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https://en.wikipedia.org/wiki/Interpress | Interpress is a page description language developed at Xerox PARC, based on the Forth programming language and an earlier graphics language called JaM. PARC was unable to commercialize Interpress. Two of its creators, Chuck Geschke and John Warnock, left Xerox, formed Adobe Systems, and produced a similar language called PostScript. Interpress is used in some Xerox printers most notable was the DocuTech Network Production Publisher, and is supported in Xerox Ventura Publisher. Interpress is also used as the output format for PARC's InterScript system, which is an editable word processor format for rich text documents.
Interpress describes the desired or ideal appearance of a document that has been completely composed by some other process (emitter). All line ending, hyphenation, and line justification decisions, and in fact all decisions about the shapes and positions of the images, are made before creating the master. Since Interpress describes a document in a device-independent manner, a master can be printed on a variety of devices, each of which renders its best approximation to the ideal represented by the master.
Functional Sets
Interpess is so extensive, some printer manufacturers may prefer to support only a part of it, perhaps to reduce development time and cost or to improve performance. Recognizing this and also the potential for chaos if every printer were to implement a different portion of the language, Interpress was designed to have defined three standard function sets:
Commercial Set
designed for text and form-printing applications, such as might be required in a data center using basic text or scanned images.
Publication Set
includes all the Commercial Set plus curved lines, filled outlines, rectangular clipping, synthetic graphics, and gray-level color capabilities.
Professional Graphics Set
consist of all of the imaging facilities (types, literals, and operators of the base language), full-color encoding, and Printing Instructions (which were expanded by Ernest L. Legg)
Printing Instructions
This feature set allows the ability to instruct the printer which media to use (paper size, type, color), number of copies, sides printed on as well as finishing actions such as stapling. These instructions are optional and their operation is dependent on the printer capability.
Example
A more complex structure would include Nested Blocks and CONTENTINSTRUCTIONS, a token used to distinguish content-instructions bodies from page bodies. In general, the content instructions are given precedence over the document instructions. Nested Blocks {BEGIN..END} allow for constructing large documents out of smaller ones.
Fonts
These are definitions that often found in the preamble since they usually apply to the entire document.
References
External links
A Usenet post from 1985 describing the history of Interpress and comparing it with PostScript
Docu + Design Daube “Interpress”
Introduction to Interpress
Computer printing
Concatenat |
https://en.wikipedia.org/wiki/IGC | IGC may stand for:
Companies
Intelligent Graphics Corporation, marketer of the VM/386 multitasking operating system or 'control program'
Istituto Geografico Centrale, an Italian private mapping company
Immortals Gaming Club, an esports company
Inquirer Group of Companies, a Philippine mass media conglomerate
Politics
Intergovernmental Conference, the formal procedure for negotiating amendments to the founding treaties of the European Union
Intergovernmental Committee on Intellectual Property and Genetic Resources, Traditional Knowledge and Folklore of the World Intellectual Property Organization
International Grains Council, an intergovernmental organisation concerned with grains trade
Iraqi Governing Council, the provisional government of Iraq from July 13, 2003 to June 1, 2004
Science
Inverse gas chromatography, an analytical technique in the analysis of the surfaces of solids
Interchromatin granule cluster, a nanostructure inside the cell nucleus
Organizations
Intergovernmental Commission, which regulates the Channel Tunnel
International Gender Champions, an organizationworking for gender equality
International Geological Congress, a convention held by the International Union of Geological Sciences
International Grains Council, an intergovernmental organization
International Growth Centre, a research institute associated with the London School of Economics, England
Institute for Global Communications or IGC Internet, an institution that provides Internet presence for groups deemed "progressive"
Instituto Gulbenkian de Ciência, a biological research-oriented institute belonging to the Gulbenkian Foundation, Oeiras, Portugal
International Gliding Commission or FAI Gliding Commission, the international governing body for the sport of gliding which standardized .igc file format.
International Gospel Centre, the headquarters of Word of Life Bible Church, Warri, Nigeria
Other uses
IAPMO Guide Criteria, IAPMO Standards for the International Association of Plumbing and Mechanical Officials
IGC Centre, a lava dome in Mount Edziza Provincial Park, British Columbia, Canada
Independent Garden Center Show or IGC Show, Chicago, Illinois, US
Instant Game Collection, a feature of PS Plus on Sony's PlayStation Network (PSN/SEN)
Intergranular corrosion or intergranular attack, a form of corrosion |
https://en.wikipedia.org/wiki/Collision%20domain | A collision domain is a network segment connected by a shared medium or through repeaters where simultaneous data transmissions collide with one another. The collision domain applies particularly in wireless networks, but also affected early versions of Ethernet. A network collision occurs when more than one device attempts to send a packet on a network segment at the same time. Members of a collision domain may be involved in collisions with one another. Devices outside the collision domain do not have collisions with those inside.
A channel access method dictates that only one device in the collision domain may transmit at any one time, and the other devices in the domain listen to the network and refrain from transmitting while others are already transmitting in order to avoid collisions. Because only one device may be transmitting at any one time, total network bandwidth is shared among all devices on the collision domain. Collisions also decrease network efficiency in a collision domain as collisions require devices to abort transmission and retransmit at a later time.
Since data bits are propagated at a finite speed, simultaneously is to be defined in terms of the size of the collision domain and the minimum packet size allowed. A smaller packet size or a larger dimension would make it possible for a sender to finish sending the packet without the first bits of the message being able to reach the most remote node. So, that node could start sending as well, without a clue to the transmission already taking place and destroying the first packet. Unless the size of the collision domain allows the initial sender to receive the second transmission attempt – the collision – within the time it takes to send the packet, they would neither be able to detect the collision nor to repeat the transmission – this is called a late collision.
Ethernet
On Ethernet using shared media, collisions are resolved using carrier-sense multiple access with collision detection (CSMA/CD) in which the competing packets are discarded and re-sent one at a time. This becomes a source of inefficiency in the network.
Early Ethernet variants (10BASE5, 10BASE2) were based on a shared wire and inherently half-duplex, representing a single, potentially large collision domain. Collision domains are also found in an Ethernet hub or repeater environment where each host segment connects to a hub, and all segments represent only one collision domain within one broadcast domain. Collision domains are also found in other shared medium networks, e. g. wireless networks such as Wi-Fi.
Modern wired networks use a network switch to reduce or eliminate collisions. By connecting each device directly to a port on the switch, either each port on a switch becomes its own collision domain (in the case of half-duplex links), or the possibility of collisions is eliminated in the case of full-duplex links. For Gigabit Ethernet and faster, no hubs or repeaters exist and all devices require ful |
https://en.wikipedia.org/wiki/Maze%20generation%20algorithm | Maze generation algorithms are automated methods for the creation of mazes.
Graph theory based methods
A maze can be generated by starting with a predetermined arrangement of cells (most commonly a rectangular grid but other arrangements are possible) with wall sites between them. This predetermined arrangement can be considered as a connected graph with the edges representing possible wall sites and the nodes representing cells. The purpose of the maze generation algorithm can then be considered to be making a subgraph in which it is challenging to find a route between two particular nodes.
If the subgraph is not connected, then there are regions of the graph that are wasted because they do not contribute to the search space. If the graph contains loops, then there may be multiple paths between the chosen nodes. Because of this, maze generation is often approached as generating a random spanning tree. Loops, which can confound naive maze solvers, may be introduced by adding random edges to the result during the course of the algorithm.
The animation shows the maze generation steps for a
graph that is not on a rectangular grid.
First, the computer creates a random planar graph G
shown in blue, and its dual F
shown in yellow. Second, the computer traverses F using a chosen
algorithm, such as a depth-first search, coloring the path red.
During the traversal, whenever a red edge crosses over a blue edge,
the blue edge is removed.
Finally, when all vertices of F have been visited, F is erased
and two edges from G, one for the entrance and one for the exit, are removed.
Randomized depth-first search
This algorithm, also known as the "recursive backtracker" algorithm, is a randomized version of the depth-first search algorithm.
Frequently implemented with a stack, this approach is one of the simplest ways to generate a maze using a computer. Consider the space for a maze being a large grid of cells (like a large chess board), each cell starting with four walls. Starting from a random cell, the computer then selects a random neighbouring cell that has not yet been visited. The computer removes the wall between the two cells and marks the new cell as visited, and adds it to the stack to facilitate backtracking. The computer continues this process, with a cell that has no unvisited neighbours being considered a dead-end. When at a dead-end it backtracks through the path until it reaches a cell with an unvisited neighbour, continuing the path generation by visiting this new, unvisited cell (creating a new junction). This process continues until every cell has been visited, causing the computer to backtrack all the way back to the beginning cell. We can be sure every cell is visited.
As given above this algorithm involves deep recursion which may cause stack overflow issues on some computer architectures. The algorithm can be rearranged into a loop by storing backtracking information in the maze itself. This also provides a quick way to displa |
https://en.wikipedia.org/wiki/AN/USQ-20 | The AN/USQ-20, or CP-642 or Naval Tactical Data System (NTDS), was designed as a more reliable replacement for the Seymour Cray-designed AN/USQ-17 with the same instruction set. The first batch of 17 computers were delivered to the Navy starting in early 1961.
A version of the AN/USQ-20 for use by the other military services and NASA was designated the UNIVAC 1206. Another version, designated the G-40, replaced the vacuum tube UNIVAC 1104 in the BOMARC Missile Program.
Technical
The machine was the size and shape of an old-fashioned double-door refrigerator, about six feet tall (roughly 1.80 meters).
Instructions were represented as 30-bit words in the following format:
f 6 bits function code
j 3 bits jump condition designator
k 3 bits partial word designator
b 3 bits which index register to use
y 15 bits operand address in memory
Numbers were represented as 30-bit words. This allowed for five 6-bit alphanumeric characters per word.
The main memory was 32,768 words of core memory.
The available processor registers were:
One 30-bit arithmetic (A) register.
A contiguous 30-bit Q register (total of 60 bits for the result of multiplication or the dividend in division).
Seven 15-bit index (B) registers (note: register B0 is always zero).
See also
CMS-2
List of UNIVAC products
History of computing hardware
Military computers
References
External links
UNIVAC-NTDS: UNIVAC 1206, AN/USQ-20 – From the Antique Computer website
UNIVAC hardware
Transistorized computers
Military computers
Avionics computers
Military electronics of the United States |
https://en.wikipedia.org/wiki/AN/UYK-8 | The AN/UYK-8 was a UNIVAC computer.
Development
In April 1967, UNIVAC received a contract from the U.S. Navy for design, development, testing and delivery of the AN/UYK-8 microelectronics computer for use with the AN/TYA-20.
The AN/UYK-8 was built to replace the CP-808 (Marine Corps air cooled AN/USQ-20 variant) in the Beach Relay Link-11 communication system, the AN/TYQ-3 in a AN/TYA-20
Technical
It used the same 30-bit words and instruction set as the AN/USQ-17 and AN/USQ-20 Naval Tactical Data System (NTDS) computers, built with "first generation integrated circuits". This made it about one quarter of the volume of the AN/USQ-20. It had two processors instead of just one.
Instructions were represented as 30-bit words, in the following format:
f 6 bits function code
j 3 bits jump condition designator
k 3 bits partial word designator
b 3 bits which seven index register to use (B0=non used)
s 2 bits which S (5bits) register to use S0,S1,S2,S3(P(17-13))
y 13 bits operand address in memory
memory address=Bb+Ss+y=18bit(262144Words)
Numbers were represented as full 30-bit words, this allowed for five 6-bit alphanumeric characters per word.
The main memory was increased to 262,144 words (256K words) of magnetic core memory.
The available processor registers were:
one 30-bit arithmetic (A) register.
a contiguous 30-bit Q register (total of 60 bits for the result of multiplication or the dividend in division).
seven 30-bit index (B) registers.
See also
List of UNIVAC products
History of computing hardware
References
UNIVAC hardware
Military computers
Military electronics of the United States |
https://en.wikipedia.org/wiki/UNIVAC%20FASTRAND | FASTRAND was a magnetic drum mass storage system built by Sperry Rand Corporation (later Sperry Univac) for their UNIVAC 1100 series and 418/490/494 series computers. A FASTRAND subsystem consisted of one or two Control Units and up to eight FASTRAND units. A dual-access FASTRAND subsystem included two complete control units, and provided parallel data paths that allowed simultaneous operations on any two FASTRAND units in the subsystem. Each control unit interfaced to one (optionally two) 1100 Series (36-bit), or 490 Series (30-bit), parallel I/O channels.
A voice coil actuator moved a bar containing multiple single track recording heads, so these drums operated much like moving head disk drives with multiple disks. The heads "flew" on self-acting hydrodynamic air bearings. The drums had a plated magnetic recording surface. An optional feature called Fastband included 24 additional tracks with fixed read/write heads. This feature provided rapid access (35 ms. average access time), and a write lockout feature.
The Fastrands were very heavy (5,000 pounds) and large, approximately 8' long. Due to their weight, FASTRAND units were usually not installed on "false floor", and required special rigging and mounts to move and/or install. There were reported cases of drum bearing failures that caused the machine to tear itself apart and send the heavy drum crashing through walls.
At the time of their introduction the storage capacity exceeded any other random access mass storage disk or drum.
There were three models of FASTRAND drives:
FASTRAND I had a single drum. The large mass of the rotating drum caused gyroscopic precession of the unit, making it tend to spin on the computer room floor as the Earth rotated under it. Very few of these devices were delivered.
FASTRAND II (the majority of units produced) had two counter-rotating drums to eliminate the gyroscopic effect. One actuator bar with heads was located between the drums.
FASTRAND III, introduced in 1970, was physically identical to the FASTRAND II, but increased the recording density by 50%.
Specifications (FASTRAND II)
Storage capacity: 22,020,096 36-bit words = 132,120,576 6-bit FIELDATA characters = 99 megabytes (8-bit bytes) per device
Drum rotation rate: 880 RPM (14.7 rotations per second)
Heads: 64
Sector size: 28 36-bit words
Track size: 64 sectors (1,792 36-bit words)
Track density: 105 tracks per inch
Average Access time (seek time plus rotational latency): 92 milliseconds
Data transfer rate: 26,283 36-bit words per second = 118 kilobytes per second (8-bit bytes) on 1100 series machines
Recording density, one-dimensional: 1,000 bits per inch (along one track)
Recording density, two-dimensional: 105,000 bits per square inch of drum surface
Max FASTRAND devices (drum units) per controller: 8
Controller price: $41,680 (1968 US dollars)
FASTRAND device price: $134,400 (1968 dollars, equivalent to $ in dollars)
Weight per FASTRAND device: 4,500 pounds
Weight per kilobyte:
S |
https://en.wikipedia.org/wiki/Set%20%28abstract%20data%20type%29 | In computer science, a set is an abstract data type that can store unique values, without any particular order. It is a computer implementation of the mathematical concept of a finite set. Unlike most other collection types, rather than retrieving a specific element from a set, one typically tests a value for membership in a set.
Some set data structures are designed for static or frozen sets that do not change after they are constructed. Static sets allow only query operations on their elements — such as checking whether a given value is in the set, or enumerating the values in some arbitrary order. Other variants, called dynamic or mutable sets, allow also the insertion and deletion of elements from the set.
A multiset is a special kind of set in which an element can appear multiple times in the set.
Type theory
In type theory, sets are generally identified with their indicator function (characteristic function): accordingly, a set of values of type may be denoted by or . (Subtypes and subsets may be modeled by refinement types, and quotient sets may be replaced by setoids.) The characteristic function of a set is defined as:
In theory, many other abstract data structures can be viewed as set structures with additional operations and/or additional axioms imposed on the standard operations. For example, an abstract heap can be viewed as a set structure with a min(S) operation that returns the element of smallest value.
Operations
Core set-theoretical operations
One may define the operations of the algebra of sets:
union(S,T): returns the union of sets S and T.
intersection(S,T): returns the intersection of sets S and T.
difference(S,T): returns the difference of sets S and T.
subset(S,T): a predicate that tests whether the set S is a subset of set T.
Static sets
Typical operations that may be provided by a static set structure S are:
is_element_of(x,S): checks whether the value x is in the set S.
is_empty(S): checks whether the set S is empty.
size(S) or cardinality(S): returns the number of elements in S.
iterate(S): returns a function that returns one more value of S at each call, in some arbitrary order.
enumerate(S): returns a list containing the elements of S in some arbitrary order.
build(x1,x2,…,xn,): creates a set structure with values x1,x2,...,xn.
create_from(collection): creates a new set structure containing all the elements of the given collection or all the elements returned by the given iterator.
Dynamic sets
Dynamic set structures typically add:
create(): creates a new, initially empty set structure.
create_with_capacity(n): creates a new set structure, initially empty but capable of holding up to n elements.
add(S,x): adds the element x to S, if it is not present already.
remove(S, x): removes the element x from S, if it is present.
capacity(S): returns the maximum number of values that S can hold.
Some set structures may allow only some of these operations. The cost of each operation will depen |
https://en.wikipedia.org/wiki/Divide-and-conquer%20algorithm | In computer science, divide and conquer is an algorithm design paradigm. A divide-and-conquer algorithm recursively breaks down a problem into two or more sub-problems of the same or related type, until these become simple enough to be solved directly. The solutions to the sub-problems are then combined to give a solution to the original problem.
The divide-and-conquer technique is the basis of efficient algorithms for many problems, such as sorting (e.g., quicksort, merge sort), multiplying large numbers (e.g., the Karatsuba algorithm), finding the closest pair of points, syntactic analysis (e.g., top-down parsers), and computing the discrete Fourier transform (FFT).
Designing efficient divide-and-conquer algorithms can be difficult. As in mathematical induction, it is often necessary to generalize the problem to make it amenable to a recursive solution. The correctness of a divide-and-conquer algorithm is usually proved by mathematical induction, and its computational cost is often determined by solving recurrence relations.
Divide and conquer
The divide-and-conquer paradigm is often used to find an optimal solution of a problem. Its basic idea is to decompose a given problem into two or more similar, but simpler, subproblems, to solve them in turn, and to compose their solutions to solve the given problem. Problems of sufficient simplicity are solved directly.
For example, to sort a given list of n natural numbers, split it into two lists of about n/2 numbers each, sort each of them in turn, and interleave both results appropriately to obtain the sorted version of the given list (see the picture). This approach is known as the merge sort algorithm.
The name "divide and conquer" is sometimes applied to algorithms that reduce each problem to only one sub-problem, such as the binary search algorithm for finding a record in a sorted list (or its analogue in numerical computing, the bisection algorithm for root finding). These algorithms can be implemented more efficiently than general divide-and-conquer algorithms; in particular, if they use tail recursion, they can be converted into simple loops. Under this broad definition, however, every algorithm that uses recursion or loops could be regarded as a "divide-and-conquer algorithm". Therefore, some authors consider that the name "divide and conquer" should be used only when each problem may generate two or more subproblems. The name decrease and conquer has been proposed instead for the single-subproblem class.
An important application of divide and conquer is in optimization, where if the search space is reduced ("pruned") by a constant factor at each step, the overall algorithm has the same asymptotic complexity as the pruning step, with the constant depending on the pruning factor (by summing the geometric series); this is known as prune and search.
Early historical examples
Early examples of these algorithms are primarily decrease and conquer – the original problem is successivel |
https://en.wikipedia.org/wiki/Lotfi%20A.%20Zadeh | Lotfi Aliasker Zadeh (; ; ; 4 February 1921 – 6 September 2017) was a mathematician, computer scientist, electrical engineer, artificial intelligence researcher, and professor of computer science at the University of California, Berkeley.
Zadeh is best known for proposing fuzzy mathematics, consisting of several fuzzy-related concepts: fuzzy sets, fuzzy logic, fuzzy algorithms, fuzzy semantics, fuzzy languages, fuzzy control, fuzzy systems, fuzzy probabilities, fuzzy events, and fuzzy information.
Zadeh was a founding member of the Eurasian Academy.
Early life and career
Azerbaijan
Zadeh was born in Baku, Azerbaijan SSR, as Lotfi Aliaskerzadeh. His father was Rahim Aleskerzade, an Iranian Muslim Azerbaijani journalist from Ardabil on assignment from Iran, and his mother was Fanya (Feyga) Korenman, a Jewish pediatrician from Odesa, Ukraine, who was an Iranian citizen. The Soviet government at this time courted foreign correspondents, and the family lived well while in Baku. Zadeh attended elementary school for three years there, which he said "had a significant and long-lasting influence on my thinking and my way of looking at things."
Iran
In 1931, when Stalin began agricultural collectivization, and Zadeh was ten, his father moved his family back to Tehran, Iran. Zadeh was enrolled in Alborz High School, a missionary school, where he was educated for the next eight years, and where he met his future wife, Fay (Faina) Zadeh, who said that he was "deeply influenced" by the "extremely decent, fine, honest and helpful" Presbyterian missionaries from the United States who ran the college. "To me they represented the best that you could find in the United States – people from the Midwest with strong roots. They were really 'Good Samaritans' – willing to give of themselves for the benefit of others. So this kind of attitude influenced me deeply. It also instilled in me a deep desire to live in the United States." During this time, Zadeh was awarded several patents.
Zadeh sat for the Iran national university exams and placed third in the nation. As a student, he ranked first in his class in his first two years. In 1942, he graduated from the University of Tehran with a degree in electrical engineering, one of only three students in that field to graduate that year, due to the turmoil created by World War II, when the United States, Britain and the Soviet Union invaded Iran. Over 30,000 American soldiers were based there, and Zadeh worked with his father, who did business with them as a contractor for hardware and building materials.
United States
In 1943, Zadeh decided to leave for the United States to continue his education. He travelled to Philadelphia by way of Cairo after months of delay waiting first for the proper papers and later for the right ship to appear. He arrived in mid-1944, lived in New York and worked for an electronic association, and entered the Massachusetts Institute of Technology (MIT) as a graduate student in September th |
https://en.wikipedia.org/wiki/Ungermann-Bass | Ungermann-Bass, also known as UB and UB Networks, was a computer networking company in the 1980s to 1990s. Located in Santa Clara, California, UB was the first large networking company independent of any computer manufacturer. Along with competitors 3Com and Sytek, UB was responsible for starting the networking business in Silicon Valley in 1979. UB was founded by Ralph Ungermann and Charlie Bass. John Davidson, vice president of engineering, was one of the creators of NCP, the transport protocol of the ARPANET before TCP.
UB specialized in large enterprise networks connecting computer systems and devices from multiple vendors, which was unusual in the 1980s. At that time most network equipment came from computer manufacturers and usually used only protocols compatible with that one manufacturer's computer systems, such as IBM's SNA or DEC's DECnet. Many UB products initially used the XNS protocol suite, including the flagship Net/One, and later transitioned to TCP/IP as it became an industry standard in the late 1980s.
Before it became the industry standard, the Internet protocol suite TCP/IP was initially a "check box" item needed to qualify on prospective enterprise sales. As a network technology supplier to both Apple Inc. and Microsoft, in 1987-88 UB helped Apple implement their initial MacTCP offering and also helped Microsoft with a Winsock compatible software/hardware bundle for the Microsoft Windows platform. With the success of these offerings and of the Internet protocol TCP/IP, both Apple and Microsoft subsequently brought the Internet technology in-house and integrated it into their core products.
UB marketed a broadband (in the original technical sense) version of Ethernet known as 10BROAD36 in the mid 1980s. It was generally seen as hard to install. UB was one of the first network manufacturers to sell equipment that implemented Ethernet over twisted pair wiring. UB's AccessOne product line initially used the pre-standard StarLAN and, when it became standard, 10BASE-T.
UB went public in 1983. It was bought by Tandem Computers in 1988. UB was sold in 1997 by Tandem to Newbridge Networks. Over the next several months, Newbridge laid off the bulk of the Ungermann-Bass employees, and closed the doors of the Santa Clara operation. Newbridge was later acquired by Alcatel, a French telecommunications company.
References
Defunct networking companies
XNS based protocols
Defunct computer companies of the United States |
https://en.wikipedia.org/wiki/Tandem%20Computers | Tandem Computers, Inc. was the dominant manufacturer of fault-tolerant computer systems for ATM networks, banks, stock exchanges, telephone switching centers, 911 systems, and other similar commercial transaction processing applications requiring maximum uptime and zero data loss. The company was founded by Jimmy Treybig in 1974 in Cupertino, California. It remained independent until 1997, when it became a server division within Compaq. It is now a server division within Hewlett Packard Enterprise, following Hewlett-Packard's acquisition of Compaq and the split of Hewlett-Packard into HP Inc. and Hewlett Packard Enterprise.
Tandem's NonStop systems use a number of independent identical processors and redundant storage devices and controllers to provide automatic high-speed "failover" in the case of a hardware or software failure. To contain the scope of failures and of corrupted data, these multi-computer systems have no shared central components, not even main memory. Conventional multi-computer systems all use shared memories and work directly on shared data objects. Instead, NonStop processors cooperate by exchanging messages across a reliable fabric, and software takes periodic snapshots for possible rollback of program memory state.
Besides handling failures well, this "shared-nothing" messaging system design also scales extremely well to the largest commercial workloads. Each doubling of the total number of processors would double system throughput, up to the maximum configuration of 4000 processors. In contrast, the performance of conventional multiprocessor systems is limited by the speed of some shared memory, bus, or switch. Adding more than 4–8 processors in that manner gives no further system speedup. NonStop systems have more often been bought to meet scaling requirements than for extreme fault tolerance. They compete well against IBM's largest mainframes, despite being built from simpler minicomputer technology.
