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Unbounded Nondeterminism
In computer science, unbounded nondeterminism or unbounded indeterminacy refers to a behavior in concurrency (multiple tasks running at once) where a process may face unpredictable delays due to competition for shared resources—such as a printer or memory—or have infinitely many options to choose from at a given point. While these delays or choices can be arbitrarily large, the process is typically guaranteed to complete eventually under certain conditions (e.g., fairness in resource allocation). This concept, explored in abstract models rather than practical systems, became significant in developing mathematical descriptions of such systems (denotational semantics) and later contributed to research on advanced computing theories (hypercomputation). Fairness Unbounded nondeterminism is often discussed alongside the concept of ''fairness''. In this context, fairness means that if a system keeps returning to a certain state forever, it must eventually try every possible next s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Science
Computer science is the study of computation, information, and automation. Computer science spans Theoretical computer science, theoretical disciplines (such as algorithms, theory of computation, and information theory) to Applied science, applied disciplines (including the design and implementation of Computer architecture, hardware and Software engineering, software). Algorithms and data structures are central to computer science. The theory of computation concerns abstract models of computation and general classes of computational problem, problems that can be solved using them. The fields of cryptography and computer security involve studying the means for secure communication and preventing security vulnerabilities. Computer graphics (computer science), Computer graphics and computational geometry address the generation of images. Programming language theory considers different ways to describe computational processes, and database theory concerns the management of re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Halting Problem
In computability theory (computer science), computability theory, the halting problem is the problem of determining, from a description of an arbitrary computer program and an input, whether the program will finish running, or continue to run forever. The halting problem is ''Undecidable problem, undecidable'', meaning that no general algorithm exists that solves the halting problem for all possible program–input pairs. The problem comes up often in discussions of computability since it demonstrates that some functions are mathematically Definable set, definable but not Computable function, computable. A key part of the formal statement of the problem is a mathematical definition of a computer and program, usually via a Turing machine. The proof then shows, for any program that might determine whether programs halt, that a "pathological" program exists for which makes an incorrect determination. Specifically, is the program that, when called with some input, passes its own s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Server (computing)
A server is a computer that provides information to other computers called " clients" on a computer network. This architecture is called the client–server model. Servers can provide various functionalities, often called "services", such as sharing data or resources among multiple clients or performing computations for a client. A single server can serve multiple clients, and a single client can use multiple servers. A client process may run on the same device or may connect over a network to a server on a different device. Typical servers are database servers, file servers, mail servers, print servers, web servers, game servers, and application servers. Client–server systems are usually most frequently implemented by (and often identified with) the request–response model: a client sends a request to the server, which performs some action and sends a response back to the client, typically with a result or acknowledgment. Designating a computer as "server-class hardwa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Link
A data link is a means of telecommunications link, connecting one location to another for the purpose of transmitting and receiving digital information (data communication). It can also refer to a set of electronics assemblies, consisting of a transmitter and a receiver (two pieces of data terminal equipment) and the interconnecting data telecommunication circuit. These are governed by a link protocol enabling digital data to be transferred from a data source to a data sink. Types There are at least three types of basic data-link configurations that can be conceived of and used: * Simplex communications, most commonly meaning all communications in one direction only. * Half-duplex communications, meaning communications in both directions, but not both ways simultaneously. * Duplex (telecommunications), Duplex communications, communications in both directions simultaneously. Aviation In civil aviation, a data-link system (known as Controller Pilot Data Link Communications) is use ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electronic Mail
Electronic mail (usually shortened to email; alternatively hyphenated e-mail) is a method of transmitting and receiving Digital media, digital messages using electronics, electronic devices over a computer network. It was conceived in the late–20th century as the digital version of, or counterpart to, mail (hence ''wikt:e-#Etymology 2, e- + mail''). Email is a ubiquitous and very widely used communication medium; in current use, an email address is often treated as a basic and necessary part of many processes in business, commerce, government, education, entertainment, and other spheres of daily life in most countries. Email operates across computer networks, primarily the Internet access, Internet, and also local area networks. Today's email systems are based on a store-and-forward model. Email Server (computing), servers accept, forward, deliver, and store messages. Neither the users nor their computers are required to be online simultaneously; they need to connect, ty ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metastability In Electronics
