a lid operated by a foot pedal
Pedal bone or coffin bone, the last phalanx and most distal bone in the front and rear legs of horses, cattle, pigs, and other ruminants
Pedals (bear)
See also
Pedal boat (disambiguation)
Pedal Pusher (disambiguation)
Peddle, to sell something by going from place to place
Peddle (surname)
Petal (disambiguation) |
https://en.wikipedia.org/wiki/Captain%20Kangaroo | Captain Kangaroo is an American children's television series that aired weekday mornings on the American television network CBS for 29 years, from 1955 to 1984, making it the longest-running nationally broadcast children's television program of its day. In 1986, the American Program Service (now American Public Television, Boston) integrated some newly produced segments into reruns of past episodes, distributing the newer version of the series to PBS and independent public stations until 1993.
The show was conceived by Bob Keeshan, who also played the title character "Captain Kangaroo", and who based the show on "the warm relationship between grandparents and children". Keeshan had portrayed the original Clarabell the Clown on NBC's The Howdy Doody Show during the network's early years.
Captain Kangaroo had a loose structure, built around life in the "Treasure House" where the Captain (the name "kangaroo" came from the bigger pockets in his coat) would tell stories, meet guests, and indulge in silly stunts with regular characters, both humans and puppets. Keeshan performed as the Captain more than 9,000 times over the nearly 30-year run of the show.
The May 17, 1971, episode had two major changes on the show: The Treasure House was renovated and renamed "The Captain's Place" and the Captain replaced his navy blue coat with a red coat. In September 1981, CBS shortened the hour-long show to a half-hour, briefly retitled it Wake Up with the Captain, and moved it to an earlier time slot; it was moved to weekends in September 1982, and returned to an hour-long format. CBS canceled Captain Kangaroo at the end of 1984.
Cast
Bob Keeshan as Captain Kangaroo, Mr. Pennywhistle, Mr. Doodle, Wally and the Town Clown
Hugh "Lumpy" Brannum as Mr. Green Jeans, the New Old Folk Singer, Percy, Uncle Backwards, Mr. McGregor, and Mr. Bainter the Painter
Cosmo Allegretti appeared as Mr. Bunny Rabbit and Mr. Moose (both of which he also created), Dennis the Apprentice, Willy, Miss Frog, Mr. Whispers, Dancing Bear, Grandfather Clock, and Uncle Ralph; he was the voice of Aniforms puppet TV Fred (a live-action on-screen puppet that appeared behind the blackboard in the Treasure House), and was the artist behind the Magic Drawing Board
Sam Levine as The Banana Man; the character was created by Adolph Proper
Bill Cosby as himself, the host of the Picture Pages segment (1980–1984)
Debbie Weems appeared as Debbie (1973–1978); the voice for the puppet character Baby Duck
James Wall as Mr. Baxter (1968–1978) - was also the stage manager
Carolyn Mignini as Kathy and other female roles (1981–1983)
Kevin Clash as the puppet character Artie (1980–1984) and as himself, acting in many of the sketches
John Burstein as Slim Goodbody (1978–1981)
Bill McCutcheon as Mr. Homan (1965–1968)
Jane Connell as Mrs. Homan (1965–1968)
Dr. Joyce Brothers as herself for three seasons
Format
The show did not have a strict format, other than the entire program taking place in and a |
https://en.wikipedia.org/wiki/TeachText | The TeachText application is a simple text editor made by Apple Computer and included with System 7.1 and earlier. It was created by Apple programmer Bryan Stearns with later versions created by Stearns and Francis Stanbach. TeachText was one of the only applications included with System 7, leading to its frequent role as the application to open "ReadMe" files. It was named "TeachText" as a nod to this role in tutorials and other introductory materials.
TeachText was derived from the Edit application, which was a simple text editor for the early pre-System 6 Apple Macintosh computers. Edit was included with early versions of the basic system software to demonstrate the use of the Macintosh user interface, and as the primary code editing tool for the original 68000 Macintosh Development System. While Edit was a tool and demonstration program for developers, TeachText was used mainly by users to display ReadMe documents.
Since the first Macintosh models came with a full-featured word processor, MacWrite, software publishers commonly shipped documentation in its native format. When Apple stopped bundling MacWrite, ownership was transferred to Claris, so developers could not distribute it on their programs' installation floppy disks. With no text program present on the disks, owners without a second floppy disk drive or hard disk could be left with no way to view documentation or installation instructions. Apple supplied TeachText as a small, freely-distributable program to address this need.
TeachText could only operate on a single document at a time and supported only the default text font (12-point Geneva at the time) in the MacRoman encoding, with formatting such as bold, italic and underline. It also included rudimentary support for embedded images; the images were stored in PICT format in the file's resource fork in ascending numbers from zero, instances of non-breaking spaces in the text loaded up the appropriately numbered image, the first instance loading image "0", the second space loading image "1", and so on.
TeachText was automatically associated with all TEXT type codes for files with an unknown Creator code. That is, if a user attempted to open any text file and the original program that created it was not known on the local computer, TeachText would be asked to open the file in its place. In this respect, TeachText was the "default editor" of the Mac system, playing a role similar to Notepad under Microsoft Windows.
The underlying text engine was the TextEdit Manager built into Mac OS. TextEdit had originally been written to support very small runs of editable text, like those found in Save as... dialogs and similar roles. As such, it had been written with a short integer as a length counter, and could thus only handle up to 32 kB of text in a file. This conflicted with the "default editor" role when it was asked to open files longer than 32k, resulting in an error.
TeachText was later replaced by SimpleText, and with the arriva |
https://en.wikipedia.org/wiki/RC | RC, R/C, Rc, or rc may refer to:
Science and technology
Computing
rc, the default Command line interface in Version 10 Unix and Plan 9 from Bell Labs
.rc (for "run commands"), a filename extension for configuration files in UNIX-like environments
rc, a file extension and compiler for Microsoft Windows resource scripts
Reconfigurable computing
Release Candidate, a term used in software engineering
Return code, used to identify errors or other aspects of software behavior
RigidChips, a rigid body simulator program
"Rivest's Cipher," a term used in cryptographic algorithms
RoundCube, a web-based IMAP e-mail client
RealityCapture, a photogrammetry software
Electronics
RC circuit, resistance/capacitance circuit, a term used in electronics
Radio control, a technology found in remote control vehicles
Reflection coefficient of a circuit
Remote control, a technology found in home entertainment devices
Other uses in science and technology
SJ Rc, a Swedish locomotive
Reinforced concrete, concrete incorporating reinforcement bars ("rebars")
Research chemicals, chemical substances intended for research purposes and laboratory use
Pharmacological Research Chemical, in laboratory use and "grey" markets for psychoactive drugs
Reverse Circulation, a term used in drilling rig
Ridge Connector
Ritchey–Chrétien telescope
Lexus RC
Arts and entertainment
RC (Toy Story), a character from the Disney Pixar film franchise
Refused Classification, a designation by the Office of Film and Literature Classification (Australia) for a banned film
Star Wars: Republic Commando, a first-person shooter game for Xbox and PC
Robot Chicken, a TV show on Adult Swim
Rubik's Cube, a toy
Businesses and organizations
Atlantic Airways (IATA airline code RC)
Rainforest Cafe
Recurse Center, a programming retreat and intentional community in New York, New York, United States
Re-evaluation Counseling, an organization for personal growth and social change
Resistance Council of Uganda
Restorative Circles, a community-based form of restorative justice
Civil Revolution, a short-lived political alliance in Italy
Union Revolutionary Council, the supreme governing body of Burma from 1962 to 1974
Royal Caribbean
Royal Commission
Royal Crown Cola, a soda producer, also known as RC Cola
Schools
Renaissance College, Hong Kong
Residential College at Mary Foust, a living-learning residence hall at UNCG
Ridley College, a private boarding school in St. Catharines, Ontario, Canada
Riverside College, Inc., a medical college in the Philippines
Roanoke College, a private college in Salem, Virginia, United States
Robert College, a private high school in Istanbul, Turkey
People
R. C. Buford, American basketball executive
R. C. Orlan, baseball player
R. C. Slocum, American football player and coach
Richard Childress, a NASCAR team owner
Roberto Carlos, a retired Brazilian football player
Ram Charan (born 1985), Indian actor
Sports
Rogers Centre, a multi-purpo |
https://en.wikipedia.org/wiki/Young%20Talent%20Time | Young Talent Time is an Australian television variety program produced by Lewis-Young Productions and screened on Network Ten. The original series ran from 1971 until 1988 and was hosted by singer-songwriter and record producer Johnny Young for its entire run. The show was briefly revived by Network Ten in 2012 and was hosted by singer and actor Rob Mills.
History
The series featured a core group of young performers, in the vein of The Mickey Mouse Club, and a weekly junior talent quest. The regular cast known as "The Young Talent Team" performed popular classic songs along with the top hit songs of the day. The original program launched the careers of a number of Australian performers including Sally Boyden, Jamie Redfern, Vikki Broughton, Debra Byrne (billed then as Debbie), Tina Arena and Dannii Minogue and spawned numerous hit singles, fifteen Young Talent Time albums, a film, as well as merchandise including swap cards, boardgames, toys, and mugs. The program won numerous Logie Awards.
Young Talent Time (1971–1988)
Production details
Young Talent Time was produced as a joint venture by Lewis-Young Productions (the production partnership between host Johnny Young and his friend and colleague Kevin Lewis, one of the directors of Festival Records) and was taped mainly at the studios of ATV-10 in Nunawading, Melbourne although occasional shows were taped at the TEN-10 studios in Sydney or on location.
Many of the episodes from the early- to mid-1970s no longer exist as the tapes were wiped for re-use, being the official Network Ten policy at the time. Some later episodes from the series were repeated by pay TV broadcaster Foxtel in the late 1990s.
On average, 44 episodes were produced per year for 18 years. The episodes were broadcast in black and white from April 1971 to April 1975, thereafter in colour. The final episode aired on 23 December 1988.
Caravan Holiday
In the Christmas break between the first and second seasons of Young Talent Time, Johnny Young and the Young Talent Team shot a 22-minute colour film. (At the time, Young Talent Time still screened in black and white on Australian television.) Sponsored by the Caravan Trade & Industries Association Caravan Holiday was completed by early 1972 and released in cinemas across Australia as a supporting feature to Peter Bogdanovich's hugely popular US comedy picture What's Up, Doc? which starred Barbra Streisand and Ryan O'Neal.
The cast featured the then-current line-up of the Young Talent Team (Jamie Redfern, Rod Kirkham, Greg Mills, Philip Gould, Julie Ryles, Debbie Byrne, Vikki Broughton and Jane Scali) prior to Redfern's departure to tour the US with Liberace. Despite not appearing in the film, new team member Trevor Hindmarch turned up to the premiere, as seen in the documentary Young Talent Time Tells All.
It featured actor/comedian Buster Fiddess (as Mr Crawley) and Addie Black, and guest appearances by Johnny Young (in multiple cameos as a service station attendant, farmer |
https://en.wikipedia.org/wiki/RAID | RAID (; "redundant array of inexpensive disks" or "redundant array of independent disks") is a data storage virtualization technology that combines multiple physical disk drive components into one or more logical units for the purposes of data redundancy, performance improvement, or both. This is in contrast to the previous concept of highly reliable mainframe disk drives referred to as "single large expensive disk" (SLED).
Data is distributed across the drives in one of several ways, referred to as RAID levels, depending on the required level of redundancy and performance. The different schemes, or data distribution layouts, are named by the word "RAID" followed by a number, for example RAID 0 or RAID 1. Each scheme, or RAID level, provides a different balance among the key goals: reliability, availability, performance, and capacity. RAID levels greater than RAID 0 provide protection against unrecoverable sector read errors, as well as against failures of whole physical drives.
History
The term "RAID" was invented by David Patterson, Garth A. Gibson, and Randy Katz at the University of California, Berkeley in 1987. In their June 1988 paper "A Case for Redundant Arrays of Inexpensive Disks (RAID)", presented at the SIGMOD Conference, they argued that the top-performing mainframe disk drives of the time could be beaten on performance by an array of the inexpensive drives that had been developed for the growing personal computer market. Although failures would rise in proportion to the number of drives, by configuring for redundancy, the reliability of an array could far exceed that of any large single drive.
Although not yet using that terminology, the technologies of the five levels of RAID named in the June 1988 paper were used in various products prior to the paper's publication, including the following:
Mirroring (RAID 1) was well established in the 1970s including, for example, Tandem NonStop Systems.
In 1977, Norman Ken Ouchi at IBM filed a patent disclosing what was subsequently named RAID 4.
Around 1983, DEC began shipping subsystem mirrored RA8X disk drives (now known as RAID 1) as part of its HSC50 subsystem.
In 1986, Clark et al. at IBM filed a patent disclosing what was subsequently named RAID 5.
