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wiki | In computing, a directory structure is the way an operating system arranges files that are accessible to the user. Files are typically displayed in a hierarchical tree structure. |
wiki | Examples of this rule may be found in the structure of many file systems' directories (also known as folders): 0 – The topmost directory has zero parent directories; that is, there is no directory that contains the topmost directory. 1 – Each subdirectory has exactly one parent directory (not including shortcuts to the... |
wiki | In computing, a directory is a file system cataloging structure which contains references to other computer files, and possibly other directories. On many computers, directories are known as folders, or drawers, analogous to a workbench or the traditional office filing cabinet. The name derives from books like a teleph... |
wiki | The terms hold-in range, pull-in range (acquisition range), and lock-in range are widely used by engineers for the concepts of frequency deviation ranges within which phase-locked loop-based circuits can achieve lock under various additional conditions. |
wiki | 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 wi... |
wiki | Shrinking phase: locks are released and no locks are acquired.Two types of locks are used by the basic protocol: Shared and Exclusive locks. Refinements of the basic protocol may use more lock types. Using locks that block processes, 2PL may be subject to deadlocks that result from the mutual blocking of two or more tr... |
wiki | Privilege escalation to root permissions by exploiting Shell Injection vulnerabilities in a setuid root binary on UNIX, or Local System by exploiting a service on Microsoft Windows. Attacking web users with HTML/script injection (Cross-site scripting).In 2008, 5.66% of all vulnerabilities reported that year were classi... |
wiki | The interrupt priority level (IPL) is a part of the current system interrupt state, which indicates the interrupt requests that will currently be accepted. The IPL may be indicated in hardware by the registers in a programmable interrupt controller, or in software by a bitmask or integer value and source code of thread... |
wiki | The Native POSIX Thread Library (NPTL) is an implementation of the POSIX Threads specification for the Linux operating system. |
wiki | Other architectures have similar data structures, but may behave differently. Use of the IDT is triggered by three types of events: hardware interrupts, software interrupts, and processor exceptions, which together are referred to as interrupts. The IDT consists of 256 interrupt vectors–the first 32 (0–31 or 0x00–0x1F)... |
wiki | Interrupts are assigned a number between 0 to 255. The interrupt vectors for each interrupt number are stored in the lower 1024 bytes of main memory. For example, interrupt 0 is stored from 0000:0000 to 0000:0003, interrupt 1 from 0000:0004 to 0000:0007, and so on. |
wiki | Similarly, code shared by two processors accessing shared data should be reentrant. Often, subroutines accessible via the operating system kernel are not reentrant. Hence, interrupt service routines are limited in the actions they can perform; for instance, they are usually restricted from accessing the file system and... |
wiki | The limit is created by the 32-bit integer limit (2,147,483,647), which is the largest possible integer that can be represented by 32 binary digits. In a computer with a 32-bit architecture, the memory address stored in one of the CPU registers will be limited to this number, thus the number of possible memory location... |
wiki | In computer architecture, 32-bit computing refers to computer systems with a processor, memory, and other major system components that operate on data in 32-bit units. Compared to smaller bit widths, 32-bit computers can perform large calculations more efficiently and process more data per clock cycle. Typical 32-bit p... |
wiki | For example, computer processors are often designed to process data grouped into words of a given length of bits (8 bit, 16 bit, 32 bit, 64 bit, etc.). The bit-length of each word defines, for one thing, how many memory locations can be independently addressed by the processor. In cryptography, the key size of an algor... |
wiki | This attack works with file systems that have soft block size of 1024 or greater. At least ext2, ext3, reiserfs and minix have such property. |
wiki | However, its use on small removable media is not advised, as the file-system headers consume from 600 KB to 2 MB, rendering floppy disks virtually useless. Like its predecessor, OFS (Old Be File System, written by Benoit Schillings - formerly BFS), it includes support for extended file attributes (metadata), with index... |
wiki | A multiblock, 3 dimensional Q file begins with a single integer for the number of blocks M on its own line. The next M lines contain three integers for each of the blocks, which give the i, j, and k dimension sizes for each block. The M blocks are read in next. |
