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Control Table
Control tables are tables that control the control flow or play a major part in program control. There are no rigid rules about the structure or content of a control table—its qualifying attribute is its ability to direct control flow in some way through "execution" by a processor or interpreter. The design of such tables is sometimes referred to as table-driven design (although this typically refers to generating code automatically from external tables rather than direct run-time tables). In some cases, control tables can be specific implementations of finite-state-machine-based automata-based programming. If there are several hierarchical levels of control table they may behave in a manner equivalent to UML state machines. Control tables often have the equivalent of conditional expressions or function references embedded in them, usually implied by their relative column position in the association list. Control tables reduce the need for programming similar structures or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Offset (computer Science)
In computer science, an offset within an array or other data structure object is an integer indicating the distance (displacement) between the beginning of the object and a given element or point, presumably within the same object. The concept of a distance is valid only if all elements of the object are of the same size (typically given in bytes or words). For example, if A is an array of characters containing "abcdef", the fourth element containing the character 'd' has an offset of three from the start of A. In assembly language In computer engineering and low-level programming (such as assembly language), an offset usually denotes the number of address locations added to a base address in order to get to a specific absolute address. In this (original) meaning of offset, only the basic address unit, usually the 8-bit byte, is used to specify the offset's size. In this context an offset is sometimes called a relative address. In IBM System/360 instructions, a 12-bit of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Constant Time
In theoretical computer science, the time complexity is the computational complexity that describes the amount of computer time it takes to run an algorithm. Time complexity is commonly estimated by counting the number of elementary operations performed by the algorithm, supposing that each elementary operation takes a fixed amount of time to perform. Thus, the amount of time taken and the number of elementary operations performed by the algorithm are taken to be related by a constant factor. Since an algorithm's running time may vary among different inputs of the same size, one commonly considers the worst-case time complexity, which is the maximum amount of time required for inputs of a given size. Less common, and usually specified explicitly, is the average-case complexity, which is the average of the time taken on inputs of a given size (this makes sense because there are only a finite number of possible inputs of a given size). In both cases, the time complexity is genera ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multimap (data Structure)
In computer science, a multimap (sometimes also multihash, multidict or multidictionary) is a generalization of a map or associative array abstract data type in which more than one value may be associated with and returned for a given key. Both map and multimap are particular cases of containers (for example, see C++ Standard Template Library containers). Often the multimap is implemented as a map with lists or sets as the map values. Examples * In a student enrollment system, where students may be enrolled in multiple classes simultaneously, there might be an association for each enrollment of a student in a course, where the key is the student ID and the value is the course ID. If a student is enrolled in three courses, there will be three associations containing the same key. * The index of a book may report any number of references for a given index term, and thus may be coded as a multimap from index terms to any number of reference locations or pages. * Querystrings may ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Algorithm
In mathematics and computer science, an algorithm () is a finite sequence of Rigour#Mathematics, mathematically rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algorithms are used as specifications for performing calculations and data processing. More advanced algorithms can use Conditional (computer programming), conditionals to divert the code execution through various routes (referred to as automated decision-making) and deduce valid inferences (referred to as automated reasoning). In contrast, a Heuristic (computer science), heuristic is an approach to solving problems without well-defined correct or optimal results.David A. Grossman, Ophir Frieder, ''Information Retrieval: Algorithms and Heuristics'', 2nd edition, 2004, For example, although social media recommender systems are commonly called "algorithms", they actually rely on heuristics as there is no truly "correct" recommendation. As an e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Computer Platform
A computing platform, digital platform, or software platform is the infrastructure on which software is executed. While the individual components of a computing platform may be obfuscated under layers of abstraction, the ''summation of the required components comprise the computing platform''. Sometimes, the most relevant layer for a specific software is called a computing platform in itself to facilitate the communication, referring to the whole using only one of its attributes – i.e. using a metonymy. For example, in a single computer system, this would be the computer's architecture, operating system (OS), and runtime libraries. In the case of an application program or a computer video game, the most relevant layer is the operating system, so it can be called a platform itself (hence the term cross-platform for software that can be executed on multiple OSes, in this context). In a multi-computer system, such as in the case of offloading processing, it would encompass bo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Software Portability