Around 1988, the Thinking Machines' DataVault used error correction codes (now known as RAID 2) in an array of disk drives. A similar approach was used in the early 1960s on the IBM 353.
Industry manufacturers later redefined the RAID acronym to stand for "redundant array of independent disks".
Overview
Many RAID levels employ an error protection scheme called "parity", a widely used method in information technology to provide fault tolerance in a given set of data. Most use simple XOR, but RAID 6 uses two separate parities based respectively on addition and multiplication in a particular Galois field or Reed–Solomon error correction.
RAID can also provide data security with solid-state drives (SSDs) without the expense of an all |
https://en.wikipedia.org/wiki/Syndication | Syndication may refer to:
Broadcast syndication, of programs to other networks
Print syndication, of printed material to other publishers
Web syndication, of web feeds to other sites
Search syndication, of keyword searches
Syndicated loan, made by a group of banks
Really Simple Syndication, Web news feeds
See also
Syndic
Syndicate
Syndicate (disambiguation)
Wikipedia:Syndication |
https://en.wikipedia.org/wiki/Recursively%20enumerable%20language | In mathematics, logic and computer science, a formal language is called recursively enumerable (also recognizable, partially decidable, semidecidable, Turing-acceptable or Turing-recognizable) if it is a recursively enumerable subset in the set of all possible words over the alphabet of the language, i.e., if there exists a Turing machine which will enumerate all valid strings of the language.
Recursively enumerable languages are known as type-0 languages in the Chomsky hierarchy of formal languages. All regular, context-free, context-sensitive and recursive languages are recursively enumerable.
The class of all recursively enumerable languages is called RE.
Definitions
There are three equivalent definitions of a recursively enumerable language:
A recursively enumerable language is a recursively enumerable subset in the set of all possible words over the alphabet of the language.
A recursively enumerable language is a formal language for which there exists a Turing machine (or other computable function) which will enumerate all valid strings of the language. Note that if the language is infinite, the enumerating algorithm provided can be chosen so that it avoids repetitions, since we can test whether the string produced for number n is "already" produced for a number which is less than n. If it already is produced, use the output for input n+1 instead (recursively), but again, test whether it is "new".
A recursively enumerable language is a formal language for which there exists a Turing machine (or other computable function) that will halt and accept when presented with any string in the language as input but may either halt and reject or loop forever when presented with a string not in the language. Contrast this to recursive languages, which require that the Turing machine halts in all cases.
All regular, context-free, context-sensitive and recursive languages are recursively enumerable.
Post's theorem shows that RE, together with its complement co-RE, correspond to the first level of the arithmetical hierarchy.
Example
The set of halting Turing machines is recursively enumerable but not recursive. Indeed, one can run the Turing machine and accept if the machine halts, hence it is recursively enumerable. On the other hand, the problem is undecidable.
Some other recursively enumerable languages that are not recursive include:
Post correspondence problem
Mortality (computability theory)
Entscheidungsproblem
Closure properties
Recursively enumerable languages (REL) are closed under the following operations. That is, if L and P are two recursively enumerable languages, then the following languages are recursively enumerable as well:
the Kleene star of L
the concatenation of L and P
the union
the intersection .
Recursively enumerable languages are not closed under set difference or complementation. The set difference is recursively enumerable if is recursive. If is recursively enumerable, then the complement of is rec |
https://en.wikipedia.org/wiki/Undecidable | Undecidable may refer to:
Undecidable problem in computer science and mathematical logic, a decision problem that no algorithm can decide, formalized as an undecidable language or undecidable set
"Undecidable", sometimes also used as a synonym of independent, something that can neither be proved nor disproved within a mathematical theory
Undecidable figure, a two-dimensional drawing of something that cannot exist in 3d, such as appeared in some of the works of M. C. Escher
See also
Decidable (disambiguation) |
https://en.wikipedia.org/wiki/Anders%20Hejlsberg | Anders Hejlsberg (, born 2 December 1960) is a Danish software engineer who co-designed several programming languages and development tools. He was the original author of Turbo Pascal and the chief architect of Delphi. He currently works for Microsoft as the lead architect of C# and core developer on TypeScript.
Early life
Hejlsberg was born in Copenhagen, Denmark, and studied Electrical Engineering at the Technical University of Denmark. While at the university in 1980, he began writing programs for the Nascom microcomputer, including a Pascal compiler which was initially marketed as the Blue Label Software Pascal for the Nascom-2. However, he soon rewrote it for CP/M and DOS, marketing it first as Compas Pascal and later as PolyPascal. Later the product was licensed to Borland, and integrated into an IDE to become the Turbo Pascal system. Turbo Pascal competed with PolyPascal. The compiler itself was largely inspired by the "Tiny Pascal" compiler in Niklaus Wirth's "Algorithms + Data Structures = Programs", one of the most influential computer science books of the time.
At Borland
In Borland's hands, Turbo Pascal became one of the most commercially successful Pascal compilers. Hejlsberg remained with PolyData until the company came under financial stress and in 1989 he moved to California to become Chief Engineer at Borland. During this time he developed Turbo Pascal further and became the chief architect for the team that produced Borland Delphi, which replaced Turbo Pascal.
At Microsoft
In 1996, Hejlsberg left Borland and joined Microsoft. One of his first achievements was the J++ programming language and the Windows Foundation Classes; he also became a Microsoft Distinguished Engineer and Technical Fellow. Since 2000, he has been the lead architect of the team developing the C# language. In 2012 Hejlsberg announced a new Microsoft project, TypeScript, a superset of JavaScript.
Awards
Hejlsberg received the 2001 Dr. Dobb's Excellence in Programming Award for his work on Turbo Pascal, Delphi, C# and the Microsoft .NET Framework.
Together with Shon Katzenberger, Scott Wiltamuth, Todd Proebsting, Erik Meijer, Peter Hallam, and Peter Sollich, Anders was awarded a Technical Recognition Award for Outstanding Technical Achievement for their work on the C# language in 2007.
See also
Timeline of programming languages
C# programming language
References
Bibliography
Published works
The C# Programming Language, 2nd edition, Addison-Wesley Professional, , 2006-06-09
The C# Programming Language, 3rd edition, Addison-Wesley Professional, , 2008-10-18
The C# Programming Language, 4th edition, Addison-Wesley Professional, , , October 2010
External links
JavaWorld of 1997 writes how Hejlsberg went to Microsoft: Microsoft offered Anders Hejlsberg a signing bonus of and stock options. Microsoft doubled the bonus to after Borland made a counter-offer. Hejlsberg left Borland in October 1996.
The C# Design Process
The Trouble with Checked |
https://en.wikipedia.org/wiki/Denotational%20semantics | In computer science, denotational semantics (initially known as mathematical semantics or Scott–Strachey semantics) is an approach of formalizing the meanings of programming languages by constructing mathematical objects (called denotations) that describe the meanings of expressions from the languages. Other approaches providing formal semantics of programming languages include axiomatic semantics and operational semantics.
Broadly speaking, denotational semantics is concerned with finding mathematical objects called domains that represent what programs do. For example, programs (or program phrases) might be represented by partial functions or by games between the environment and the system.
An important tenet of denotational semantics is that semantics should be compositional: the denotation of a program phrase should be built out of the denotations of its subphrases.
Historical development
Denotational semantics originated in the work of Christopher Strachey and Dana Scott published in the early 1970s. As originally developed by Strachey and Scott, denotational semantics provided the meaning of a computer program as a function that mapped input into output. To give meanings to recursively defined programs, Scott proposed working with continuous functions between domains, specifically complete partial orders. As described below, work has continued in investigating appropriate denotational semantics for aspects of programming languages such as sequentiality, concurrency, non-determinism and local state.
Denotational semantics has been developed for modern programming languages that use capabilities like concurrency and exceptions, e.g., Concurrent ML, CSP, and Haskell. The semantics of these languages is compositional in that the meaning of a phrase depends on the meanings of its subphrases. For example, the meaning of the applicative expression f(E1,E2) is defined in terms of semantics of its subphrases f, E1 and E2. In a modern programming language, E1 and E2 can be evaluated concurrently and the execution of one of them might affect the other by interacting through shared objects causing their meanings to be defined in terms of each other. Also, E1 or E2 might throw an exception which could terminate the execution of the other one. The sections below describe special cases of the semantics of these modern programming languages.
Meanings of recursive programs
Denotational semantics is ascribed to a program phrase as a function from an environment (holding current values of its free variables) to its denotation. For example, the phrase produces a denotation when provided with an environment that has binding for its two free variables: and . If in the environment has the value 3 and has the value 5, then the denotation is 15.
A function can be represented as a set of ordered pairs of argument and corresponding result values. For example, the set {(0,1), (4,3)} denotes a function with result 1 for argument 0, result 3 for the argumen |
https://en.wikipedia.org/wiki/Seattle%20Wireless | Seattle Wireless was an American non-profit project created by Matt Westervelt and Ken Caruso in June 2000. It seeks to develop a free, locally owned wireless community network using widely available, license-free technology wireless broadband Internet access. It is a metropolitan area network. As of 2016, Seattle Wireless is no longer operational.
Seattle Wireless is one of the first Community Wireless Networks and one of the first project focused wikis. It also had a short lived (7 episode) online television show, called Seattle Wireless TV. It was created by Peter Yorke and Michael Pierce and ran July 2003 - June 2004. SWTV was an early adopter of Bittorrent to distribute its shows.
References
External links
Official website
Matt's Blog
Seattle Wireless Blog Planet
Peter Yorke's Blog
Kahney, Leander, "Home-grown Wireless Networks", TheFeature, 2001-05-07
Fleishman, Glenn, "The revolution may be wireless", Seattle Weekly, 2001-07-18
O'Shea, Dan, "Peace, Love & Wi-Fi", Telephony Online, 2002-05-18
Kharif, Olga, "Footing the Bill for Free Wi-Fi", BusinessWeek, 2002-09-17
"The Insider: Lucky few are going locomotive over Wi-Fi access", Seattle PI, 2005-03-28
Wireless network organizations |
https://en.wikipedia.org/wiki/Hierarchical%20File%20System%20%28Apple%29 | Hierarchical File System (HFS) is a proprietary file system developed by Apple Inc. for use in computer systems running Mac OS. Originally designed for use on floppy and hard disks, it can also be found on read-only media such as CD-ROMs. HFS is also referred to as Mac OS Standard (or HFS Standard), while its successor, HFS Plus, is also called Mac OS Extended (or HFS Extended).
With the introduction of Mac OS X 10.6, Apple dropped support for formatting or writing HFS disks and images, which remained supported as read-only volumes until macOS 10.15. Starting with macOS 10.15, HFS disks can no longer be read.
History
Apple introduced HFS in September 1985, specifically to support Apple's first hard disk drive for the Macintosh, replacing the Macintosh File System (MFS), the original file system which had been introduced over a year and a half earlier with the first Macintosh computer. HFS drew heavily upon Apple's first operating system with a hierarchical file system, SOS for the failed Apple III, which also served as the basis for hierarchical file systems on the Apple IIe and Apple Lisa. HFS was developed by Patrick Dirks and Bill Bruffey. It shared a number of design features with MFS that were not available in other file systems of the time (such as DOS's FAT). Files could have multiple forks (normally a data and a resource fork), which allowed the main data of the file to be stored separately from resources such as icons that might need to be localized. Files were referenced with unique file IDs rather than file names, and file names could be up to 31 characters long.
However, MFS had been optimized to be used on very small and slow media, namely floppy disks, so HFS was introduced to overcome some of the performance problems that arrived with the introduction of larger media, notably hard drives. The main concern was the time needed to display the contents of a folder. Under MFS all of the file and directory listing information was stored in a single file, which the system had to search to build a list of the files stored in a particular folder. This worked well with a system with a few hundred kilobytes of storage and perhaps a hundred files, but as the systems grew into megabytes and thousands of files, the performance degraded rapidly.
The solution was to replace MFS's directory structure with one more suitable to larger file systems. HFS replaced the flat table structure with the Catalog File which uses a B-tree structure that could be searched very quickly regardless of size. HFS also redesigned various structures to be able to hold larger numbers, 16-bit integers being replaced by 32-bit almost universally. Oddly, one of the few places this "upsizing" did not take place was the file directory itself, which limits HFS to a total of 65,535 files on each logical disk.
While HFS is a proprietary file system format, it is well-documented; there are usually solutions available to access HFS-formatted disks from most modern ope |
https://en.wikipedia.org/wiki/RAM%20drive | A RAM drive (also called a RAM disk) is a block of random-access memory (primary storage or volatile memory) that a computer's software is treating as if the memory were a disk drive (secondary storage). RAM drives provide high-performance temporary storage for demanding tasks and protect non-volatile storage devices from wearing down, since RAM is not prone to wear from writing, unlike non-volatile flash memory. They are in a sense the reverse of virtual memory: RAM drive uses a volatile fast memory as if it's a nonvolatile slow memory. Virtual memory is the opposite.
