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Page Replacement Algorithm
In a computer operating system that uses paging for virtual memory management, page replacement algorithms decide which memory pages to page out, sometimes called swap out, or write to disk, when a page of memory needs to be allocated. Page replacement happens when a requested page is not in memory (page fault) and a free page cannot be used to satisfy the allocation, either because there are none, or because the number of free pages is lower than some threshold. When the page that was selected for replacement and paged out is referenced again it has to be paged in (read in from disk), and this involves waiting for I/O completion. This determines the ''quality'' of the page replacement algorithm: the less time waiting for page-ins, the better the algorithm. A page replacement algorithm looks at the limited information about accesses to the pages provided by hardware, and tries to guess which pages should be replaced to minimize the total number of page misses, while balancing thi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer
A computer is a machine that can be Computer programming, programmed to automatically Execution (computing), carry out sequences of arithmetic or logical operations (''computation''). Modern digital electronic computers can perform generic sets of operations known as Computer program, ''programs'', which enable computers to perform a wide range of tasks. The term computer system may refer to a nominally complete computer that includes the Computer hardware, hardware, operating system, software, and peripheral equipment needed and used for full operation; or to a group of computers that are linked and function together, such as a computer network or computer cluster. A broad range of Programmable logic controller, industrial and Consumer electronics, consumer products use computers as control systems, including simple special-purpose devices like microwave ovens and remote controls, and factory devices like industrial robots. Computers are at the core of general-purpose devices ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Journaling File System
A journaling file system is a file system that keeps track of changes not yet committed to the file system's main part by recording the goal of such changes in a data structure known as a " journal", which is usually a circular log. In the event of a system crash or power failure, such file systems can be brought back online more quickly with a lower likelihood of becoming corrupted. Depending on the actual implementation, a journaling file system may only keep track of stored metadata, resulting in improved performance at the expense of increased possibility for data corruption. Alternatively, a journaling file system may track both stored data and related metadata, while some implementations allow selectable behavior in this regard. History In 1990 IBM introduced JFS in AIX 3.1 as one of the first UNIX commercial filesystems that implemented journaling. The next year the idea was popularized in a widely cited paper on log-structured file systems. This was subsequentl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fernando J
Fernando is a Spanish and Portuguese given name and a surname common in Spain, Portugal, Italy, France, Switzerland, and former Spanish or Portuguese colonies in Latin America, Africa and Asia (like the Philippines, India, and Sri Lanka). It is equivalent to the Germanic given name Ferdinand, with an original meaning of "adventurous, bold journey". Given name * Fernando el Católico, king of Aragon A * Fernando Acevedo, Peruvian track and field athlete * Fernando Aceves Humana, Mexican painter * Fernando Alegría, Chilean poet and writer * Fernando Alonso, Spanish Formula One driver * Fernando Amorebieta, Venezuelan footballer * Fernando Amorsolo, Filipino painter * Fernando Antogna, Argentine track and road cyclist * Fernando de Araújo (other), multiple people B * Fernando Balzaretti (1946–1998), Mexican actor * Fernando Barrichello (born 2005), Brazilian racing driver * Fernando Baudrit Solera, Costa Rican president of the supreme court * Fernando Boter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
OpenVMS
OpenVMS, often referred to as just VMS, is a multi-user, multiprocessing and virtual memory-based operating system. It is designed to support time-sharing, batch processing, transaction processing and workstation applications. Customers using OpenVMS include banks and financial services, hospitals and healthcare, telecommunications operators, network information services, and industrial manufacturers. During the 1990s and 2000s, there were approximately half a million VMS systems in operation worldwide. It was first announced by Digital Equipment Corporation (DEC) as VAX/VMS (''Virtual Address eXtension/Virtual Memory System'') alongside the VAX-11/780 minicomputer in 1977. OpenVMS has subsequently been ported to run on DEC Alpha systems, the Itanium-based HPE Integrity Servers, and select x86-64 hardware and hypervisors. Since 2014, OpenVMS is developed and supported by VMS Software Inc. (VSI). OpenVMS offers high availability through computer cluster, clustering—the ability t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amortized Analysis
In computer science, amortized analysis is a method for analyzing a given algorithm's complexity, or how much of a resource, especially time or memory, it takes to execute. The motivation for amortized analysis is that looking at the worst-case run time can be too pessimistic. Instead, amortized analysis averages the running times of operations in a sequence over that sequence. As a conclusion: "Amortized analysis is a useful tool that complements other techniques such as worst-case and average-case analysis." For a given operation of an algorithm, certain situations (e.g., input parametrizations or data structure contents) may imply a significant cost in resources, whereas other situations may not be as costly. The amortized analysis considers both the costly and less costly operations together over the whole sequence of operations. This may include accounting for different types of input, length of the input, and other factors that affect its performance. History Amortize ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Online Algorithm