Founding
Tandem Computers was founded in 1974 by James Treybig. Treybig first saw the market need for fault tolerance in OLTP (online transaction processing) systems while running a marketing team for Hewlett-Packard 's HP 3000 computer division, but HP was not interested in developing for this niche. He then joined the venture capital firm Kleiner & Perkins and developed the Tandem business plan there. Treybig pulled together a core engineering team hired away from the HP 3000 division: Mike Green, Jim Katzman, Dave Mackie and Jack Loustaunou. Their business plan called for ultra-reliable systems that never had outages and never lost or corrupted data. These were modular in a new way that was safe from all "single-point failures", yet would be only marginally more expensive than conventional non-fault-tolerant systems. They would be less expensive and support more throughput than some existing ad-hoc toughened systems that used redundant but usually required "hot spares".
Each engineer was confident they could quickly |
https://en.wikipedia.org/wiki/Adam%20Osborne | Adam Osborne (March 6, 1939 – March 18, 2003) was a British American author, software publisher, and computer designer who founded several companies in the United States and elsewhere. He introduced the Osborne 1, the first commercially successful portable computer.
Early life
Osborne was born to British parents in Bangkok, Thailand on March 6, 1939. His father, Arthur Osborne, was a teacher of eastern religion and philosophy and a lecturer in English at Chulalongkorn University. All members of the family were fluent in the Tamil language. He spent World War II in Tiruvannamalai,southern India, with his mother. There they were frequent visitors to Sri Ramana Maharshi's Ashram He attended Presentation Convent School in Kodaikanal until Class 6. In 1950, the Osborne family moved back to England. From the age of 11, he was educated at a Catholic boarding school in Warwickshire but from 1954 to 1957 was a pupil at the grammar school Leamington College for Boys, where he played chess. He graduated with a degree in chemical engineering from the University of Birmingham in 1961, and received his PhD from the University of Delaware in 1968. It was while living in the United States that he learned to write computer code. He obtained a position as a chemical engineer with Shell Oil, in California, but was dismissed.
Publishing
Osborne was a pioneer in the computer book field, founding a company in 1972 that specialized in easy-to-read computer manuals. By 1977, Osborne & Associates had 40 titles in its catalogue. In 1979, it was bought by McGraw-Hill and continued as an imprint of McGraw-Hill, "McGraw-Hill/Osborne". He also wrote several books. One of them, An Introduction To Microcomputers, sold 300,000 copies.
Computers
Osborne was known to frequent the Homebrew Computer Club's meetings around 1975. He created the first commercially available portable computer, the Osborne 1, released in April 1981. It weighed 24.5 pounds (12 kg), cost US$1795—just over half the cost of a computer from other manufacturers with comparable features—and ran the popular CP/M 2.2 operating system. It was designed to fit under an airline seat. At its peak, Osborne Computer Corporation shipped 10,000 units of "Osborne 1" per month. Osborne was one of the first personal computing pioneers to understand fully that there was a wide market of buyers who were not computing hobbyists: the Osborne 1 included word processing and spreadsheet software. This was at a time when IBM would not bundle hardware and software with their PCs, selling separately the operating systems, monitors, and even cables for the monitor.
Adam Osborne's experience in the computer industry gave his new company credibility. Osborne Computer Corporation advertisements compared Adam Osborne's influence on the personal computer market to Henry Ford's influence on transportation. It is said that in 1983, Osborne bragged about two advanced new computers his company was developing. These statements destroyed |
https://en.wikipedia.org/wiki/UNIVAC%201100/2200%20series | The UNIVAC 1100/2200 series is a series of compatible 36-bit computer systems, beginning with the UNIVAC 1107 in 1962, initially made by Sperry Rand. The series continues to be supported today by Unisys Corporation as the ClearPath Dorado Series. The solid-state 1107 model number was in the same sequence as the earlier vacuum-tube computers, but the early computers were not compatible with the solid-state successors.
Architecture
Data formats
Fixed-point, either integer or fraction
Whole word – 36-bit (ones' complement)
Half word – two 18-bit fields per word (unsigned or ones' complement)
Third word – three 12-bit fields per word (ones' complement)
Quarter word – four 9-bit fields per word (unsigned)
Sixth word – six 6-bit fields per word (unsigned)
Floating point
Single precision – 36 bits: sign bit, 8-bit characteristic, 27-bit mantissa
Double precision – 72 bits: sign bit, 11-bit characteristic, 60-bit mantissa
Alphanumeric
FIELDATA – UNIVAC 6-bit code variant (no lower case characters) six characters in each 36-bit word. (FIELDATA was originally a seven-bit code of which only 64 code positions (occupying six bits) were formally defined.)
ASCII – 9 bits per character (right-most eight used for an ASCII character) four characters in each 36-bit word
Instruction format
Instructions are 36 bits long with the following fields:
f (6 bits) - function designator (opcode),
j (4 bits) - partial word designator, J-register designator, or minor function designator,
a (4 bits) - register (A, X, or R) designator or I/O designator,
x (4 bits) - index register (X) designator,
h (1 bit ) - index register increment designator,
i (1 bit) - indirect address designator,
u (16 bits) - address or operand designator.
Registers
The 128 registers of the high-speed "general register stack" ("integrated circuit registers" on the UNIVAC 1108 and UNIVAC 1106 models), map to the current data space in main storage starting at memory address zero. These registers include both user and executive copies of the A, X, R, and J registers and many special function executive registers.
The table on the right shows the addresses (in octal) of the user registers.
There are 15 index registers (X1 ... X15), 16 accumulators (A0 ... A15), and 15 special function user registers (R1 .. R15). The 4 J registers and 3 "staging registers" are uses of some of the special function R registers.
One interesting feature is that the last four index registers (X12 ... X15) and the first four accumulators (A0 ... A3) overlap, allowing data to be interpreted either way in these registers. This also results in four unassigned accumulators (A15+1 ... A15+4) that can only be accessed by their memory address (double word instructions on A15 do operate on A15+1).
Vacuum tube machines not mutually compatible
Prior to the UNIVAC 1107, UNIVAC produced several vacuum-tube-based machines with model numbers from 1101 to 1105. These machines had different architectures and word sizes and were not compatib |
https://en.wikipedia.org/wiki/Gradient%20descent | In mathematics, gradient descent (also often called steepest descent) is a first-order iterative optimization algorithm for finding a local minimum of a differentiable function. The idea is to take repeated steps in the opposite direction of the gradient (or approximate gradient) of the function at the current point, because this is the direction of steepest descent. Conversely, stepping in the direction of the gradient will lead to a local maximum of that function; the procedure is then known as gradient ascent.
It is particularly useful in machine learning for minimizing the cost or loss function. Gradient descent should not be confused with local search algorithms, although both are iterative methods for optimization.
Gradient descent is generally attributed to Augustin-Louis Cauchy, who first suggested it in 1847. Jacques Hadamard independently proposed a similar method in 1907. Its convergence properties for non-linear optimization problems were first studied by Haskell Curry in 1944, with the method becoming increasingly well-studied and used in the following decades.
A simple extension of gradient descent, stochastic gradient descent, serves as the most basic algorithm used for training most deep networks today.
Description
Gradient descent is based on the observation that if the multi-variable function is defined and differentiable in a neighborhood of a point , then decreases fastest if one goes from in the direction of the negative gradient of at . It follows that, if
for a small enough step size or learning rate , then . In other words, the term is subtracted from because we want to move against the gradient, toward the local minimum. With this observation in mind, one starts with a guess for a local minimum of , and considers the sequence such that
We have a monotonic sequence
so, hopefully, the sequence converges to the desired local minimum. Note that the value of the step size is allowed to change at every iteration.
It is possible to guarantee the convergence to a local minimum under certain assumptions on the function (for example, convex and Lipschitz) and particular choices of . Those include the sequence
as in the Barzilai-Borwein method, or a sequence satisfying the Wolfe conditions (which can be found by using line search). When the function is convex, all local minima are also global minima, so in this case gradient descent can converge to the global solution.
This process is illustrated in the adjacent picture. Here, is assumed to be defined on the plane, and that its graph has a bowl shape. The blue curves are the contour lines, that is, the regions on which the value of is constant. A red arrow originating at a point shows the direction of the negative gradient at that point. Note that the (negative) gradient at a point is orthogonal to the contour line going through that point. We see that gradient descent leads us to the bottom of the bowl, that is, to the point where the value of the func |
https://en.wikipedia.org/wiki/Osborne%201 | The Osborne 1 is the first commercially successful portable computer, released on April 3, 1981 by Osborne Computer Corporation. It weighs , cost US$1,795, and runs the CP/M 2.2 operating system. It is powered from a wall socket, as it has no on-board battery, but it is still classed as a portable device since it can be hand-carried when the keyboard is closed.
The computer shipped with a large bundle of software that was almost equivalent in value to the machine itself, a practice adopted by other CP/M computer vendors. Competitors quickly appeared, such as the Kaypro II.
History
The Osborne 1 was developed by Adam Osborne and designed by Lee Felsenstein, first announced in early 1981. Osborne, an author of computer books decided that he wanted to break the price of computers. The computer's design was based largely on the Xerox NoteTaker, a prototype developed at Xerox PARC in 1976 by Alan Kay. It was designed to be portable, with a rugged ABS plastic case and a handle. The Osborne 1 is about the size and weight of a sewing machine and was advertised as the only computer that would fit underneath an airline seat. It is now classified as a "luggable" computer when compared to those later "laptop" designs such as the Epson HX-20.
The Osborne 1 was described as "a cross between a World War II field radio and a shrunken instrument panel of a DC-3", and Felstenstein admitted that carrying two of them to a trade show "nearly pulled my arms out of their sockets". The computer nonetheless amazed observers; InfoWorld reported that "By far the most frequently asked question at" the West Coast Computer Faire "was, 'What do you think of the new Osborne computer?'" BYTE Magazine wrote: "(1) it will cost $1795, and (2) it's portable!" The word processing, spreadsheet, and other bundled software alone was worth $1,500; as InfoWorld stated in an April 1981 front-page article on the new computer after listing the included software, "In case you think the price printed above was a mistake, we'll repeat it: $1795".
West Coast Computer Faire attendees stated, InfoWorld said, that the Osborne 1 "represented an advancement of the price/performance ratio for microcomputers". Adam Osborne agreed but emphasized the price, stating that its performance was "merely adequate": "It is not the fastest microcomputer, it doesn't have huge amounts of disk storage space, and it is not especially expandable." Beyond the price, advertisements emphasized the computer's portability and bundled software. The company sold 11,000 units in the first eight months of sales, and sales at their peak reached 10,000 units per month.
The Osborne 1's principal deficiencies are a tiny display screen, use of single-sided, single-density floppy disk drives that store 90 kB per disk, and considerable unit weight. Adam Osborne decided to use single-sided disk drives out of concern about double-sided drives suffering head damage from rough handling. A single-density disk controller was used to |
https://en.wikipedia.org/wiki/Bus%20mastering | In computing, bus mastering is a feature supported by many bus architectures that enables a device connected to the bus to initiate direct memory access (DMA) transactions. It is also referred to as first-party DMA, in contrast with third-party DMA where a system DMA controller actually does the transfer.
Some types of buses allow only one device (typically the CPU, or its proxy) to initiate transactions. Most modern bus architectures, such as PCI, allow multiple devices to bus master because it significantly improves performance for general-purpose operating systems. Some real-time operating systems prohibit peripherals from becoming bus masters, because the scheduler can no longer arbitrate for the bus and hence cannot provide deterministic latency.
While bus mastering theoretically allows one peripheral device to directly communicate with another, in practice almost all peripherals master the bus exclusively to perform DMA to main memory.
If multiple devices are able to master the bus, there needs to be a bus arbitration scheme to prevent multiple devices attempting to drive the bus simultaneously. A number of different schemes are used for this; for example SCSI has a fixed priority for each SCSI ID. PCI does not specify the algorithm to use, leaving it up to the implementation to set priorities.
See also
Master/slave (technology)
SCSI initiator and target
References
How Bus Mastering Works - Tweak3D
What is bus mastering?- Brevard User's Group
Computer buses
Motherboard |
https://en.wikipedia.org/wiki/Raphael%20Finkel | Raphael Finkel (born 1951) is an American computer scientist and a professor at the University of Kentucky. He compiled the first version of the Jargon File. He is the author of An Operating Systems Vade Mecum, a textbook on operating systems, and Advanced Programming Language Design, an introductory book on programming paradigms. Finkel and J.L. Bentley created the data structure called the quadtree.
Biography
Finkel was born in Chicago. He entered the University of Chicago, where he earned his BA in mathematics and MA in teaching. He then earned a PhD at Stanford University under the supervision of Vinton Cerf.
Finkel is also an activist for the survival of the Yiddish language, promoting its use and providing fonts, various texts, and tools for writing Yiddish in personal computers.
Notes
External links
http://goanna.cs.rmit.edu.au/~santhas/research/paper1/node4.html
Living people
1951 births
American computer scientists
University of Chicago alumni
Stanford University alumni
University of Kentucky faculty
20th-century American Jews
21st-century American Jews |
https://en.wikipedia.org/wiki/Frequency-division%20multiple%20access | Frequency-division multiple access (FDMA) is a channel access method used in some multiple-access protocols. FDMA allows multiple users to send data through a single communication channel, such as a coaxial cable or microwave beam, by dividing the bandwidth of the channel into separate non-overlapping frequency sub-channels and allocating each sub-channel to a separate user. Users can send data through a subchannel by modulating it on a carrier wave at the subchannel's frequency. It is used in satellite communication systems and telephone trunklines.
FDMA splits the total bandwidth into multiple channels. Each ground station on the earth is allocated a particular frequency group (or a range of frequencies). Within each group, the ground station can allocate different frequencies to individual channels, which are used by different stations connected to that ground station. Before the transmission begins, the transmitting ground station looks for an empty channel within the frequency range that is allocated to it and once it finds an empty channel, it allocates it to the particular transmitting station.
Method
Alternatives include time-division multiple access (TDMA), code-division multiple access (CDMA), or space-division multiple access (SDMA). These protocols are utilized differently, at different levels of the theoretical OSI model.
Disadvantage: Crosstalk may cause interference among frequencies and disrupt the transmission.
In FDMA, all users share the satellite transponder or frequency channel simultaneously but each user transmits at single frequency.
FDMA can be used with both analog and digital signal but it generally used with analog signal.
FDMA requires high-performing filters in the radio hardware, in contrast to TDMA and CDMA.
FDMA is not vulnerable to the timing problems that TDMA has. Since a predetermined frequency band is available for the entire period of communication, stream data (a continuous flow of data that may not be packetized) can easily be used with FDMA.
Due to the frequency filtering, FDMA is not sensitive to near–far problem which is pronounced for CDMA.
Each user transmits and receives at different frequencies as each user gets a unique frequency slot.
FDMA is distinct from frequency division duplexing (FDD). While FDMA allows multiple users simultaneous access to a transmission system, FDD refers to how the radio channel is shared between the uplink and downlink (for instance, the traffic going back and forth between a mobile-phone and a mobile phone base station). Frequency-division multiplexing (FDM) is also distinct from FDMA. FDM is a physical layer technique that combines and transmits low-bandwidth channels through a high-bandwidth channel, like in a car radio. FDMA, on the other hand, is an access method in the data link layer.
FDMA also supports demand assignment in addition to fixed assignment. Demand assignment allows all users apparently continuous access of the radio spectrum by assigning |
https://en.wikipedia.org/wiki/Network%2023 | Network 23 may refer to:
Network 23 (record label), a defunct Czech record label
Network 23 (company), a defunct British video game development company
Network 23, a fictional television network on the TV series Max Headroom
"Network 23", a song by Tangerine Dream from their album Exit |
https://en.wikipedia.org/wiki/RAN | RAN may refer to:
Radio access network, a part of a mobile telecommunication system
Rainforest Action Network
Ran (gene) (RAs-related Nuclear protein), also known as GTP-binding nuclear protein Ran, a protein that in humans is encoded by the RAN gene
Ran (Sufism), a concept of Sufism
RAN translation (Repeat Associated Non-AUG translation), an irregular mode of mRNA translation
Ran Online (stylized as RAN Online), a massively multiplayer online role-playing game developed by Min Communications, Inc.
RAN Remote Area Nurse (TV series)
Rapid automatized naming, a predictor of reading ability
Ravenna Airport, an airport in Ravenna, Italy by IATA code
Régie du Chemin de Fer Abidjan-Niger, a railway in French West Africa, linking Côte d'Ivoire to Upper Volta (now called Burkina Faso)
Remote Area Nurse, in Australia
Royal Australian Navy, the naval branch of the Australian Defence Force
Rugby Americas North, the administrative body of rugby union in North America and the Caribbean
Russian Academy of Sciences (transliteration of its Russian acronym Rossiiskaya Akademiya Nauk)
RAN (Indonesian group)
See also
Ran (disambiguation) |
https://en.wikipedia.org/wiki/MATH-MATIC | MATH-MATIC is the marketing name for the AT-3 (Algebraic Translator 3) compiler, an early programming language for the UNIVAC I and UNIVAC II.
MATH-MATIC was written beginning around 1955 by a team led by Charles Katz under the direction of Grace Hopper. A preliminary manual was produced in 1957 and a final manual the following year.
Syntactically, MATH-MATIC was similar to Univac's contemporaneous business-oriented language, FLOW-MATIC, differing in providing algebraic-style expressions and floating-point arithmetic, and arrays rather than record structures.
Notable features
Expressions in MATH-MATIC could contain numeric exponents, including decimals and fractions, by way of a custom typewriter.
MATH-MATIC programs could include inline assembler sections of ARITH-MATIC code and UNIVAC machine code.
The UNIVAC I had only 1000 words of memory, and the successor UNIVAC II as little as 2000. MATH-MATIC allowed for larger programs, automatically generating code to read overlay segments from UNISERVO tape as required. The compiler attempted to avoid splitting loops across segments.
Influence
In proposing the collaboration with the ACM that led to ALGOL 58, the Gesellschaft für Angewandte Mathematik und Mechanik wrote that it considered MATH-MATIC the closest available language to its own proposal.
In contrast to Backus' FORTRAN, MATH-MATIC did not emphasise execution speed of compiled programs. The UNIVAC machines did not have floating-point hardware, and MATH-MATIC was translated via A-3 (ARITH-MATIC) pseudo-assembler code rather than directly to UNIVAC machine code, limiting its usefulness.
MATH-MATIC Sample program
A sample MATH-MATIC program:
Notes
References
Numerical programming languages
Programming languages
Programming languages created in 1957 |
https://en.wikipedia.org/wiki/MOS%20Technology%206581 | The MOS Technology 6581/8580 SID (Sound Interface Device) is the built-in programmable sound generator chip of the Commodore CBM-II, Commodore 64, Commodore 128, and MAX Machine home computers.
Together with the VIC-II graphics chip, the SID was instrumental in making the C64 the best-selling home computer in history, and is partly credited for initiating the demoscene.
History
The SID was devised by engineer Bob Yannes, who later co-founded the Ensoniq digital synthesizer and sampler company. Yannes headed a team that included himself, two technicians and a CAD operator, who designed and completed the chip in five months in the latter half of 1981. Yannes was inspired by previous work in the synthesizer industry and was not impressed by the current state of computer sound chips. Instead, he wanted a high-quality instrument chip, which is the reason why the SID has features like the envelope generator, previously not found in home computer sound chips.
Emphasis during chip design was on high-precision frequency control, and the SID was originally designed to have 32 independent voices, sharing a common wavetable lookup scheme that would be time multiplexed. However, these features could not be finished in time, so instead the mask work for a certain working oscillator was simply replicated three times across the chip's surface, creating three voices each with its own oscillator. Another feature that was not incorporated in the final design was a frequency look-up table for the most common musical notes, a feature that was dropped because of space limitations. The support for an audio input pin was a feature Yannes added without asking, which in theory would have allowed the chip to be used as a simple effect processor. The masks were produced in 7-micrometer technology to gain a high yield; the state of the art at the time was 6-micrometer technologies.
The chip, like the first product using it (the Commodore 64), was finished in time for the Consumer Electronics Show in the first weekend of January 1982. Even though Yannes was partly displeased with the result, his colleague Charles Winterble said: "This thing is already 10 times better than anything out there and 20 times better than it needs to be."
The specifications for the chip were not used as a blueprint. Rather, they were written as the development work progressed, and not all planned features made it into the final product. Yannes claims he had a feature-list of which three quarters made it into the final design. The later revision (8580) was revised to more closely match the specifications. For example, the 8580 slightly improved upon the ability to perform a binary AND between two waveforms, which the SID can only do in an odd and illogical manner that results in messy, and in some cases nearly silent, waveforms. Wave combinations on the 8580 result in cleaner waveforms than on the 6581, although irregularities are still present. Another feature that differs between the two rev |
https://en.wikipedia.org/wiki/Normal%20form | Normal form may refer to:
Normal form (databases)
Normal form (game theory)
Canonical form
Normal form (dynamical systems)
Hesse normal form
Normal form in music
Jordan normal form
in formal language theory:
Chomsky normal form
Greibach normal form
Kuroda normal form
Normal form (abstract rewriting), an element of a rewrite system which cannot be further rewritten
in logic:
Normal form (natural deduction)
Algebraic normal form
Canonical normal form
Clausal normal form
Conjunctive normal form
Disjunctive normal form
Negation normal form
Prenex normal form
Skolem normal form
in lambda calculus:
Beta normal form
See also
Normalization (disambiguation)
Normalization property |
https://en.wikipedia.org/wiki/First%20normal%20form | First normal form (1NF) is a property of a relation in a relational database. A relation is in first normal form if and only if no attribute domain has relations as elements. Or more informally, that no table column can have tables as values. Database normalization is the process of representing a database in terms of relations in standard normal forms, where first normal is a minimal requirement. SQL-92 does not support creating or using table-valued columns, which means that using only the "traditional relational database features" (excluding extensions even if they were later standardized) most relational databases will be in first normal form by necessity. Database systems which do not require first normal form are often called NoSQL systems. Newer SQL standards like SQL:1999 have started to allow so called non-atomic types, which include composite types. Even newer versions like SQL:2016 allow JSON.
Overview
In a hierarchical database, a record can contain sets of child records ― known as repeating groups or table-valued attributes. If such a data model is represented as relations, a repeating group would be an attribute where the value is itself a relation. First normal form eliminates nested relations by turning them into separate "top-level" relations associated with the parent row through foreign keys rather than through direct containment.
The purpose of this normalization is to increase flexibility and data independence, and to simplify the data language. It also opens the door to further normalization, which eliminates redundancy and anomalies.
Most relational database management systems do not support nested records, so tables are in first normal form by default. In particular, SQL does not have any facilities for creating or exploiting nested tables. Normalization to first normal form would therefore be a necessary step when moving data from a hierarchical database to a relational database.
Rationale
The rationale for normalizing to 1NF:
Allows presenting, storing and interchanging relational data in the form of regular two-dimensional arrays. Supporting nested relations would require more complex data structures.
Simplifies the data language, since any data item can be identified just by relation name, attribute name and key. Supporting nested relations would require a more complex language with support for hierarchical data paths in order to address nested data items.
Representing relationships using foreign keys is more flexible, where a hierarchical model only can represent one-to many relationships.
Since locating data items is not directly coupled to the parent-child hierarchy, the database is more resilient to structural changes over time.
Makes further normalization levels possible which eliminate data redundancy and anomalies.
Drawbacks and criticism
Performance for certain operations. In a hierarchical model, nested records are physically stored after the parent record, which means a whole sub-tree can be |
https://en.wikipedia.org/wiki/Second%20normal%20form | Second normal form (2NF) is a normal form used in database normalization. 2NF was originally defined by E. F. Codd in 1971.
A relation is in the second normal form if it fulfills the following two requirements:
It is in first normal form.
It does not have any non-prime attribute that is functionally dependent on any proper subset of any candidate key of the relation (i.e. it lacks partial dependencies). A non-prime attribute of a relation is an attribute that is not a part of any candidate key of the relation.
Put simply, a relation is in 2NF if it is in 1NF and every non-prime attribute of the relation is dependent on the whole of every candidate key. Note that it does not put any restriction on the non-prime to non-prime attribute dependency. That is addressed in third normal form.
2NF and candidate keys
A functional dependency on a proper subset of any candidate key is a violation of 2NF. In addition to the primary key, the relation may contain other candidate keys; it is necessary to establish that no non-prime attributes have part-key dependencies on any of these candidate keys.
How to decompose into 2NF
To make a 1NF relation a 2NF relation, remove the functionally dependent attributes in the partial dependencies of the first normal form relation, and place those partial dependency dependent attributes in a relation where their corresponding determinant attributes are an entire candidate key.
Example
The following relation does not satisfy 2NF because:
{Manufacturer country} is functionally dependent on {Manufacturer}.
{Manufacturer country} is not part of a candidate key, so it is a non-prime attribute. (It is assumed that it is possible for two manufacturers in the same country to make a toothbrush with the same model name, so {Manufacturer country, Model} is not a candidate key even though in the current table the pair uniquely identify rows.)
{Manufacturer} is a proper subset of the {Manufacturer, Model} candidate key.
In other words, since {Manufacturer country} is a non-prime attribute functionally dependent on a proper subset of a candidate key, the relation is in violation of 2NF.