It is sometimes referred to as a virtual RAM drive or software RAM drive to distinguish it from a hardware RAM drive that uses separate hardware containing RAM, which is a type of battery-backed solid-state drive.
Historically primary storage based mass storage devices were conceived to bridge the performance gap between internal memory and secondary storage devices. In the advent of solid-state devices this advantage lost most of its appeal. However, solid-state devices do suffer from wear from frequent writing. Primary memory writes do not so or in far lesser effect. So RAM devices do offer an advantage to store frequently changing data, like temporary or cached information.
Performance
The performance of a RAM drive is generally orders of magnitude faster than other forms of digital storage, such as SSD, tape, optical, hard disk, and floppy drives. This performance gain is due to multiple factors, including access time, maximum throughput, and file system characteristics.
File access time is greatly reduced since a RAM drive is solid state (no moving parts). A physical hard drive, optical (e.g, CD-ROM, DVD, and Blu-ray) or other media (e.g. magnetic bubble, acoustic storage, magnetic tape) must move the information to a particular position before reading or writing can occur. RAM drives can access data with only the address, eliminating this latency.
Second, the maximum throughput of a RAM drive is limited by the speed of the RAM, the data bus, and the CPU of the computer. Other forms of storage media are further limited by the speed of the storage bus, such as IDE (PATA), SATA, USB or FireWire. Compounding this limitation is the speed of the actual mechanics of the drive motors, heads, or eyes.
Third, the file system in use, such as NTFS, HFS, UFS, ext2, etc., uses extra accesses, reads and writes to the drive, which although small, can add up quickly, especially in the event of many small files vs. few larger files (temporary internet folders, web caches, etc.).
Because the storage is in RAM, it is volatile memory, which means it will be lost in the event of power loss, whether intentional (computer reboot or shutdown) or accidental (power failure or system crash). This is, in general, a weakness (the data must periodically be backed up to a persistent-storage medium to avoid loss), but is sometimes desirable: for example, when working with a decrypted copy of a |
https://en.wikipedia.org/wiki/Single%20instruction%2C%20multiple%20data | Single instruction, multiple data (SIMD) is a type of parallel processing in Flynn's taxonomy. SIMD can be internal (part of the hardware design) and it can be directly accessible through an instruction set architecture (ISA), but it should not be confused with an ISA. SIMD describes computers with multiple processing elements that perform the same operation on multiple data points simultaneously.
Such machines exploit data level parallelism, but not concurrency: there are simultaneous (parallel) computations, but each unit performs the exact same instruction at any given moment (just with different data). SIMD is particularly applicable to common tasks such as adjusting the contrast in a digital image or adjusting the volume of digital audio. Most modern CPU designs include SIMD instructions to improve the performance of multimedia use. SIMD has three different subcategories in Flynn's 1972 Taxonomy, one of which is SIMT. SIMT should not be confused with software threads or hardware threads, both of which are task time-sharing (time-slicing). SIMT is true simultaneous parallel hardware-level execution.
History
The first use of SIMD instructions was in the ILLIAC IV, which was completed in 1966.
SIMD was the basis for vector supercomputers of the early 1970s such as the CDC Star-100 and the Texas Instruments ASC, which could operate on a "vector" of data with a single instruction. Vector processing was especially popularized by Cray in the 1970s and 1980s. Vector processing architectures are now considered separate from SIMD computers: Duncan's Taxonomy includes them where Flynn's Taxonomy does not, due to Flynn's work (1966, 1972) pre-dating the Cray-1 (1977).
The first era of modern SIMD computers was characterized by massively parallel processing-style supercomputers such as the Thinking Machines CM-1 and CM-2. These computers had many limited-functionality processors that would work in parallel. For example, each of 65,536 single-bit processors in a Thinking Machines CM-2 would execute the same instruction at the same time, allowing, for instance, to logically combine 65,536 pairs of bits at a time, using a hypercube-connected network or processor-dedicated RAM to find its operands. Supercomputing moved away from the SIMD approach when inexpensive scalar MIMD approaches based on commodity processors such as the Intel i860 XP became more powerful, and interest in SIMD waned.
The current era of SIMD processors grew out of the desktop-computer market rather than the supercomputer market. As desktop processors became powerful enough to support real-time gaming and audio/video processing during the 1990s, demand grew for this particular type of computing power, and microprocessor vendors turned to SIMD to meet the demand. Hewlett-Packard introduced MAX instructions into PA-RISC 1.1 desktops in 1994 to accelerate MPEG decoding. Sun Microsystems introduced SIMD integer instructions in its "VIS" instruction set extensions in 1995, in its Ultra |
https://en.wikipedia.org/wiki/MMX%20%28instruction%20set%29 | MMX is a single instruction, multiple data (SIMD) instruction set architecture designed by Intel, introduced on January 8, 1997 with its Pentium P5 (microarchitecture) based line of microprocessors, named "Pentium with MMX Technology". It developed out of a similar unit introduced on the Intel i860, and earlier the Intel i750 video pixel processor. MMX is a processor supplementary capability that is supported on IA-32 processors by Intel and other vendors .
The New York Times described the initial push, including Super Bowl advertisements, as focused on "a new generation of glitzy multimedia products, including videophones and 3-D video games."
MMX has subsequently been extended by several programs by Intel and others: 3DNow!, Streaming SIMD Extensions (SSE), and ongoing revisions of Advanced Vector Extensions (AVX).
Overview
Naming
MMX is officially a meaningless initialism trademarked by Intel; unofficially, the initials have been variously explained as standing for
MultiMedia eXtension,
Multiple Math eXtension, or
Matrix Math eXtension.
Advanced Micro Devices (AMD), during one of its many court battles with Intel, produced marketing material from Intel indicating that MMX stood for "Matrix Math Extensions". Since an initialism cannot be trademarked, this was an attempt to invalidate Intel's trademark. In 1995, Intel filed suit against AMD and Cyrix Corp. for misuse of its trademark MMX. AMD and Intel settled, with AMD acknowledging MMX as a trademark owned by Intel, and with Intel granting AMD rights to use the MMX trademark as a technology name, but not a processor name.
Technical details
MMX defines eight processor registers, named MM0 through MM7, and operations that operate on them. Each register is 64 bits wide and can be used to hold either 64-bit integers, or multiple smaller integers in a "packed" format: one instruction can then be applied to two 32-bit integers, four 16-bit integers, or eight 8-bit integers at once.
MMX provides only integer operations. When originally developed, for the Intel i860, the use of integer math made sense (both 2D and 3D calculations required it), but as graphics cards that did much of this became common, integer SIMD in the CPU became somewhat redundant for graphical applications. Alternatively, the saturation arithmetic operations in MMX could significantly speed up some digital signal processing applications.
To avoid compatibility problems with the context switch mechanisms in existing operating systems, the MMX registers are aliases for the existing x87 floating-point unit (FPU) registers, which context switches would already save and restore. Unlike the x87 registers, which behave like a stack, the MMX registers are each directly addressable (random access).
Any operation involving the floating-point stack might also affect the MMX registers and vice versa, so this aliasing makes it difficult to work with floating-point and SIMD operations in the same program. To maximize performance |
https://en.wikipedia.org/wiki/Streaming%20SIMD%20Extensions | In computing, Streaming SIMD Extensions (SSE) is a single instruction, multiple data (SIMD) instruction set extension to the x86 architecture, designed by Intel and introduced in 1999 in their Pentium III series of central processing units (CPUs) shortly after the appearance of Advanced Micro Devices (AMD's) 3DNow!. SSE contains 70 new instructions (65 unique mnemonics using 70 encodings), most of which work on single precision floating-point data. SIMD instructions can greatly increase performance when exactly the same operations are to be performed on multiple data objects. Typical applications are digital signal processing and graphics processing.
Intel's first IA-32 SIMD effort was the MMX instruction set. MMX had two main problems: it re-used existing x87 floating-point registers making the CPUs unable to work on both floating-point and SIMD data at the same time, and it only worked on integers. SSE floating-point instructions operate on a new independent register set, the XMM registers, and adds a few integer instructions that work on MMX registers.
SSE was subsequently expanded by Intel to SSE2, SSE3, SSSE3 and SSE4. Because it supports floating-point math, it had wider applications than MMX and became more popular. The addition of integer support in SSE2 made MMX largely redundant, though further performance increases can be attained in some situations by using MMX in parallel with SSE operations.
SSE was originally called Katmai New Instructions (KNI), Katmai being the code name for the first Pentium III core revision. During the Katmai project Intel sought to distinguish it from their earlier product line, particularly their flagship Pentium II. It was later renamed Internet Streaming SIMD Extensions (ISSE), then SSE. AMD eventually added support for SSE instructions, starting with its Athlon XP and Duron (Morgan core) processors.
Registers
SSE originally added eight new 128-bit registers known as XMM0 through XMM7. The AMD64 extensions from AMD (originally called x86-64) added a further eight registers XMM8 through XMM15, and this extension is duplicated in the Intel 64 architecture. There is also a new 32-bit control/status register, MXCSR. The registers XMM8 through XMM15 are accessible only in 64-bit operating mode.
SSE used only a single data type for XMM registers:
four 32-bit single-precision floating-point numbers
SSE2 would later expand the usage of the XMM registers to include:
two 64-bit double-precision floating-point numbers or
two 64-bit integers or
four 32-bit integers or
eight 16-bit short integers or
sixteen 8-bit bytes or characters.
Because these 128-bit registers are additional machine states that the operating system must preserve across task switches, they are disabled by default until the operating system explicitly enables them. This means that the OS must know how to use the FXSAVE and FXRSTOR instructions, which is the extended pair of instructions that can save all x86 and SSE register states a |
https://en.wikipedia.org/wiki/Hercules%20%28emulator%29 | Hercules is a computer emulator allowing software written for IBM mainframe computers (System/370, System/390, and zSeries/System z) and for plug compatible mainframes (such as Amdahl machines) to run on other types of computer hardware, notably on low-cost personal computers. Development started in 1999 by Roger Bowler, a mainframe systems programmer.
Hercules runs under multiple parent operating systems including Linux, Microsoft Windows, FreeBSD, NetBSD, Solaris, and macOS and is released under the open source software license QPL. It is analogous to Bochs and QEMU in that it emulates CPU instructions and select peripheral devices only. A vendor (or distributor) must still provide an operating system, and the user must install it. Hercules was the first mainframe emulator to incorporate 64-bit z/Architecture support.
Design
The emulator is written almost entirely in C. Its developers ruled out using machine-specific assembly code to avoid problems with portability even though such code could significantly improve performance. There are two exceptions: Hercules uses hardware assists to provide inter-processor consistency when emulating multiple CPUs on SMP host systems, and Hercules uses assembler assists to convert between little-endian and big-endian data on platforms where the operating system provides such services and on x86/x86-64 processors.
Operating systems status
Hercules is technically compatible with all IBM mainframe operating systems, even older versions which no longer run on newer mainframes. However, many mainframe operating systems require vendor licenses to run legally. Newer licensed operating systems, such as OS/390, z/OS, VSE/ESA, z/VSE, VM/ESA, z/VM, TPF/ESA, and z/TPF are technically compatible but cannot legally run on the Hercules emulator except in very limited circumstances, and they must always be licensed from IBM. IBM's Coupling Facility control code, which enables Parallel Sysplex, and UTS also require licenses to run.
Operating systems which may legally be run, without license costs, on Hercules include:
Older IBM operating systems including OS/360, DOS/360, DOS/VS, MVS, VM/370, and TSS/370 which are either public domain or "copyrighted software provided without charge."
The MUSIC/SP operating system may be available for educational and demonstration purposes upon request to its copyright holder, McGill University. Some of MUSIC/SP's features, notably networking, require z/VM (and thus an IBM license). However, a complete demonstration version of MUSIC/SP, packaged with the alternative Sim390 mainframe emulator, is available.
The Michigan Terminal System (MTS) version 6.0A has been tailored to run under Hercules.
There is no known legal restriction to running open-source operating systems Linux on IBM Z and OpenSolaris for System z on the Hercules emulator. They run well on Hercules, and many Linux on IBM Z developers do their work using Hercules. Several distributors provide 64-bit z/Architecture versio |
https://en.wikipedia.org/wiki/ELDIS | Eldis is a database and email service of information sources on international development. It aims to share the best knowledge on development, policy, practice and research.
Background
"Eldis" was originally an acronym for "Electronic Development and Environment Information System". It is one of a family of knowledge services produced at the Institute of Development Studies, Sussex, England.
Funding
Eldis is funded by the UK Department for International Development (DFID), Swedish International Development Cooperation Agency (Sida), the Norwegian Agency for Development Cooperation (Norad) and the Swiss Agency for Development and Cooperation (SDC).
Database
The information in Eldis is organised into subject-focused "resource guides" and regional and country "profiles."
References
Bibliography
External links
Eldis community site and social network.