In computer science, an online algorithm is one that can process its input piece-by-piece in a serial fashion, i.e., in the order that the input is fed to the algorithm, without having the entire input available from the start. In contrast, an offline algorithm is given the whole problem data from the beginning and is required to output an answer which solves the problem at hand. In operations research Operations research () (U.S. Air Force Specialty Code: Operations Analysis), often shortened to the initialism OR, is a branch of applied mathematics that deals with the development and application of analytical methods to improve management and ..., the area in which online algorithms are developed is called online optimization. As an example, consider the sorting algorithms selection sort and insertion sort: selection sort repeatedly selects the minimum element from the unsorted remainder and places it at the front, which requires access to the entire input; it is thus a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
László Bélády
László "Les" Bélády (April 29, 1928, in Budapest – November 6, 2021) was a Hungarian computer scientist notable for devising the Bélády's Min theoretical memory caching algorithm in 1966 while working at IBM Research. He also demonstrated the existence of a Bélády's anomaly. During the 1980s, he was the editor-in-chief of the IEEE Transactions on Software Engineering. Education Bélády earned B.S. in Mechanical Engineering, then an M.S. in Aeronautical Engineering at the Technical University of Budapest in 1950. Life and career He left Hungary after the Hungarian Revolution of 1956. Then he worked as a draftsman at Ford Motor Company in Cologne and as an aerodynamics engineer at Dassault in Paris. In 1961, he immigrated to the United States. In the 1960s and 1970s, he primarily lived in New York City with stints in California and England, where he joined International Business Machines and did early work in operating systems, virtual machine architectures, program ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clairvoyance
Clairvoyance (; ) is the claimed ability to acquire information that would be considered impossible to get through scientifically proven sensations, thus classified as extrasensory perception, or "sixth sense". Any person who is claimed to have such ability is said to be a clairvoyant () (). Claims for the existence of paranormal and psychic abilities such as clairvoyance have not been supported by scientific evidence.Robert Todd Carroll, Carroll, Robert Todd. (2003)"Clairvoyance" Retrieved 2014-04-30. Parapsychology explores this possibility, but the existence of the paranormal is not accepted by the scientific community. The scientific community widely considers parapsychology, including the study of clairvoyance, a pseudoscience. Usage Pertaining to the ability of clear-sightedness, clairvoyance refers to the paranormal ability to see persons and events that are distant in time or space. It can be divided into roughly three classes: precognition, the ability to perceive o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Full Duplex
A duplex communication system is a point-to-point system composed of two or more connected parties or devices that can communicate with one another in both directions. Duplex systems are employed in many communications networks, either to allow for simultaneous communication in both directions between two connected parties or to provide a reverse path for the monitoring and remote adjustment of equipment in the field. There are two types of duplex communication systems: full-duplex (FDX) and half-duplex (HDX). In a full-duplex system, both parties can communicate with each other simultaneously. An example of a full-duplex device is plain old telephone service; the parties at both ends of a call can speak and be heard by the other party simultaneously. The earphone reproduces the speech of the remote party as the microphone transmits the speech of the local party. There is a two-way communication channel between them, or more strictly speaking, there are two communication channel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Page Table
A page table is a data structure used by a virtual memory system in a computer to store mappings between virtual addresses and physical addresses. Virtual addresses are used by the program executed by the accessing process, while physical addresses are used by the hardware, or more specifically, by the random-access memory (RAM) subsystem. The page table is a key component of virtual address translation that is necessary to access data in memory. The page table is set up by the computer's operating system, and may be read and written during the virtual address translation process by the memory management unit or by low-level system software or firmware. Role of the page table In operating systems that use virtual memory, every process is given the impression that it is working with large, contiguous sections of memory. Physically, the memory of each process may be dispersed across different areas of physical memory, or may have been moved ( paged out) to secondary storage ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Memory Management (operating Systems)
In operating systems, memory management is the function responsible for managing the computer's primary memory. The memory management function keeps track of the status of each memory location, either ''allocated'' or ''free''. It determines how memory is allocated among competing processes, deciding which gets memory, when they receive it, and how much they are allowed. When memory is allocated it determines which memory locations will be assigned. It tracks when memory is freed or ''unallocated'' and updates the status. This is distinct from application memory management, which is how a process manages the memory assigned to it by the operating system. Memory management techniques Single contiguous allocation ''Single allocation'' is the simplest memory management technique. All the computer's memory, usually with the exception of a small portion reserved for the operating system, is available to a single application. MS-DOS is an example of a system that allocates memory ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