To make the design conform to 2NF, it is necessary to have two relations. To create these relations:
Remove the functionally dependent attributes in the partial dependencies of the first normal form relation. In this example, {Manufacturer country} is the functionally dependent attribute which will be removed.
Place those partial dependency dependent attributes (i.e. {Manufacturer country}) in a relation where their corresponding determinant attributes are a candidate key (i.e. {Manufacturer}).
As seen below, {Manufacturer country} is removed from the original table:
As seen below, the partial dependency is put into a new relation where the dependency can exist without being a partial dependency:
See also
Attribute-value system
References
Further reading
Litt's Tips: Normalization
External links
Database Normalization Basics by Mik |
https://en.wikipedia.org/wiki/Third%20normal%20form | Third normal form (3NF) is a database schema design approach for relational databases which uses normalizing principles to reduce the duplication of data, avoid data anomalies, ensure referential integrity, and simplify data management. It was defined in 1971 by Edgar F. Codd, an English computer scientist who invented the relational model for database management.
A database relation (e.g. a database table) is said to meet third normal form standards if all the attributes (e.g. database columns) are functionally dependent on solely the primary key. Codd defined this as a relation in second normal form where all non-prime attributes depend only on the candidate keys and do not have a transitive dependency on another key.
A hypothetical example of a failure to meet third normal form would be a hospital database having a table of patients which included a column for the telephone number of their doctor. The phone number is dependent on the doctor, rather than the patient, thus would be better stored in a table of doctors. The negative outcome of such a design is that a doctor's number will be duplicated in the database if they have multiple patients, thus increasing both the chance of input error and the cost and risk of updating that number should it change (compared to a third normal form-compliant data model that only stores a doctor's number once on a doctor table).
Codd later realized that 3NF did not eliminate all undesirable data anomalies and developed a stronger version to address this in 1974, known as Boyce–Codd normal form.
Definition of third normal form
The third normal form (3NF) is a normal form used in database normalization. 3NF was originally defined by E. F. Codd in 1971.
Codd's definition states that a table is in 3NF if and only if both of the following conditions hold:
The relation R (table) is in second normal form (2NF).
No non-prime attribute of R is transitively dependent on the primary key.
A non-prime attribute of R is an attribute that does not belong to any candidate key of R. A transitive dependency is a functional dependency in which X → Z (X determines Z) indirectly, by virtue of X → Y and Y → Z (where it is not the case that Y → X).
A 3NF definition that is equivalent to Codd's, but expressed differently, was given by Carlo Zaniolo in 1982. This definition states that a table is in 3NF if and only if for each of its functional dependencies X → Y, at least one of the following conditions holds:
X contains Y (that is, Y is a subset of X, meaning X → Y is a trivial functional dependency),
X is a superkey,
every element of Y \ X, the set difference between Y and X, is a prime attribute (i.e., each attribute in Y \ X is contained in some candidate key).
To rephrase Zaniolo's definition more simply, the relation is in 3NF if and only if for every non-trivial functional dependency X → Y, X is a superkey or Y \ X consists of prime attributes. Zaniolo's definition gives a clear sense of the difference between |
https://en.wikipedia.org/wiki/Fourth%20normal%20form | Fourth normal form (4NF) is a normal form used in database normalization. Introduced by Ronald Fagin in 1977, 4NF is the next level of normalization after Boyce–Codd normal form (BCNF). Whereas the second, third, and Boyce–Codd normal forms are concerned with functional dependencies, 4NF is concerned with a more general type of dependency known as a multivalued dependency. A table is in 4NF if and only if, for every one of its non-trivial multivalued dependencies X Y, X is a superkey—that is, X is either a candidate key or a superset thereof.
Multivalued dependencies
If the column headings in a relational database table are divided into three disjoint groupings X, Y, and Z, then, in the context of a particular row, we can refer to the data beneath each group of headings as x, y, and z respectively. A multivalued dependency X Y signifies that if we choose any x actually occurring in the table (call this choice xc), and compile a list of all the xcyz combinations that occur in the table, we will find that xc is associated with the same y entries regardless of z. So essentially the presence of z provides no useful information to constrain the possible values of y.
A trivial multivalued dependency X Y is one where either Y is a subset of X, or X and Y together form the whole set of attributes of the relation.
A functional dependency is a special case of multivalued dependency. In a functional dependency X → Y, every x determines exactly one y, never more than one.
Example
Consider the following example:
Each row indicates that a given restaurant can deliver a given variety of pizza to a given area.
The table has no non-key attributes because its only candidate key is {Restaurant, Pizza Variety, Delivery Area}. Therefore, it meets all normal forms up to BCNF. If we assume, however, that pizza varieties offered by a restaurant are not affected by delivery area (i.e. a restaurant offers all pizza varieties it makes to all areas it supplies), then it does not meet 4NF. The problem is that the table features two non-trivial multivalued dependencies on the {Restaurant} attribute (which is not a superkey). The dependencies are:
{Restaurant} {Pizza Variety}
{Restaurant} {Delivery Area}
These non-trivial multivalued dependencies on a non-superkey reflect the fact that the varieties of pizza a restaurant offers are independent from the areas to which the restaurant delivers. This state of affairs leads to redundancy in the table: for example, we are told three times that A1 Pizza offers Stuffed Crust, and if A1 Pizza starts producing Cheese Crust pizzas then we will need to add multiple rows, one for each of A1 Pizza's delivery areas. There is, moreover, nothing to prevent us from doing this incorrectly: we might add Cheese Crust rows for all but one of A1 Pizza's delivery areas, thereby failing to respect the multivalued dependency {Restaurant} {Pizza Variety}.
To eliminate the possibility of these anomalies, we must place the facts about var |
https://en.wikipedia.org/wiki/Tim%20Paterson | Tim Paterson (born 1 June 1956) is an American computer programmer, best known for creating 86-DOS, an operating system for the Intel 8086. This system emulated the application programming interface (API) of CP/M, which was created by Gary Kildall. 86-DOS later formed the basis of MS-DOS, the most widely used personal computer operating system in the 1980s.
Biography
Paterson was educated in the Seattle Public Schools, graduating from Ingraham High School in 1974. He attended the University of Washington, working as a repair technician for The Retail Computer Store in the Green Lake area of Seattle, Washington, and graduated magna cum laude with a degree in Computer Science in June 1978. He went to work for Seattle Computer Products as a designer and engineer. He designed the hardware of Microsoft's Z-80 SoftCard which had a Z80 CPU and ran the CP/M operating system on an Apple II.
A month later, Intel released the 8086 CPU, and Paterson went to work designing an S-100 8086 board, which went to market in November 1979. The only commercial software that existed for the board was Microsoft's Standalone Disk BASIC-86. The standard CP/M operating system at the time was not available for this CPU and without a true operating system, sales were slow. Paterson began work on QDOS (Quick and Dirty Operating System) in April 1980 to fill that void, copying the APIs of CP/M from references, including the published CP/M manual, so that it would be highly compatible. QDOS was soon renamed as 86-DOS. Version 0.10 was complete by July 1980. By version 1.14, 86-DOS had grown to lines of assembly code. In December 1980, Microsoft secured the rights to market 86-DOS to other hardware manufacturers.
While acknowledging that he made 86-DOS compatible with CP/M, Paterson has maintained that the 86-DOS program was his original work and has denied allegations that he referred to CP/M code while writing it. When a book appeared in 2004 claiming that 86-DOS was an unoriginal "rip-off" of CP/M, Paterson sued the authors and publishers for defamation.
The judge found that Paterson failed to "provide any evidence regarding 'serious doubts' about the accuracy of the Gary Kildall chapter. Instead, a careful review of the Lefer notes ... provides a research picture tellingly close to the substance of the final chapter" and the case was dismissed on the basis that the book's claims were constitutionally protected opinions and not provably false. Gary Kildall Gary Kildall - The Man That Should Have Been Bill Gates - Part II
Paterson left SCP in April 1981 and worked for Microsoft from May 1981 to April 1982. Microsoft renamed 86-DOS to MS-DOS on 27 July 1981. After a brief second stint with SCP, Paterson started his own company, Falcon Technology, a.k.a. Falcon Systems. In 1983, Microsoft contracted Paterson to port MS-DOS to the MSX computers standard they were developing with ASCII Corporation. Paterson accepted the contract to help fund his company and completed the work |
https://en.wikipedia.org/wiki/Composite%20B%C3%A9zier%20curve | In geometric modelling and in computer graphics, a composite Bézier curve or Bézier spline is a spline made out of Bézier curves that is at least continuous. In other words, a composite Bézier curve is a series of Bézier curves joined end to end where the last point of one curve coincides with the starting point of the next curve. Depending on the application, additional smoothness requirements (such as or continuity) may be added.
A continuous composite Bézier is also called a polybezier, by similarity to polyline, but whereas in polylines the points are connected by straight lines, in a polybezier the points are connected by Bézier curves. A beziergon (also called bezigon) is a closed path composed of Bézier curves. It is similar to a polygon in that it connects a set of vertices by lines, but whereas in polygons the vertices are connected by straight lines, in a beziergon the vertices are connected by Bézier curves. Some authors even call a composite Bézier curve a "Bézier spline"; the latter term is however used by other authors as a synonym for the (non-composite) Bézier curve, and they add "composite" in front of "Bézier spline" to denote the composite case.
Perhaps the most common use of composite Béziers is to describe the outline of each letter in a PostScript or PDF file. Such outlines are composed of one beziergon for open letters, or multiple beziergons for closed letters. Modern vector graphics and computer font systems like PostScript, Asymptote, Metafont, OpenType, and SVG use composite Bézier curves composed of cubic Bézier curves (3rd order curves) for drawing curved shapes.
Smooth joining
A commonly desired property of splines is for them to join their individual curves together with a specified level of parametric or geometric continuity. While individual curves in the spline are fully continuous within their own interval, there is always some amount of discontinuity where different curves meet.
The Bézier spline is fairly unique in that it's one of the few splines that doesn't guarantee any higher degree of continuity than . It is, however, possible to arrange control points to guarantee various levels of continuity across joins, though this can come at a loss of local control if the constraint is too strict for the given degree of the Bézier spline.
Smoothly joining cubic Béziers
Given two cubic Bézier curves with control points and respectively, the constraints for ensuring continuity at can be defined as follows:
(positional continuity) requires that they meet at the same point, which all Bézier splines do by definition. In this example, the shared point is
(velocity continuity) requires the neighboring control points around the join to be mirrors of each other. In other words, they must follow the constraint of
(tangent continuity) requires the neighboring control points to be collinear with the join. This is less strict than continuity, leaving an extra degree of freedom which can be parameterize |
https://en.wikipedia.org/wiki/Bogon%20filtering | Bogon filtering is the practice of filtering bogons, which are bogus (fake) IP addresses of a computer network. Bogons include IP packets on the public Internet that contain addresses that are not in any range allocated or delegated by the Internet Assigned Numbers Authority (IANA) or a delegated regional Internet registry (RIR) and allowed for public Internet use. The areas of unallocated address space are called the bogon space.
Bogons also include some address ranges from allocated space, also known as Martian packets, mainly when they are being used as source address. Addresses reserved for private networks, such as those in , , and , loopback interfaces like and , and link-local addresses like and are part of it. Also addresses for Carrier-grade NAT, Teredo, and 6to4 and documentation prefixes fall into this category.
Many ISPs and end-user firewalls filter and block bogons, because they have no legitimate use, and usually are the result of accidental misconfiguration or malicious intent. Bogons can be filtered by using router access-control lists (ACLs), or by BGP blackholing.
IP addresses that are currently in the bogon space may not be bogons at a later date because IANA and other registries frequently assign new address space to ISPs. Announcements of new assignments are often published on network operators' mailing lists (such as NANOG) to ensure that operators have a chance to remove bogon filtering for addresses that have become legitimate. For example, addresses in were not allocated prior to August 2010, but are now used by APNIC. , the Internet Engineering Task Force (IETF) recommends that, since there are no longer any unallocated IPv4 s, IPv4 bogon filters based on registration status should be removed.
However, bogon filters still need to check for Martian packets.
Etymology
The term bogon stems from hacker jargon, with the earliest appearance in the Jargon File in version 1.5.0 (dated 1983). It is defined as the quantum of bogosity, or the property of being bogus. A bogon packet is frequently bogus both in the conventional sense of being forged for illegitimate purposes, and in the hackish sense of being incorrect, absurd, and useless.
These unused IP addresses are collectively known as a bogon, a contraction of "bogus logon", or a logon from a place you know no one can actually logon.
See also
Reverse-path forwarding
IP hijacking
IP address spoofing
Ingress filtering
Internet background noise
References
External links
Bogons Ate My Website
Bogon traffic analysis report, netflow and spam analysis
RIPE NCC: De-Bogonising New Address Blocks
Team Cymru Bogon Reference
Computer jargon
Internet Protocol |
https://en.wikipedia.org/wiki/NAPT | NAPT may refer to
Network Address and Port Translation, the most common type of network address translation
NAPT (electronic music artist), English breakbeat duo
Native American Public Telecommunications
North American Poker Tour, a series of televised poker tournaments
Needs assessment and planning tools
The Navy Advanced Placement Test, used to select applicants to the US Navy nuclear program |
https://en.wikipedia.org/wiki/Algebraic%20notation | Algebraic notation may refer to:
In mathematics and computers, infix notation, the practice of representing a binary operator and operands with the operator between the two operands (as in "2 + 2")
Algebraic notation (chess), the standard system for recording movement of pieces in a chess game
In linguistics, recursive categorical syntax, also known as "algebraic syntax", a theory of how natural languages are structured
Mathematical notation for algebra |
https://en.wikipedia.org/wiki/Flooding%20algorithm | A flooding algorithm is an algorithm for distributing material to every part of a graph. The name derives from the concept of inundation by a flood.
Flooding algorithms are used in computer networking and graphics. Flooding algorithms are also useful for solving many mathematical problems, including maze problems and many problems in graph theory.
Different flooding algorithms can be applied for different problems, and run with different time complexities. For example, the flood fill algorithm is a simple but relatively robust algorithm that works for intricate geometries and can determine which part of the (target) area that is connected to a given (source) node in a multi-dimensional array, and is trivially generalized to arbitrary graph structures. If there instead are several source nodes, there are no obstructions in the geometry represented in the multi-dimensional array, and one wishes to segment the area based on which of the source nodes the target nodes are closest to, while the flood fill algorithm can still be used, the jump flooding algorithm is potentially much faster as it has a lower time complexity. Unlike the flood fill algorithm, however, the jump flooding algorithm cannot trivially be generalized to unstructured graphs.
See also
Flooding (computer networking)
Water retention on mathematical surfaces
Flood fill
Graph traversal
Spanning tree
Spanning Tree Protocol
External links
Flooding edge or node weighted graphs, Fernand Meyer
Water Retention Utility |
https://en.wikipedia.org/wiki/Polynomial%20interpolation | In numerical analysis, polynomial interpolation is the interpolation of a given bivariate data set by the polynomial of lowest possible degree that passes through the points of the dataset.
Given a set of data points , with no two the same, a polynomial function is said to interpolate the data if for each .
There is always a unique such polynomial, commonly given by two explicit formulas, the Lagrange polynomials and Newton polynomials.
Applications
The original use of interpolation polynomials was to approximate values of important transcendental functions such as natural logarithm and trigonometric functions. Starting with a few accurately computed data points, the corresponding interpolation polynomial will approximate the function at an arbitrary nearby point. Polynomial interpolation also forms the basis for algorithms in numerical quadrature (Simpson's rule) and numerical ordinary differential equations (multigrid methods).
In computer graphics, polynomials can be used to approximate complicated plane curves given a few specified points, for example the shapes of letters in typography. This is usually done with Bézier curves, which are a simple generalization of interpolation polynomials (having specified tangents as well as specified points).
In numerical analysis, polynomial interpolation is essential to perform sub-quadratic multiplication and squaring, such as Karatsuba multiplication and Toom–Cook multiplication, where interpolation through points on a product polynomial yields the specific product required. For example, given a = f(x) = a0x0 + a1x1 + ··· and b = g(x) = b0x0 + b1x1 + ···, the product ab is a specific value of W(x) = f(x)g(x). One may easily find points along W(x) at small values of x, and interpolation based on those points will yield the terms of W(x) and the specific product ab. As fomulated in Karatsuba multiplication, this technique is substantially faster than quadratic multiplication, even for modest-sized inputs, especially on parallel hardware.
In computer science, polynomial interpolation also leads to algorithms for secure multi party computation and secret sharing.
Interpolation theorem
For any bivariate data points , where no two are the same, there exists a unique polynomial of degree at most that interpolates these points, i.e. .
Equivalently, for a fixed choice of interpolation nodes , polynomial interpolation defines a linear bijection between the (n+1)-tuples of real-number values and the vector space of real polynomials of degree at most n:
This is a type of unisolvence theorem. The theorem is also valid over any infinite field in place of the real numbers , for example the rational or complex numbers.
First proof
Consider the Lagrange basis functions given by:
Notice that is a polynomial of degree , and we have for each , while . It follows that the linear combination:
has , so is an interpolating polynomial of degree .
To prove uniqueness, assume that there exists ano |
https://en.wikipedia.org/wiki/Handwriting%20recognition | Handwriting recognition (HWR), also known as handwritten text recognition (HTR), is the ability of a computer to receive and interpret intelligible handwritten input from sources such as paper documents, photographs, touch-screens and other devices. The image of the written text may be sensed "off line" from a piece of paper by optical scanning (optical character recognition) or intelligent word recognition. Alternatively, the movements of the pen tip may be sensed "on line", for example by a pen-based computer screen surface, a generally easier task as there are more clues available. A handwriting recognition system handles formatting, performs correct segmentation into characters, and finds the most possible words.
Offline recognition
Offline handwriting recognition involves the automatic conversion of text in an image into letter codes that are usable within computer and text-processing applications. The data obtained by this form is regarded as a static representation of handwriting. Offline handwriting recognition is comparatively difficult, as different people have different handwriting styles. And, as of today, OCR engines are primarily focused on machine printed text and ICR for hand "printed" (written in capital letters) text.
Traditional techniques
Character extraction
Offline character recognition often involves scanning a form or document. This means the individual characters contained in the scanned image will need to be extracted. Tools exist that are capable of performing this step. However, there are several common imperfections in this step. The most common is when characters that are connected are returned as a single sub-image containing both characters. This causes a major problem in the recognition stage. Yet many algorithms are available that reduce the risk of connected characters.
Character recognition
After individual characters have been extracted, a recognition engine is used to identify the corresponding computer character. Several different recognition techniques are currently available.
Feature extraction
Feature extraction works in a similar fashion to neural network recognizers. However, programmers must manually determine the properties they feel are important. This approach gives the recognizer more control over the properties used in identification. Yet any system using this approach requires substantially more development time than a neural network because the properties are not learned automatically.
Modern techniques
Where traditional techniques focus on segmenting individual characters for recognition, modern techniques focus on recognizing all the characters in a segmented line of text. Particularly they focus on machine learning techniques that are able to learn visual features, avoiding the limiting feature engineering previously used. State-of-the-art methods use convolutional networks to extract visual features over several overlapping windows of a text line image which a recurrent neural ne |
https://en.wikipedia.org/wiki/Critical%20path%20method | The critical path method (CPM), or critical path analysis (CPA), is an algorithm for scheduling a set of project activities. A critical path is determined by identifying the longest stretch of dependent activities and measuring the time required to complete them from start to finish. It is commonly used in conjunction with the program evaluation and review technique (PERT).
History
The CPM is a project-modeling technique developed in the late 1950s by Morgan R. Walker of DuPont and James E. Kelley Jr. of Remington Rand. Kelley and Walker related their memories of the development of CPM in 1989. Kelley attributed the term "critical path" to the developers of the PERT, which was developed at about the same time by Booz Allen Hamilton and the U.S. Navy. The precursors of what came to be known as critical path were developed and put into practice by DuPont between 1940 and 1943 and contributed to the success of the Manhattan Project.
Critical path analysis is commonly used with all forms of projects, including construction, aerospace and defense, software development, research projects, product development, engineering, and plant maintenance, among others. Any project with interdependent activities can apply this method of mathematical analysis. CPM was used for the first time in 1966 for the major skyscraper development of constructing the former World Trade Center Twin Towers in New York City. Although the original CPM program and approach is no longer used, the term is generally applied to any approach used to analyze a project network logic diagram.
Basic techniques
Components
The essential technique for using CPM is to construct a model of the project that includes:
A list of all activities required to complete the project (typically categorized within a work breakdown structure)
The time (duration) that each activity will take to complete
The dependencies between the activities
Logical end points such as milestones or deliverable items
Using these values, CPM calculates the longest path of planned activities to logical end points or to the end of the project, and the earliest and latest that each activity can start and finish without making the project longer. This process determines which activities are "critical" (i.e., on the longest path) and which have "total float" (i.e., can be delayed without making the project longer). In project management, a critical path is the sequence of project network activities that adds up to the longest overall duration, regardless of whether that longest duration has float or not. This determines the shortest time possible to complete the project. "Total float" (unused time) can occur within the critical path. For example, if a project is testing a solar panel and task 'B' requires 'sunrise', a scheduling constraint on the testing activity could be that it would not start until the scheduled time for sunrise. This might insert dead time (total float) into the schedule on the activities on that path |
https://en.wikipedia.org/wiki/WMS | WMS can refer to:
Technology and computing
Warehouse management system
Workflow management system
Web Map Service, a standard for Internet map servers
Windows Media Services, the streaming media server from Microsoft
Windows MultiPoint Server, a Microsoft Windows Server for Remote Desktops
WMS (hydrology software), watershed simulation software
Welfare Management System (NYC), New York, US
Workload management system, a component of gLite
Medicine
Wilderness Medical Society, US, for medical personnel working in the wilderness
Wechsler Memory Scale of memory function
Warwick Medical School, British medical school of Warwick University
Companies
WMS Industries and subsidiary WMS Gaming, US electronic gaming and amusement companies
Williams Medical Supplies, a medical supplies company, Rhymney, Wales
Schools
West Monmouth School in Pontypool, Wales
White Mountain School, in Bethlehem, New Hampshire, US
Other
Written ministerial statement, a formal announcement by a government minister that is released to the media (as opposed to being given in person in Parliament). |
https://en.wikipedia.org/wiki/Coverage%20data | A coverage is the digital representation of some spatio-temporal phenomenon. ISO 19123 provides the definition:
[a] feature that acts as a function to return values from its range for any direct position within its spatial, temporal or spatiotemporal domain
Coverages play an important role in geographic information systems (GIS), geospatial content and services, GIS data processing, and data sharing.
A coverage is represented by its "domain" (the universe of extent) and a collection representing the coverage's values at each defined location within its range. For example, a satellite image derived from remote sensing might record varying degrees of light pollution. Aerial photography, land cover data, and digital elevation models all provide coverage data. Generally, a coverage can be multi-dimensional, such as 1-D sensor timeseries, 2-D satellite images, 3-D x/y/t image time series or x/y/z geo tomograms, or 4-D x/y/z/t climate and ocean data.
However, coverages are more general than just regularly gridded imagery. The corresponding standards (see below) address regular and irregular grids, point clouds, and general meshes.
An interoperable service definition for navigating, accessing, processing, and aggregation of coverages is provided by the Open Geospatial Consortium (OGC) Web Coverage Service (WCS) suite and Web Coverage Processing Service (WCPS), a spatio-temporal coverage query language.
Standards
Coverages represent digital geospatial information representing space/time-varying phenomena. OGC Abstract Topic 6 - which is identical to ISO 19123 - defines an abstract model of coverages.
Many implementations are conceivable which all conform to this abstract model while not being interoperable.
This abstract coverage model is concretized to the level of interoperability by the OGC standard GML 3.2.1 Application Schema - Coverages (often referred to as GMLCOV) which in turn is based on the Geography Markup Language (GML) 3.2, an XML grammar written in XML Schema for the description of application schemas as well as the transport and storage of geographic information.
The European legal framework for a unified Spatial Data Infrastructure, INSPIRE, in its Annex II and III relies on the OGC definitions of coverages as well, but modifies them in places in a way making them less compatible and interoperable with the OGC standard. For example, components of the coverage concept are selectively recombined into new, different definitions of a coverage.
Coverage model
Formally, in GMLCOV AbstractCoverage is a subtype of AbstractFeature (indicating its close relation).
An abstract coverage consists of the following components:
coverage domain: the extent where valid values are available;
range set: the set of values ("pixels", "voxels") the coverage consists of, together with their locations
range type: a type definition of the range set values
metadata: a slot where any kind of metadata can be added
This abstract coverage is refined i |
https://en.wikipedia.org/wiki/Feature%20data | In geographic information systems, a feature is an object that can have a geographic location and other properties. Common types of geometries include points, arcs, and polygons. Carriageways and cadastres are examples of feature data. Features can be labeled when displayed on a map.
Feature types
The definition of features that share membership of a common theme is a feature type, though there are a number of terms for this characteristic, including category, feature class, group, layer, level, object, and theme.
Layer served as the traditional term of choice, but use of this word has declined as data has become more object-oriented and less concerned with cartographic layering.
Data modelers can use feature types to create a hierarchical structure. For example, a dataset may consist of types called highways, streets and lanes. The system may group these particular types together under a category called "Roads".
See also
Feature class
References
Cartography |
https://en.wikipedia.org/wiki/League%20for%20Programming%20Freedom | League for Programming Freedom (LPF) was founded in 1989 by Richard Stallman to unite free software developers as well as developers of proprietary software to fight against software patents and the extension of the scope of copyright. Their logo is the Statue of Liberty holding a floppy disk and tape spool.