wiki | A race condition or race hazard is the condition of an electronics, software, or other system where the system's substantive behavior is dependent on the sequence or timing of other uncontrollable events. It becomes a bug when one or more of the possible behaviors is undesirable. The term race condition was already in ... |
wiki | High performance computing applications run on massively parallel supercomputers consist of concurrent programs designed using multi-threaded, multi-process models. The applications may consist of various constructs (threads, local processes, distributed processes, etc.) with varying degree of parallelism. Although hig... |
wiki | To avoid a race condition, every access to this global variable would have to be protected by a mutex. Alternatively, each thread might accumulate into a thread-local variable (that, by definition, cannot be read from or written to from other threads, implying that there can be no race conditions). Threads then only ha... |
wiki | A translation lookaside buffer (TLB) is a memory cache that stores the recent translations of virtual memory to physical memory. It is used to reduce the time taken to access a user memory location. It can be called an address-translation cache. It is a part of the chip's memory-management unit (MMU). |
wiki | If the requested address is not in the TLB, it is a miss, and the translation proceeds by looking up the page table in a process called a page walk. The page walk is time-consuming when compared to the processor speed, as it involves reading the contents of multiple memory locations and using them to compute the physic... |
wiki | A page table is the data structure used by a virtual memory system in a computer operating system to store the mapping 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, b... |
wiki | The task state segment (TSS) is a structure on x86-based computers which holds information about a task. It is used by the operating system kernel for task management. Specifically, the following information is stored in the TSS: Processor register state I/O port permissions Inner-level stack pointers Previous TSS link... |
wiki | In digital computers, an interrupt (sometimes referred to as a trap) is a request for the processor to interrupt currently executing code (when permitted), so that the event can be processed in a timely manner. If the request is accepted, the processor will suspend its current activities, save its state, and execute a ... |
wiki | An interruptible operating system is an operating system with ability to handle multiple interrupts concurrently, or in other words, which allow interrupts to be interrupted. Concurrent interrupt handling essentially mean concurrent execution of kernel code and hence induces the additional complexity of concurrency con... |
wiki | Instead of giving direct references to DOM objects, the host page typically gives references to wrappers that sanitize HTML, proxy URLs, and prevent redirecting the page; this allowed Caja to prevent certain phishing and cross-site scripting attacks, and prevent downloading malware. Also, since all rewritten programs r... |
wiki | Since the two windows may be handled by two different applications, these mechanisms require two different clients connected with the same X server to exchange data. The X Window System core protocol includes some requests and events that are specific to selection exchange, but the transfer is mainly done using event s... |
wiki | Next, the user touches the other device he or she wants to paste/pass the saved content into. Sparsh uses touch-based interactions as indications for what to copy and where to pass it. Technically, the actual transfer of media happens via the information cloud. |
wiki | In computing, a system call (commonly abbreviated to syscall) is the programmatic way in which a computer program requests a service from the operating system on which it is executed. This may include hardware-related services (for example, accessing a hard disk drive or accessing the device's camera), creation and exe... |
wiki | Java Optimized Processor (JOP) is a Java processor, an implementation of Java virtual machine (JVM) in hardware. JOP is free hardware under the GNU General Public License, version 3. The intention of JOP is to provide a small hardware JVM for embedded real-time systems. The main feature is the predictability of the exe... |
wiki | The Pick Operating System, also known as the Pick System or simply Pick, is a demand-paged, multi-user, virtual memory, time-sharing computer operating system based around a MultiValue database. Pick is used primarily for business data processing. It is named after one of its developers, Dick Pick.The term "Pick system... |
wiki | 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 o... |
wiki | Journaled File System (JFS) is a 64-bit journaling file system created by IBM. There are versions for AIX, OS/2, eComStation, ArcaOS and Linux operating systems. The latter is available as free software under the terms of the GNU General Public License (GPL). HP-UX has another, different filesystem named JFS that is ac... |