International development
Document-oriented databases
University of Sussex |
https://en.wikipedia.org/wiki/Hard%20disk%20drive%20platter | A hard disk drive platter or hard disk is the circular magnetic disk on which digital data is stored in a hard disk drive. The rigid nature of the platters is what gives them their name (as opposed to the flexible materials which are used to make floppy disks). Hard drives typically have several platters which are mounted on the same spindle. A platter can store information on both sides, typically requiring two recording heads per platter, one per surface.
Design
The magnetic surface of each platter is divided into small sub-micrometer-sized magnetic regions, each of which is used to represent a single binary unit of information. A typical magnetic region on a hard-disk platter (as of 2006) is about 200–250 nanometers wide (in the radial direction of the platter) and extends about 25–30 nanometers in the down-track direction (the circumferential direction on the platter), corresponding to about 100 billion bits per square inch of disk area (15.5 Gbit/cm2). The material of the main magnetic medium layer is usually a cobalt-based alloy. In today's hard drives each of these magnetic regions is composed of a few hundred magnetic grains, which are the base material that gets magnetized. As a whole, each magnetic region will have a magnetization.
One reason magnetic grains are used as opposed to a continuous magnetic medium is that they reduce the space needed for a magnetic region. In continuous magnetic materials, formations called Néel spikes tend to appear. These are spikes of opposite magnetization, and form for the same reason that bar magnets will tend to align themselves in opposite directions. These cause problems because the spikes cancel each other's magnetic field out, so that at region boundaries, the transition from one magnetization to the other will happen over the length of the Néel spikes. This is called the transition width.
Grains help solve this problem because each grain is in theory a single magnetic domain (though not always in practice). This means that the magnetic domains cannot grow or shrink to form spikes, and therefore the transition width will be on the order of the diameter of the grains. Thus, much of the development in hard drives has been in reduction of grain size.
Manufacture
Platters are typically made using an aluminium, glass or ceramic substrate. As of 2015, laptop hard drive platters are made from glass while aluminum platters are often found in desktop computers. In disk manufacturing, a thin coating is deposited on both sides of the substrate, mostly by a vacuum deposition process called magnetron sputtering. The coating has a complex layered structure consisting of various metallic (mostly non-magnetic) alloys as underlayers, optimized for the control of the crystallographic orientation and the grain size of the actual magnetic media layer on top of them, i.e. the film storing the bits of information. On top of it a protective carbon-based overcoat is deposited in the same sputtering process. In p |
https://en.wikipedia.org/wiki/History%20of%20operating%20systems | Computer operating systems (OSes) provide a set of functions needed and used by most application programs on a computer, and the links needed to control and synchronize computer hardware. On the first computers, with no operating system, every program needed the full hardware specification to run correctly and perform standard tasks, and its own drivers for peripheral devices like printers and punched paper card readers. The growing complexity of hardware and application programs eventually made operating systems a necessity for everyday use.
Background
The earliest computers were mainframes that lacked any form of operating system. Each user had sole use of the machine for a scheduled period of time and would arrive at the computer with program and data, often on punched paper cards and magnetic or paper tape. The program would be loaded into the machine, and the machine would be set to work until the program completed or crashed. Programs could generally be debugged via a control panel using dials, toggle switches and panel lights.
Symbolic languages, assemblers, and compilers were developed for programmers to translate symbolic program code into machine code that previously would have been hand-encoded. Later machines came with libraries of support code on punched cards or magnetic tape, which would be linked to the user's program to assist in operations such as input and output. This was the genesis of the modern-day operating system; however, machines still ran a single job at a time. At Cambridge University in England the job queue was at one time a string from which tapes attached to corresponding job tickets were hung with stationery pegs.
As machines became more powerful the time to run programs diminished, and the time to hand off the equipment to the next user became large by comparison. Accounting for and paying for machine usage moved on from checking the wall clock to automatic logging by the computer. Run queues evolved from a literal queue of people at the door, to a heap of media on a jobs-waiting table, or batches of punched cards stacked one on top of the other in the reader, until the machine itself was able to select and sequence which magnetic tape drives processed which tapes. Where program developers had originally had access to run their own jobs on the machine, they were supplanted by dedicated machine operators who looked after the machine and were less and less concerned with implementing tasks manually. When commercially available computer centers were faced with the implications of data lost through tampering or operational errors, equipment vendors were put under pressure to enhance the runtime libraries to prevent misuse of system resources. Automated monitoring was needed not just for CPU usage but for counting pages printed, cards punched, cards read, disk storage used and for signaling when operator intervention was required by jobs such as changing magnetic tapes and paper forms. Security features were adde |
https://en.wikipedia.org/wiki/Drive%20letter%20assignment | In computer data storage, drive letter assignment is the process of assigning alphabetical identifiers to volumes. Unlike the concept of UNIX mount points, where volumes are named and located arbitrarily in a single hierarchical namespace, drive letter assignment allows multiple highest-level namespaces. Drive letter assignment is thus a process of using letters to name the roots of the "forest" representing the file system; each volume holds an independent "tree" (or, for non-hierarchical file systems, an independent list of files).
Origin
The concept of drive letters, as used today, presumably owes its origins to IBM's VM family of operating systems, dating back to CP/CMS in 1967 (and its research predecessor CP-40), by way of Digital Research's (DRI) CP/M. The concept evolved through several steps:
CP/CMS uses drive letters to identify minidisks attached to a user session. A full file reference (pathname in today's parlance) consists of a filename, a filetype, and a disk letter called a filemode (e.g. A or B). Minidisks can correspond to physical disk drives, but more typically refer to logical drives, which are mapped automatically onto shared devices by the operating system as sets of virtual cylinders.
CP/CMS inspired numerous other operating systems, including the CP/M microcomputer operating system, which uses a drive letter to specify a physical storage device. Early versions of CP/M (and other microcomputer operating systems) implemented a flat file system on each disk drive, where a complete file reference consists of a drive letter, a colon, a filename (up to eight characters), a dot, and a filetype (three characters); for instance A:README.TXT. (This was the era of 8-inch floppy disks, where such small namespaces did not impose practical constraints.) This usage was influenced by the device prefixes used in Digital Equipment Corporation's (DEC) TOPS-10 operating system.
The drive letter syntax chosen for CP/M was inherited by Microsoft for its operating system MS-DOS by way of Seattle Computer Products' (SCP) 86-DOS, and thus also by IBM's OEM version PC DOS. Originally, drive letters always represented physical volumes, but support for logical volumes eventually appeared.
Through their designated position as DOS successor, the concept of drive letters was also inherited by OS/2 and the Microsoft Windows family.
The important capability of hierarchical directories within each drive letter was initially absent from these systems. This was a major feature of UNIX and other similar operating systems, where hard disk drives held thousands (rather than tens or hundreds) of files. Increasing microcomputer storage capacities led to their introduction, eventually followed by long filenames. In file systems lacking such naming mechanisms, drive letter assignment proved a useful, simple organizing principle.
Operating systems that use drive letter assignment
CP/M family
CP/M, MP/M, Concurrent CP/M, Concurrent DOS, FlexOS, 4680 OS, |
https://en.wikipedia.org/wiki/NeWS | NeWS (Network extensible Window System) is a discontinued windowing system developed by Sun Microsystems in the mid-1980s. Originally known as "SunDew", its primary authors were James Gosling and David S. H. Rosenthal. The NeWS interpreter was based on PostScript (as was the later Display PostScript, although the two projects were otherwise unrelated) extending it to allow interaction and multiple "contexts" to support windows. Like PostScript, NeWS could be used as a complete programming language, but unlike PostScript, NeWS could be used to make complete interactive programs with mouse support and a GUI.
Design
NeWS started by implementing a PostScript interpreter running in a cooperative multitasking fashion, since, unlike PostScript in a printer, NeWS would be displaying a number of PostScript programs at the same time on one screen. It also added a complete view hierarchy, based on viewports known as canvases, and a synchronous event distribution system, supporting events, interests, threads and monitors.
Like the view system in most GUIs, NeWS included the concept of a tree of embedded views along which events were passed. For instance, a mouse click would generate an event that would be passed to the object directly under the mouse pointer, say a button. If this object did not respond to the event, the object "under" the button would then receive the message, and so on. NeWS included a complete model for these events, including timers and other automatic events, input queues for devices such as mice and keyboards, and other functionality required for full interaction. The input handling system was designed to provide strong event synchronization guarantees that were not possible with asynchronous protocols like X.
To support user interface widgets, NeWS expanded the original PostScript stack-based language into a complete object-oriented (OO) programming style with inheritance. This eliminated the need for an external OO language to build a complete application. Since all of these additions were implemented as extensions to PostScript, it was possible to write simple PostScript code that would result in a running, onscreen, interactive program. Two popular demonstration programs were an onscreen clock, which required about two pages of code, and a program which drew a pair of eyes that followed the cursor as it moved around the screen. The eyeball program was shown at SIGGRAPH in 1988 and was the inspiration for the later well-known X application xeyes.
NeWS included several libraries of user interface elements (widgets), themselves written in NeWS. These widgets ran all of their behavior in the NeWS interpreter, and only required communications to an outside program (or more NeWS code) when the widget demanded it. For example, a toggle button's display routine can query the button's state (pressed or not) and change its display accordingly. The button's PostScript code can also react to mouse clicks by changing its state from "presse |
https://en.wikipedia.org/wiki/Timeslip | Timeslip is a British children's science fiction television series made by ATV for the ITV network, and broadcast in 1970 and 1971. It was first shown on Monday evenings at around 5:15-5:20pm, beginning on 28th September 1970, in all ITV regions, apart from Thames (London) and Southern which broadcast the series the following Friday.
Overview
The series is centred on two children, Simon Randall (Spencer Banks) and Liz Skinner (Cheryl Burfield), who discover of a strange anomaly, known as the Time Barrier, which enables them to travel in time, and visit the past as well as alternative futures. The time barrier, which operates in a field at a disused military base, moves the children not only through time but also through space: for example, they travel from St Oswald's in the UK in 1940 to the Antarctic in one projection of 1990.
The children have contrasting personalities: Simon is studious, but Liz is something of a crybaby. This often leads to conflict, but as the series progresses, their antagonism matures into a deep bond of friendship.
The main theme of the series is the way humankind uses and abuses science and technology, and tends to support the idea that the pursuit of scientific knowledge and advancement leads to the depersonalisation of individuals and the abandonment of moral principles. A secondary theme, explored in the instances where Liz and Simon encounter potential future versions of themselves, is the extent to which an individual can change, or be changed, depending on the situations he or she encounters.
List of serials
Summary
Wrong End of Time
Simon, whose mother has died recently, has been taken on holiday in 1970 by the Skinner family – father Frank (Derek Benfield), mother Jean (Iris Russell) and daughter Liz – to the village of St Oswald. Frank had served at the (now abandoned) naval research base in St Oswald during World War II, where he had suffered amnesia. This has left him with no recollection of what happened during his time there. A local girl, Sarah, disappears through an invisible time barrier, witnessed by a local man, but nobody believes him when he tells the story in the pub where the Skinners are staying; but his story attracts a man called Charles Traynor (Denis Quilley), who arrives in the village and reveals that he was Skinner's commanding officer at the base during the war. Traynor had ordered Skinner to destroy the apparatus which the scientists at the base were working on, and he is eager to learn from Skinner if he succeeded in the task. This is because a German expeditionary team attacked and took over the base for a short time in 1940. The German commander, Gottfried (Sandor Elès), is now a prominent scientist, kidnapped and forced to work on the other side of the Iron Curtain, and Traynor is concerned that if the research work done at the base had fallen into his hands, it could be used against the West. While out playing near the ruins of the naval base, Liz and Simon encounter the Time |
https://en.wikipedia.org/wiki/ATA | ATA or Ata may refer to:
Computing
AT Attachment (ATA/ATAPI), the old name of Parallel ATA, an older interface for computer storage devices
Analog telephone adapter, a device for connecting analog telephones to a Voice-over-IP system
Education
Ashcroft Technology Academy, Wandsworth, London, England
Advanced Technologies Academy, a high school in Las Vegas, Nevada, USA
Asia Theological Association
Alberta Teachers' Association, Canada
Automotive Technician Accreditation, scheme in the UK for vehicle mechanics
Science, technology, and medicine
Anti-transglutaminase antibodies, in certain autoimmune diseases
Anti-topoisomerase antibodies
Anti-thyroglobulin antibodies
Allen Telescope Array
Atmosphere absolute, a variant of the standard atmosphere (unit)
American Telemedicine Association
American Thyroid Association
ATA chapter numbers
Alternating timed automaton
ATA, a codon for the amino acid isoleucine
Sports
American Taekwondo Association
American Tennis Association
Amateur Trapshooting Association
Archery Trade Association
A.T.A. (Greenland)
Organizations
Africa Travel Association
Air Transport Auxiliary
Albanian Telegraphic Agency
American Telugu Association
American Topical Association, a philatelic organization
American Tinnitus Association
American Translators Association
Association of Talent Agents, Los Angeles, US
Associazione Traffico e Ambiente, a transport association in Switzerland
Atlantic Treaty Association
Aberri Ta Askatasuna, the original name of the Basque organization ETA
Artists' Television Access microcinema, San Francisco, US
Places
Antarctica's ISO 3166-1 alpha-3 country code
Áta, a village in Hungary
Ața, a river in Romania
ʻAta, Tonga, a depopulated island
ʻAtā, Tonga, an island used as an open prison
Transportation
ATA Airlines, an American airline operating from 1973 to 2008
ATA Holdings, owner of ATA Airlines
ATA Airlines (Iran), Tabriz
ATA Cruiser, a 1920s aircraft
Air Transport Association of America, later Airlines for America
Air Transport Auxiliary of the UK RAF
American Trucking Associations
ATA Carnet, a customs document
Comandante FAP Germán Arias Graziani Airport, Anta, Peru, IATA code
Hall-Miller Municipal Airport, Atlanta, Cass County, Texas, US, FAA location identifier
Station code for Alastua railway station
Other uses
Ata (name), people with the first name or family name
Ata language (disambiguation)
Ata Gears, a transmission part producer
Atacama skeleton, skeletal remains of a human that were found during 2003 in a deserted Chilean town
See also |
https://en.wikipedia.org/wiki/UDMA | The Ultra DMA (Ultra Direct Memory Access, UDMA) modes were the fastest method used to transfer data through the ATA hard disk interface, usually between the computer and an ATA device. UDMA succeeded Single/Multiword DMA as the interface of choice between ATA devices and the computer. There are eight different UDMA modes, ranging from 0 to 6 for ATA (0 to 7 for CompactFlash), each with its own timing.