Among other initiatives, the League started the "Burn all GIFs" campaign in opposition to the actions of Unisys in enforcing their patent on LZW compression used by CompuServe when creating the image format.
The League produced a newsletter, Programming Freedom, in 11 issues from 1991 to 1995. These primary source materials chronicle the work of the organization.
The single event that had the most influence on the creation of the League was Apple's lawsuits against Microsoft about supposed copyrights violations of the look and feel of the Macintosh in the development of Windows. After the lawsuit ended, the League went dormant, to be resurrected by those who were increasingly troubled by the enforcement of software patents.
In September 2009, LPF President Dean Anderson sent a notice to former members announcing the return of the LPF and reviving its membership, with plans for an election on 12 May 2010.
See also
Electronic Frontier Foundation
Free Software Foundation
References
External links
Official website
LPF history page
Political organizations based in the United States
Intellectual property activism
Non-profit technology
Free Software Foundation
Information technology organizations based in North America |
https://en.wikipedia.org/wiki/Acrobat%20%28disambiguation%29 | An acrobat is one who practises acrobatics.
Acrobat may also refer to:
Computers
Adobe Acrobat, a family of computer programs
Acrobat.com, a suite of hosted document exchange services from Adobe Systems
Music
"Acrobat" (U2 song), from U2's album Achtung Baby
"Acrobat", a song from Maxïmo Park's album A Certain Trigger
"Acrobat" (Jo Gwang-il song), from Jo Gwang-il's album Dark Adaptation
Acrobat Records, an American independent record company
Film
The Acrobat, a 1941 French comedy
The Acrobat (2019 film), a 2019 Canadian drama
Visual arts
The Acrobats (Doré), a 1874 painting by Gustave Doré
Other uses
Paraavis Acrobat, a Russian paraglider design
Acrobats (1927), a sculpture by Alan Durst |
https://en.wikipedia.org/wiki/Bayesian%20network | A Bayesian network (also known as a Bayes network, Bayes net, belief network, or decision network) is a probabilistic graphical model that represents a set of variables and their conditional dependencies via a directed acyclic graph (DAG). It is one of several forms of causal notation. Bayesian networks are ideal for taking an event that occurred and predicting the likelihood that any one of several possible known causes was the contributing factor. For example, a Bayesian network could represent the probabilistic relationships between diseases and symptoms. Given symptoms, the network can be used to compute the probabilities of the presence of various diseases.
Efficient algorithms can perform inference and learning in Bayesian networks. Bayesian networks that model sequences of variables (e.g. speech signals or protein sequences) are called dynamic Bayesian networks. Generalizations of Bayesian networks that can represent and solve decision problems under uncertainty are called influence diagrams.
Graphical model
Formally, Bayesian networks are directed acyclic graphs (DAGs) whose nodes represent variables in the Bayesian sense: they may be observable quantities, latent variables, unknown parameters or hypotheses. Each edge represents a direct conditional dependency. Any pair of nodes that are not connected (i.e. no path connects one node to the other) represent variables that are conditionally independent of each other. Each node is associated with a probability function that takes, as input, a particular set of values for the node's parent variables, and gives (as output) the probability (or probability distribution, if applicable) of the variable represented by the node. For example, if parent nodes represent Boolean variables, then the probability function could be represented by a table of entries, one entry for each of the possible parent combinations. Similar ideas may be applied to undirected, and possibly cyclic, graphs such as Markov networks.
Example
Let us use an illustration to enforce the concepts of a Bayesian network. Suppose we want to model the dependencies between three variables: the sprinkler (or more appropriately, its state - whether it is on or not), the presence or absence of rain and whether the grass is wet or not. Observe that two events can cause the grass to become wet: an active sprinkler or rain. Rain has a direct effect on the use of the sprinkler (namely that when it rains, the sprinkler usually is not active). This situation can be modeled with a Bayesian network (shown to the right). Each variable has two possible values, T (for true) and F (for false).
The joint probability function is, by the chain rule of probability,
where G = "Grass wet (true/false)", S = "Sprinkler turned on (true/false)", and R = "Raining (true/false)".
The model can answer questions about the presence of a cause given the presence of an effect (so-called inverse probability) like "What is the probability that it is rain |
https://en.wikipedia.org/wiki/Directed%20acyclic%20graph | In mathematics, particularly graph theory, and computer science, a directed acyclic graph (DAG) is a directed graph with no directed cycles. That is, it consists of vertices and edges (also called arcs), with each edge directed from one vertex to another, such that following those directions will never form a closed loop. A directed graph is a DAG if and only if it can be topologically ordered, by arranging the vertices as a linear ordering that is consistent with all edge directions. DAGs have numerous scientific and computational applications, ranging from biology (evolution, family trees, epidemiology) to information science (citation networks) to computation (scheduling).
Directed acyclic graphs are sometimes instead called acyclic directed graphs or acyclic digraphs.
Definitions
A graph is formed by vertices and by edges connecting pairs of vertices, where the vertices can be any kind of object that is connected in pairs by edges. In the case of a directed graph, each edge has an orientation, from one vertex to another vertex. A path in a directed graph is a sequence of edges having the property that the ending vertex of each edge in the sequence is the same as the starting vertex of the next edge in the sequence; a path forms a cycle if the starting vertex of its first edge equals the ending vertex of its last edge. A directed acyclic graph is a directed graph that has no cycles.
A vertex of a directed graph is said to be reachable from another vertex when there exists a path that starts at and ends at . As a special case, every vertex is considered to be reachable from itself (by a path with zero edges). If a vertex can reach itself via a nontrivial path (a path with one or more edges), then that path is a cycle, so another way to define directed acyclic graphs is that they are the graphs in which no vertex can reach itself via a nontrivial path.
Mathematical properties
Reachability relation, transitive closure, and transitive reduction
The reachability relation of a DAG can be formalized as a partial order on the vertices of the DAG. In this partial order, two vertices and are ordered as exactly when there exists a directed path from to in the DAG; that is, when can reach (or is reachable from ). However, different DAGs may give rise to the same reachability relation and the same partial order. For example, a DAG with two edges and has the same reachability relation as the DAG with three edges , , and . Both of these DAGs produce the same partial order, in which the vertices are ordered as .
The transitive closure of a DAG is the graph with the most edges that has the same reachability relation as the DAG. It has an edge for every pair of vertices (, ) in the reachability relation of the DAG, and may therefore be thought of as a direct translation of the reachability relation into graph-theoretic terms. The same method of translating partial orders into DAGs works more generally: for every finite partially ordere |
https://en.wikipedia.org/wiki/List%20of%20U.S.%20states%20and%20territories%20by%20unemployment%20rate | The list of U.S. states and territories by unemployment rate compares the seasonally adjusted unemployment rates by state and territory, sortable by name, rate, and change. Data are provided by the Bureau of Labor Statistics in its Geographic Profile of Employment and Unemployment publication.
While the non-seasonally adjusted data reflects the actual unemployment rate, the seasonally adjusted data removes time from the equation.
Unemployment rate by jurisdiction
Data for all U.S. states, the District of Columbia and Puerto Rico is from June 2023 and September 2021, respectively. Data for Guam is from September 2019, and data for American Samoa is from 2018. Data for the Northern Mariana Islands is from April 2010 (more than ten years old) it is included but not ranked in the table below.
Note that italics represent an insular possession of the United States
See also
List of U.S. States by employment rate
Job creation index
Unemployment in the United States
References
External links
Comparison of Unemployment Benefits by State
Economy of the United States
Unemployment rate
States
unemployment rate
United States, unemployment rate
Labor in the United States |
https://en.wikipedia.org/wiki/Adobe%20PageMaker | Adobe PageMaker (formerly Aldus PageMaker) was a desktop publishing computer program introduced in 1985 by the Aldus Corporation on the Apple Macintosh. The combination of the Macintosh's graphical user interface, PageMaker publishing software, and the Apple LaserWriter laser printer marked the beginning of the desktop publishing revolution. Ported to PCs running Windows 1.0 in 1987, PageMaker helped to popularize both the Macintosh platform and the Windows environment.
A key component that led to PageMaker's success was its native support for Adobe Systems' PostScript page description language. After Adobe purchased the majority of Aldus's assets (including FreeHand, PressWise, PageMaker, etc.) in 1994 and subsequently phased out the Aldus name, version 6 was released. The program remained a major force in the high-end DTP market through the early 1990s, but new features were slow in coming. By the mid-1990s, it faced increasing competition from QuarkXPress on the Mac, and to a lesser degree, Ventura on the PC, and by the end of the decade it was no longer a major force. Quark proposed buying the product and canceling it, but instead, in 1999 Adobe released their "Quark Killer", Adobe InDesign. The last major release of PageMaker came in 2001, and customers were offered InDesign licenses at a lower cost.
Release history
Aldus Pagemaker 1.0 was released in July 1985 for the Macintosh and in December 1986 for the IBM PC.
Aldus Pagemaker 1.2 for Macintosh was released in 1986 and added support for PostScript fonts built into LaserWriter Plus or downloaded to the memory of other output devices. PageMaker was awarded a Codie award for Best New Use of a Computer in 1986. In October 1986, a version of Pagemaker was made available for Hewlett-Packard's HP Vectra computers. In 1987, Pagemaker was available on Digital Equipment's VAXstation computers.
Aldus Pagemaker 2.0 was released in 1987. Until May 1987, the initial Windows release was bundled with a full version of Windows 1.0.3; after that date, a "Windows-runtime" without task-switching capabilities was included. Thus, users who did not have Windows could run the application from MS-DOS.
Aldus Pagemaker 3.0 for Macintosh was shipped in April 1988. PageMaker 3.0 for the PC was shipped in May 1988 and required Windows 2.0, which was bundled as a run-time version. Version 3.01 was available for OS/2 and took extensive advantage of multithreading for improved user responsiveness.
Aldus PageMaker 4.0 for Macintosh was released in 1990 and offered new word-processing capabilities, expanded typographic controls, and enhanced features for handling long documents. A version for the PC was available by 1991.
Aldus PageMaker 5.0 was released in January 1993.
Adobe PageMaker 6.0 was released in 1995, a year after Adobe Systems acquired Aldus Corporation.
Adobe PageMaker 6.5 was released in 1996. Support for versions 4.0, 5.0, 6.0, and 6.5 is no longer offered through the official Adobe support sy |
https://en.wikipedia.org/wiki/Whitespace%20%28programming%20language%29 | Whitespace is an esoteric programming language developed by Edwin Brady and Chris Morris at the University of Durham (also developers of the Kaya and Idris programming languages). It was released on 1 April 2003 (April Fool's Day). Its name is a reference to whitespace characters. Unlike most programming languages, which ignore or assign little meaning to most whitespace characters, the Whitespace interpreter ignores any non-whitespace characters. Only spaces, tabs and linefeeds have meaning.
A consequence of this property is that a Whitespace program can easily be contained within the whitespace characters of a program written in a language which ignores whitespace, making the text a polyglot.
The language itself is an imperative stack-based language. The virtual machine on which the programs run has a stack and a heap. The programmer is free to push arbitrary-width integers onto the stack (currently there is no implementation of floating point numbers) and can also access the heap as a permanent store for variables and data structures.
History
Whitespace was created by Edwin Brady and Chris Morris in 2002. Slashdot published a review of the programming language on 1 April 2003.
The idea of using whitespace characters as operators for the C++ language had been facetiously suggested five years earlier by Bjarne Stroustrup.
Syntax
Commands are composed of sequences of spaces, tab stops and linefeeds. All other characters are ignored and thus can be used for comments. For example, tab-space-space-space performs arithmetic addition of the top two elements on the stack.
Code is written as an Instruction Modification Parameter (IMP) followed by the operation. The table below shows a list of all the IMPs in Whitespace.
Each IMP is followed by one operation defined for that IMP, and a parameter if needed. The list of operations supported in Whitespace is:
The "copy" and "slide" operations were added in Whitespace 0.3 and may not be supported by all implementations.
Numbers
Numbers are composed of spaces (0) and tabs (1), and they are terminated by a linefeed. The first space/tab in the number represents the sign of the number, if it's a space the number is positive, if it's a tab the number is negative. The rest of the trailing spaces and tabs represent the rest of the binary number.
Examples
space-tab-space-space-tab-space-tab-tab-linefeed (STSSTSTTL) represents the binary number 1001011 (positive, because the number starts with a space)
75 in decimal.
tab-tab-tab-space-space-tab-space-linefeed (TTTSSTSL) represents the binary number 110010 (negative, because the number starts with a tab)
−50 in decimal.
Labels
Labels are simply [LF] terminated lists of spaces and tabs. There is only one global namespace so all labels must be unique.
Sample code
The following is a commented Whitespace program that simply prints "Hello, world!", where each Space, Tab, or Linefeed character is preceded by the identifying comment "S", "T", or "L", r |
https://en.wikipedia.org/wiki/Li%20Gong%20%28computer%20scientist%29 | Gong Li (), also known in English as Li Gong, is a Chinese businessman and computer scientist. He currently serves as CEO of Linaro Ltd, a British software company headquartered in Cambridge, U.K., developing systems software for the Arm ecosystem. He was previously the Founder and CEO of Acadine Technologies, a systems software company specializing in mobile operating systems for mobile, wearable, and IoT devices. Acadine’s core product H5OS was a web-centric operating system that was primarily based on the open web standard HTML5. It was derived from Firefox OS, whose development Li had overseen as President of Mozilla Corporation.
Education
Born and raised in Beijing, Gong obtained B.S./M.S. at Tsinghua University, Beijing, and a PhD at the University of Cambridge, UK, all in computer science.
Academic achievements
Li Gong has 22 issued US patents and co-authored three books (published by Addison Wesley and O'Reilly), many technical articles, and 8 general articles in the science journal Nature. He won the Best Paper Award at the 1989 IEEE Symposium on Security and Privacy, and received the 1994 Leonard G. Abraham Prize given by the IEEE Communications Society for "the most significant contribution to technical literature in the field of interest of the IEEE."
Career
Li Gong started his career as a researcher, primarily in the fields of computer systems, networking, and information security. He served as both Program Chair and General Conference Chair for ACM CCS, IEEE S&P, and IEEE CSFW. He was Associate Editor of ACM TISSEC and Associate Editor-in-Chief of IEEE Internet Computing. Before going into the industry, he first worked at Odyssey Research in Ithaca, New York, and later at the Computer Science Laboratory at SRI International in Menlo Park, California. He held visiting positions at Cornell and Stanford and was a Guest Chair Professor at Tsinghua University, Beijing.
In 1996, he joined the JavaSoft division at Sun Microsystems (in Cupertino, California) as Chief Java Security Architect and designed the security architecture of the Java platform. He became a Distinguished Engineer and later headed engineering for Java Embedded Server and JXTA, and was the founding Chair of the Java Expert Group at the international standard organization OSGi and led the OSGi 1.0 specification.
In 2001, he founded the Sun Microsystems Engineering and Research Institute (ERI) in China, where he served as general manager and led the team working on Solaris system, browser, OpenOffice and related desktop software research and development.
In 2005, he joined Microsoft as general manager to lead MSN in China and served as vice president of the Microsoft China R&D Group. He led Beijing and Shanghai teams working in many areas across all the services MSN offered — including Messenger, Hotmail, Spaces, Safety, Mobile, Search, Ads platform, and Virtual Earth.
In 2007, Gong joined Mozilla Corporation to found its China subsidiary Mozilla Online Ltd where |
https://en.wikipedia.org/wiki/Split%20horizon%20route%20advertisement | In computer networking, split-horizon route advertisement is a method of preventing routing loops in distance-vector routing protocols by prohibiting a router from advertising a route back onto the interface from which it was learned.
The concept was suggested in 1974 by Torsten Cegrell, and originally implemented in the ARPANET-inspired Swedish network TIDAS.
Terminology
Here is some basic terminology:
Route poisoning: if a node N learns that its route to a destination D is unreachable, inform that to all nodes in the network by sending them a message stating that the distance from N to D, as perceived by N, is infinite.
Split horizon rule: if a node N uses interface I to transmit to a given destination D, N should not send through I new information about D.
Poison reverse rule: if a node N uses interface I to transmit to a given destination D, N sends through I the information that its cost-to-go to D is infinite.
Whereas under split horizon N does not send any information through I, under poison reverse node N tells a white-lie.
Example
In this example, network node A routes packets to node B in order to reach node C. The links between the nodes are distinct point-to-point links.
According to the split-horizon rule, node A does not advertise its route for C (namely A to B to C) back to B. On the surface, this seems redundant since B will never route via node A because the route costs more than the direct route from B to C. However, if the link between B and C goes down, and B had received a route from A to C, B could end up using that route via A. A would send the packet right back to B, creating a loop. This is the Count to Infinity Problem. With the split-horizon rule in place, this particular loop scenario cannot happen, improving convergence time in complex, highly-redundant environments.
Split-horizon routing with poison reverse is a variant of split-horizon route advertising in which a router actively advertises routes as unreachable over the interface over which they were learned by setting the route metric to infinite (16 for RIP). The effect of such an announcement is to immediately remove most looping routes before they can propagate through the network.
The main disadvantage of poison reverse is that it can significantly increase the size of routing announcements in certain fairly common network topologies, but it allows for the improvement of the overall efficiency of the network in case of faults.
Split horizon states that if a neighboring router sends a route to a router, the receiving router will not propagate this route back to the advertising router on the same interface.
With route poisoning, when a router detects that one of its connected routes has failed, the router will poison the route by assigning an infinite metric to it and advertising it to neighbors. When a router advertises a poisoned route to its neighbors, its neighbors break the rule of split horizon and send back to the originator the same pois |
https://en.wikipedia.org/wiki/Elche | Elche () is a city and municipality of Spain, belonging to the province of Alicante, in the Valencian Community. According to 2014 data, Elche has a population of 228,647 inhabitants, making it the third most populated municipality in the region (after Valencia and Alicante) and the 20th largest Spanish municipality. It is part of the comarca of Baix Vinalopó.
Part of the municipality is coastal yet the city proper is roughly away from the Mediterranean Sea. A small creek called Vinalopó flows through the city. Elche is the centre of the footwear industry in Spain. The main airport of the province of Alicante (Alicante–Elche Miguel Hernández Airport) is located inside Elche's municipality, and it serves both Elche and Alicante, being the fifth-busiest airport in Spain.
Together with Alicante and other municipalities, Elche forms a conurbation of some 800,000 inhabitants. The city is noted for its urban Palm Grove, designated as World Heritage Site.
History
L'Alcúdia is 10 km from the current city's location and the immediate predecessor of current day Elche. This original location was settled by the Greeks and then occupied by Carthaginians and Romans. Greek Ionian colonists from the Achaean city Helike established their new colony, naming it Helíkē () around 600BC. It was a point of resistance against Carthaginian advance in Spain between the First and Second Punic Wars. The Romans called the city Ilici or Illice and granted it the status of colonia; after a brief Byzantine rule, the Goths took over, establishing an episcopal see.
Elche lost importance during the period of Moorish occupation, when it was moved slightly north to its present location. James II of Aragon took the city from the Moors in the 13th century, during the Reconquista. The city grew throughout the 18th century and became more important during the 19th century with the arrival of the railway and a booming industrial development of what used to be the traditional footwear industry.
Many archaeological remains have been found in Elche, with the stone bust of the Lady of Elche (Dama de Elche/Dama d'Elx in Spanish and Valencian, respectively) being the most important. This may date from the Iberian period (4th century BC). The original is in the National Archaeological Museum of Spain.
Elche was granted the title of city by King Amadeo in 1871.
The espadrille industry developed in the 19th century, eventually becoming the leading Spanish municipality at producing textile footwear. By the late century, local entrepreneurs began to invest in leather footwear factories. The footwear industry grew during the Great War and thereafter.
Geography
The city is known for the Palmeral de Elche, that is an UNESCO World Heritage Site and is the only palm grove in Europe with North African origins and the largest on the continent. The Palm Grove also constitutes the northernmost and one of the largest palm groves in the world. Today, the city of Elche contains 97 orchards composed |
https://en.wikipedia.org/wiki/Stephen%20R.%20Bourne | Stephen Richard "Steve" Bourne (born 7 January 1944) is an English computer scientist based in the United States for most of his career. He is well known as the author of the Bourne shell (sh), which is the foundation for the standard command-line interfaces to Unix.
Biography
Bourne has a Bachelor of Science (BSc) degree in mathematics from King's College London, England. He has a Diploma in Computer Science and a Doctor of Philosophy (Ph.D.) in mathematics from Trinity College, Cambridge. Subsequently, he worked on an ALGOL 68 compiler at the University of Cambridge Computer Laboratory (see ALGOL 68C). He also worked on CAMAL, a system for algebraic manipulation used for lunar theory calculations.
After the University of Cambridge, Bourne spent nine years at Bell Labs with the Seventh Edition Unix team. Besides the Bourne shell, he wrote the adb debugger and The Unix System, the second book on the topic, intended for general readers.
After Bell Labs, Bourne worked in senior engineering management positions at Silicon Graphics, Digital Equipment Corporation, Sun Microsystems, and Cisco Systems.
He was involved with developing international standards in programming and informatics, as a member of the International Federation for Information Processing (IFIP) IFIP Working Group 2.1 on Algorithmic Languages and Calculi, which specified, maintains, and supports the programming languages ALGOL 60 and ALGOL 68.
From 2000 to 2002 he was president of the Association for Computing Machinery (ACM). For his work on computing, Bourne was awarded the ACM's Presidential Award in 2008 and was made a Fellow of the organization in 2005. He is also a Fellow of the Royal Astronomical Society.
Bourne was chief technology officer at Icon Venture Partners, a venture capital firm based in Menlo Park, California through 2014. He is also chairperson of the editorial advisory board for ACM Queue, a magazine he helped found when he was president of the ACM.
References
External links
Living people
British computer scientists
American computer scientists
Unix people
Alumni of King's College London
Alumni of Trinity College, Cambridge
Members of the University of Cambridge Computer Laboratory
Fellows of the Association for Computing Machinery
Presidents of the Association for Computing Machinery
British expatriate academics in the United States
Silicon Graphics people
Digital Equipment Corporation people
Sun Microsystems people
Programming language designers
Computer science writers
Cellular automatists
1944 births
Chief technology officers |
https://en.wikipedia.org/wiki/Mac%20OS%209 | Mac OS 9 is the ninth and final major release of Apple's classic Mac OS operating system which was succeeded by Mac OS X (renamed to OS X in 2011 and macOS in 2016) in 2001. Introduced on October 23, 1999, it was promoted by Apple as "The Best Internet Operating System Ever", highlighting Sherlock 2's Internet search capabilities, integration with Apple's free online services known as iTools and improved Open Transport networking. While Mac OS 9 lacks protected memory and full pre-emptive multitasking, lasting improvements include the introduction of an automated Software Update engine and support for multiple users.
Apple discontinued development of Mac OS 9 in late 2001, transitioning all future development to Mac OS X. The final updates to Mac OS 9 addressed compatibility issues with Mac OS X while running in the Classic Environment and compatibility with Carbon applications. At the 2002 Worldwide Developers Conference, Steve Jobs began his keynote address by staging a mock funeral for OS 9.
Features
Apple billed Mac OS 9 as including "50 new features" and heavily marketed its Sherlock 2 software, which introduced a "channels" feature for searching different online resources and introduced a QuickTime-like metallic appearance. Mac OS 9 also featured integrated support for Apple's suite of Internet services known as iTools (later re-branded as .Mac, then MobileMe, which was replaced by iCloud) and included improved TCP/IP functionality with Open Transport 2.5.
Other features new to Mac OS 9 include:
Integrated support for multiple user accounts without using At Ease.
Support for voice login through VoicePrint passwords.
Keychain, a feature allowing users to save passwords and textual data encrypted in protected keychains.
A Software Update control panel for automatic download and installation of Apple system software updates.
A redesigned Sound control panel and support for USB audio.
Speakable Items 2.0, also known as PlainTalk, featuring improved speech synthesis and recognition along with AppleScript integration.
Improved font management through FontSync.
Remote Access Personal Server 3.5, including support for TCP/IP clients over Point-to-Point Protocol (PPP).
An updated version of AppleScript with support for TCP/IP.
Personal File Sharing over TCP/IP.
USB Printer Sharing, a control panel allowing certain USB printers to be shared across a TCP/IP network.
128-bit file encryption in the Finder.
Support for files larger than 2 GB.
Unix volume support.
CD Burning in the Finder (introduced in Mac OS 9.1).
Addition of a "Window" menu to the Finder (introduced in Mac OS 9.1)
Mac OS 9 and the Classic Environment
PowerPC versions of Mac OS X prior to 10.5 include a compatibility layer (a shell) called Classic, enabling users to run applications and hardware requiring Mac OS 9 from within OS X. This is achieved through running Mac OS 9 without access to its Finder inside OS X. This requires Mac OS 9 to be installed on the computer even though |
https://en.wikipedia.org/wiki/Compress%20%28software%29 | compress is a Unix shell compression program based on the LZW compression algorithm. Compared to gzip's fastest setting, compress is slightly slower at compression, slightly faster at decompression, and has a significantly lower compression ratio. 1.8 MiB of memory is used to compress the Hutter Prize data, slightly more than gzip's slowest setting.
The uncompress utility will restore files to their original state after they have been compressed using the compress utility. If no files are specified, the standard input will be uncompressed to the standard output.