wiki | In file system area, intent log is used more often.Before performing an operation, a record of the intent to perform it is written, usually to some relatively permanent medium such as a hard disk drive. After the operation is performed, another record is written. Usually, an operation will change some data in a system. |
wiki | Most file systems are based on a block device, which is a level of abstraction for the hardware responsible for storing and retrieving specified blocks of data, though the block size in file systems may be a multiple of the physical block size. This leads to space inefficiency due to internal fragmentation, since file ... |
wiki | Some newer file systems, such as Btrfs and FreeBSD UFS2, attempt to solve this through techniques called block suballocation and tail merging. Other file systems such as ZFS support variable block sizes.Block storage is normally abstracted by a file system or database management system (DBMS) for use by applications an... |
wiki | This interface must provide sufficiently fast read operations with a random access pattern. The file system, if one is used, needs to expose appropriate mapping functions. The program must either be linked to be aware of the address the storage appears at in the system or be position-independent. The program must not m... |
wiki | A process can also receive capabilities via Unix sockets. These file descriptors not only control access to the file system, but also to other devices like the network sockets. Flags are also used to control more fine-grained access like reads and writes. |
wiki | Enforcing restrictions on file permissions can also close gaps in W^X enforcement caused by memory mapped files. Outright forbidding the usage of arbitrary native code can also mitigate kernel and CPU vulnerabilities not exposed via the existing code on the computer. A less intrusive approach is to lock a file for the ... |
wiki | It handles the rest of startup as well as memory, peripherals, and input/output (I/O) requests from software, translating them into data-processing instructions for the central processing unit. The critical code of the kernel is usually loaded into a separate area of memory, which is protected from access by applicatio... |
wiki | Processes can in some cases install a custom signal handler, allowing them to recover on their own, but otherwise the OS default signal handler is used, generally causing abnormal termination of the process (a program crash), and sometimes a core dump. Segmentation faults are a common class of error in programs written... |
wiki | In such cases, an NMI can execute an interrupt handler that transfers control to a special monitor program. From this program, a developer can inspect the machine's memory and examine the internal state of the program at the instant of its interruption. This also allows the debugging or diagnosing of computers which ap... |
wiki | In computing, a page fault (sometimes called PF or hard fault) is an exception that the memory management unit (MMU) raises when a process accesses a memory page without proper preparations. Accessing the page requires a mapping to be added to the process's virtual address space. Besides, the actual page contents may n... |
wiki | Modern block storage devices do not require interleaving. Data is now commonly stored as clusters (groups of sectors), and the data buffer is sufficiently large to allow all sectors in a block to be read at once without any delay between sectors. == References == |
wiki | Free-space bitmaps are one method used to track allocated sectors by some file systems. While the most simplistic design is highly inefficient, advanced or hybrid implementations of free-space bitmaps are used by some modern file systems. |
wiki | In some other instruction sets, such as the ARM architectures, SPARC, and OpenRISC, subroutine call instructions put the return address into a specific general-purpose register, so that register is designated by the instruction set architecture as the link register. In some others, such as PA-RISC, RISC-V, and the IBM ... |
wiki | In computer science, a call stack is a stack data structure that stores information about the active subroutines of a computer program. This kind of stack is also known as an execution stack, program stack, control stack, run-time stack, or machine stack, and is often shortened to just "the stack". Although maintenance... |
wiki | In computer operating system design, kernel preemption is a property possessed by some kernels (the cores of operating systems), in which the CPU can be interrupted in the middle of executing kernel code and assigned other tasks (from which it later returns to finish its kernel tasks). |
wiki | The kernel's interface is a low-level abstraction layer. When a process requests a service from the kernel, it must invoke a system call, usually through a wrapper function. |