Modes faster than UDMA mode 2 require an 80-conductor cable to reduce data settling times, lower impedance and reduce crosstalk.
See also
PIO—The first interface type used between devices (mainly hard disks) and the computer.
Parallel ATA
Serial ATA
References
AT Attachment |
https://en.wikipedia.org/wiki/MAD%20%28programming%20language%29 | MAD (Michigan Algorithm Decoder) is a programming language and compiler for the IBM 704 and later the IBM 709, IBM 7090, IBM 7040, UNIVAC 1107, UNIVAC 1108, Philco 210-211, and eventually IBM System/370 mainframe computers. Developed in 1959 at the University of Michigan by Bernard Galler, Bruce Arden and Robert M. Graham, MAD is a variant of the ALGOL language. It was widely used to teach programming at colleges and universities during the 1960s and played a minor role in the development of Compatible Time-Sharing System (CTSS), Multics, and the Michigan Terminal System computer operating systems. The original version of the chatbot ELIZA was written in MAD-SLIP.
The archives at the Bentley Historical Library of the University of Michigan contain reference materials on the development of MAD and MAD/I, including three linear feet of printouts with hand-written notations and original printed manuals.
MAD, MAD/I, and GOM
Three MAD compilers exist:
Original MAD, the compiler developed in 1959 at the University of Michigan for the IBM 704 and later the IBM 709 and IBM 7090 mainframe computers running the University of Michigan Executive System (UMES) and the Compatible Time-Sharing System (CTSS) operating systems. In the mid-1960s MAD was ported at the University of Maryland to the UNIVAC 1108. Versions of MAD were also available for the Philco 210-211 and UNIVAC 1107.
MAD/I, an "extended" version of MAD for the IBM System/360 series of computers running under the Michigan Terminal System (MTS). Work on the new compiler started in 1965 as part of the ARPA sponsored CONCOMP project at the University of Michigan. As work progressed it gradually became clear that MAD/I was a new language independent of the original 7090 version of MAD.
GOM (Good Old MAD), a reimplementation of the original 7090 MAD for the IBM System/370 series of mainframe computers running the Michigan Terminal System (MTS). GOM was created in the early 1980s by Don Boettner at the University of Michigan Computing Center.
History
While MAD was motivated by ALGOL 58, it does not resemble ALGOL 58 in any significant way.
Programs written in MAD included MAIL, RUNOFF, one of the first text processing systems, and several other utilities all under Compatible Time-Sharing System (CTSS). Work was done on a design for a MAD compiler for Multics, but it was never implemented.
The following is an interesting quote from An Interview with Brian Kernighan when he was asked "What hooked you on programming?":
I think that the most fun I had programming was a summer job at Project MAC at MIT in the summer of 1966, where I worked on a program that created a job tape for the brand new GE 645 in the earliest days of Multics. I was writing in MAD, which was much easier and more pleasant than the FORTRAN and COBOL that I had written earlier, and I was using CTSS, the first time-sharing system, which was infinitely easier and more pleasant than punch cards.
MAD was quite fast compared to some |
https://en.wikipedia.org/wiki/Discriminant | In mathematics, the discriminant of a polynomial is a quantity that depends on the coefficients and allows deducing some properties of the roots without computing them. More precisely, it is a polynomial function of the coefficients of the original polynomial. The discriminant is widely used in polynomial factoring, number theory, and algebraic geometry.
The discriminant of the quadratic polynomial is
the quantity which appears under the square root in the quadratic formula. If this discriminant is zero if and only if the polynomial has a double root. In the case of real coefficients, it is positive if the polynomial has two distinct real roots, and negative if it has two distinct complex conjugate roots. Similarly, the discriminant of a cubic polynomial is zero if and only if the polynomial has a multiple root. In the case of a cubic with real coefficients, the discriminant is positive if the polynomial has three distinct real roots, and negative if it has one real root and two distinct complex conjugate roots.
More generally, the discriminant of a univariate polynomial of positive degree is zero if and only if the polynomial has a multiple root. For real coefficients and no multiple roots, the discriminant is positive if the number of non-real roots is a multiple of 4 (including none), and negative otherwise.
Several generalizations are also called discriminant: the discriminant of an algebraic number field; the discriminant of a quadratic form; and more generally, the discriminant of a form, of a homogeneous polynomial, or of a projective hypersurface (these three concepts are essentially equivalent).
Origin
The term "discriminant" was coined in 1851 by the British mathematician James Joseph Sylvester.
Definition
Let
be a polynomial of degree (this means ), such that the coefficients belong to a field, or, more generally, to a commutative ring. The resultant of and its derivative,
is a polynomial in with integer coefficients, which is the determinant of the Sylvester matrix of and . The nonzero entries of the first column of the Sylvester matrix are and and the resultant is thus a multiple of Hence the discriminant—up to its sign—is defined as the quotient of the resultant of and by :
Historically, this sign has been chosen such that, over the reals, the discriminant will be positive when all the roots of the polynomial are real. The division by may not be well defined if the ring of the coefficients contains zero divisors. Such a problem may be avoided by replacing by 1 in the first column of the Sylvester matrix—before computing the determinant. In any case, the discriminant is a polynomial in with integer coefficients.
Expression in terms of the roots
When the above polynomial is defined over a field, it has roots, , not necessarily all distinct, in any algebraically closed extension of the field. (If the coefficients are real numbers, the roots may be taken in the field of complex numbers, where the fundament |
https://en.wikipedia.org/wiki/Cash%20and%20carry | Cash and carry may refer to:
Cash and Carry (game show), the first network-televised game show
Cash and carry (World War II), a revision of the Neutrality Acts, designed to aid the British
Cash and carry (wholesale), a type of sales operation within the wholesale sector
Cash and Carry (film), a 1937 Three Stooges short film
Cash and Carry, alternate title of the 1941 film Ringside Maisie
Cash & Carry, the United States grocery chain
Kash n' Karry, the United States supermarket chain
Basis trading, a form of arbitrage in which securities are bought in the cash market
An episode of the animated TV-series Garfield and Friends |
https://en.wikipedia.org/wiki/Trusted%20system | In the security engineering subspecialty of computer science, a trusted system is one that is relied upon to a specified extent to enforce a specified security policy. This is equivalent to saying that a trusted system is one whose failure would break a security policy (if a policy exists that the system is trusted to enforce).
The word "trust" is critical, as it does not carry the meaning that might be expected in everyday usage. A trusted system is one that the user feels safe to use, and trusts to perform tasks without secretly executing harmful or unauthorized programs; trusted computing refers to whether programs can trust the platform to be unmodified from the expected, and whether or not those programs are innocent or malicious or whether they execute tasks that are undesired by the user.
A trusted system can also be seen as a level-based security system where protection is provided and handled according to different levels. This is commonly found in the military, where information is categorized as unclassified (U), confidential (C), secret (S), top secret (TS), and beyond. These also enforce the policies of no read-up and no write-down.
Trusted systems in classified information
A subset of trusted systems ("Division B" and "Division A") implement mandatory access control (MAC) labels, and as such, it is often assumed that they can be used for processing classified information. However, this is generally untrue. There are four modes in which one can operate a multilevel secure system: multilevel, compartmented, dedicated, and system-high modes. The National Computer Security Center's "Yellow Book" specifies that B3 and A1 systems can only be used for processing a strict subset of security labels, and only when operated according to a particularly strict configuration.
Central to the concept of U.S. Department of Defense-style trusted systems is the notion of a "reference monitor", which is an entity that occupies the logical heart of the system and is responsible for all access control decisions. Ideally, the reference monitor is
tamper-proof
always invoked
small enough to be subject to independent testing, the completeness of which can be assured.
According to the U.S. National Security Agency's 1983 Trusted Computer System Evaluation Criteria (TCSEC), or "Orange Book", a set of "evaluation classes" were defined that described the features and assurances that the user could expect from a trusted system.
The dedication of significant system engineering toward minimizing the complexity (not size, as often cited) of the trusted computing base (TCB) is key to the provision of the highest levels of assurance (B3 and A1). This is defined as that combination of hardware, software, and firmware that is responsible for enforcing the system's security policy. An inherent engineering conflict would appear to arise in higher-assurance systems in that, the smaller the TCB, the larger the set of hardware, software, and firmware that lies outsid |
https://en.wikipedia.org/wiki/Cocoa%20%28API%29 | Cocoa is Apple's native object-oriented application programming interface (API) for its desktop operating system macOS.
Cocoa consists of the Foundation Kit, Application Kit, and Core Data frameworks, as included by the Cocoa.h header file, and the libraries and frameworks included by those, such as the C standard library and the Objective-C runtime.
Cocoa applications are typically developed using the development tools provided by Apple, specifically Xcode (formerly Project Builder) and Interface Builder (now part of Xcode), using the programming languages Objective-C or Swift. However, the Cocoa programming environment can be accessed using other tools. It is also possible to write Objective-C Cocoa programs in a simple text editor and build it manually with GNU Compiler Collection (GCC) or Clang from the command line or from a makefile.
For end users, Cocoa applications are those written using the Cocoa programming environment. Such applications usually have a familiar look and feel, since the Cocoa programming environment provides a lot of common UI elements (such as buttons, scroll bars, etc.), and automates many aspects of an application to comply with Apple's human interface guidelines.
For iOS, iPadOS, tvOS, and watchOS, a similar API exists, named Cocoa Touch, which includes gesture recognition, animation, and a different set of graphical control elements. It is used in applications for Apple devices such as the iPhone, the iPod Touch, the iPad, the Apple TV, and the Apple Watch.
History
Cocoa continues the lineage of several software frameworks (mainly the App Kit and Foundation Kit) from the NeXTSTEP and OpenStep programming environments developed by NeXT in the 1980s and 1990s. Apple acquired NeXT in December 1996, and subsequently went to work on the Rhapsody operating system that was to be the direct successor of OpenStep. It was to have had an emulation base for classic Mac OS applications, named Blue Box. The OpenStep base of libraries and binary support was termed Yellow Box. Rhapsody evolved into Mac OS X, and the Yellow Box became Cocoa. Thus, Cocoa classes begin with the letters NS, such as NSString or NSArray. These stand for the original proprietary term for the OpenStep framework, NeXTSTEP.
Much of the work that went into developing OpenStep was applied to developing Mac OS X, Cocoa being the most visible part. However, differences exist. For example, NeXTSTEP and OpenStep used Display PostScript for on-screen display of text and graphics, while Cocoa depends on Apple's Quartz (which uses the Portable Document Format (PDF) imaging model, but not its underlying technology). Cocoa also has a level of Internet support, including the NSURL and WebKit HTML classes, and others, while OpenStep had only rudimentary support for managed network connections via NSFileHandle classes and Berkeley sockets.
The resulting software framework received the name Cocoa for the sake of expediency, because the name had already been trad |
https://en.wikipedia.org/wiki/GNUstep | GNUstep is a free software implementation of the Cocoa (formerly OpenStep) Objective-C frameworks, widget toolkit, and application development tools for Unix-like operating systems and Microsoft Windows. It is part of the GNU Project.