In the upcoming POSIX and Single Unix Specification revision, it is planned that DEFLATE algorithm used in gzip format be supported in those utilities.
Description of program
Files compressed by compress are typically given the extension ".Z" (modeled after the earlier pack program which used the extension ".z"). Most tar programs will pipe their data through compress when given the command line option "-Z". (The tar program in its own does not compress; it just stores multiple files within one tape archive.)
Files can be returned to their original state using uncompress. The usual action of uncompress is not merely to create an uncompressed copy of the file, but also to restore the timestamp and other attributes of the compressed file.
For files produced by compress on other systems, uncompress supports 9- to 16-bit compression.
History
The LZW algorithm used in was patented by Sperry Research Center in 1983. Terry Welch published an IEEE article on the algorithm in 1984, but failed to note that he had applied for a patent on the algorithm. Spencer Thomas of the University of Utah took this article and implemented in 1984, without realizing that a patent was pending on the LZW algorithm. The GIF image format also incorporated LZW compression in this way, and Unisys later claimed royalties on implementations of GIF. Joseph M. Orost led the team and worked with Thomas et al. to create the 'final' (4.0) version of and published it as free software to the 'net.sources' USENET group in 1985. was granted in 1985, and this is why could not be used without paying royalties to Sperry Research, which was eventually merged into Unisys.
has fallen out of favor in particular user-groups because it makes use of the LZW algorithm, which was covered by a Unisys patent because of this, gzip and bzip2 increased in popularity on Linux-based operating systems due to their alternative algorithms, along with better file compression. compress has, however, maintained a presence on Unix and BSD systems and the and commands have also been ported to the IBM i operating system.
The US LZW patent expired in 2003, so it is now in the public domain in the United States. All patents on the LZW worldwide have also expired (see Graphics Interchange Format#Unisys and LZW patent enforcement).
In the up-coming POSIX and Single Unix Specification revision, it is planned that DEFLATE algorithm used in gzi |
https://en.wikipedia.org/wiki/Functional%20dependency | In relational database theory, a functional dependency is a constraint between two sets of attributes in a relation from a database. In other words, a functional dependency is a constraint between two attributes in a relation.
Given a relation R and sets of attributes , X is said to functionally determine Y (written X → Y) if and only if each X value in R is associated with precisely one Y value in R; R is then said to satisfy the functional dependency X → Y. Equivalently, the projection is a function, i.e. Y is a function of X. In simple words, if the values for the X attributes are known (say they are x), then the values for the Y attributes corresponding to x can be determined by looking them up in any tuple of R containing x. Customarily X is called the determinant set and Y the dependent set. A functional dependency FD: X → Y is called trivial if Y is a subset of X.
In other words, a dependency FD: X → Y means that the values of Y are determined by the values of X. Two tuples sharing the same values of X will necessarily have the same values of Y.
The determination of functional dependencies is an important part of designing databases in the relational model, and in database normalization and denormalization. A simple application of functional dependencies is Heath's theorem; it says that a relation R over an attribute set U and satisfying a functional dependency X → Y can be safely split in two relations having the lossless-join decomposition property, namely into where Z = U − XY are the rest of the attributes. (Unions of attribute sets are customarily denoted by there juxtapositions in database theory.) An important notion in this context is a candidate key, defined as a minimal set of attributes that functionally determine all of the attributes in a relation. The functional dependencies, along with the attribute domains, are selected so as to generate constraints that would exclude as much data inappropriate to the user domain from the system as possible.
A notion of logical implication is defined for functional dependencies in the following way: a set of functional dependencies logically implies another set of dependencies , if any relation R satisfying all dependencies from also satisfies all dependencies from ; this is usually written . The notion of logical implication for functional dependencies admits a sound and complete finite axiomatization, known as Armstrong's axioms.
Examples
Cars
Suppose one is designing a system to track vehicles and the capacity of their engines. Each vehicle has a unique vehicle identification number (VIN). One would write VIN → EngineCapacity because it would be inappropriate for a vehicle's engine to have more than one capacity. (Assuming, in this case, that vehicles only have one engine.) On the other hand, EngineCapacity → VIN is incorrect because there could be many vehicles with the same engine capacity.
This functional dependency may suggest that the attribute EngineCapacity be placed i |
https://en.wikipedia.org/wiki/HSL | HSL may refer to:
Science, technology and computing
HSL (Fortran library), a numerical software library
HSL and HSV color space
Health and Safety Laboratory, UK
Hormone-sensitive lipase, a protein
Hybrid solar lighting
Transport
Bell HSL, a 1950s U.S. Navy antisubmarine helicopter
Haslemere railway station in England
Helsinki Regional Transport Authority (Helsingin seudun liikenne), Finland
Hindustan Shipyard, in Visakhapatnam, Andhra Pradesh, India
Hispania Líneas Aéreas, a defunct Spanish airline
HSL Logistik, a German train operator
Huslia Airport, in Alaska, US
High-speed rail lines in Benelux HSL 1, HSL 2 HSL 3 HSL 4, and HSL-Zuid
HSL-34 to HSL-94: Former US Navy helicopter Anti-submarine (Light) squadrons
Other uses
Hausa Sign Language, Kano, Nigeria
Hawaiʻi Sign Language, Hawaii, United States
Hamburg School of Logistics, now Kühne Logistics University, Germany
Staff Selection Commission Combined Higher Secondary Level Exam or CHSL/HSL, civil service examination by the Staff Selection Commission for governmental posts in India |
https://en.wikipedia.org/wiki/ECL | ECL may refer to:
Science and technology
Electrochemiluminescence
Enhanced chemiluminescence
Emitter-coupled logic
Enterochromaffin-like cell
Computing
ECL programming language, an extensible programming language
ECL (data-centric programming language)
Embeddable Common Lisp
Sport
East Cornwall League, an English football league
Eastern Colored League, a defunct American baseball league
Eastern Counties Football League, in England
European Cricket League, a professional cricket league organized by ICC member federations
UEFA Europa Conference League, annual football club competition organised by UEFA
European Champions League (table tennis), annual table tennis club competition
Other uses
Eccleston Park railway station, in England
Ecolab, a sanitation supply company
École centrale de Lyon, a graduate engineering school in Lyon, France
Educational Community License, a software license
Exit Control List, system of border control maintained by the Government of Pakistan
Extended collective licensing, collective copyright and related rights laws and licensing agreement |
https://en.wikipedia.org/wiki/CAR%20and%20CDR | In computer programming, CAR (car) and CDR (cdr) ( or ) are primitive operations on cons cells (or "non-atomic S-expressions") introduced in the Lisp programming language. A cons cell is composed of two pointers; the car operation extracts the first pointer, and the cdr operation extracts the second.
Thus, the expression (car (cons x y)) evaluates to x, and (cdr (cons x y)) evaluates to y.
When cons cells are used to implement singly linked lists (rather than trees and other more complicated structures), the car operation returns the first element of the list, while cdr returns the rest of the list. For this reason, the operations are sometimes given the names first and rest or head and tail.
Etymology
Lisp was originally implemented on the IBM 704 computer, in the late 1950s.
The popular explanation that CAR and CDR stand for "Contents of the Address Register" and "Contents of the Decrement Register" does not quite match the IBM 704 architecture; the IBM 704 does not have a programmer-accessible address register and the three address modification registers are called "index registers" by IBM.
The 704 and its successors have a 36-bit word length and a 15-bit address space. These computers had two instruction formats, one of which, the Type A, had a short, 3-bit, operation code prefix and two 15-bit fields separated by a 3-bit tag. The first 15-bit field was the operand address and the second held a decrement or count. The tag specified one of three index registers. Indexing was a subtractive process on the 704, hence the value to be loaded into an index register was called a "decrement". The 704 hardware had special instructions for accessing the address and decrement fields in a word. As a result it was efficient to use those two fields to store within a single word the two pointers needed for a list.
Thus, "CAR" is "Contents of the Address part of the Register". The term "register" in this context refers to "memory location".
Precursors to Lisp included functions:
car ("contents of the address part of register number"),
cdr ("contents of the decrement part of register number"),
cpr ("contents of the prefix part of register number"), and
ctr ("contents of the tag part of register number"),
each of which took a machine address as an argument, loaded the corresponding word from memory, and extracted the appropriate bits.
704 macros
The 704 assembler macro for car was:
LXD JLOC 4 # C( Decrement of JLOC ) → C( C ) # Loads the Decrement of location JLOC into Index Register C
CLA 0,4 # C( 0 - C( C ) ) → C( AC ) # The AC register receives the start address of the list
PAX 0,4 # C( Address of AC ) → C( C ) # Loads the Address of AC into Index Register C
PXD 0,4 # C( C ) → C( Decrement of AC ) # Clears AC and loads Index Register C into the Decrement of AC
The 704 assembler macro for cdr was:
LXD JLOC 4 # C( Decrement of JLOC ) → C( C ) # Loads the Decrement of location JLOC into Index Register C
CLA 0,4 # |
https://en.wikipedia.org/wiki/Discrete%20Hartley%20transform | A discrete Hartley transform (DHT) is a Fourier-related transform of discrete, periodic data similar to the discrete Fourier transform (DFT), with analogous applications in signal processing and related fields. Its main distinction from the DFT is that it transforms real inputs to real outputs, with no intrinsic involvement of complex numbers. Just as the DFT is the discrete analogue of the continuous Fourier transform (FT), the DHT is the discrete analogue of the continuous Hartley transform (HT), introduced by Ralph V. L. Hartley in 1942.
Because there are fast algorithms for the DHT analogous to the fast Fourier transform (FFT), the DHT was originally proposed by Ronald N. Bracewell in 1983 as a more efficient computational tool in the common case where the data are purely real. It was subsequently argued, however, that specialized FFT algorithms for real inputs or outputs can ordinarily be found with slightly fewer operations than any corresponding algorithm for the DHT.
Definition
Formally, the discrete Hartley transform is a linear, invertible function H: Rn → Rn (where R denotes the set of real numbers). The N real numbers x0, ..., xN−1 are transformed into the N real numbers H0, ..., HN−1 according to the formula
The combination is sometimes denoted , and should not be confused with , or which appears in the DFT definition (where i is the imaginary unit).
As with the DFT, the overall scale factor in front of the transform and the sign of the sine term are a matter of convention. Although these conventions occasionally vary between authors, they do not affect the essential properties of the transform.
Properties
The transform can be interpreted as the multiplication of the vector (x0, ...., xN−1) by an N-by-N matrix; therefore, the discrete Hartley transform is a linear operator. The matrix is invertible; the inverse transformation, which allows one to recover the xn from the Hk, is simply the DHT of Hk multiplied by 1/N. That is, the DHT is its own inverse (involutory), up to an overall scale factor.
The DHT can be used to compute the DFT, and vice versa. For real inputs xn, the DFT output Xk has a real part (Hk + HN−k)/2 and an imaginary part (HN−k − Hk)/2. Conversely, the DHT is equivalent to computing the DFT of xn multiplied by 1 + i, then taking the real part of the result.
As with the DFT, a cyclic convolution z = x∗y of two vectors x = (xn) and y = (yn) to produce a vector z = (zn), all of length N, becomes a simple operation after the DHT. In particular, suppose that the vectors X, Y, and Z denote the DHT of x, y, and z respectively. Then the elements of Z are given by:
where we take all of the vectors to be periodic in N (XN = X0, et cetera). Thus, just as the DFT transforms a convolution into a pointwise multiplication of complex numbers (pairs of real and imaginary parts), the DHT transforms a convolution into a simple combination of pairs of real frequency components. The inverse DHT then yields the desired vect |
https://en.wikipedia.org/wiki/Constraint | Constraint may refer to:
Constraint (computer-aided design), a demarcation of geometrical characteristics between two or more entities or solid modeling bodies
Constraint (mathematics), a condition of an optimization problem that the solution must satisfy
Constraint (classical mechanics), a relation between coordinates and momenta
Constraint (information theory), the degree of statistical dependence between or among variables
Constraints (journal), a scientific journal
Constraint (database), a concept in relational database
See also
Biological constraints, factors which make populations resistant to evolutionary change
Carrier's constraint
Constrained optimization, in finance, linear programming, economics and cost modeling
Constrained writing, in literature
Constraint algorithm, such as SHAKE, or LINCS
Constraint satisfaction, in computer science
Finite domain constraint
First class constraint in Hamiltonian mechanics
Integrity constraints
Loading gauge, a constraint in engineering
Optimality theory, in linguistics, a constraint-based theory which is primarily influential in phonology
Primary constraint in Hamiltonian mechanics
Restraint (disambiguation)
Second class constraint in Hamiltonian mechanics
Secondary constraint in Hamiltonian mechanics
Structure gauge, a constraint in engineering
Theory of constraints, in business management |
https://en.wikipedia.org/wiki/Dependency%20%28project%20management%29 | In a project network, a dependency is a link among a project's terminal elements.
The A Guide to the Project Management Body of Knowledge (PMBOK Guide) does not define the term dependency, but refers for this term to a logical relationship, which in turn is defined as dependency between two activities, or between an activity and a milestone.
Standard types of dependencies
There are four standard types of dependencies:
Finish to start (FS)
A FS B means "activity A must finish before activity B can begin" (or "B can't start until A has finished").
(Foundations dug) FS (Concrete poured)
Finish to finish (FF)
A FF B means "activity A must finish before activity B can finish" (or "B can't finish before A is finished") .
(Last chapter written) FF (Entire book written)
Start to start (SS).
A SS B means "activity A must start before activity B can start" (or "B can't start until A has started").
(Project work started) SS (Project management activities started)
Start to finish (SF)
A SF B means "activity A must start before activity B finishes" (or "B can't finish until A has started")
(New shift started) SF (Previous shift finished)
Finish-to-start is considered a "natural dependency". The Practice Standard for Scheduling recommends, that "Typically, each predecessor activity would finish prior to the start of its successor activity (or activities)(known as finish-to-start (FS) relationship). Sometimes it is necessarily to overlap activities; an option may be selected to use start-to-start (SS), finish-to-finish (FF) or start-to-finish (SF) relationships....Whenever possible, the FS logical relationship should be used. If other types of relationships are used, they shall be used sparingly and with full understanding of how the relationships have been implemented in the scheduling software being used. Ideally, the sequence of all activities will be defined in such a way that the start of every activity has a logical relationship from a predecessor and the finish of every activity has a logical relationship to a successor".
SF is rarely used, and should generally be avoided. Microsoft recommends to use SF dependency for just-in-time scheduling. It can be easily shown however, that this would only work if resource levelling is not used, because resource levelling can delay a successor activity (an activity, which shall be finished just-in-time) in such a way, that it will finish later than the start of its logical predecessor activity, thus not fulfilling the just-in-time requirement.
There are three kinds of dependencies with respect to the reason for the existence of dependency:
Causal (logical)
It is impossible to edit a text before it is written
It is illogical to pour concrete before you dig the foundations of a building
Resource constraints
It is logically possible to paint four walls in a room simultaneously but there is only one painter
Discretionary (preferential)
I want to paint the living room before painting th |
https://en.wikipedia.org/wiki/YTV | YTV or ytv may refer to:
YTV (Canadian TV channel), a Canadian youth television station owned by Corus Entertainment
YTV (Burmese TV network), a Burmese television channel owned by MY Multimedia Co.,ltd
Helsinki Metropolitan Area Council, a co-operation agency operating in the Helsinki Metropolitan Area
Yale TV, the broadcast desk of the student newspaper Yale Daily News
Yomiuri Telecasting Corporation, a TV station joining Nippon News Network and Nippon Television Network System in Osaka, Japan
Yorkshire Television, former name of ITV Yorkshire, United Kingdom
Yumurcak TV, a Turkish channel
See also
KYTV (TV station), an NBC affiliated television station in Springfield, Missouri
WYTV, an ABC affiliated television station in Youngstown, Ohio
WHYY-TV, a PBS member station in Philadelphia, Pennsylvania |
https://en.wikipedia.org/wiki/UNIVAC%201105 | The UNIVAC 1105 was a follow-on computer to the UNIVAC 1103A introduced by Sperry Rand in September 1958. The UNIVAC 1105 used 21 types of vacuum tubes, 11 types of diodes, 10 types of transistors, and three core types.
The UNIVAC 1105 had either 8,192 or 12,288 words of 36-bit magnetic core memory, in two or three banks of 4,096 words each. Magnetic drum memory provided either 16,384 or 32,768 words, in one or two drums with 16,384 words each. Sixteen to twenty-four UNISERVO II tape drives were connected, with a maximum capacity (not counting block overhead) of 1,200,000 words per tape.
Fixed-point numbers had a one-bit sign and a 35-bit value, with negative values represented in ones' complement format. Floating-point numbers had a one-bit sign, an eight-bit characteristic, and a 27-bit mantissa. Instructions had a six-bit operation code and two 15-bit operand addresses.
A complete UNIVAC 1105 computer system required 160 kW of power (175 KVA, 0.9 power factor) and an air conditioning unit with a power of at least 35 tons (123 kW) for cooling input water. The computer system weighed about with a floor loading of 47 lb/ft2 (230 kg/m2) and required a room 49 x 64 x 10 ft (15 x 20 x 3 m). The floor space for the computer was approximately 3,752 ft2 (350 m2). The power, refrigeration and equipment room was approximately 2,450 ft2 (230 m2).
Cost, price and rental rates
Chapel Hill
In 1959, a Univac 1105 located in the basement of Phillips Hall of The University of North Carolina at Chapel Hill was one of three computers of its type. It was intended primarily for the United States Census Bureau, which had one of its own; Armour Institute of Technology had the other. The Chapel Hill unit cost $2.4 million, with the improvements to the basement, including 16-inch concrete walls to protect it from nuclear attack, added $1.2 million. Its memory was less than 50 kilobytes, or one 8 1/2 x 11 document, with the capability of adding 30,000 numbers per second. The Univac was 60 feet long, weighed 19 tons, and used 7200 vacuum tubes. Its printer had a speed of 600 lines per minute.
See also
List of UNIVAC products
History of computing hardware
List of vacuum tube computers
References
External links
BRL REPORT NO. 1115 March 1961: UNIVAC 1105 by Martin H. Weik
1105
Vacuum tube computers
36-bit computers
Computer-related introductions in 1958 |
https://en.wikipedia.org/wiki/UNIVAC%201103 | The UNIVAC 1103 or ERA 1103, a successor to the UNIVAC 1101, was a computer system designed by Engineering Research Associates and built by the Remington Rand corporation in October 1953. It was the first computer for which Seymour Cray was credited with design work.
History
Even before the completion of the Atlas (UNIVAC 1101), the Navy asked Engineering Research Associates to design a more powerful machine. This project became Task 29, and the computer was designated Atlas II.
In 1952, Engineering Research Associates asked the Armed Forces Security Agency (the predecessor of the NSA) for approval to sell the Atlas II commercially. Permission was given, on the condition that several specialized instructions would be removed. The commercial version then became the UNIVAC 1103. Because of security classification, Remington Rand management was unaware of this machine before this. The first commercially sold UNIVAC 1103 was sold to the aircraft manufacturer Convair, where Marvin Stein worked with it.
Remington Rand announced the UNIVAC 1103 in February 1953. The machine competed with the IBM 701 in the scientific computation market. In early 1954, a committee of the Joint Chiefs of Staff requested that the two machines be compared for the purpose of using them for a Joint Numerical Weather Prediction project. Based on the trials, the two machines had comparable computational speed, with a slight advantage for IBM's machine, but the latter was favored unanimously for its significantly faster input-output equipment.
The successor machine was the UNIVAC 1103A or Univac Scientific, which improved upon the design by replacing the unreliable Williams tube memory with magnetic-core memory, adding hardware floating-point instructions, and perhaps the earliest occurrence of a hardware interrupt feature.
Technical details
The system used electrostatic storage, consisting of 36 Williams tubes with a capacity of 1024 bits each, giving a total random-access memory of 1024 words of 36 bits each. Each of the 36 Williams tubes was five inches in diameter. A magnetic drum memory provided 16,384 words. Both the electrostatic and drum memories were directly addressable: addresses 0 through 01777 (Octal) were in electrostatic memory and 040000 through 077777 (Octal) were on the drum.
Fixed-point numbers had a 1-bit sign and a 35-bit value, with negative values represented in ones' complement format.
Instructions had a 6-bit operation code and two 15-bit operand addresses.
Programming systems for the machine included the RECO regional coding assembler by Remington-Rand, the RAWOOP one-pass assembler and SNAP floating point interpretive system authored by the Ramo-Wooldridge Corporation of Los Angeles, the FLIP floating point arithmetic interpretive system by Consolidated Vultee Aircraft of San Diego, and the CHIP floating point interpretive system by Wright Field in Ohio.
UNIVAC 1103/A weighed about .
1103A
The UNIVAC 1103A or Univac Scientific was an upgraded |
https://en.wikipedia.org/wiki/Zend%20Engine | The Zend Engine is a compiler and runtime environment for the PHP scripting language and consists of the Zend Virtual Machine, which is composed of the Zend Compiler and the Zend Executor, that compiles and executes the PHP code. It was originally developed by Andi Gutmans and Zeev Suraski while they were students at the Technion – Israel Institute of Technology. They later founded a company called Zend Technologies in Ramat Gan, Israel. The name Zend is a combination of their forenames, Zeev and Andi.
The first version of the Zend Engine appeared in 1999 in PHP version 4. It was written in C as a highly optimized modular back-end, which for the first time could be used in applications outside of PHP. The Zend Engine provides memory and resource management, and other standard services for the PHP language. Its performance, reliability and extensibility played a significant role in PHP's increasing popularity.
This was followed by Zend Engine 2 at the heart of PHP 5.
This was followed by Zend Engine 3, originally codenamed phpng, which was developed for PHP 7 and significantly improves performance.
The newest version is Zend Engine 4, which was developed for PHP 8.
The source code for the Zend Engine has been freely available under the Zend Engine License (although some parts are under the PHP License) since 1999, as part of the official releases from php.net, as well as the official git repository or the GitHub mirror. Various volunteers contribute to the PHP/Zend Engine codebase.
Architecture
Zend Engine is used internally by PHP as a compiler and runtime engine.
PHP Scripts are loaded into memory and compiled into Zend opcodes.
These opcodes are executed and the HTML generated is sent to the client.
To implement a Web script interpreter requires three parts:
The interpreter part analyzes the input code, translates it, and executes it.
The functionality part implements the functionality of the language (its functions, etc.).
The interface part talks to the Web server, etc.
Zend takes part 1 completely and a bit of part 2; PHP takes parts 2 and 3.
Zend itself really forms only the language core, implementing PHP at its very basics with some predefined functions.
See also
References
External links
Official git repository
1999 software
C (programming language) software
PHP
PHP software |
https://en.wikipedia.org/wiki/Trapdoor%20function | In theoretical computer science and cryptography, a trapdoor function is a function that is easy to compute in one direction, yet difficult to compute in the opposite direction (finding its inverse) without special information, called the "trapdoor". Trapdoor functions are a special case of one-way functions and are widely used in public-key cryptography.
In mathematical terms, if f is a trapdoor function, then there exists some secret information t, such that given f(x) and t, it is easy to compute x. Consider a padlock and its key. It is trivial to change the padlock from open to closed without using the key, by pushing the shackle into the lock mechanism. Opening the padlock easily, however, requires the key to be used. Here the key t is the trapdoor and the padlock is the trapdoor function.
An example of a simple mathematical trapdoor is "6895601 is the product of two prime numbers. What are those numbers?" A typical "brute-force" solution would be to try dividing 6895601 by many prime numbers until finding the answer. However, if one is told that 1931 is one of the numbers, one can find the answer by entering "6895601 ÷ 1931" into any calculator. This example is not a sturdy trapdoor function – modern computers can guess all of the possible answers within a second – but this sample problem could be improved by using the product of two much larger primes.
Trapdoor functions came to prominence in cryptography in the mid-1970s with the publication of asymmetric (or public-key) encryption techniques by Diffie, Hellman, and Merkle. Indeed, coined the term. Several function classes had been proposed, and it soon became obvious that trapdoor functions are harder to find than was initially thought. For example, an early suggestion was to use schemes based on the subset sum problem. This turned out rather quickly to be unsuitable.
, the best known trapdoor function (family) candidates are the RSA and Rabin families of functions. Both are written as exponentiation modulo a composite number, and both are related to the problem of prime factorization.
Functions related to the hardness of the discrete logarithm problem (either modulo a prime or in a group defined over an elliptic curve) are not known to be trapdoor functions, because there is no known "trapdoor" information about the group that enables the efficient computation of discrete logarithms.
A trapdoor in cryptography has the very specific aforementioned meaning and is not to be confused with a backdoor (these are frequently used interchangeably, which is incorrect). A backdoor is a deliberate mechanism that is added to a cryptographic algorithm (e.g., a key pair generation algorithm, digital signing algorithm, etc.) or operating system, for example, that permits one or more unauthorized parties to bypass or subvert the security of the system in some fashion.
Definition
A trapdoor function is a collection of one-way functions { fk : Dk → Rk } (k ∈ K), in which all of K, Dk, Rk are su |
https://en.wikipedia.org/wiki/IBM%20709 | The IBM 709 was a computer system, initially announced by IBM in January 1957 and first installed during August 1958. The 709 was an improved version of its predecessor, the IBM 704, and was the third of the IBM 700/7000 series of scientific computers. The improvements included overlapped input/output, indirect addressing, and three "convert" instructions which provided support for decimal arithmetic, leading zero suppression, and several other operations. The 709 had 32,768 words of 36-bit magnetic core memory and could execute 42,000 add or subtract instructions per second. It could multiply two 36-bit integers at a rate of 5000 per second.