wiki | In computing, Physical Address Extension (PAE), sometimes referred to as Page Address Extension, is a memory management feature for the x86 architecture. PAE was first introduced by Intel in the Pentium Pro, and later by AMD in the Athlon processor. It defines a page table hierarchy of three levels (instead of two), wi... |
wiki | A page address register (PAR) contains the physical addresses of pages currently held in the main memory of a computer system. PARs are used in order to avoid excessive use of an address table in some operating systems. A PAR may check a page's number against all entries in the PAR simultaneously, allowing it to retrie... |
wiki | The pages most frequently accessed at any point are called the working set, which may change over time. When the working set is not significantly greater than the system's total number of real storage page frames, virtual memory systems work most efficiently and an insignificant amount of computing is spent resolving p... |
wiki | Some operating systems may also classify some exceptions not related to access violations, such as illegal opcode exceptions, as general protection faults, even though they have nothing to do with memory protection. If a CPU detects a protection violation, it stops executing the code and sends a GPF interrupt. In most ... |
wiki | A single-core processor is a microprocessor with a single core on its die. It performs the fetch-decode-execute cycle once per clock-cycle, as it only runs on one thread. A computer using a single core CPU is generally slower than a multi-core system. |
wiki | A multi-core processor implements multiprocessing in a single physical package. Designers may couple cores in a multi-core device tightly or loosely. |
wiki | Some older legacy systems like those running antiquated operating systems (e.g. Windows 98) cannot gain any benefit from multi-core processors. Single core processors are also used in hobbyist computers like the Raspberry Pi and Single-board microcontrollers. The production of single-core desktop processors ended in 20... |
wiki | For each of C, E, and F, it is 20, 12, and 10 respectively. The lowest is F with 10. Since Activity A's duration is 20 which is higher than F's drag-plus-lag of 10, A's drag is 10. |
wiki | Activities A and E have nothing in parallel and therefore have drags of 10 days and 20 days respectively. Activities B and C are both parallel to F (float of 15) and H (float of 20). B has a duration of 20 and drag of 15 (equal to F's float), while C has a duration of only 5 days and thus drag of only 5. |
wiki | A CCS (centacall-second) is often used to describe 100 call-seconds, so 3600 call-seconds = 36 CCS = 1 call-hour. In a communication network, a trunk (link) can carry numerous concurrent calls by means of multiplexing. Hence a particular number of call-seconds can be carried in infinitely many ways as calls are establi... |
wiki | Systems Tool Kit (formerly Satellite Tool Kit), often referred to by its initials STK, is a multi-physics software application from Analytical Graphics, Inc. (an Ansys company) that enables engineers and scientists to perform complex analyses of ground, sea, air, and space platforms, and to share results in one integra... |
wiki | STK is free software, but a number of its classes, particularly some physical modelling algorithms, are covered by patents held by Stanford University and Yamaha.The STK is used widely in creating software synthesis applications. Versions of the STK instrument classes have been integrated into ChucK, Csound, Real-Time ... |
wiki | SIM Application Toolkit (STK) is a standard of the GSM system which enables the subscriber identity module (SIM card) to initiate actions which can be used for various value-added services. Similar standards exist for other network and card systems, with the USIM Application Toolkit (USAT) for USIMs used by newer-gener... |
wiki | This limitation is because with only one GB reserved for the kernel, there isn't enough memory for the page table entries to map more than 16 GB of memory. Additional restrictions on the maximum amount of memory addressable thorough AWE are imposed by the Windows licensing scheme. For example, Windows 2000 Advanced Ser... |
wiki | A page, memory page, or virtual page is a fixed-length contiguous block of virtual memory, described by a single entry in the page table. It is the smallest unit of data for memory management in a virtual memory operating system. Similarly, a page frame is the smallest fixed-length contiguous block of physical memory i... |
wiki | ("until completely extinguished, repeat the last third of Des — F once or twice. In no case, however, conclude to Des!") Presumably an expression of unrequited love (Santos 2014: 35). |
wiki | Subversive affirmation is not to be confused with transgression, parody, deception or masquerade. It does not emerge from a place of aggression or as what the French philosopher Michel Foucault defines as a counter-discourse. In this sense Léger compares over-identification to Lacan's Discourse of the Analyst, as oppos... |