Software consists of computer programs that instruct the execution of a computer. Software also includes design documents and specifications. The history of software is closely tied to the development of digital computers in the mid-20th century. Early programs were written in the machine language specific to the hardware. The introduction of high-level programming languages in 1958 allowed for more human-readable instructions, making software development easier and more portable across different computer architectures. Software in a programming language is run through a compiler or interpreter to execute on the architecture's hardware. Over time, software has become complex, owing to developments in networking, operating systems, and databases. Software can generally be categorized into two main types: # operating systems, which manage hardware resources and provide services for applications # application software, which performs specific tasks for users The r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Variable Length Code
Variable may refer to: Computer science * Variable (computer science), a symbolic name associated with a value and whose associated value may be changed Mathematics * Variable (mathematics), a symbol that represents a quantity in a mathematical expression, as used in many sciences * Propositional variable, taking the value true or false in mathematical logic * Random variable, a variable in statistics whose value depends on random events ** Categorical variable, taking one of a finite number of values in a statistical problem, such as the head or tail result of a tossed coin ** Independent and identically distributed random variables, statistically independent and having the same probability distribution * Fluent (mathematics), a time-varying quantity as coined by Isaac Newton in his early calculus * State variable, used to describe the mathematical "state" of a dynamical system * Slack variable, inserted to transform an inequality constraint in an optimization problem int ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bytecode
Bytecode (also called portable code or p-code) is a form of instruction set designed for efficient execution by a software interpreter. Unlike human-readable source code, bytecodes are compact numeric codes, constants, and references (normally numeric addresses) that encode the result of compiler parsing and performing semantic analysis of things like type, scope, and nesting depths of program objects. The name ''bytecode'' stems from instruction sets that have one- byte opcodes followed by optional parameters. Intermediate representations such as bytecode may be output by programming language implementations to ease interpretation, or it may be used to reduce hardware and operating system dependence by allowing the same code to run cross-platform, on different devices. Bytecode may often be either directly executed on a virtual machine (a p-code machine, i.e., interpreter), or it may be further compiled into machine code for better performance. Since bytecode instruct ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Virtual Machine
In computing, a virtual machine (VM) is the virtualization or emulator, emulation of a computer system. Virtual machines are based on computer architectures and provide the functionality of a physical computer. Their implementations may involve specialized hardware, software, or a combination of the two. Virtual machines differ and are organized by their function, shown here: * ''System virtual machines'' (also called full virtualization VMs, or SysVMs) provide a substitute for a real machine. They provide the functionality needed to execute entire operating systems. A hypervisor uses native code, native execution to share and manage hardware, allowing for multiple environments that are isolated from one another yet exist on the same physical machine. Modern hypervisors use hardware-assisted virtualization, with virtualization-specific hardware features on the host CPUs providing assistance to hypervisors. * ''Process virtual machines'' are designed to execute computer programs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Online Transaction Processing
Online transaction processing (OLTP) is a type of database system used in transaction-oriented applications, such as many operational systems. "Online" refers to the fact that such systems are expected to respond to user requests and process them in real-time (process transactions). The term is contrasted with online analytical processing (OLAP) which instead focuses on data analysis (for example planning and management systems). Meaning of the term transaction The term "transaction" can have two different meanings, both of which might apply: in the realm of computers or database transactions it denotes an atomic change of state, whereas in the realm of business or finance, the term typically denotes an exchange of economic entities (as used by, e.g., Transaction Processing Performance Council or commercial transactions.) OLTP may use transactions of the first type to record transactions of the second type. Compared to OLAP OLTP is typically contrasted to online analytical p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
State Transition
In automata theory and sequential logic, a state-transition table is a table showing what state (or states in the case of a nondeterministic finite automaton) a finite-state machine will move to, based on the current state and other inputs. It is essentially a truth table in which the inputs include the current state along with other inputs, and the outputs include the next state along with other outputs. A state-transition table is one of many ways to specify a finite-state machine. Other ways include a state diagram. Common forms One-dimension State-transition tables are sometimes one-dimensional tables, also called ''characteristic tables''. They are much more like truth tables than their two-dimensional form. The single dimension indicates inputs, current states, next states and (optionally) outputs associated with the state transitions. : Two-dimensions State-transition tables are typically two-dimensional tables. There are two common ways for arranging them. In th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