An optional hardware emulator executed old IBM 704 programs on the IBM 709. This was the first commercially available emulator. Registers and most 704 instructions were emulated in 709 hardware. Complex 704 instructions such as floating point trap and input-output routines were emulated in 709 software.
The FORTRAN Assembly Program was first introduced for the 709.
It was a large system; customer installations used 100 to 250 kW to run them and almost as much again on the cooling. It weighed about (without peripheral equipment).
The 709 was built using vacuum tubes.
IBM announced a transistorized version of the 709, called the IBM 7090, in 1958, only a year after the announcement of the 709, thus cutting short the 709's product life.
Registers
The IBM 709 has a 38-bit accumulator, a 36-bit multiplier quotient register, and three 15-bit index registers whose contents are subtracted from the base address instead of being added to it. All three index registers can participate in an instruction: the 3-bit tag field in the instruction is a bit map specifying which of the registers participate in the operation, however if more than one index register is specified, their contents are combined by a logical or operation, not addition.p. 12
Instruction and data formats
There are five instruction formats, referred to as Types A, B,C, D and E. Most instructions are of type B.
Type A instructions have, in sequence, a 3-bit prefix (instruction code), a 15-bit decrement field, a 3-bit tag field, and a 15-bit address field. They are conditional jump operations based on the values in the decrement registers specified in the tag field. Some also subtract the decrement field from the contents of the index registers. The implementation requires that the second two bits of the instruction code be non-zero, giving a total of six possible type A instructions. One (STR, instruction code binary 101) was not implemented until the IBM 709.
Type B instructions have, in sequence, a 12-bit instruction code (with the second and third bits set to 0 to distinguish them from type A instructions), a 2-bit flag field, four unused bits, a 3-bit tag field, and a 15-bit address field.
Types C, D and E are used for specialized instructions.
Fixed point numbers are stored in binary sign/magnitude format.
Single precision floatin |
https://en.wikipedia.org/wiki/Operating%20environment | In computer software, an operating environment or integrated applications environment is the environment in which users run application software. The environment consists of a user interface provided by an applications manager and usually an application programming interface (API) to the applications manager.
An operating environment is not a full operating system, but is a form of middleware that rests between the OS and the application. For example, the first version of Microsoft Windows, Windows 1.0, was not a full operating system, but a GUI laid over DOS albeit with an API of its own. Similarly, the IBM U2 system operates on both Unix/Linux and Windows NT. Usually the user interface is text-based or graphical, rather than a command-line interface (e.g., DOS or the Unix shell), which is often the interface of the underlying operating system.
In the mid 1980s, text-based and graphical user interface operating environments surrounded DOS operating systems with a shell that turned the user's display into a menu-oriented "desktop" for selecting and running PC applications. These operating environment systems allow users much of the convenience of integrated software without locking them into a single package.
History
DOS operating environments
In the mid 1980s, text-based and graphical user interface operating environments such as IBM TopView, Microsoft Windows, Digital Research's GEM Desktop, GEOS and Quarterdeck Office Systems's DESQview surrounded DOS operating systems with a shell that turned the user's display into a menu-oriented "desktop" for selecting and running PC applications. These programs were more than simple menu systems—as alternate operating environments they were substitutes for integrated programs such as Framework and Symphony, that allowed switching, windowing, and cut-and-paste operations among dedicated applications. These operating environment systems gave users much of the convenience of integrated software without locking them into a single package. Alternative operating environments made terminate-and-stay-resident pop-up utilities such as Borland Sidekick redundant. Windows provided its own version of these utilities, and placing them under central control could eliminate memory conflicts that RAM-resident utilities create. In later versions, Windows evolved from an operating environment into a complete operating system with DOS as a bootloader (Windows 9x) and a complete operating system, Windows NT, was developed at the same time. All versions after Windows ME have been based on the Windows NT kernel.
See also
Desktop environment, the graphical user interface to the computer
File manager
Integrated environment
Integrated development environment, a type of computer software that assists computer programmers in developing software
Runtime environment, a virtual machine state which provides software services for processes or programs while a computer is running
X Window System
References
Computing te |
https://en.wikipedia.org/wiki/Observer | An observer is one who engages in observation or in watching an experiment.
Observer may also refer to:
Computer science and information theory
In information theory, any system which receives information from an object
State observer in control theory, a system that models a real system in order to provide an estimate of its internal state
Observer pattern, a design pattern used in computer programming
Fiction
Observer (novel), a 2023 science fiction novel by Robert Lanza and Nancy Kress
Observer (video game), a cyberpunk horror video game
Observer (Mystery Science Theater 3000), a fictional television character
Observers, beings in the television show Fringe
Military
Air observer, an aircrew member
Artillery observer, a front line personnel who directs fire discipline for artillery strikes
Royal Observer Corps, a civil defence organisation, originally tasked with reporting enemy aircraft
Observer, a non-participating officer, or umpire, tasked with observing the actions of soldiers during a field training or military exercise
Music
"Observer", a song by Gary Numan on his album The Pleasure Principle
"The Observer", a track from The Flaming Lips' 1999 album The Soft Bulletin
The Observers, an alternative name for reggae session band Soul Syndicate
Niney the Observer (born 1951), Jamaican record producer and singer
Publications
Observer.com, an online-only version of the weekly newspaper The New York Observer
Sunday Observer (Sri Lanka), a weekly newspaper
Observer (APS), a member magazine of Association for Psychological Science
The Observer (disambiguation), any of various periodicals
Science
Observer (general relativity)
Observer (meteorological)
Observer (physics)
Observer (quantum physics)
Observer (special relativity)
Observational astronomy
Other uses
Observer status, granted by an organization to allow a non-member limited participation
An election observer, one who assists in election monitoring
A game official sometimes used in the sport Ultimate
The Observer type in the Enneagram of Personality model
Donald Alaster Macdonald (1859–1932), Australian journalist who wrote under the pseudonym 'Observer'
See also
Observer effect (disambiguation)
National Observer (disambiguation), a variety of publications
United Nations Military Observer |
https://en.wikipedia.org/wiki/Antz | Antz is a 1998 American animated adventure comedy film produced by DreamWorks Animation (in its debut film) and Pacific Data Images and released by DreamWorks Pictures. It was directed by Eric Darnell and Tim Johnson (in their feature directorial debuts) from a screenplay by Todd Alcott, Chris Weitz, and Paul Weitz. The film features the voices of Woody Allen, Sharon Stone, Jennifer Lopez, Sylvester Stallone, Christopher Walken, Dan Aykroyd, Anne Bancroft, Danny Glover and Gene Hackman. Some of the main characters share facial similarities with the actors who voice them. The film involves an anxious worker ant, Z (Allen), who falls in love with Princess Bala (Stone). When the treacherous scheming of the arrogant officer General Mandible (Hackman) threatens to wipe out the entire worker population, Z must save the ant colony from the flooded tunnel and strives to make social inroads.
Development began in 1988 when Walt Disney Feature Animation pitched a film called Army Ants, about a pacifist worker ant teaching lessons of independent thinking to his militaristic colony. Meanwhile, Jeffrey Katzenberg had left the company in a feud with CEO Michael Eisner over the vacant president position after the death of Frank Wells. Katzenberg would later go on to help co-found DreamWorks with Steven Spielberg and David Geffen, and the three planned to rival Disney with the company's new animation division. Production began in May 1996, after production had already commenced on The Prince of Egypt (1998). DreamWorks had contracted Pacific Data Images (PDI) in Palo Alto, California, to begin working on computer-animated films to rival Pixar's features. Harry Gregson-Williams and John Powell composed the music for the film, marking their first animated film. During its production, a controversial public feud erupted between Jeffrey Katzenberg of DreamWorks and Steve Jobs and John Lasseter of Pixar, due to the production of their similar film A Bug's Life, which was released a month later. The feud worsened when Disney refused to avoid competition with DreamWorks' intended first animated release, The Prince of Egypt.
Antz premiered at the Toronto International Film Festival on September 19, 1998, and was released theatrically in the United States on October 2, 1998. It grossed $171.8 million worldwide on a budget of $42–105 million and received positive reviews, with critics praising the voice cast, animation, humor, and its appeal towards adults.
Plot
Z is an anxious worker ant who is suffering an existential crisis due to the fact that everyone in the colony, even his psychiatrist, reminds him of his insignificance. While at the local bar one night, Z falls in love with the colony's princess Bala when she visits the bar to escape her suffocating royal life. The ant colony declares war on an encroaching termite colony, and soldiers are sent to engage the invaders. To see Bala again, Z exchanges places with his soldier friend, Weaver, and joins the army, where |
https://en.wikipedia.org/wiki/Confused%20deputy%20problem | In information security, a confused deputy is a computer program that is tricked by another program (with fewer privileges or less rights) into misusing its authority on the system. It is a specific type of privilege escalation. The confused deputy problem is often cited as an example of why capability-based security is important.
Capability systems protect against the confused deputy problem, whereas access-control list–based systems do not.
Example
In the original example of a confused deputy, there was a compiler program provided on a commercial timesharing service. Users could run the compiler and optionally specify a filename where it would write debugging output, and the compiler would be able to write to that file if the user had permission to write there.
The compiler also collected statistics about language feature usage. Those statistics were stored in a file called "(SYSX)STAT", in the directory "SYSX". To make this possible, the compiler program was given permission to write to files in SYSX.
But there were other files in SYSX: in particular, the system's billing information was stored in a file "(SYSX)BILL". A user ran the compiler and named "(SYSX)BILL" as the desired debugging output file.
This produced a confused deputy problem. The compiler made a request to the operating system to open (SYSX)BILL. Even though the user did not have access to that file, the compiler did, so the open succeeded. The compiler wrote the compilation output to the file (here "(SYSX)BILL") as normal, overwriting it, and the billing information was destroyed.
The confused deputy
In this example, the compiler program is the deputy because it is acting at the request of the user. The program is seen as 'confused' because it was tricked into overwriting the system's billing file.
Whenever a program tries to access a file, the operating system needs to know two things: which file the program is asking for, and whether the program has permission to access the file. In the example, the file is designated by its name, “(SYSX)BILL”. The program receives the file name from the user, but does not know whether the user had permission to write the file. When the program opens the file, the system uses the program's permission, not the user's. When the file name was passed from the user to the program, the permission did not go along with it; the permission was increased by the system silently and automatically.
It is not essential to the attack that the billing file be designated by a name represented as a string. The essential points are that:
the designator for the file does not carry the full authority needed to access the file;
the program's own permission to access the file is used implicitly.
Other examples
A cross-site request forgery (CSRF) is an example of a confused deputy attack that uses the web browser to perform sensitive actions against a web application. A common form of this attack occurs when a web application uses a cookie to authe |
https://en.wikipedia.org/wiki/Combinatorial%20search | In computer science and artificial intelligence, combinatorial search studies search algorithms for solving instances of problems that are believed to be hard in general, by efficiently exploring the usually large solution space of these instances. Combinatorial search algorithms achieve this efficiency by reducing the effective size of the search space or employing heuristics. Some algorithms are guaranteed to find the optimal solution, while others may only return the best solution found in the part of the state space that was explored.
Classic combinatorial search problems include solving the eight queens puzzle or evaluating moves in games with a large game tree, such as reversi or chess.
A study of computational complexity theory helps to motivate combinatorial search. Combinatorial search algorithms are typically concerned with problems that are NP-hard. Such problems are not believed to be efficiently solvable in general. However, the various approximations of complexity theory suggest that some instances (e.g. "small" instances) of these problems could be efficiently solved. This is indeed the case, and such instances often have important practical ramifications.
Examples
Common algorithms for solving combinatorial search problems include:
A* search algorithm
Alpha–beta pruning
Branch-and-bound
Minimax
Lookahead
Lookahead is an important component of combinatorial search, which specifies, roughly, how deeply the graph representing the problem is explored. The need for a specific limit on lookahead comes from the large problem graphs in many applications, such as computer chess and computer Go. A naive breadth-first search of these graphs would quickly consume all the memory of any modern computer. By setting a specific lookahead limit, the algorithm's time can be carefully controlled; its time increases exponentially as the lookahead limit increases.
More sophisticated search techniques such as alpha–beta pruning are able to eliminate entire subtrees of the search tree from consideration. When these techniques are used, lookahead is not a precisely defined quantity, but instead either the maximum depth searched or some type of average.
See also
Brute-force search
Combinatorial explosion
Combinatorial optimization
Search algorithm
State space search
References
Russell and Norvig. Artificial Intelligence: A Modern Approach.
Analysis of algorithms
Combinatorial optimization
Computational complexity theory
Game artificial intelligence |
https://en.wikipedia.org/wiki/Star%20Trek%3A%2025th%20Anniversary%20%28computer%20game%29 | Star Trek: 25th Anniversary is an adventure video game developed and published by Interplay Productions in 1992, based on the Star Trek universe. The game chronicles various missions of James T. Kirk and his crew of the USS Enterprise. Its 1993 sequel, Star Trek: Judgment Rites, continues and concludes this two-game series.
The game was originally released on floppy discs, but was later rereleased on CD-ROM with expansions as well as enhanced audio including the entire principal cast of the original television series performing the game's dialogue.
Gameplay
The player takes on the role of Captain James T. Kirk on board the USS Enterprise, a Starfleet vessel as seen in the American science fiction television series Star Trek: The Original Series. It is split into two main modes, a main bridge view, and a third-person mode whenever an away team is transported to a planet or space station. During several combat sequences the player controls the Enterprise in battle against enemies in space; originally required, Interplay later offered a patch making them optional. The controls on the bridge are split across the crew, with Montgomery Scott allowing access to the shield and power controls, Pavel Chekov controlling navigation, and Hikaru Sulu controlling the orbit of the ship, for example. The away team always consists of Kirk, Spock and Leonard McCoy, as well as one of eight different redshirts, many of whom can die during the mission. The player interacts with these modes using a point and click interface via the mouse.
Plot
The game was broken up into a series of episodes, with each episode opening with a message received in-game from Starfleet Command. They are typically structured to have a ship to ship combat before the game moves onto a third-person adventure game featuring an away team.
The Episodes are as follows:
Demon World: Settlers belonging to a religious sect have reported being attacked by "Demons" near their mines. Kirk must discover the truth behind these "Demons".
Hijacked: The USS Masada has not reported in. Upon investigation, The Enterprise discovers that the ship has been captured by Elasi Pirates who are holding the crew hostage. Kirk must discover a way to recover the ship and crew unharmed.
Love's Labor Jeopardized: Romulans have crossed the Neutral Zone and attacked the Federation Research Station Ark 7. Unfortunately, the attack has created a biohazard situation that Enterprise crew must deal with, as well as the Romulans.
Another Fine Mess.....: When responding to a distress call from a ship under attack by pirates, the Enterprise discovers none other than Harry Mudd is involved. He is traced to a derelict alien spacecraft. The Enterprise crew must discover the connection between the derelict, the pirates and Mudd.
Feathered Serpent: A Klingon battle fleet is about to cross into Federation space, in pursuit of a "War Criminal". The Enterprise must find this "War Criminal" to prevent a war.
That Old Devil Moon: Strange |
https://en.wikipedia.org/wiki/Processor%20power%20dissipation | Processor power dissipation or processing unit power dissipation is the process in which computer processors consume electrical energy, and dissipate this energy in the form of heat due to the resistance in the electronic circuits.
Power management
Designing CPUs that perform tasks efficiently without overheating is a major consideration of nearly all CPU manufacturers to date. Historically, early CPUs implemented with vacuum tubes consumed power on the order of many kilowatts. Current CPUs in general-purpose personal computers, such as desktops and laptops, consume power in the order of tens to hundreds of watts. Some other CPU implementations use very little power; for example, the CPUs in mobile phones often use just a few watts of electricity, while some microcontrollers used in embedded systems may consume only a few milliwatts or even as little as a few microwatts.
There are a number of engineering reasons for this pattern:
For a given CPU core, energy usage will scale up as its clock rate increases. Reducing the clock rate or undervolting usually reduces energy consumption; it is also possible to undervolt the microprocessor while keeping the clock rate the same.
New features generally require more transistors, each of which uses power. Turning unused areas off saves energy, such as through clock gating.
As a processor model's design matures, smaller transistors, lower-voltage structures, and design experience may reduce energy consumption.
Processor manufacturers usually release two power consumption numbers for a CPU:
typical thermal power, which is measured under normal load (for instance, AMD's average CPU power)
maximum thermal power, which is measured under a worst-case load
For example, the Pentium 4 2.8 GHz has a 68.4 W typical thermal power and 85 W maximum thermal power. When the CPU is idle, it will draw far less than the typical thermal power. Datasheets normally contain the thermal design power (TDP), which is the maximum amount of heat generated by the CPU, which the cooling system in a computer is required to dissipate. Both Intel and Advanced Micro Devices (AMD) have defined TDP as the maximum heat generation for thermally significant periods, while running worst-case non-synthetic workloads; thus, TDP is not reflecting the actual maximum power of the processor. This ensures the computer will be able to handle essentially all applications without exceeding its thermal envelope, or requiring a cooling system for the maximum theoretical power (which would cost more but in favor of extra headroom for processing power).
In many applications, the CPU and other components are idle much of the time, so idle power contributes significantly to overall system power usage. When the CPU uses power management features to reduce energy use, other components, such as the motherboard and chipset, take up a larger proportion of the computer's energy. In applications where the computer is often heavily loaded, such as scientif |
https://en.wikipedia.org/wiki/X%20Games | The X Games are a series of action sports events founded by ESPN Inc. which air on the ESPN family of networks including ABC. The events are mainly held in the United States, with disciplines such as skateboarding, BMX, motocross, skiing and snowboarding. Participants compete to win bronze, silver, and gold medals, as well as prize money. Concurrent with competition is the "X Fest" sports and music festival, which offers live music, athlete autograph sessions, and interactive elements.
The inaugural X Games were held during the summer of 1995 in Providence and Newport in Rhode Island. The competition often features new tricks such as Tony Hawk's 900 in skateboarding, Shaun White's Double McTwist 1260 in snowboard, Dave Mirra's Double Backflip in BMX, Travis Pastrana's Double Backflip in freestyle motocross, Heath Frisby's first snowmobile frontflip, Chuck Carothers's first body varial in Moto X Best Trick, Henrik Harlaut's first nose-butter triple cork in Ski Big Air, Gus Kenworthy's first switch triple rodeo in a ski slopestyle competition and Torstein Horgmo's first landed triple cork in a snowboard competition.
The X Games gained media exposure due to their big name sponsors, top-tier athletes, and consistent fan attendance. As the Journal of Sport Management (2006) explains, Generation X and Millennials are the two demographics most highly valued by marketers. This creates a broad approach on marketing towards that certain demographic, which is why the X Games marketing and economic outlook is so "out of the box". According to a 2008 report by ESPN, in 1997, the Winter X Games inaugural year, 38,000 spectators attended the four-day event. In 1998, the attendance dropped to 25,000 spectators. But just two years later, a record attendance of 83,500 people attended the Winter X Games East Coast debut. The X Games and Winter X Games continue to grow with the popularity of action sports and the athletes who compete in them.
As part of the X Games, there have been performances by various rock bands over the years, as well as a DJ being on-site at all events. The X Games have made it a point since its founding to stage an eco-friendly event. Such measures include using biodiesel fuel in their vehicles and organizing recycling campaigns.
The X Games has never carried out drug tests on competitors, a position which has been criticized by the World Anti-Doping Agency director general David Howman and the International Olympic Committee president Thomas Bach.
In late 2022, ESPN sold the event to MSP Sports Capital, a private equity firm co-founded by Jahm Najafi and Jeff Moorad.
Winter X Games
The Winter X Games VIII in 2002 was the first time an X Games event was televised live and also had coverage by ESPN's flagship news program, SportsCenter. Viewership across the three networks that carried coverage of the event – ABC Sports, ESPN, and ESPN2 – exceeded 2001's household average by 30% according to Nielsen Media Research. The event also reach |
https://en.wikipedia.org/wiki/Window%20%28computing%29 | In computing, a window is a graphical control element. It consists of a visual area containing some of the graphical user interface of the program it belongs to and is framed by a window decoration. It usually has a rectangular shape that can overlap with the area of other windows. It displays the output of and may allow input to one or more processes.
Windows are primarily associated with graphical displays, where they can be manipulated with a pointer by employing some kind of pointing device. Text-only displays can also support windowing, as a way to maintain multiple independent display areas, such as multiple buffers in Emacs. Text windows are usually controlled by keyboard, though some also respond to the mouse.
A graphical user interface (GUI) using windows as one of its main "metaphors" is called a windowing system, whose main components are the display server and the window manager.
History
The idea was developed at the Stanford Research Institute (led by Douglas Engelbart). Their earliest systems supported multiple windows, but there was no obvious way to indicate boundaries between them (such as window borders, title bars, etc.).
Research continued at Xerox Corporation's Palo Alto Research Center / PARC (led by Alan Kay). They used overlapping windows.
During the 1980s the term "WIMP", which stands for window, icon, menu, pointer, was coined at PARC.
Apple had worked with PARC briefly at that time. Apple developed an interface based on PARC's interface. It was first used on Apple's Lisa and later Macintosh computers. Microsoft was developing Office applications for the Mac at that time. Some speculate that this gave them access to Apple's OS before it was released and thus influenced the design of the windowing system in what would eventually be called Microsoft Windows.
Properties
Windows are two dimensional objects arranged on a plane called the desktop metaphor. In a modern full-featured windowing system they can be resized, moved, hidden, restored or closed.
Windows usually include other graphical objects, possibly including a menu-bar, toolbars, controls, icons and often a working area. In the working area, the document, image, folder contents or other main object is displayed. Around the working area, within the bounding window, there may be other smaller window areas, sometimes called panes or panels, showing relevant information or options. The working area of a single document interface holds only one main object. "Child windows" in multiple document interfaces, and tabs for example in many web browsers, can make several similar documents or main objects available within a single main application window. Some windows in macOS have a feature called a drawer, which is a pane that slides out the side of the window and to show extra options.
Applications that can run either under a graphical user interface or in a text user interface may use different terminology. GNU Emacs uses the term 'window' to refer to an area wit |
https://en.wikipedia.org/wiki/IBM%20700/7000%20series | The IBM 700/7000 series is a series of large-scale (mainframe) computer systems that were made by IBM through the 1950s and early 1960s. The series includes several different, incompatible processor architectures. The 700s use vacuum-tube logic and were made obsolete by the introduction of the transistorized 7000s. The 7000s, in turn, were eventually replaced with System/360, which was announced in 1964. However the 360/65, the first 360 powerful enough to replace 7000s, did not become available until November 1965. Early problems with OS/360 and the high cost of converting software kept many 7000s in service for years afterward.
Architectures
The IBM 700/7000 series has six completely different ways of storing data and instructions:
First scientific (36/18-bit words): 701 (Defense Calculator)
Later scientific (36-bit words, hardware floating-point): 704, 709, 7040, 7044, 7090, 7094
Commercial (variable-length character strings): 702, 705, 7080
1400 series (variable-length character strings): 7010
Decimal (10-digit words): 7070, 7072, 7074
Supercomputer (64-bit words): 7030 "Stretch"
The 700 class use vacuum tubes, the 7000 class is transistorized. All machines (like most other computers of the time) use magnetic core memory; except for early 701 and 702 models, which initially used Williams tube CRT memory and were later converted to magnetic core memory.
Software compatibility issues
Early computers were sold without software. As operating systems began to emerge, having four different mainframe architectures plus the 1400 midline architectures became a major problem for IBM since it meant at least four different programming efforts were required.
The System/360 combines the best features of the 7000 and 1400 series architectures into a single design both for commercial computing and for scientific and engineering computing. However, its architecture is not compatible with those of the 7000 and 1400 series, so some 360 models have optional features that allow them to emulate the 1400 and 7000 instruction sets in microcode. One of the selling points of the System/370, the successor of the 360 introduced in mid-1970, was improved 1400/7000 series emulation, which could be done under operating system control rather than shutting down and restarting in emulation mode as was required for emulation of 7040/44, 7070/72/74, 7080 and 7090/94 on all of the 360s except the 360/85.
Peripherals
While the architectures differ, the machines in the same class use the same electronics technologies and generally use the same peripherals. Tape drives generally use 7-track format, with the IBM 727 for vacuum tube machines and the 729 for transistor machines. Both the vacuum tube and most transistor models use the same card readers, card punches, and line printers that were introduced with the 701. These units, the IBM 711, 721, and 716, are based on IBM accounting machine technology and even include plugboard control panels. They are relatively slow and it wa |
https://en.wikipedia.org/wiki/Multiface | The Multiface was a hardware peripheral released by Romantic Robot for several 1980s home computers. The primary function of the device was to dump the computer's memory to external storage. Pressing a red button on the Multiface activated it. As most games of the era did not have a save game feature, the Multiface allowed players to save their position by saving a loadable snapshot of the game. Home computer software of the early 1980s was typically loaded into RAM in one go, with copy protection measures concentrating the loading phase or just after it. The snapshot feature could be used after copy protection routines had been executed, to create a backup that was effectively unprotected against unauthorised distribution. Later models of the Multiface mitigated this by requiring the device to be present when re-loading the dumps into memory, making the dumps useless to people without a Multiface. Software producers also reacted to the threat by using routines that would prevent execution of the product if it detected that a Multiface was present and by loading the software in multiple parts, thus requiring the presence of the original, copy-protected media.