wiki | In French grammar, verbs are a part of speech. Each verb lexeme has a collection of finite and non-finite forms in its conjugation scheme. Finite forms depend on grammatical tense and person/number. There are eight simple tense–aspect–mood forms, categorized into the indicative, subjunctive and imperative moods, with t... |
wiki | The genomic DNA of eukaryotes associates with histones to form chromatin. The level of chromatin compaction depends heavily on histone methylation and other post-translational modifications of histones. Histone methylation is a principal epigenetic modification of chromatin that determines gene expression, genomic stab... |
wiki | Histone-modifying enzymes are enzymes involved in the modification of histone substrates after protein translation and affect cellular processes including gene expression. To safely store the eukaryotic genome, DNA is wrapped around four core histone proteins (H3, H4, H2A, H2B), which then join to form nucleosomes. The... |
wiki | Histones may be chemically modified through the action of enzymes to regulate gene transcription. The most common modification are the methylation of arginine or lysine residues or the acetylation of lysine. Methylation can affect how other protein such as transcription factors interact with the nucleosomes. Lysine ace... |
wiki | Discourse on the Method of Rightly Conducting One's Reason and of Seeking Truth in the Sciences (French: Discours de la Méthode Pour bien conduire sa raison, et chercher la vérité dans les sciences) is a philosophical and autobiographical treatise published by René Descartes in 1637. It is best known as the source of t... |
wiki | Nietzschean affirmation (German: Bejahung) is a concept that has been scholarly identified in the philosophy of Friedrich Nietzsche. An example used to describe the concept is a fragment in Nietzsche's The Will to Power: Suppose that we said yes to a single moment, then we have not only said yes to ourselves, but to th... |
wiki | ∴ If p, then r.A mixed hypothetical syllogism consists of one conditional statement and one statement that expresses either affirmation or denial with either the antecedent or consequence of that conditional. Therefore, such a mixed hypothetical syllogism has four possible forms, of which two are valid, while the other... |
wiki | A nucleosome is the basic structural unit of DNA packaging in eukaryotes. The structure of a nucleosome consists of a segment of DNA wound around eight histone proteins and resembles thread wrapped around a spool. The nucleosome is the fundamental subunit of chromatin. Each nucleosome is composed of a little less than ... |
wiki | In biology, histones are highly basic proteins abundant in lysine and arginine residues that are found in eukaryotic cell nuclei. They act as spools around which DNA winds to create structural units called nucleosomes. Nucleosomes in turn are wrapped into 30-nanometer fibers that form tightly packed chromatin. |
wiki | Technically, a nucleosome is defined as the core particle plus one of these linker regions; however the word is often synonymous with the core particle. Genome-wide nucleosome positioning maps are now available for many model organisms and human cells.Linker histones such as H1 and its isoforms are involved in chromati... |
wiki | In queueing theory, a discipline within the mathematical theory of probability, the M/M/c queue (or Erlang–C model: 495 ) is a multi-server queueing model. In Kendall's notation it describes a system where arrivals form a single queue and are governed by a Poisson process, there are c servers, and job service times are... |
wiki | PolyQ is a biological database of polyglutamine repeats in disease and non-disease associated proteins. |
wiki | In queueing theory, a discipline within the mathematical theory of probability, an M/D/c queue represents the queue length in a system having c servers, where arrivals are determined by a Poisson process and job service times are fixed (deterministic). The model name is written in Kendall's notation. Agner Krarup Erlan... |
wiki | For subversive affirmation to be effective, its address must be anonymous rather than targeted. In contrast to film theories that give a specific gender identification to Lacan's notion of the gaze, subversive affirmation emphasizes the inconsistency of symbolic mandates and the fact that there is no Big Other. This is... |
wiki | Self-affirmation theory is a psychological theory that focuses on how individuals adapt to information or experiences that are threatening to their self-concept. Claude Steele originally popularized self-affirmation theory in the late 1980s, and it remains a well-studied theory in social psychological research.Self-aff... |
wiki | In enzymology, a L-fucose isomerase (EC 5.3.1.25) is an enzyme that catalyzes the chemical reaction L-fucose ⇌ {\displaystyle \rightleftharpoons } L-fuculoseHence, this enzyme has one substrate, L-fucose, and one product, L-fuculose. This enzyme belongs to the family of isomerases, specifically those intramolecular oxi... |