GNUstep features a cross-platform, object-oriented IDE. Apart from the default Objective-C interface, GNUstep also has bindings for Java, Ruby, GNU Guile and Scheme. The GNUstep developers track some additions to Apple's Cocoa to remain compatible. The roots of the GNUstep application interface are the same as the roots of Cocoa: NeXTSTEP and OpenStep. GNUstep thus predates Cocoa, which emerged when Apple acquired NeXT's technology and incorporated it into the development of the original Mac OS X, while GNUstep was initially an effort by GNU developers to replicate the technically ambitious NeXTSTEP's programmer-friendly features.
History
GNUstep began when Paul Kunz and others at Stanford Linear Accelerator Center wanted to port HippoDraw from NeXTSTEP to another platform. Instead of rewriting HippoDraw from scratch and reusing only the application design, they decided to rewrite the NeXTSTEP object layer on which the application depended. This was the first version of libobjcX. It enabled them to port HippoDraw to Unix systems running the X Window System without changing a single line of their application source. After the OpenStep specification was released to the public in 1994, they decided to write a new objcX which would adhere to the new APIs. The software would become known as "GNUstep".
Software architecture
Rendering
GNUstep contains a set of graphical control elements written in the Objective-C programming language.
The graphical user interface (GUI) of GNUMail is composed of graphics control elements. GNUMail has to interact with the windowing system, e.g. X11 or Wayland, and its graphical user interface has to be rendered. GNUstep's backend provides a small set of functions used by the user interface library to interface to the actual windowing system. It also has a rendering engine which emulates common Postscript functions. The package gnustep-back provides the following backends:
cairo – default backend using the Cairo 2D graphics library.
winlib – default backend on Microsoft Windows systems. Cairo and Windows API variants.
art – old (deprecated) backend on unix-like systems. Uses the vector-based PostScript-like 2D graphics library Libart.
xlib – old (deprecated) X11 backend.
Paradigms
GNUstep inherits some design principles proposed in OPENSTEP (GNUstep predates Cocoa, but Cocoa is based on OPENSTEP) as well as the Objective-C language.
Model–view–controller paradigm
Target–action
Drag-and-drop
Delegation
Message forwarding (through NSInvocation)
Other interfaces
In addition to the Objective-C interface, some small projects under the GNUstep umbrella implement other APIs from Apple:
The Boron library aims to implement the Carbon API. It is very incomplete.
The CoreBase li |
https://en.wikipedia.org/wiki/Flare%20Technology | Flare Technology was a computer hardware company based in Cambridge, United Kingdom. It was founded in 1986 by Martin Brennan, Ben Cheese, and John Mathieson, former engineers at Sinclair Research.
History
Flare Technology first worked for Amstrad before developing a technology-demonstrator system called Flare One. The Flare One was intended as a home computer or games console with extensive audio and video capabilities.
Related to the Loki project they had worked on previously at Sinclair Research, which in turn was derived from the ZX Spectrum home computer, Flare One was based around a Zilog Z80B CPU (working as an 8-bit-per-pixel blitter and a video controller) and a custom 16-bit DSP chip (responsible for 8 channel sound and 3D computation), 1 MB or RAM, with a display resolution of 256 x 256 with 256 colors or 512 x 256 with 16 colors, and an expected price of £200 in 1988.
Flare One was used in some arcade game cabinets including a line of video quiz machines produced by Bellfruit (A Question of Sport, Beeline , Every Second Counts, Inquizitor, Quizvaders and Treble Top). The Flare One chipset was further developed into the Konix Multisystem Slipstream prototype.
In 1989 Martin Brennan was contracted by Atari Corp. to complete and implement the chip design of the unreleased Atari Panther.
Martin Brennan and John Mathieson went on to design the Flare II, which was purchased by Atari and became Atari Jaguar.
References
Defunct computer hardware companies
Defunct computer companies of the United Kingdom
Companies based in Cambridge
Computer companies established in 1986
1986 establishments in England |
https://en.wikipedia.org/wiki/Gouraud%20shading | Gouraud shading, named after Henri Gouraud, is an interpolation method used in computer graphics to produce continuous shading of surfaces represented by polygon meshes. In practice, Gouraud shading is most often used to achieve continuous lighting on triangle meshes by computing the lighting at the corners of each triangle and linearly interpolating the resulting colours for each pixel covered by the triangle. Gouraud first published the technique in 1971.
Description
Gouraud shading works as follows: An estimate to the surface normal of each vertex in a polygonal 3D model is either specified for each vertex or found by averaging the surface normals of the polygons that meet at each vertex. Using these estimates, lighting computations based on a reflection model, e.g. the Phong reflection model, are then performed to produce colour intensities at the vertices. For each screen pixel that is covered by the polygonal mesh, colour intensities can then be interpolated from the colour values calculated at the vertices.
Comparison with other shading techniques
Gouraud shading is considered superior to flat shading and requires significantly less processing than Phong shading, but usually results in a faceted look.
In comparison to Phong shading, Gouraud shading's strength and weakness lies in its interpolation. If a mesh covers more pixels in screen space than it has vertices, interpolating colour values from samples of expensive lighting calculations at vertices is less processor intensive than performing the lighting calculation for each pixel as in Phong shading. However, highly localized lighting effects (such as specular highlights, e.g. the glint of reflected light on the surface of an apple) will not be rendered correctly, and if a highlight lies in the middle of a polygon, but does not spread to the polygon's vertex, it will not be apparent in a Gouraud rendering; conversely, if a highlight occurs at the vertex of a polygon, it will be rendered correctly at this vertex (as this is where the lighting model is applied), but will be spread unnaturally across all neighboring polygons via the interpolation method.
The problem is easily spotted in a rendering which ought to have a specular highlight moving smoothly across the surface of a model as it rotates. Gouraud shading will instead produce a highlight continuously fading in and out across neighboring portions of the model, peaking in intensity when the intended specular highlight aligns with a vertex of the model. While this problem can be fixed by increasing the density of vertices in the object, at some point the diminishing returns of this approach will favour switching to a more detailed shading model.
Linear vs. hyperbolic interpolation
Gouraud's original paper described linear color interpolation. In 1992, Blinn published an efficient algorithm for hyperbolic interpolation that is used in GPUs as a perspective correct alternative to linear interpolation. Both the linear and hyper |
https://en.wikipedia.org/wiki/Instant%20messaging | Instant messaging (IM) technology is a type of online chat allowing real-time text transmission over the Internet or another computer network. Messages are typically transmitted between two or more parties, when each user inputs text and triggers a transmission to the recipient(s), who are all connected on a common network. It differs from email in that conversations over instant messaging happen in real-time (hence "instant"). Most modern IM applications (sometimes called "social messengers", "messaging apps", "chat apps" or "chat clients") use push technology and also add other features such as emojis (or graphical smileys), file transfer, chatbots, voice over IP, or video chat capabilities.
Instant messaging systems tend to facilitate connections between specified known users (often using a contact list also known as a "buddy list" or "friend list"), and can be standalone applications or integrated into e.g. a wider social media platform, or a website where it can for instance be used for conversational commerce. IM can also consist of conversations in "chat rooms". Depending on the IM protocol, the technical architecture can be peer-to-peer (direct point-to-point transmission) or client–server (an IM service center retransmits messages from the sender to the communication device). It is usually distinguished from text messaging which is typically simpler and normally uses cellular phone networks.
Instant messaging applications can store messages with either local-based device storage (e.g WhatsApp, Viber, Line, WeChat, Signal etc.) or cloud-based server storage (e.g Telegram, Skype, Facebook Messenger, Google Meet/Chat, Discord, Slack etc.).
Instant messaging was pioneered in the early Internet era; the IRC protocol was the earliest to achieve wide adoption. Later in the 1990s, ICQ was among the first closed and commercialized instant messengers, and several rival services appeared afterwards as it became a popular use of the Internet. Beginning with its first introduction in 2005, BlackBerry Messenger, which initially had been available only on BlackBerry smartphones, soon became one of the most popular mobile instant messaging apps worldwide. BBM was for instance the most used mobile messaging app in the United Kingdom and Indonesia. Instant messaging remains very popular today; IM apps are the most widely used smartphone apps: in 2018 there were over 50 million Signal users, 980 million monthly active users of WeChat and 1.3 billion monthly users of WhatsApp Messenger.
Overview
Instant messaging is a set of communication technologies used for text-based communication between two (private messaging) or more (chat room) participants over the Internet or other types of networks (see also LAN messenger). IM chats happen in real-time. Online chat and instant messaging differ from other technologies such as email due to the perceived quasi-synchrony of the communications by the users, although some systems allow users to send offline messag |
https://en.wikipedia.org/wiki/Version%20control | In software engineering, version control (also known as revision control, source control, or source code management) is a class of systems responsible for managing changes to computer programs, documents, large web sites, or other collections of information. Version control is a component of software configuration management.
Changes are usually identified by a number or letter code, termed the "revision number", "revision level", or simply "revision". For example, an initial set of files is "revision 1". When the first change is made, the resulting set is "revision 2", and so on. Each revision is associated with a timestamp and the person making the change. Revisions can be compared, restored, and, with some types of files, merged.
The need for a logical way to organize and control revisions has existed for almost as long as writing has existed, but revision control became much more important, and complicated, when the era of computing began. The numbering of book editions and of specification revisions are examples that date back to the print-only era. Today, the most capable (as well as complex) revision control systems are those used in software development, where a team of people may concurrently make changes to the same files.
Version control systems are most commonly run as stand-alone applications, but revision control is also embedded in various types of software, such as word processors and spreadsheets, collaborative web docs, and content management systems, e.g., Wikipedia's page history. Revision control enables reverting a document to a previous revision, which is critical for allowing editors to track each other's edits, correct mistakes, and defend against vandalism and spamming in wikis.
Overview
In computer software engineering, revision control is any kind of practice that tracks and provides control over changes to source code. Software developers sometimes use revision control software to maintain documentation and configuration files as well as source code.
As teams design, develop and deploy software, it is common for multiple versions of the same software to be deployed in different sites and for the software's developers to be working simultaneously on updates. Bugs or features of the software are often only present in certain versions (because of the fixing of some problems and the introduction of others as the program develops). Therefore, for the purposes of locating and fixing bugs, it is vitally important to be able to retrieve and run different versions of the software to determine in which version(s) the problem occurs. It may also be necessary to develop two versions of the software concurrently: for instance, where one version has bugs fixed, but no new features (branch), while the other version is where new features are worked on (trunk).
At the simplest level, developers could simply retain multiple copies of the different versions of the program, and label them appropriately. This simple approach |
https://en.wikipedia.org/wiki/Monte%20Carlo%20method | Monte Carlo methods, or Monte Carlo experiments, are a broad class of computational algorithms that rely on repeated random sampling to obtain numerical results. The underlying concept is to use randomness to solve problems that might be deterministic in principle. They are often used in physical and mathematical problems and are most useful when it is difficult or impossible to use other approaches. Monte Carlo methods are mainly used in three problem classes: optimization, numerical integration, and generating draws from a probability distribution.
In physics-related problems, Monte Carlo methods are useful for simulating systems with many coupled degrees of freedom, such as fluids, disordered materials, strongly coupled solids, and cellular structures (see cellular Potts model, interacting particle systems, McKean–Vlasov processes, kinetic models of gases).
Other examples include modeling phenomena with significant uncertainty in inputs such as the calculation of risk in business and, in mathematics, evaluation of multidimensional definite integrals with complicated boundary conditions. In application to systems engineering problems (space, oil exploration, aircraft design, etc.), Monte Carlo–based predictions of failure, cost overruns and schedule overruns are routinely better than human intuition or alternative "soft" methods.
In principle, Monte Carlo methods can be used to solve any problem having a probabilistic interpretation. By the law of large numbers, integrals described by the expected value of some random variable can be approximated by taking the empirical mean ( the 'sample mean') of independent samples of the variable. When the probability distribution of the variable is parameterized, mathematicians often use a Markov chain Monte Carlo (MCMC) sampler. The central idea is to design a judicious Markov chain model with a prescribed stationary probability distribution. That is, in the limit, the samples being generated by the MCMC method will be samples from the desired (target) distribution. By the ergodic theorem, the stationary distribution is approximated by the empirical measures of the random states of the MCMC sampler.
In other problems, the objective is generating draws from a sequence of probability distributions satisfying a nonlinear evolution equation. These flows of probability distributions can always be interpreted as the distributions of the random states of a Markov process whose transition probabilities depend on the distributions of the current random states (see McKean–Vlasov processes, nonlinear filtering equation). In other instances we are given a flow of probability distributions with an increasing level of sampling complexity (path spaces models with an increasing time horizon, Boltzmann–Gibbs measures associated with decreasing temperature parameters, and many others). These models can also be seen as the evolution of the law of the random states of a nonlinear Markov chain. A natural way to simulate t |
https://en.wikipedia.org/wiki/Metropolis%E2%80%93Hastings%20algorithm | In statistics and statistical physics, the Metropolis–Hastings algorithm is a Markov chain Monte Carlo (MCMC) method for obtaining a sequence of random samples from a probability distribution from which direct sampling is difficult. This sequence can be used to approximate the distribution (e.g. to generate a histogram) or to compute an integral (e.g. an expected value). Metropolis–Hastings and other MCMC algorithms are generally used for sampling from multi-dimensional distributions, especially when the number of dimensions is high. For single-dimensional distributions, there are usually other methods (e.g. adaptive rejection sampling) that can directly return independent samples from the distribution, and these are free from the problem of autocorrelated samples that is inherent in MCMC methods.