Operation
Pressing the red button on the Multiface raised the non-maskable interrupt line on the computer's processor, effectively taking control of the computer. The Multiface would then page in its own ROM, temporarily replacing the computer's operating system with that within the Multiface.
Additional features
All Multifaces had the ability to view and edit the contents of memory. This made cheating in games especially easy: magazines used to print codes every month, known as 'pokes'. By changing the memory, various aspects of the game could be altered, such as the number of lives one had before the game was over.
Some models of Multiface allowed the user to save a screenshot, and this is how Your Sinclair and likely other magazines produced screenshots of games.
Multifaces contained an extra 8 kilobytes of RAM that could be used by specially written software. Examples of such software included Genie, a machine code disassembler, and Lifeguard, a program for analysing the memory of a game during play in order to identify which memory locations should be changed to aid cheating. These programs could be loaded into the Multiface RAM and activated by pressing the red button.
Some later Multifaces had a 'thru-port', an additional interface on the back of the unit which allowed other peripherals to be plugged into the back. This solved the problem of the Multiface using up the computer's only expansion port.
Models of Multiface
Multifaces were released for 8-bit and 16-bit microcomputers, such as the ZX Spectrum, Amstrad CPC & Atari ST. Different models had slightly different features.
Multiface One
The Multiface One was released in 1986 for the ZX Spectrum 48K. It initially cost £39.95 and had the capability of saving data to cassette tape, ZX Microdrive, Opus Discovery (an exte |
https://en.wikipedia.org/wiki/Amstrad%20Action | Amstrad Action was a monthly magazine, published in the United Kingdom, which catered to owners of home computers from the Amstrad CPC range and later the GX4000 console.
It was the first magazine published by Chris Anderson's Future Publishing, which with a varied line-up of computing and non-computing related titles has since become one of the foremost magazine publishers in the UK.
The publication, often abbreviated to AA by staff and readers, had the longest lifetime of any Amstrad magazine, running for 117 issues from October 1985 until June 1995 - long after the CPC had ceased production and games were no longer available.
History
Published by Future plc, a company set up by Chris Anderson (ex-Personal Computer Games and Zzap!64 editor). Launch Editor, Peter Connor, also an ex-PCG staff member, shared the writing duties with the only other staff writer, Bob Wade. Bob, another ex-PCG/Zzap!64 staff member, was given the title ‘Software Editor’ and would review the vast majority of the games featured, with Peter given a second opinion. Trevor Gilham, Art Editor, would complete the four man team.
Issue 1 dated October 1985 was released in September 1985 with the cover price of £1; 1p for every one of the 100 pages. It took the new publication a few issues to find its readers, but with the help of a bumper 116 page Christmas 1985 issue with a cover mounted tape, the circulation figures grew rapidly. In October 1986 Amstrad Action split into three separate publications. AA still catered for the CPC range, while 8000 Plus and PC Plus focused on the Amstrad PCW and PC range respectively.
AA eventually gave in to reader's pleas to have a permanent cover tape. An announcement was made, in AA66, that the following issue would not only include a cover tape, but contain more colour and be printed on different paper. Review pages were also slightly re-designed.
In April 1992 the Audit Bureau of Circulation figures showed an increase to 37,120, the highest circulation since July–December 1988's 38,457.
AA100 looked at the top 100 products for the CPC and took a trip down memory lane, looking back at past editors and staff. As circulation figures wound down further still there was a drastic drop in page numbers from 60 to 36 in July 1994's AA106. More compact issues mean no superfluous columns or features. AA107 became the first issue with only one member of official staff.
In AA111 there was no credits list, but the new editor, Karen Levell, answered the Reaction letters and confirmed her appointment. Although everything appeared as normal in June 1995's AA117, with AA118 advertised in the next month box, this was the last AA ever. The final headline (on issue AA117) was Publish and be Damned.
Features and editorial style
AA covered both 'games' and 'serious' side of the CPC, maintaining a 50/50 coverage throughout its run. The editorial coverage was always seen as being one of the three main areas; games/leisure, serious (programming, business |
https://en.wikipedia.org/wiki/PowerOpen%20Environment | The PowerOpen Environment (POE), created in 1991 from the AIM alliance, is an open standard for running a Unix-based operating system on the PowerPC computer architecture.
History
The AIM alliance was announced on October 2, 1991, yielding the historic first technology partnership between Apple and IBM. One of its many lofty goals was to somehow eventually merge Apple's user-friendly graphical interface and desktop applications market with IBM's highly scalable Unix server market, allowing the two companies to enter what Apple believed to be an emerging "general desktop open systems market". This was touched upon by Apple's November 1991 announcement of A/UX 3.0. The upcoming A/UX 4.0 (never actually released) would target the PowerOpen Environment ABI, merge features of IBM's AIX variant of Unix into A/UX, and use the OSF/1 kernel from the Open Software Foundation. A/UX 3.0 would serve as an "important migration path" to this new system, making Unix and System 7 applications compliant with PowerOpen. A/UX 4.0 and AIX were intended to run on a variety of IBM's POWER and PowerPC hardware, and on Apple's PowerPC based hardware.
The need for the POE reduced due to the increasing availability of Unix-like operating systems on PowerPC, such as Linux distributions and AIX. The PowerOpen Association was formed to promote the POE and test for conformance, and disbanded in 1995. That year, other AIM elements disbanded
Overview
The POE contains API and ABI specifications. The presence of the ABI specification in the POE distinguishes it from other open systems such as POSIX and XPG4, since it allows platform-independent binary compatibility, which is otherwise typically limited to particular hardware. Derived from AIX, the POE conforms to industry open standards including POSIX, XPG4, and Motif.
The POE is hardware bus independent. System implementations can range from laptop computers to supercomputers. It requires a multi-user, multitasking operating system. It provides networking support, an X Window System extension, a Macintosh Application Services extension, and Motif.
See also
PowerPC Reference Platform
References
PowerOpen ABI specification
This article was originally based on material from the Free On-line Dictionary of Computing and is used under the GFDL.
IBM software |
https://en.wikipedia.org/wiki/IBM%207040 | The IBM 7040 was a historic but short-lived model of transistor computer built in the 1960s.
History
It was announced by IBM in December 1961, but did not ship until April 1963. A later member of the IBM 700/7000 series of scientific computers, it was a scaled-down version of the IBM 7090. It was not fully compatible with the 7090. Some 7090 features, including index registers, character instructions and floating point, were extra-cost options. It also featured a different input/output architecture, based on the IBM 1414 data synchronizer, allowing more modern IBM peripherals to be used. A model designed to be compatible with the 7040 with more performance was announced as the 7044 at the same time.
Peter Fagg headed the development of the 7040 under executive Bob O. Evans.
A number of IBM 7040 and 7044 computers were shipped, but it was eventually made obsolete by the IBM System/360 family, announced in 1964. The schedule delays caused by IBM's multiple incompatible architectures provided motivation for the unified System/360 family.
The 7040 proved popular for use at universities, due to its comparatively low price. For example, one was installed in May 1965 at Columbia University.
One of the first in Canada was at the University of Waterloo, bought by professor J. Wesley Graham. A team of students was frustrated with the slow performance of the Fortran compiler. In the summer of 1965 they wrote the WATFOR compiler for their 7040, which became popular with many newly formed computer science departments.
IBM also offered the 7040 (or 7044) as an input-output processor attached to a 7090, in a configuration known as the 7090/7040 Direct Coupled System (DCS). Each computer was slightly modified to be able to interrupt the other.
IBM used similar numbers for a model of its eServer pSeries 690 RS/6000 architecture much later. The 7040-681, for example, was withdrawn in 2005.
See also
List of IBM products
IBM mainframe
History of IBM
References
External links
7040
7 7040
36-bit computers
ja:IBM 7040 |
https://en.wikipedia.org/wiki/Windows%20Server%202003 | Windows Server 2003, codenamed "Whistler Server", is the second version of the Windows Server operating system produced by Microsoft. It is part of the Windows NT family of operating systems and was released to manufacturing on March 28, 2003 and generally available on April 24, 2003. Windows Server 2003 is the successor to the Server editions of Windows 2000 and the predecessor to Windows Server 2008. An updated version, Windows Server 2003 R2, was released to manufacturing on December 6, 2005. Windows Server 2003 is based on Windows 2000.
Windows Server 2003's kernel has also been used in Windows XP 64-bit Edition and Windows XP Professional x64 Edition, and was the starting point for the development of Windows Vista.
Windows Server 2003 is the final version of Windows Server that supports processors without ACPI. Its successor, Windows Server 2008, requires a processor with ACPI in any supported architecture (x86, x64 and Itanium).
As of July 2016, 18% of organizations used servers that were running Windows Server 2003.
Overview
Windows Server 2003 is the follow-up to Windows 2000 Server, incorporating compatibility and other features from Windows XP. Unlike Windows 2000, Windows Server 2003's default installation has none of the server components enabled, to reduce the attack surface of new machines. Windows Server 2003 includes compatibility modes to allow older applications to run with greater stability. It was made more compatible with Windows NT 4.0 domain-based networking. Windows Server 2003 brought in enhanced Active Directory compatibility and better deployment support to ease the transition from Windows NT 4.0 to Windows Server 2003 and Windows XP Professional.
Windows Server 2003 is the first server edition of Windows to support the IA64 and x64 architectures.
The product went through several name changes during the course of development. When first announced in 2000, it was known by its codename "Whistler Server"; it was named "Windows 2002 Server" for a brief time in mid-2001, followed by "Windows .NET Server" and "Windows .NET Server 2003". After Microsoft chose to focus the ".NET" branding on the .NET Framework, the OS was finally released as "Windows Server 2003".
Development
Windows Server 2003 was the first Microsoft Windows version which was thoroughly subjected to semi-automated testing for bugs with a software system called PREfast developed by computer scientist Amitabh Srivastava at Microsoft Research. The automated bug checking system was first tested on Windows 2000 but not thoroughly. Amitabh Srivastava's PREfast found 12% of Windows Server 2003's bugs, the remaining 88% being found by human computer programmers. Microsoft employs more than 4,700 programmers who work on Windows, 60% of whom are software testers whose job is to find bugs in Windows source code. Microsoft co-founder Bill Gates stated that Windows Server 2003 was Microsoft's "most rigorously tested software to date."
Microsoft used Windows Server |
https://en.wikipedia.org/wiki/Cons | In computer programming, ( or ) is a fundamental function in most dialects of the Lisp programming language. constructs memory objects which hold two values or pointers to two values. These objects are referred to as (cons) cells, conses, non-atomic s-expressions ("NATSes"), or (cons) pairs. In Lisp jargon, the expression "to cons x onto y" means to construct a new object with (cons x y). The resulting pair has a left half, referred to as the (the first element, or contents of the address part of register), and a right half, referred to as the (the second element, or contents of the decrement part of register).
It is loosely related to the object-oriented notion of a constructor, which creates a new object given arguments, and more closely related to the constructor function of an algebraic data type system.
The word "cons" and expressions like "to cons onto" are also part of a more general functional programming jargon. Sometimes operators that have a similar purpose, especially in the context of list processing, are pronounced "cons". (A good example is the :: operator in ML, Scala, F#, Lean, Coq, and Elm or the : operator in Haskell, which adds an element to the beginning of a list.)
Use
Although cons cells can be used to hold ordered pairs of data, they are more commonly used to construct more complex compound data structures, notably lists and binary trees.
Ordered pairs
For example, the Lisp expression constructs a cell holding 1 in its left half (the so-called field) and 2 in its right half (the field). In Lisp notation, the value looks like:
(1 . 2)
Note the dot between 1 and 2; this indicates that the S-expression is a "dotted pair" (a so-called "cons pair"), rather than a "list."
Lists
In Lisp, lists are implemented on top of cons pairs. More specifically, any list structure in Lisp is either:
An empty list , which is a special object usually called .
A cons cell whose is the first element of the list and whose is a list containing the rest of the elements.
This forms the basis of a simple, singly linked list structure whose contents can be manipulated with , , and . Note that is the only list that is not also a cons pair. As an example, consider a list whose elements are 1, 2, and 3. Such a list can be created in three steps:
Cons 3 onto , the empty list
Cons 2 onto the result
Cons 1 onto the result
which is equivalent to the single expression:
(cons 1 (cons 2 (cons 3 nil)))
or its shorthand:
(list 1 2 3)
The resulting value is the list:
(1 . (2 . (3 . nil)))
i.e.
*--*--*--nil
| | |
1 2 3
which is generally abbreviated as:
(1 2 3)
Thus, can be used to add one element to the front of an existing linked list. For example, if x is the list we defined above, then will produce the list:
(5 1 2 3)
Another useful list procedure is append, which concatenates two existing lists (i.e. combines two lists into a single list).
Trees
Binary trees that only store data in their leaves are also easil |
https://en.wikipedia.org/wiki/Sanford%20and%20Son | Sanford and Son is an American sitcom television series that ran on the NBC television network from January 14, 1972, to March 25, 1977. It was based on the British sitcom Steptoe and Son, which initially aired on BBC1 in the United Kingdom from 1962 to 1974.
Known for its edgy racial humor, running gags, and catchphrases, the series was adapted by Norman Lear and considered NBC's answer to CBS's All in the Family. Sanford and Son has been hailed as the precursor to many other African-American sitcoms. It was a rating hit throughout its six-season run, finishing in the Nielsen top ten for five of those seasons.
While the role of Fred G. Sanford was known for his bigotry and cantankerousness, the role of Lamont Sanford was that of Fred's long-suffering, conscientious, peacemaker son. At times, both characters involved themselves in schemes, usually as a means of earning cash quickly to pay off their various debts. Other colorful and unconventional characters on the show included Aunt Esther, Grady Wilson, Bubba Bexley, and Rollo Lawson.
Plot
Sanford and Son stars Redd Foxx as Fred G. Sanford, a widower and junk dealer living at 9114 South Central Avenue in the Watts neighborhood of Los Angeles, California, and Demond Wilson as his son Lamont Sanford. In the show, Fred moved to South Central Los Angeles from his hometown St. Louis during his youth.
After the show premiered in 1972, newspapers touted Foxx as NBC's answer to Archie Bunker, the bigoted white protagonist of All in the Family. Both shows were adapted by Norman Lear from BBC programs. Sanford and Son was adapted from Steptoe and Son and All in the Family from Till Death Us Do Part.
An earlier pilot for an American version of Steptoe and Son was produced by Joseph E. Levine in 1965. It starred Lee Tracy and Aldo Ray as Albert and Harold Steptoe. This version was unscreened and did not lead to a series. The pilot was released on DVD in the UK in 2018.
Characters
Main
Fred Sanford
Redd Foxx plays Fred G. Sanford, portraying him as a sarcastic, streetwise, irascible schemer whose frequent get-rich-quick ideas routinely backfired. His son Lamont longs for independence but loves his father too much to move out and leave him unsupervised. Though each owns an equal share in the business, Lamont often finds himself doing all the work and demanding that his father contribute to the effort, which he rarely does. Fred often insults his son, usually calling him "dummy". Despite their disagreements, the two share a close bond and regularly come to each other's aid.
Fred's wife Elizabeth died before the events of the series, around 1950. In a running gag in the series, during times of distress, Fred looks up (as to heaven) with his hand across his chest, faking a heart attack and saying, "This is the big one, Elizabeth! I'm coming to join ya, honey," but Lamont knows that it is merely a dramatic ploy. Fred raised Lamont alone and misses Elizabeth deeply.
Fred Sanford was named after Foxx's r |
https://en.wikipedia.org/wiki/Jumper%20%28computing%29 | In electronics and particularly computing, a jumper is a short length of conductor used to close, open or bypass part of an electronic circuit. They are typically used to set up or configure printed circuit boards, such as the motherboards of computers. The process of setting a jumper is often called strapping.
A strapping option is a hardware configuration setting usually sensed only during power-up or bootstrapping of a device (or even a single chip).
Design
Jumper pins (points to be connected by the jumper) are arranged in groups called jumper blocks, each group having at least one pair of contact points. An appropriately sized conductive sleeve called a jumper, or more technically, a shunt jumper, is slipped over the pins to complete the circuit.
A two-pin jumper only allows to choose between two Boolean states, whereas a three-pin jumper allows to select between three states.
Jumpers must be electrically conducting; they are usually encased in a non-conductive block of plastic for convenience. This also avoids the risk that an unshielded jumper will accidentally short out something critical (particularly if it is dropped on a live circuit).
Jumper shunts can be categorized by their pitch (uniform distance between pins measured from center to center). Some common pitches are:
Use
When a jumper is placed over two or more jumper pins, an electrical connection is made between them, and the equipment is thus instructed to activate certain settings accordingly. For example, with older PC systems, CPU speed and voltage settings were often made by setting jumpers.
Some documentation may refer to setting the jumpers to on, off, closed, or open. When a jumper is on or covering at least two pins it is a closed jumper, when a jumper is off, is covering only one pin, or the pins have no jumper it is an open jumper.
Jumperless designs have the advantage that they are usually fast and easy to set up, often require little technical knowledge, and can be adjusted without having physical access to the circuit board. With PCs, the most common use of jumpers is in setting the operating mode for ATA drives (master, slave, or cable select), though this use declined with the rise of SATA drives and Plug and Play devices. Jumpers have been used since the beginning of printed circuit boards.
Permanent parts of a circuit
Some printed wiring assemblies, particularly those using single-layer circuit boards, include short lengths of wire soldered between pairs of points. These wires are called wire bridges or jumpers, but unlike jumpers used for configuration settings, they are intended to permanently connect the points in question. They are used to solve layout issues of the printed wiring, providing connections that would otherwise require awkward (or in some cases, impossible) routing of the conductive traces. In some cases a resistor of 0 ohms is used instead of a wire, as these may be installed by the same robotic assembly machines that install real re |
https://en.wikipedia.org/wiki/John%20the%20Ripper | John the Ripper is a free password cracking software tool. Originally developed for the Unix operating system, it can run on fifteen different platforms (eleven of which are architecture-specific versions of Unix, DOS, Win32, BeOS, and OpenVMS). It is among the most frequently used password testing and breaking programs as it combines a number of password crackers into one package, autodetects password hash types, and includes a customizable cracker. It can be run against various encrypted password formats including several crypt password hash types most commonly found on various Unix versions (based on DES, MD5, or Blowfish), Kerberos AFS, and Windows NT/2000/XP/2003 LM hash. Additional modules have extended its ability to include MD4-based password hashes and passwords stored in LDAP, MySQL, and others.
Sample output
Here is a sample output in a Debian environment.
$ cat pass.txt
user:AZl.zWwxIh15Q
$ john -w:password.lst pass.txt
Loaded 1 password hash (Traditional DES [24/32 4K])
example (user)
guesses: 1 time: 0:00:00:00 100% c/s: 752 trying: 12345 - pookie
The first line is a command to expand the data stored in the file "pass.txt". The next line is the contents of the file, i.e. the user (AZl) and the hash associated with that user (zWwxIh15Q). The third line is the command for running John the Ripper utilizing the "-w" flag. "password.lst" is the name of a text file full of words the program will use against the hash, pass.txt makes another appearance as the file we want John to work on.
Then we see output from John working. Loaded 1 password hash — the one we saw with the "cat" command — and the type of hash John thinks it is (Traditional DES). We also see that the attempt required one guess at a time of 0 with a 100% guess rate.
Attack types
One of the modes John can use is the dictionary attack. It takes text string samples (usually from a file, called a wordlist, containing words found in a dictionary or real passwords cracked before), encrypting it in the same format as the password being examined (including both the encryption algorithm and key), and comparing the output to the encrypted string. It can also perform a variety of alterations to the dictionary words and try these. Many of these alterations are also used in John's single attack mode, which modifies an associated plaintext (such as a username with an encrypted password) and checks the variations against the hashes.
John also offers a brute force mode. In this type of attack, the program goes through all the possible plaintexts, hashing each one and then comparing it to the input hash. John uses character frequency tables to try plaintexts containing more frequently used characters first. This method is useful for cracking passwords that do not appear in dictionary wordlists, but it takes a long time to run.
See also
Brute-force search
Brute-force attack
Crack (password software)
References
External links
Password cracking software
Free security s |
https://en.wikipedia.org/wiki/Text%20file | A text file (sometimes spelled textfile; an old alternative name is flatfile) is a kind of computer file that is structured as a sequence of lines of electronic text. A text file exists stored as data within a computer file system. In operating systems such as CP/M and DOS, where the operating system does not keep track of the file size in bytes, the end of a text file is denoted by placing one or more special characters, known as an end-of-file (EOF) marker, as padding after the last line in a text file. On modern operating systems such as Microsoft Windows and Unix-like systems, text files do not contain any special EOF character, because file systems on those operating systems keep track of the file size in bytes. Most text files need to have end-of-line delimiters, which are done in a few different ways depending on operating system. Some operating systems with record-orientated file systems may not use new line delimiters and will primarily store text files with lines separated as fixed or variable length records.
"Text file" refers to a type of container, while plain text refers to a type of content.
At a generic level of description, there are two kinds of computer files: text files and binary files.
Data storage
Because of their simplicity, text files are commonly used for storage of information. They avoid some of the problems encountered with other file formats, such as endianness, padding bytes, or differences in the number of bytes in a machine word. Further, when data corruption occurs in a text file, it is often easier to recover and continue processing the remaining contents. A disadvantage of text files is that they usually have a low entropy, meaning that the information occupies more storage than is strictly necessary.
A simple text file may need no additional metadata (other than knowledge of its character set) to assist the reader in interpretation. A text file may contain no data at all, which is a case of zero-byte file.
Encoding
The ASCII character set is the most common compatible subset of character sets for English-language text files, and is generally assumed to be the default file format in many situations. It covers American English, but for the British pound sign, the euro sign, or characters used outside English, a richer character set must be used. In many systems, this is chosen based on the default locale setting on the computer it is read on. Prior to UTF-8, this was traditionally single-byte encodings (such as ISO-8859-1 through ISO-8859-16) for European languages and wide character encodings for Asian languages.
Because encodings necessarily have only a limited repertoire of characters, often very small, many are only usable to represent text in a limited subset of human languages. Unicode is an attempt to create a common standard for representing all known languages, and most known character sets are subsets of the very large Unicode character set. Although there are multiple character encodings a |
https://en.wikipedia.org/wiki/List%20%28abstract%20data%20type%29 | In computer science, a list or sequence is an abstract data type that represents a finite number of ordered values, where the same value may occur more than once. An instance of a list is a computer representation of the mathematical concept of a tuple or finite sequence; the (potentially) infinite analog of a list is a stream. Lists are a basic example of containers, as they contain other values. If the same value occurs multiple times, each occurrence is considered a distinct item.
The name list is also used for several concrete data structures that can be used to implement abstract lists, especially linked lists and arrays. In some contexts, such as in Lisp programming, the term list may refer specifically to a linked list rather than an array. In class-based programming, lists are usually provided as instances of subclasses of a generic "list" class, and traversed via separate iterators.
Many programming languages provide support for list data types, and have special syntax and semantics for lists and list operations. A list can often be constructed by writing the items in sequence, separated by commas, semicolons, and/or spaces, within a pair of delimiters such as parentheses '()', brackets '[]', braces '{}', or angle brackets '<>'. Some languages may allow list types to be indexed or sliced like array types, in which case the data type is more accurately described as an array.
In type theory and functional programming, abstract lists are usually defined inductively by two operations: nil that yields the empty list, and cons, which adds an item at the beginning of a list.
Operations
Implementation of the list data structure may provide some of the following operations:
a constructor for creating an empty list;
an operation for testing whether or not a list is empty;
an operation for prepending an entity to a list
an operation for appending an entity to a list
an operation for determining the first component (or the "head") of a list
an operation for referring to the list consisting of all the components of a list except for its first (this is called the "tail" of the list.)
an operation for accessing the element at a given index.
Implementations
Lists are typically implemented either as linked lists (either singly or doubly linked) or as arrays, usually variable length or dynamic arrays.
The standard way of implementing lists, originating with the programming language Lisp, is to have each element of the list contain both its value and a pointer indicating the location of the next element in the list. This results in either a linked list or a tree, depending on whether the list has nested sublists. Some older Lisp implementations (such as the Lisp implementation of the Symbolics 3600) also supported "compressed lists" (using CDR coding) which had a special internal representation (invisible to the user). Lists can be manipulated using iteration or recursion. The former is often preferred in imperative programming languages, whil |
https://en.wikipedia.org/wiki/OMT | OMT may refer to:
Technology
OMT-G, configuration in object-based spatial databases
Object-modeling technique, language for software modeling and designing
Object model template, architecture for distributed computer simulation systems
Open microchip technology, the technology of implanting microchips in animals for research or tracking
Orthomode transducer, also polarisation duplexer, microwave duct component of the class of microwave circulators
Health and wellness
Osteopathic manipulative treatment, hands-on application of manipulative techniques on the patient by a Doctor of Osteopathic Medicine
Ocular tremor, also ocular microtremor, type of eye tremor
Orofacial Myofunctional Therapy, most commonly used to retrain oral rest posture, swallowing patterns, and speech
Other
Outright Monetary Transactions, which denotes the European Central Bank's purchases of bonds issued by Eurozone member-states
O-methyltransferase, type of methyltransferase enzyme transferring a methyl group on a molecule |
https://en.wikipedia.org/wiki/Charles%20Geschke | Charles Matthew "Chuck" Geschke (September 11, 1939 – April 16, 2021) was an American businessman and computer scientist best known for founding the graphics and publishing software company Adobe Inc. with John Warnock in 1982, with whom he also co-created the PDF document format.