wiki | Peptide:N-glycosidase F, commonly referred to as PNGase F, is an amidase of the peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase class. PNGase F works by cleaving between the innermost GlcNAc and asparagine residues of high mannose, hybrid, and complex oligosaccharides from N-linked glycoproteins and glycopept... |
wiki | The enzyme α-L-fucosidase (EC 3.2.1.51) catalyzes the following chemical reaction: an α-L-fucoside + H2O ⇌ {\displaystyle \rightleftharpoons } L-fucose + an alcohol This enzyme belongs to the family of hydrolases, specifically those glycosidases that hydrolyse O- and S-glycosyl compounds. The systematic name of this en... |
wiki | Histone H3.1 is a protein in humans that is encoded by the H3C1 gene.Histones are basic nuclear proteins that are responsible for the nucleosome structure of the chromosomal fiber in eukaryotes. This structure consists of approximately 146 bp of DNA wrapped around a nucleosome, an octamer composed of pairs of each of t... |
wiki | Histone H1 is one of the five main histone protein families which are components of chromatin in eukaryotic cells. Though highly conserved, it is nevertheless the most variable histone in sequence across species. |
wiki | In molecular biology, the linker histone H1 is a protein family forming a critical component of eukaryotic chromatin. H1 histones bind to the linker DNA exiting from the nucleosome core particle, while the core histones (H2A, H2B, H3 and H4) form the octamer core of the nucleosome around which the DNA is wrapped.H1 for... |
wiki | These phosphorylations play important and well-characterized roles in signaling pathways and metabolism. However, other amino acids can also be phosphorylated post-translationally, including arginine, lysine, aspartic acid, glutamic acid and cysteine, and these phosphorylated amino acids have recently been identified t... |
wiki | Protein phosphorylation is a reversible post-translational modification of proteins in which an amino acid residue is phosphorylated by a protein kinase by the addition of a covalently bound phosphate group. Phosphorylation alters the structural conformation of a protein, causing it to become either activated or deacti... |
wiki | Autophosphorylation is a type of post-translational modification of proteins. It is generally defined as the phosphorylation of the kinase by itself. In eukaryotes, this process occurs by the addition of a phosphate group to serine, threonine or tyrosine residues within protein kinases, normally to regulate the catalyt... |
wiki | In addition to nucleosome wrapping, eukaryotic chromatin is further compacted by being folded into a series of more complex structures, eventually forming a chromosome. Each human cell contains about 30 million nucleosomes.Nucleosomes are thought to carry epigenetically inherited information in the form of covalent mod... |
wiki | They can cause replication fork stalling and are bypassed by translesion synthesis. In E. coli, adenine is preferentially inserted across from AP sites, known as the "A rule". The situation is more complex in higher eukaryotes, with different nucleotides showing a preference depending on the organism and experimental c... |
wiki | Escherichia coli (AIEC) NC101 is a mouse isolate, serotype O2:H6/41, that is pro-carcinogenic, adherent-invasive (AIEC), probiotic strain of Escherichia coli, a species of bacteria that thrives in the intestines of mammals. NC101 has also been identified as a nicotinic acid (NA) auxotroph, a pathobiont, which is an org... |
wiki | The genome sequences reveal much diversity in bacteria. Analysis of over 2000 Escherichia coli genomes reveals an E. coli core genome of about 3100 gene families and a total of about 89,000 different gene families. Genome sequences show that parasitic bacteria have 500–1200 genes, free-living bacteria have 1500–7500 ge... |
wiki | D-loop replication is a proposed process by which circular DNA like chloroplasts and mitochondria replicate their genetic material. An important component of understanding D-loop replication is that many chloroplasts and mitochondria have a single circular chromosome like bacteria instead of the linear chromosomes foun... |
wiki | The Mesodinium nuclear code (translation table 29) is a genetic code used by the nuclear genome of the ciliates Mesodinium and Myrionecta. |
wiki | Optimistic replication, also known as lazy replication, is a strategy for replication, in which replicas are allowed to diverge.Traditional pessimistic replication systems try to guarantee from the beginning that all of the replicas are identical to each other, as if there was only a single copy of the data all along. ... |
wiki | During oxidative phosphorylation, electrons are transferred from the electron donors to a series of electron acceptors in a series of redox reactions ending in oxygen, whose reaction releases half of the total energy.In eukaryotes, these redox reactions are catalyzed by a series of protein complexes within the inner me... |
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