In electronics, metastability is the ability of a digital electronic system to persist for an unbounded time in an unstable equilibrium or metastable state. In digital logic circuits, a digital signal is required to be within certain voltage or current limits to represent a '0' or '1' logic level for correct circuit operation; if the signal is within a forbidden intermediate range it may cause faulty behavior in logic gates the signal is applied to. In metastable states, the circuit may be unable to settle into a stable '0' or '1' logic level within the time required for proper circuit operation. As a result, the circuit can act in unpredictable ways, and may lead to a system failure, sometimes referred to as a "glitch". Metastability is an instance of the Buridan's ass paradox. Metastable states are inherent features of asynchronous digital systems, and of systems with more than one independent clock domain. In self-timed asynchronous systems, arbiters are designed to al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arbiter (electronics)
Arbiters are electronic devices that allocate access to shared resources. Bus arbiter There are multiple ways to perform a computer bus arbitration, with the most popular varieties being: * ''dynamic centralized parallel'' where one central arbiter is used for all masters as discussed in this article; * ''centralized serial'' (or "daisy chain") where, upon accessing the bus, the active master passes the opportunity to the next one. In essence, each connected master contains its own arbiter; * ''distributed arbitration by self-selection'' ( distributed bus arbitration) where the access is self-granted based on the decision made locally by using information from other masters; * ''distributed arbitration by collision detection'' where each master tries to access the bus on its own, but detects conflicts and retries the failed operations. A bus arbiter is a device used in a multi-master bus system to decide which bus master will be allowed to control the bus for each bu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Indeterminacy In Concurrent Computation
Indeterminacy in concurrent computation is concerned with the effects of indeterminacy in concurrent computation. Computation is an area in which indeterminacy is becoming increasingly important because of the massive increase in concurrency due to networking and the advent of many-core computer architectures. These computer systems make use of arbiters which gives rise to indeterminacy. A supposed limitation of logic programming Patrick Hayes 973argued that the "usual sharp distinction that is made between the processes of computation and deduction, is misleading". Robert Kowalski developed the thesis that ''computation could be subsumed by deduction'' and quoted with approval "Computation is controlled deduction." which he attributed to Hayes in his 1988 paper on the early history of Prolog. Contrary to Kowalski and Hayes, Carl Hewitt claimed that logical deduction was incapable of carrying out concurrent computation in open systems. Hewitt 985and Agha 991 and other publis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Recursion (computer Science)
In computer science, recursion is a method of solving a computational problem where the solution depends on solutions to smaller instances of the same problem. Recursion solves such recursion, recursive problems by using function (computer science), functions that call themselves from within their own code. The approach can be applied to many types of problems, and recursion is one of the central ideas of computer science. Most computer programming languages support recursion by allowing a function to call itself from within its own code. Some functional programming languages (for instance, Clojure) do not define any looping constructs but rely solely on recursion to repeatedly call code. It is proved in computability theory that these recursive-only languages are Turing complete; this means that they are as powerful (they can be used to solve the same problems) as imperative languages based on control structures such as and . Repeatedly calling a function from within itse ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Actor Model
The actor model in computer science is a mathematical model of concurrent computation that treats an ''actor'' as the basic building block of concurrent computation. In response to a message it receives, an actor can: make local decisions, create more actors, send more messages, and determine how to respond to the next message received. Actors may modify their own private state, but can only affect each other indirectly through messaging (removing the need for lock-based synchronization). The actor model originated in 1973. It has been used both as a framework for a theoretical understanding of computation and as the theoretical basis for several practical implementations of concurrent systems. The relationship of the model to other work is discussed in actor model and process calculi. History According to Carl Hewitt, unlike previous models of computation, the actor model was inspired by physics, including general relativity and quantum mechanics. It was also influenced ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carl Hewitt
Carl Eddie Hewitt (; 1944 – 7 December 2022)''Carl Hewitt'' Stanford. 2022. was an American computer scientist who designed the Planner programming language for Carl Hewitt ''PLANNER: A Language for Proving Theorems in Robots'' IJCAI. 1969. and the |