History
The algorithm is named in part for Nicholas Metropolis, the first coauthor of a 1953 paper, entitled Equation of State Calculations by Fast Computing Machines, with Arianna W. Rosenbluth, Marshall Rosenbluth, Augusta H. Teller and Edward Teller. For many years the algorithm was known simply as the Metropolis algorithm. The paper proposed the algorithm for the case of symmetrical proposal distributions, but in 1970, W.K. Hastings extended it to the more general case. The generalized method was eventually identified by both names, although the first use of the term "Metropolis-Hastings algorithm" is unclear.
Some controversy exists with regard to credit for development of the Metropolis algorithm. Metropolis, who was familiar with the computational aspects of the method, had coined the term "Monte Carlo" in an earlier article with Stanisław Ulam, and led the group in the Theoretical Division that designed and built the MANIAC I computer used in the experiments in 1952. However, prior to 2003 there was no detailed account of the algorithm's development. Shortly before his death, Marshall Rosenbluth attended a 2003 conference at LANL marking the 50th anniversary of the 1953 publication. At this conference, Rosenbluth described the algorithm and its development in a presentation titled "Genesis of the Monte Carlo Algorithm for Statistical Mechanics". Further historical clarification is made by Gubernatis in a 2005 journal article recounting the 50th anniversary conference. Rosenbluth makes it clear that he and his wife Arianna did the work, and that Metropolis played no role in the development other than providing computer time.
This contradicts an account by Edward Teller, who states in his memoirs that the five authors of the 1953 article worked together for "days (and nights)". In contrast, the detailed account by Rosenbluth credits Teller with a crucial but early suggestion to "take advantage of statistical mechanics and take ensemble averages instead of following detailed kinematics". This, says Rosenbluth, started him thinking about the generalized Monte Carlo approach – a topic which he says he had discussed often with John Von Neuman |
https://en.wikipedia.org/wiki/Battle%20Angel%20Alita | Gunnm (, ), also known as Battle Angel Alita in English, is a Japanese cyberpunk manga series created by Yukito Kishiro and originally published in Shueisha's Business Jump magazine from 1990 to 1995. The second of the comic's nine volumes was adapted in 1993 into a two-part anime original video animation titled Battle Angel for North American release by ADV Films and the UK and Australian release by Manga Entertainment. Manga Entertainment also dubbed Battle Angel Alita into English. A live-action film adaptation titled Alita: Battle Angel was released on February 14, 2019.
The series is set in the post-apocalyptic future and focuses on Alita ("Gally" in the original Japanese version, and several other countries), a female cyborg who has lost all memories and is found in a junkyard by a cybernetics doctor who rebuilds and takes care of her. She discovers that there is one thing she remembers, the legendary cyborg martial art Panzer Kunst, which leads to her becoming a Hunter Warrior, or bounty hunter. The story traces Alita's attempts to rediscover her past and the characters whose lives she impacts on her journey. The manga series is continued in Battle Angel Alita: Last Order and Battle Angel Alita: Mars Chronicle.
Plot
Battle Angel Alita tells the story of Alita, an amnesiac female cyborg. Her intact head and chest, in suspended animation, are found by cybermedic expert Daisuke Ido in the local garbage dump. Ido manages to revive her, and finding she has lost her memory, names her Alita after his recently deceased cat. The rebuilt Alita soon discovers that she instinctively remembers the legendary martial art Panzer Kunst, although she does not recall anything else. Alita uses her Panzer Kunst to first become a bounty hunter, killing cyborg criminals in the Scrapyard, and then as a star player in the brutal gladiator sport of Motorball. While in combat, Alita awakens memories of her earlier life on Mars. She becomes involved with the floating city of Zalem (Tiphares in some older translations) as one of their agents, and is sent to hunt down criminals. Foremost is the mad genius Desty Nova, who has a complex, ever-changing relationship with Alita.
The futuristic dystopian world of Battle Angel Alita revolves around the city of Scrapyard (Kuzutetsu in the Japanese and various other versions), which has grown up around a massive scrap heap that rains down from Zalem. Ground dwellers have no access to Zalem and are forced to make a living in the sprawl below. Many are heavily modified by cybernetics to better cope with their hard life.
Zalem exploits the Scrapyard and surrounding farms, paying bounty hunters (called Hunter-Warriors) to hunt criminals and arranging violent sports to keep the population entertained. Massive tubes connect the Scrapyard to Zalem, and the city uses robots for carrying out errands and providing security on the ground. Occasionally, Zalemites (such as Daisuke Ido and Desty Nova) are exiled and sent to the ground. |
https://en.wikipedia.org/wiki/BBC%20BASIC | BBC BASIC is a version of the BASIC programming language released in 1981 as the native programming language for the BBC Micro home/personal computer, providing a standardized language for a UK computer literacy project of the BBC. It was written mainly by Sophie Wilson.
BBC BASIC, based on the older Atom BASIC for the Acorn Atom, extended contemporary microcomputer BASICs with named DEF PROC/DEF FN procedures and functions, REPEAT UNTIL loops, and IF THEN ELSE structures inspired by COMAL. The interpreter also included statements for controlling the BBC Micro's four-channel sound output and its low-/high-resolution eight-mode graphics display.
Due to a number of optimizations, BBC BASIC ran programs much faster than Microsoft BASIC running on similar machines. The optimizations included using multiple linked lists for variable lookup rather than a single long list, pre-defining the location of integer variables, and having separate integer maths routines. Speed was further improved on the BBC machine by its fast RAM chips, which allowed the MOS Technology 6502 processor and Motorola 6845 display driver to share memory without either pausing for access. As a result of these design features, BBC BASIC ran David Ahl's Creative Computing Benchmark in 21 seconds, besting even the IBM Personal Computer, and far outpacing most other 8-bit platforms. The only commercial 8-bit BASIC computers that were as fast as the BBC Micro were the Swedish ABC 80 and ABC 800. The improved BASIC 4 on the BBC Master executes the same benchmark in about seven seconds.
One of the unique features of BBC BASIC was the inline assembler, allowing users to write assembly language programs for the 6502 and, later, the Zilog Z80, NS32016 and ARM. The assembler was fully integrated into the BASIC interpreter and shared variables with it, which could be included between the [ and ] characters, saved via *SAVE and *LOAD, and called via the CALL or USR commands. This allowed developers to write not just assembly language code, but also BASIC code to emit assembly language, making it possible to use code-generation techniques and even write simple compilers in BASIC.
History
In 1978 Hermann Hauser and Chris Curry founded Acorn Computers. Much of the code was developed at Cambridge University by Sophie Wilson and her colleagues. Starting with the original Acorn dialect of BASIC — "12K of working language which could be 'bent at will'" that had been informed by Algol W and BCPL in its design — Wilson "set about bending it towards Pascal" in collaboration with John Coll, creating a language combining "Microsoft necessities" and "Pascal-ish variations". Some Pascal-influenced features such as labels and multi-line conditional statements had to be dropped, however, due to broad compatibility expectations with Microsoft BASIC, ostensibly imposed by the requirements of the BBC.
Platforms and versions
BBC Micro
The full version list is available here:
BASIC I, the original version, |
https://en.wikipedia.org/wiki/Acorn%20Computers | Acorn Computers Ltd. was a British computer company established in Cambridge, England, in 1978. The company produced a number of computers which were especially popular in the UK, including the Acorn Electron and the Acorn Archimedes. Acorn's computer dominated the UK educational computer market during the 1980s.
Though the company was acquired and largely dismantled in early 1999, with various activities being dispersed amongst new and established companies, its legacy includes the development of reduced instruction set computing (RISC) personal computers. One of its operating systems, , continues to be developed by RISC OS Open. Some activities established by Acorn lived on: technology developed by Arm, created by Acorn as a joint venture with Apple and VLSI in 1990, is dominant in the mobile phone and personal digital assistant (PDA) microprocessor market.
Acorn is sometimes referred to as the "British Apple" and has been compared to Fairchild Semiconductor for being a catalyst for start-ups. In 2010, the company was listed by David Meyer in ZDNet as number nine in a feature of top ten "Dead IT giants". Many British IT professionals gained their early experiences on Acorns, which were often more technically advanced than commercially successful US hardware.
History
Early history
On 25 July 1961, Clive Sinclair founded Sinclair Radionics to develop and sell electronic devices such as calculators. The failure of the Black Watch wristwatch and the calculator market's move from LEDs to LCDs led to financial problems, and Sinclair approached government body the National Enterprise Board (NEB) for help. After losing control of the company to the NEB, Sinclair encouraged Chris Curry to leave Radionics and get Science of Cambridge (SoC—an early name for Sinclair Research) up and running. In June 1978, SoC launched a microcomputer kit, the Mk 14, that Curry wanted to develop further, but Sinclair could not be persuaded so Curry resigned. During the development of the Mk 14, Hermann Hauser, a friend of Curry's, had been visiting SoC's offices and had grown interested in the product.
CPU Ltd. (1978–1983)
Curry and Hauser decided to pursue their joint interest in microcomputers and, on 5 December 1978, they set up Cambridge Processor Unit Ltd. (CPU) as the vehicle with which to do this. CPU soon obtained a consultancy contract to develop a microprocessor-based controller for a fruit machine for Ace Coin Equipment (ACE) of Wales. The ACE project was started at office space obtained at 4a Market Hill in Cambridge. Initially, the ACE controller was based on a National Semiconductor SC/MP microprocessor, but soon the switch to a MOS Technology 6502 was made.
The microcomputer systems
CPU had financed the development of a SC/MP based microcomputer system using the income from its design-and-build consultancy.
This system was launched in January 1979 as the first product of Acorn Computer Ltd., a trading name used by CPU to keep the risks of the two |
https://en.wikipedia.org/wiki/Sophie%20Wilson | Sophie Mary Wilson (born Roger Wilson; June 1957) is an English computer scientist, who helped design the BBC Micro and ARM architecture.
Wilson first designed a microcomputer during a break from studies at Selwyn College, Cambridge. She subsequently joined Acorn Computers and was instrumental in designing the BBC Micro, including the BBC BASIC programming language whose development she led for the next 15 years. She first began designing the ARM reduced instruction set computer (RISC) in 1983, which entered production two years later. It became popular in embedded systems and is now the most widely used processor architecture in smartphones. Wilson is currently a director at the technology conglomerate Broadcom Inc. In 2011, she was listed in Maximum PC as number 8 in an article titled "The 15 Most Important Women in Tech History". She was made a Commander of the British Empire in 2019.
Early life and education
Wilson was born in 1957 and brought up in Leeds, Yorkshire. Her parents were both teachers, with her father specialising in English and her mother in physics. From 1975, she studied computer science and the Mathematical Tripos at Selwyn College, University of Cambridge and was a member of their Microprocessor society. In an Easter break from university, Wilson designed a microcomputer with a MOS Technology 6502 microprocessor, inspired by the earlier MK14, which was used to electronically control feed for cows.
Career
In 1978, she joined Acorn Computers Ltd, after designing a device to prevent cigarette lighter sparks triggering payouts on fruit machines. Wilson's computer design was used by Chris Curry and Hermann Hauser to build the Acorn Micro-Computer, the first of a long line of computers sold by the company.
In July 1981, Wilson extended the Acorn Atom's BASIC programming language dialect into an improved version for the Acorn Proton, a microcomputer that enabled Acorn to win the contract with the British Broadcasting Corporation (BBC) for their ambitious computer education project. Hauser employed a deception, telling both Wilson and colleague Steve Furber that the other had agreed a prototype could be built within a week. Taking up the challenge, she designed the system including the circuit board and components from Monday to Wednesday, which required fast new DRAM integrated circuits to be sourced directly from Hitachi. By Thursday evening, a prototype had been built, but the software had bugs, requiring her to stay up all night and into Friday debugging. Wilson recalled watching the wedding of Prince Charles and Lady Diana Spencer on a small portable television while attempting to debug and re-solder the prototype. It was a success with the BBC, who awarded Acorn the contract. Along with Furber, Wilson was present backstage at the machine's first airing on television, in case any software fixes were required. She later described the event as "a unique moment in time when the public wanted to know how this stuff works and |
https://en.wikipedia.org/wiki/Christopher%20Evans%20%28computer%20scientist%29 | Christopher Riche Evans (29 May 1931 – 10 October 1979) was a British psychologist, computer scientist, and author.