Early life and education
Charles Matthew Geschke was born in Cleveland, Ohio, on September 11, 1939. He attended Saint Ignatius High School.
Geschke earned an AB in classics in 1962 and an MS in mathematics in 1963, both from Xavier University. He taught mathematics at John Carroll University from 1963 to 1968. In 1972, he completed his PhD studies in computer science at Carnegie Mellon University under the advice of William Wulf. He was a co-author of Wulf's 1975 book The Design of an Optimizing Compiler.
Career
Geschke started working at Xerox's Palo Alto Research Center (PARC) in October 1972. His first project was to build a mainframe computer. Afterward, he worked on programming languages and developed tools that were used to build the Xerox Star workstation.
In 1978, Geschke started the Imaging Sciences Laboratory at PARC, and conducted research in the areas of graphics, optics, and image processing. He hired John Warnock, and together they developed Interpress, a page description language (PDL) that could describe forms as complex as typefaces. Unable to convince Xerox management of the commercial value of Interpress, the two left Xerox to start their own company.
Geschke’s interviews are often featured in documentary films produced by the Silicon Valley Historical Association, including the PBS Silicon Valley, a One Hundred Year Renaissance, narrated by Walter Cronkite (1998)
Adobe
Geschke and Warnock founded Adobe in Warnock's garage in 1982, naming the company after the Adobe Creek that ran behind Warnock's home. Interpress eventually evolved into PostScript. Its use on Apple computers resulted in one of the first desktop publishing (DTP) systems which allowed users to compose documents on a personal computer and see them on screen exactly as they would appear in print, a process known as WYSIWYG, an acronym for What You See Is What You Get. Previously, graphic designers had been forced to view their work in text-only format while they worked, until they printed, or hit "print preview". Because of the high quality and speed at which printing and composing could be done in WYSIWYG, the innovation "spawned an entire industry" in modern printing and publishing.
From December 1986 until July 1994, Geschke was Adobe's Chief Operating Officer, and from April 1989 until April 2000 he was the company's president. Geschke retired as president of Adobe in 2000, shortly before his partner Warnock left as CEO. Geschke had also served as Co-Chairman of the Board of Adobe from September 1997 to 2017.
Adobe was mentioned in Forbes 400 Best Big Companies in 2009, and was ranked 1,069th on the Forbes Global 2000 list in 2010.
1992 kidnapping
On the morni |
https://en.wikipedia.org/wiki/John%20Warnock | John Edward Warnock (October 6, 1940 – August 19, 2023) was an American computer scientist, inventor, technology businessman, and philanthropist best known for co-founding Adobe Systems Inc., the graphics and publishing software company, with Charles Geschke in 1982. Warnock was President of Adobe for his first two years and chairman and CEO for his remaining sixteen years at the company. Although he retired as CEO in 2001, he continued to co-chair the Adobe Board of Directors with Geschke until 2017. Warnock pioneered the development of graphics, publishing, web and electronic document technologies that have revolutionized the field of publishing and visual communications.
Early life and education
Warnock was born on October 6, 1940, and raised in Salt Lake City, Utah. He failed mathematics in ninth grade before graduating from Olympus High School in 1958, however, Warnock went on to earn a Bachelor of Science degree in mathematics and philosophy, a Doctor of Philosophy degree in electrical engineering (computer science), and an honorary degree in science, all from the University of Utah. At the University of Utah he was a member of the Gamma Beta Chapter of the Beta Theta Pi fraternity. He also received an honorary degree from the American Film Institute. He lived in the San Francisco Bay Area with his wife Marva M. Warnock, marrying in 1965. Marva is a former partner and graphic designer at Marsh Design in Palo Alto, California, and is known not only for creating the iconic Adobe logo, but also as a designer for nonprofit organizations. They have three children.
Career
He is known as the creative driving force behind Adobe System's initial software products: PostScript, Adobe Illustrator, and the PDF, and he continued to be involved in new product development throughout his career. "The thing I really enjoy is the invention process. I enjoy figuring out how to do things other people don't know how to do."
Warnock's earliest publication and subject of his master's thesis was his 1964 proof of a theorem solving the Jacobson radical for row-finite matrices, which was originally posed by the American mathematician Nathan Jacobson in 1956.
In his 1969 doctoral thesis, Warnock invented the Warnock algorithm for hidden surface determination in computer graphics. It works by recursive subdivision of a scene until areas are obtained that are trivial to compute. It solves the problem of rendering a complicated image by avoiding the problem. If the scene is simple enough to compute then it is rendered; otherwise it is divided into smaller parts and the process is repeated. Warnock noted that for this work he received "the dubious distinction of having written the shortest doctoral thesis in University of Utah history". The Warnock algorithm solving the hidden surface problem enabled computers to render solid objects at a time when most computer renderings were only line drawings and was featured on the cover of Scientific American in 1970 with acc |
https://en.wikipedia.org/wiki/List%20of%20computers%20running%20CP/M | Many microcomputer makes and models could run some version or derivation of the CP/M disk operating system. Eight-bit computers running CP/M 80 were built around an Intel 8080/8085, Zilog Z80, or compatible CPU. CP/M 86 ran on the Intel 8086 and 8088. Some computers were suitable for CP/M as delivered. Others needed hardware modifications such as a memory expansion or modification, new boot ROMs, or the addition of a floppy disk drive. A few very popular home computers using processors not supported by CP/M had plug-in Z80 or compatible processors, allowing them to use CP/M and retaining the base machine's keyboard, peripherals, and sometimes video display and memory.
The following is an alphabetical list of some computers running CP/M.
A
Ai Electronics ABC-24 / ABC-26 (Japan, running Dosket, CP/M & M/PM)
Action Computer Enterprise ACE-1000
Action Computer Enterprise Discovery D-500 (CP/M-80 on each of up to 4 user processors, DPC/OS on service processor)
Action Computer Enterprise Discovery D-1600 (CP/M-80 on each of up to 15 user processors, DPC/OS on service processor)
Actrix Computer Corp. Actrix (Access Matrix)
Advanced Digital Corporation Super Six
Allen Bradley Advisor - Industrial Programmable controller graphical user interface (development mode only), fl. ca. 1985
Alspa
MITS Altair 8800
Altos 580
Amada Aries 222/245 CNC turret punch press
Amstrad CPC 464 (w/DDI-1 disk drive interface), 664, 6128, 6128Plus
Amstrad PCW 8256/8512/9512/9256/10
Amust Executive 816
Apple II (with a Z-80 card like the Microsoft SoftCard; on some clones a SoftCard equivalent was built into the mainboard)
Apple III (with a Z-80 card like the Apple SoftCard III)
Applied Technology MicroBee (56KB+ RAM models)
Aster CT-80
Atari 800 and XL/XE (with ATR8000 module, LDW Super 2000, CA-2001 or Indus GT disk drives expanded to 64k)
Atari ST - runs GEMDOS, which was DRI's more advanced replacement for CP/M for use with their GEM GUI
ATM-turbo - Soviet/Russian clone of ZX-Spectrum with extension graphic and 512/1024Kb RAM: CP/M 2.2 in ROM
AT&T 6300 with CPU 3 upgrade
AT&T 6300 PLUS
B
Basis 108
BBC Micro (with external Z80 module)
Beehive Topper II
BMC if-800
Bondwell II,12, 14
BT Merlin M2215 series based on ICL PC-2 (CP/M) (also ran MP/M II+)
BT Merlin M4000 series based on Logica Kennett (Concurrent CP/M-86)
C
Camputers Lynx (96k/128k models)
Casio FP1000 FL
CASU Super-C - Z80 based with a 21 slot S100 bus (Networkable with MP/M) - UK manufactured
CASU Mini-C - Z80 based with a 7 slot S100 bus and twin 8" floppy disk drives (Networkable with MP/M) - UK manufactured
Challenger III - Ohio Scientific OSI-CP/M
Cifer Systems 2684, 2887, 1887 - Melksham, England.
CIP04 - Romanian computer
CoBra - Romanian computer
Coleco Adam (with a CP/M digital data pack)
Comart Communicator (CP/M-80), C-Frame, K-Frame, Workstation and Quad (Concurrent CP/M-86)
Commodore 64 (with Z80 plug-in cartridge)
Commodore 128 (using its internal Z80 proce |
https://en.wikipedia.org/wiki/Hellfire%20Caves | The Hellfire Caves (also known as the West Wycombe Caves) are a network of man-made chalk and flint caverns which extend 260m underground. They are situated above the village of West Wycombe, at the southern edge of the Chiltern Hills near High Wycombe in Buckinghamshire, Southeast England.
They were excavated between 1748 and 1752 for Francis Dashwood, 11th Baron le Despencer (2nd Baronet), founder of the Society of Dilettanti and co-founder of the Hellfire Club, whose meetings were held in the caves. The caves have been operating as a tourist attraction since 1863.
Location and layout
The caves run into the hillside above West Wycombe village and directly beneath St Lawrence's Church and Mausoleum (which were also constructed by Sir Francis Dashwood around the same time the caves were excavated). West Wycombe Park, ancestral seat of the Dashwood family and also a National Trust property, lies directly across the valley. This area can be viewed directly from West Wycombe House.
The unusual design of the caves was much inspired by Sir Francis Dashwood's visits to Italy, Greece, Turkey, Syria and other areas of the Ottoman Empire during his Grand Tour. The caves extend underground, with the individual caves or "chambers" connected by a series of long, narrow tunnels and passageways.
A route through the underground chambers proceeds, from the Entrance Hall, to the Steward's Chamber and Whitehead's Cave, through Lord Sandwich's Circle (named after John Montagu, 4th Earl of Sandwich), Franklin's Cave (named after Benjamin Franklin, a friend of Dashwood who visited West Wycombe), the Banqueting Hall (allegedly the largest man-made chalk cavern in the world), the Triangle, to the Miner's Cave; and finally, across a subterranean river named the Styx, lies the final cave, the Inner Temple, where the meetings of the Hellfire Club were held, and which is said to lie directly beneath the church on top of West Wycombe hill. In Greek mythology, the River Styx separated the mortal world from Hades, and the subterranean position of the Inner Temple directly beneath St Lawrence's Church was supposed to signify Heaven and Hell.
History
Alteration and extension
A chalk mine of supposedly ancient origin is believed to have existed above West Wycombe for centuries.
During the late 1740s, to try to combat local poverty, Sir Francis Dashwood commissioned an ambitious project to supply chalk for a straight three mile (5 km) road between West Wycombe and High Wycombe (then on the busy London-Oxford road, now the A40). Local farm workers, impoverished by a succession of droughts and failed harvests, were employed here.
Hellfire Club
Members of a club founded by Sir Francis Dashwood included various politically and socially important 18th-century figures such as William Hogarth, John Wilkes, Thomas Potter and John Montagu, 4th Earl of Sandwich. Though not believed to have been a member, Benjamin Franklin was a close friend of Dashwood who visited the cave |
https://en.wikipedia.org/wiki/Raster | Raster may refer to:
Raster graphics, graphical techniques using arrays of pixel values
Raster graphics editor, a computer program
Raster scan, the pattern of image readout, transmission, storage, and reconstruction in television and computer images
Rasterisation, or rasterization, conversion of a vector image to a raster image
Raster image processor, or RIP, a component of a printing system that performs rasterisation
Raster interrupt, a computer interrupt signal
Raster to vector, an image conversion process
Raster bar, an effect used in computer demos
Raster-Noton, a record label
Rastrum, a device used in medieval music manuscripts to draw staff lines
Raster Document Object, a file format
People
Christian Raster, statesman in Anhalt-Dessau
Hermann Raster (1827–1891), German Forty-Eighter |
https://en.wikipedia.org/wiki/FITS | Flexible Image Transport System (FITS) is an open standard defining a digital file format useful for storage, transmission and processing of data: formatted as multi-dimensional arrays (for example a 2D image), or tables. FITS is the most commonly used digital file format in astronomy. The FITS standard was designed specifically for astronomical data, and includes provisions such as describing photometric and spatial calibration information, together with image origin metadata.
The FITS format was first standardized in 1981; it has evolved gradually since then, and the most recent version (4.0) was standardized in 2016. FITS was designed with an eye towards long-term archival storage, and the maxim once FITS, always FITS represents the requirement that developments to the format must be backward compatible.
Image metadata is stored in a human-readable ASCII header. The information in this header is designed to calculate the byte offset of some information in the subsequent data unit to support direct access to the data cells. Each FITS file consists of one or more headers containing ASCII card images that carry keyword/value pairs, interleaved between data blocks. The keyword/value pairs provide information such as size, origin, coordinates, binary data format, free-form comments, history of the data, and anything else the creator desires: while many keywords are reserved for FITS use, the standard allows arbitrary use of the rest of the name-space.
FITS is also often used to store non-image data, such as spectra, photon lists, data cubes, or structured data such as multi-table databases. A FITS file may contain several extensions, and each of these may contain a data object. For example, it is possible to store x-ray and infrared exposures in the same file.
Images
The earliest and still most commonly used type of FITS data is an image header/data block. The term 'image' is somewhat loosely applied, as the format supports data arrays of arbitrary dimension—normal image data are usually 2-D or 3-D, with the third dimension representing for example time or the color plane. The data themselves may be in one of several integer and floating-point formats, specified in the header.
FITS image headers can contain information about one or more scientific coordinate systems that are overlaid on the image itself. Images contain an implicit Cartesian coordinate system that describes the location of each pixel in the image, but scientific uses usually require working in 'world' coordinates, for example the celestial coordinate system. As FITS has been generalized from its original form, the world coordinate system (WCS) specifications have become more and more sophisticated: early FITS images allowed a simple scaling factor to represent the size of the pixels; but recent versions of the standard permit multiple nonlinear coordinate systems, representing arbitrary distortions of the image. The WCS standard includes many different spherical projections |
https://en.wikipedia.org/wiki/Quotient%20of%20a%20formal%20language | In mathematics and computer science, the right quotient (or simply quotient) of a language with respect to language is the language consisting of strings w such that wx is in for some string x in Formally:
In other words, we take all the strings in that have a suffix in , and remove this suffix.
Similarly, the left quotient of with respect to is the language consisting of strings w such that xw is in for some string x in . Formally:
In other words, we take all the strings in that have a prefix in , and remove this prefix.
Note that the operands of are in reverse order: the first operand is and is second.
Example
Consider
and
Now, if we insert a divider into an element of , the part on the right is in only if the divider is placed adjacent to a b (in which case i ≤ n and j = n) or adjacent to a c (in which case i = 0 and j ≤ n). The part on the left, therefore, will be either or ; and can be written as
Properties
Some common closure properties of the quotient operation include:
The quotient of a regular language with any other language is regular.
The quotient of a context free language with a regular language is context free.
The quotient of two context free languages can be any recursively enumerable language.
The quotient of two recursively enumerable languages is recursively enumerable.
These closure properties hold for both left and right quotients.
See also
Brzozowski derivative
References
Formal languages |
https://en.wikipedia.org/wiki/Underclocking | Underclocking, also known as downclocking, is modifying a computer or electronic circuit's timing settings to run at a lower clock rate than is specified. Underclocking is used to reduce a computer's power consumption, increase battery life, reduce heat emission, and it may also increase the system's stability, lifespan/reliability and compatibility. Underclocking may be implemented by the factory, but many computers and components may be underclocked by the end user.
Types
CPU underclocking
For microprocessors, the purpose is generally to decrease the need for heat dissipation devices or decrease the electrical power consumption. This can provide increased system stability in high-heat environments, or can allow a system to run with a lower airflow (and therefore quieter) cooling fan or without one at all. For example, a Pentium 4 processor normally clocked at 3.4 GHz can be "underclocked" to 2 GHz and can then be safely run with reduced fan speeds. This invariably comes at the expense of some system performance. However, the proportional performance reduction is usually less than the proportional reduction in clock speed because performance is often limited by other bottlenecks: the hard disk, GPU, disk controller, Internet, network, etc. Underclocking refers to alterations of the timing of a synchronous circuit in order to lower a device's energy needs. Deliberate underclocking involves limiting a processor's speed, which may affect the speed of operations, but may or may not make a device noticeably less able, depending on other hardware and desired use.
Many computers and other devices allow for underclocking. Manufacturers add underclocking options for many reasons. Underclocking can help with excessive heat buildup, because lower performance will not generate as much heat inside the device. It can also lower the amount of energy needed to run the device. Laptop computers and other battery-operated devices often have underclocking settings, so that batteries can last longer without being charged.
In addition to providing underclocking features, manufacturers can choose to limit the capability of a machine in order to make it more efficient. Reduced instruction set computer (RISC) models can help makers build devices that work on less power.
Graphics cards
Underclocking can also be performed on graphics card processor's GPUs, usually with the aim of reducing heat output. For instance, it is possible to set a GPU to run at lower clock rates when performing everyday tasks (e.g. internet browsing and word processing), thus allowing the card to operate at lower temperature and thus lower, quieter fan speeds. The GPU can then be overclocked for more graphically intense applications, such as games. Underclocking a GPU will reduce performance, but this decrease will probably not be noticeable except in graphically intensive applications.
Memory underclocking
Newer and faster RAM may be underclocked to match older systems as an inexpensive way |
https://en.wikipedia.org/wiki/EDGAR | EDGAR, the Electronic Data Gathering, Analysis, and Retrieval is an internal database system that performs automated collection, validation, indexing, acceptance, and forwarding of submissions by companies and others who are required by law to file forms with the U.S. Securities and Exchange Commission (the "SEC"). The database contains a wealth of information about the Commission and the securities industry which is freely available to the public via the Internet.
In September 2017, SEC Chairman Clayton revealed the database had been hacked and that companies' data may have been used by criminals for insider trading.
Filings
Not all SEC filings by public companies are available on EDGAR. Development began in 1993, and companies were phased in to EDGAR filing over a three-year period, ending 6 May 1996. As of that date, all public domestic companies were required to submit their filings via EDGAR, except for hardcopy paper filings, which were allowed under a hardship exemption. Third-party filings with respect to these companies, such as tender offers and Schedule 13D filings, are also filed via EDGAR.
The vast majority of documents are now filed electronically, with over 3,000 filings per day.
As of 4 November 2002, the SEC required all foreign companies and foreign governments to file their documents via EDGAR. Prior to that time, electronic filing by foreign companies also was voluntary.
Actual annual reports to shareholders (except in the case of mutual fund companies) need not be submitted on EDGAR, although some companies do so voluntarily. However, the annual report on Form 10-K is required to be filed on EDGAR. As of March 31, 2018, there are over 12 million filings filed to SEC EDGAR.
See also
Securities and Exchange Commission
Central Index Key
Electronic Municipal Market Access system (EMMA), providing disclosure information for the municipal securities market
Form N-1A
List of company registers
Other countries' equivalents to EDGAR
Federal Public Service Economy (Belgium)
SEDAR, Canada
Central Business Register (Denmark)
Companies Registration Office (Ireland)
Kamer van Koophandel, Netherlands
Brønnøysund Register Centre, Norway
Comisión Nacional del Mercado de Valores, Spain
Companies House, United Kingdom
Securities and Exchange Board of India, India
FinancialReports, Europe
References
External links
U.S. Securities and Exchange Commission
Government databases in the United States |
https://en.wikipedia.org/wiki/Visual%20Basic%20%28.NET%29 | Visual Basic (VB), originally called Visual Basic .NET (VB.NET), is a multi-paradigm, object-oriented programming language, implemented on .NET, Mono, and the .NET Framework. Microsoft launched VB.NET in 2002 as the successor to its original Visual Basic language, the last version of which was Visual Basic 6.0. Although the ".NET" portion of the name was dropped in 2005, this article uses "Visual Basic [.NET]" to refer to all Visual Basic languages released since 2002, in order to distinguish between them and the classic Visual Basic. Along with C# and F#, it is one of the three main languages targeting the .NET ecosystem. Microsoft updated its VB language strategy on 6 February 2023, stating that VB is a stable language now and Microsoft will keep maintaining it.
Microsoft's integrated development environment (IDE) for developing in Visual Basic is Visual Studio. Most Visual Studio editions are commercial; the only exceptions are Visual Studio Express and Visual Studio Community, which are freeware. In addition, the .NET Framework SDK includes a freeware command-line compiler called vbc.exe. Mono also includes a command-line VB.NET compiler.
Visual Basic is often used in conjunction with the Windows Forms GUI library to make desktop apps for Windows. Programming for Windows Forms with Visual Basic involves dragging and dropping controls on a form using a GUI designer and writing corresponding code for each control.
Use in making GUI programs
The Windows Forms library is most commonly used to create GUI interfaces in Visual Basic. All visual elements in the Windows Forms class library derive from the Control class. This provides the minimal functionality of a user interface element such as location, size, color, font, text, as well as common events like click and drag/drop. The Control class also has docking support to let a control rearrange its position under its parent.
Forms are typically designed in the Visual Studio IDE. In Visual Studio, forms are created using drag-and-drop techniques. A tool is used to place controls (e.g., text boxes, buttons, etc.) on the form (window). Controls have attributes and event handlers associated with them. Default values are provided when the control is created, but may be changed by the programmer. Many attribute values can be modified during run time based on user actions or changes in the environment, providing a dynamic application. For example, code can be inserted into the form resize event handler to reposition a control so that it remains centered on the form, expands to fill up the form, etc. By inserting code into the event handler for a keypress in a text box, the program can automatically translate the case of the text being entered, or even prevent certain characters from being inserted.
Syntax
Visual Basic uses statements to specify actions. The most common statement is an expression statement, consisting of an expression to be evaluated, on a single line. As part of that evaluati |
https://en.wikipedia.org/wiki/Nand | Nand or NAND may refer to:
Computing
Logical NAND or nand, a binary operation in logic (Not AND)
NAND gate, an electronic gate that implements a logical NAND
NAND logic, methods of building other logic gates using just NAND gates
NAND flash memory, a type of non-volatile computer memory
People
Nand Kishore (cricketer, born 1970), Indian former cricketer
Nand Kishore Garg (born 1949), senior social worker
Nand Gopal Gupta (born 1974), former Minister of Homeopathy in the Government of Uttar Pradesh
Nainendra Nand, Solicitor-General of Fiji from 1997 to 2006
Nand Kumar Patel (1953–2013), Indian National Congress politician from the Chhattisgarh
Nand Singh (1914–1947), Indian recipient of the Victoria Cross
Lisa Francesca Nand (born 1974), journalist
Nand Lal Noorpuri (died 1966), Punjabi poet, writer and lyricist
Other uses
Nand Dam, the Lower Wunna Dam over the Nand river
Nanda Baba or Nand, a figure in Hindu mythology
Nand (TV series), a Pakistani TV series produced by ARY Digital
See also
Nanda (disambiguation) |
https://en.wikipedia.org/wiki/Open%20Firmware | Open Firmware is a standard defining the interfaces of a computer firmware system, formerly endorsed by the Institute of Electrical and Electronics Engineers (IEEE). It originated at Sun Microsystems where it was known as OpenBoot, and has been used by multiple vendors including Sun, Apple, IBM and ARM.
Open Firmware allows a system to load platform-independent drivers directly from a PCI device, improving compatibility.
Open Firmware may be accessed through its command line interface, which uses the Forth programming language.
History
Open Firmware was described by IEEE standard as IEEE 1275-1994. This standard was not reaffirmed by the Open Firmware Working Group (OFWG) since 1998, and was therefore officially withdrawn by IEEE in May 2005.
Features
Open Firmware defines a standard way to describe the hardware configuration of a system, called the device tree. This helps the operating system to better understand the configuration of the host computer, relying less on user configuration and hardware polling. For example, Open Firmware is essential for reliably identifying slave I2C devices like temperature sensors for hardware monitoring, whereas the alternative solution of performing a blind probe of the I2C bus, as has to be done by software like lm_sensors on generic hardware, is known to result in serious hardware issues under certain circumstances.
Open Firmware Forth Code may be compiled into FCode, a bytecode which is independent of instruction set architecture. A PCI card may include a program, compiled to FCode, which runs on any Open Firmware system. In this way, it can provide boot-time diagnostics, configuration code, and device drivers. FCode is also very compact, so that a disk driver may require only one or two kilobytes. Therefore, many of the same I/O cards can be used on Sun systems and Macintoshes that used Open Firmware. FCode implements ANS Forth and a subset of the Open Firmware library.
Being based upon an interactive programming language, Open Firmware can be used to efficiently test and bring up new hardware. It allows drivers to be written and tested interactively. Operational video and mouse drivers are the only prerequisite for a graphical interface suitable for end-user diagnostics. Apple shipped such a diagnostic "operating system" in many Power Macintoshes. Sun also shipped an FCode-based diagnostic tool suite called OpenBoot Diagnostics (OBDiag) used by customer service support and hardware manufacturing teams
Implementations and licensing
Several commercial implementations of Open Firmware have been released to the Open Source community since 2006, including Sun OpenBoot, Firmworks OpenFirmware and Codegen SmartFirmware. The source code is available from the OpenBIOS project. Sun's implementation is available under a BSD license.
See also
References
External links
OPEN FIRMWARE HOME PAGE (via Internet Archive)
Sun's OpenBoot 2.x command reference manual (Revision A, November 1995)
Sun's SPAR |
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