Biography
Born in Aberdyfi, Christopher Evans spent his childhood in Wales and was educated at Christ College, Brecon (1941–49). He spent two years in the RAF (1950–52), and worked as a science journalist and writer until 1957, when he began a B.A. course in Psychology at University College London, graduating with honours in 1960. After a summer fellowship at Duke University in the United States, where he first met his American wife, Nancy Fullmer, he took up a research assistant post in the Physics Laboratory, University of Reading, working on eye movements under Professor R. W. Ditchburn. Upon receiving his PhD (the title of his thesis was "Pattern Perception and the Stabilised Retinal Image"), he went to the Division of Computer Science, National Physical Laboratory, Teddington, in 1964, where he remained until his death from cancer in 1979. He had two children, Christopher Samuel Evans and Victoria Evans-Theiler.
Works
In 1979, Christopher Evans wrote a book about the oncoming microcomputer revolution, The Mighty Micro: The Impact of the Computer Revolution, which included predictions for the future up to the year 2000. This book was also printed in the US as The Micro Millennium (New York: The Viking Press, ). He subsequently scripted and presented for ATV a six-part television series based on this book and broadcast posthumously by ITV between October and December 1979.
His other books include Cults of Unreason, a study of Scientology and other pseudoscience, and Landscapes of the Night: How and Why We Dream.
In the 1970s, Evans undertook a set of interviews with computer pioneers such as Konrad Zuse and Grace Hopper. These were released through the Science Museum, London, as Pioneers of Computing, a set of cassette tapes.
Christopher Evans also edited two anthologies of psychological science fiction/horror stories, Mind at Bay and Mind in Chains, a collection of science writings, Cybernetics: Key Papers, a reference book Psychology: A Dictionary of Mind, Brain and Behaviour, and was a contributing editor to the science magazine Omni. A keen pilot, he also edited a yearly pilot's diary of rural airfields in Great Britain.
Evans had a significant friendship and collaboration with the writer J. G. Ballard. Together around 1968 they developed ideas for a play about a car crash, offered to
the Institute of Contemporary Arts but not produced.
Later came an exhibition of crashed cars at The New Arts Lab in London in 1970, and ultimately Ballard's novel
Crash, published in 1973. Evans' charismatic appearance as a "hoodlum scientist" (in Ballard's description) was an inspiration for the
character of Dr. Robert Vaughan in Crash. Evans also appears in Ballard's fictionalised life story The Kindness of Women
as the psychologist Dr. Richard Sutherland. (Ballard recounts his friendship with Evans in his autobiography Miracles of Li |
https://en.wikipedia.org/wiki/Clive%20Sinclair | Sir Clive Marles Sinclair (30 July 1940 – 16 September 2021) was an English entrepreneur and inventor, best known for being a pioneer in the computing industry and also as the founder of several companies that developed consumer electronics in the 1970s and early 1980s.
After spending several years as assistant editor of Instrument Practice, Sinclair founded Sinclair Radionics Ltd in 1961. He produced the world's first slimline electronic pocket calculator (the Sinclair Executive) in 1972. Sinclair then moved into the production of home computers in 1980 with Sinclair Research Ltd, producing the Sinclair ZX80 (the UK's first mass-market home computer for less than £100) and in the early 1980s, the ZX81, ZX Spectrum and the Sinclair QL. Sinclair Research is widely recognised for its importance in the early days of the British and European home computer industry, as well as helping to give rise to the British video game industry.
Sinclair also had several commercial failures, including the Sinclair Radionics Black Watch wristwatch, the Sinclair Vehicles C5 battery electric vehicle, and the Sinclair Research TV80 flatscreen CRT handheld television set. The failure of the C5, along with a weakened computer market, forced Sinclair to sell most of his companies by 1986. Through 2010, Sinclair concentrated on personal transport, including the A-bike, a folding bicycle for commuters which was small enough to fit in a handbag. He also developed the Sinclair X-1, a revised version of the C5 electric vehicle, which never made it to the market.
Sinclair was appointed Knight Bachelor in the 1983 Birthday Honours for his contributions to the personal computer industry in the UK.
Early life, family and education
Sinclair's father and grandfather were engineers; both had been apprentices at the shipbuilders Vickers. His grandfather George Sinclair was a naval architect who got the paravane, a mine sweeping device, to work. George Sinclair's son, George William "Bill" Sinclair, wanted to take religious orders or become a journalist. His father suggested he train as an engineer first; Bill became a mechanical engineer and remained in the field. At the outbreak of World War II in 1939, he was running his own machine tools business in London, and later worked for the Ministry of Supply.
Clive Sinclair was born to George Sinclair and Thora Edith Ella Marles in 1940 in Ealing, Middlesex. He and his mother left London for safety to stay with an aunt in Devon, where they eventually moved to Teignmouth. A telegram arrived shortly afterwards, bringing the news that their home in Ealing had been bombed. Sinclair's father found a house in Bracknell in Berkshire. His brother Iain was born in 1943 and his sister Fiona in 1947.
Sinclair attended Boxgrove Preparatory School, excelling in mathematics. Sinclair had little interest in sports and found himself out of place at school. By the time he was ten, his father had financial problems. He had branched out from machine t |
https://en.wikipedia.org/wiki/Framing%20error | Framing error can refer to the following:
General form of a framing error is the result of starting to read a sequence of data at the wrong point.
In serial communications, a framing error is the result of reading a data frame -- a string of symbols which are grouped in blocks -- at the wrong starting point. The symbols are bits and the blocks are bytes, ten bits in asynchronous transmission and eight in synchronous. A framing error in an asynchronous stream usually recovers quickly, but a framing error in a synchronous stream produces gibberish at the end of the packet. Framing errors can be detected with parity bits.
In genetics, a framing error (also called a frameshift or a frameshift mutation) is a mutation that inserts or deletes a single nucleotide from a DNA sequence. Due to the triplet nature of gene expression, the insertion/deletion can disrupt the grouping of the codons, resulting in a completely different translation from the original.
In psychology, the framing effect (psychology) is an example of cognitive bias in which people react to a particular choice in different ways depending on how it is presented. Cognitive errors as a result of this bias are commonly called framing errors. |
https://en.wikipedia.org/wiki/EDS | EDS or Eds may refer to:
Organisations
Electronic Data Systems, a defunct American technology company
Education
Episcopal Divinity School, an Episcopal Seminary in Cambridge, Massachusetts, US
Evansville Day School, an independent college-prep school in Evansville, Indiana, US
University of Ottawa English Debating Society, Canada
Politics
Environmental Defence Society, a New Zealand environmental organisation
European Democrat Students, a centre-right political students union
European Democratic Party (Czech Republic) (), a Czech political party
Science and technology
Electrodynamic suspension
Elliptic divisibility sequence
Energy-dispersive X-ray spectroscopy
Effluent decontamination system
Chemistry
Estradiol distearate
Ethane dimethanesulfonate
Computing
Electronic Document System, an early hypertext system
Evolution Data Server, data management server in GNOME
Extended Data Services, a data transmission standard
Electronic Data Sheet, a file format, part of the CANopen protocol
Medicine
Egg drop syndrome
Ehlers-Danlos Society, a medical charity
Ehlers–Danlos syndromes
Episodic dyscontrol syndrome
Excessive daytime sleepiness
Exhalation delivery system
Military and space
Electronic Data System, a command, control, and coordination system of the US Navy
Earth Departure Stage, of the Ares V and Block II rockets
Emergency Detection System, used on crewed rocket missions
Plant immunity
The EDS1 family of plant immunity mediating proteins, the best studied examples of which are discussed at Arabidopsis thaliana § EDS1 family
Other uses
Educational specialist (Ed.S.), an academic degree in the US
Eds FF, a Swedish football club
See also
ED (disambiguation) |
https://en.wikipedia.org/wiki/Carbon%20%28API%29 | Carbon was one of two primary C-based application programming interfaces (APIs) developed by Apple for the macOS (formerly Mac OS X and OS X) operating system. Carbon provided a good degree of backward compatibility for programs that ran on Mac OS 8 and 9. Developers could use the Carbon APIs to port (“carbonize”) their “classic” Mac applications and software to the Mac OS X platform with little effort, compared to porting the app to the entirely different Cocoa system, which originated in OPENSTEP. With the release of macOS 10.15 Catalina, the Carbon API was officially discontinued and removed, leaving Cocoa as the sole primary API for developing macOS applications.
Carbon was an important part of Apple's strategy for bringing Mac OS X to market, offering a path for quick porting of existing software applications, as well as a means of shipping applications that would run on either Mac OS X or the classic Mac OS. As the market has increasingly moved to the Cocoa-based frameworks, especially after the release of iOS, the need for a porting library was diluted. Apple did not create a 64-bit version of Carbon while updating their other frameworks in the 2007 time-frame, and eventually deprecated the entire API in OS X 10.8 Mountain Lion, which was released on July 24, 2012.
History
Classic Mac OS programming
The original Mac OS used Pascal as its primary development platform, and the APIs were heavily based on Pascal's call semantics. Much of the Macintosh Toolbox consisted of procedure calls, passing information back and forth between the API and program using a variety of data structures based on Pascal's variant record concept.
Over time, a number of object libraries evolved on the Mac, notably the Object Pascal library MacApp and the THINK C Think Class Library, and later versions of MacApp and CodeWarrior's PowerPlant in C++. By the mid-1990s, most Mac software was written in C++ using CodeWarrior.
Rhapsody
With the purchase of NeXT in late 1996, Apple developed a new operating system strategy based largely on the existing OpenStep platform. The new Rhapsody was relatively simple; it retained most of OpenStep's existing object libraries under the name "Yellow Box", ported OpenStep's existing GUI and made it look more Mac-like, ported several major APIs from the Mac OS to Rhapsody's underlying Unix-like system (notably QuickTime and AppleSearch), and added an emulator known as the "Blue Box" that ran existing Mac OS software.
When this plan was revealed at the Worldwide Developers Conference in 1997 there was some push-back from existing Mac OS developers, who were upset that their code bases would effectively be locked into an emulator that was unlikely to ever be updated. They took to calling the Blue Box the "penalty box". Larger developers like Microsoft and Adobe balked outright, and refused to consider porting to OpenStep, which was so different from the existing Mac OS that there was little or no compatibility.
Apple took these co |
https://en.wikipedia.org/wiki/Transport%20in%20Uganda | Transport in Uganda refers to the transportation structure in Uganda. The country has an extensive network of paved and unpaved roads.
Roadways
As of 2017, according to the Uganda Ministry of Works and Transport, Uganda had about of roads, with approximately (4 percent) paved. Most paved roads radiate from Kampala, the country's capital and largest city.
International highways
The Lagos-Mombasa Highway, part of the Trans-Africa Highway and aiming to link East Africa and West Africa, passes through Uganda. This is complete only eastwards from the Uganda–DR Congo border to Mombasa, linking the African Great Lakes region to the sea. In East Africa, this roadway is part of the Northern Corridor.
It cannot be used to reach West Africa because the route westwards across DR Congo to Bangui in the Central African Republic (CAR) is impassable after the Second Congo War and requires reconstruction. An alternative route (not part of the Trans-African network) to Bangui based on gravel roads and earth roads runs from Gulu in northern Uganda via Nimule and Juba, South Sudan and Obo in south-east CAR. This is used by trucks but sections are impassable after rain.
The route has been closed at times during war and conflict in northern Uganda (the Lord's Resistance Army rebellion) and South Sudan, but up to July 2007 had not been affected by the Darfur conflict and was the only usable road between East and West Africa. The security situation should be checked with authorities in northern Uganda, South Sudan and south-eastern CAR before use.
Railways
As of 2017, Uganda's railway network measures about in length. Of this, about 56% (), is operational.
All existing railway is metre gauge. A new standard gauge rail network is planned.
A railroad originating at Mombasa on the Indian Ocean connects with Tororo, where it branches westward to Jinja, Kampala, and Kasese and northward to Mbale, Soroti, Lira, Gulu, and Pakwach. The only railway line still operating, however, is the Malaba–Kampala line.
Railway links with neighboring countries
Kenya: Yes; same gauge
South Sudan: Proposed; break of gauge /
Democratic Republic of the Congo: No; break of gauge /
Rwanda: No; Does not yet have railways
Tanzania: No direct connection except via train ferry; same gauge
Couplings and brakes
Couplings : Meatchopper (Norwegian)
Brakes : Air
Standards
Plans
Standard Gauge Railway
The six countries of the East African Community are in the process of constructing railway lines with standard gauge tracks. Kenya had, by June 2018, completed the construction of the Mombasa–Nairobi section of its Standard Gauge Railway (SGR), which cost US$4.47 billion (original budget was US$3.2 billion), borrowed from the Exim Bank of China. The country now plans to extend he SGR line to Nakuru, Kisumu and Malaba, when funds become available.
Uganda plans to construct a total of four SGR lines, totaling , at an estimated cost of US$12.6 billion. Uganda's SGR is planned |
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