Glossary of Computer Science

What's inside

Abstract data type

(ADT), is a mathematical model for data types, where a data type is defined by its behavior (semantics) from the point of view of a user of the data, specifically in terms of possible values, possible operations on data of this type, and the behavior of these operations. This contrasts with data structures, which are concrete representations of data, and are the point of view of an implementer, not a user.

Abstract method

Is one with only a signature and no implementation body. It is often used to specify that a subclass must provide an implementation of the method. Abstract methods are used to specify interfaces in some computer languages.[[1]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-1)

Abstraction

In software engineering and computer science, abstraction is:
the process of removing physical, spatial, or temporal details[[2]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-2) or attributes in the study of objects or systems in order to more closely attend to other details of interest;[[3]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-abstraction-3) it is also very similar in nature to the process of generalization;

the abstract concept-objects which are created by keeping common features or attributes to various concrete objects or systems of study[[3]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-abstraction-3) — the result of the process of abstraction.

Agent architecture

Is a blueprint for software agents and intelligent control systems, depicting the arrangement of components. The architectures implemented by intelligent agents are referred to as cognitive architectures.[[4]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-4)

Agent-based model

(ABM), is a class of computational models for simulating the actions and interactions of autonomous agents (both individual or collective entities such as organizations or groups) with a view to assessing their effects on the system as a whole. It combines elements of game theory, complex systems, emergence, computational sociology, multi-agent systems, and evolutionary programming. Monte Carlo methods are used to introduce randomness.

Aggregate function

In database management an aggregate function is a function where the values of multiple rows are grouped together to form a single value of more significant meaning or measurement such as a set, a bag or a list.

Agile software development

Is an approach to software development under which requirements and solutions evolve through the collaborative effort of self-organizing and cross-functional teams and their customer(s)/end user(s).[[5]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-Collier_2011-5) It advocates adaptive planning, evolutionary development, early delivery, and continual improvement, and it encourages rapid and flexible response to change.[[6]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-WhatIsAgile-6)

Algorithm

Is an unambiguous specification of how to solve a class of problems. Algorithms can perform calculation, data processing and automated reasoning tasks.

Algorithm design

Refers to a method or mathematical process for problem solving and engineering algorithms. The design of algorithms is part of many solution theories of operation research, such as dynamic programming and divide-and-conquer. Techniques for designing and implementing algorithm designs are also called algorithm design patterns,[[7]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-7) such as the template method pattern and decorator pattern.

Algorithmic efficiency

Is a property of an algorithm which relates to the number of computational resources used by the algorithm. An algorithm must be analyzed to determine its resource usage, and the efficiency of an algorithm can be measured based on usage of different resources. Algorithmic efficiency can be thought of as analogous to engineering productivity for a repeating or continuous process.

ASCII

Abbreviated from American Standard Code for Information Interchange, is a character encoding standard for electronic communication. ASCII codes represent text in computers, telecommunications equipment, and other devices. Most modern character-encoding schemes are based on ASCII, although they support many additional characters.

Application programming interface

(API) is a set of subroutine definitions, communication protocols, and tools for building software. In general terms, it is a set of clearly defined methods of communication among various components. A good API makes it easier to develop a computer program by providing all the building blocks, which are then put together by the programmer.

Application software

(app or application for short) is computer software designed to perform a group of coordinated functions, tasks, or activities for the benefit of the user. Examples of an application include a word processor, a spreadsheet, an accounting application, a web browser, a media player, an aeronautical flight simulator, a console game or a photo editor. The collective noun application software refers to all applications collectively.[[8]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-8) This contrasts with system software, which is mainly involved with running the computer.

Array data structure

Or simply an array, is a data structure consisting of a collection of elements (values or variables), each identified by at least one array index or key. An array is stored such that the position of each element can be computed from its index tuple by a mathematical formula.[[9]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-9)[[10]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-andres-10)[[11]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-garcia-11) The simplest type of data structure is a linear array, also called one-dimensional array.

Artifact

Is one of many kinds of tangible by-products produced during the development of software. Some artifacts (e.g., use cases, class diagrams, and other Unified Modeling Language (UML) models, requirements and design documents) help describe the function, architecture, and design of software. Other artifacts are concerned with the process of development itself—such as project plans, business cases, and risk assessments.

Artificial intelligence

(AI), sometimes called machine intelligence, is intelligence demonstrated by machines, in contrast to the [natural](https://en.wikipedia.org/wiki/Natural) intelligence displayed by humans and other animals. In computer science AI research is defined as the study of "intelligent agents": any device that perceives its environment and takes actions that maximize its chance of successfully achieving its goals.[[12]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-Definition_of_AI-12) Colloquially, the term "artificial intelligence" is applied when a machine mimics "cognitive" functions that humans associate with other human minds, such as "learning" and "problem solving".[[13]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-FOOTNOTERussellNorvig20092-13)

Assertion

In computer programming, an assertion is a statement that a predicate (Boolean-valued function, i.e. a true–false expression) is always true at that point in code execution. It can help a programmer read the code, help a compiler compile it, or help the program detect its own defects. For the latter, some programs check assertions by actually evaluating the predicate as they run and if it is not in fact true, an assertion failure, the program considers itself to be broken and typically deliberately crashes or throws an assertion failure exception.

Automata theory

Is the study of abstract machines and automata, as well as the computational problems that can be solved using them. It is a theory in theoretical computer science and discrete mathematics (a subject of study in both mathematics and computer science). The word automata (the plural of automaton) comes from the Greek word αὐτόματα, which means "self-acting".

Automated reasoning

Is an area of computer science and mathematical logic dedicated to understanding different aspects of reasoning. The study of automated reasoning helps produce computer programs that allow computers to reason completely, or nearly completely, automatically. Although automated reasoning is considered a sub-field of artificial intelligence, it also has connections with theoretical computer science, and even philosophy.

Bandwidth

Is the maximum rate of data transfer across a given path. Bandwidth may be characterized as network bandwidth,[[14]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-14) data bandwidth,[[15]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-15) or digital bandwidth.[[16]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-16)[[17]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-17)

Bayesian programming

Is a formalism and a methodology for having a technique to specify probabilistic models and solve problems when less than the necessary information is available.

Benchmark

Is the act of running a computer program, a set of programs, or other operations, in order to assess the relative performance of an object, normally by running a number of standard tests and trials against it.[[18]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-18) The term benchmark is also commonly utilized for the purposes of elaborately designed benchmarking programs themselves.

Best, worst and average case

best, worst, and average cases of a given algorithm express what the resource usage is at least, at most and on average, respectively. Usually the resource being considered is running time, i.e. time complexity, but it could also be memory or other resource. Best case is the function which performs the minimum number of steps on input data of n elements. Worst case is the function which performs the maximum number of steps on input data of size n. Average case is the function which performs an average number of steps on input data of n elements.

Big data

Is a term used to refer to data sets that are too large or complex for traditional data-processing application software to adequately deal with. Data with many cases (rows) offer greater statistical power, while data with higher complexity (more attributes or columns) may lead to a higher false discovery rate.[[19]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-19)

Big O notation

Is a mathematical notation that describes the limiting behavior of a function when the argument tends towards a particular value or infinity. It is a member of a family of notations invented by Paul Bachmann,[[20]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-Bachmann-20) Edmund Landau,[[21]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-Landau-21) and others, collectively called Bachmann–Landau notation or asymptotic notation.

Binary number

In mathematics and digital electronics, a binary number is a number expressed in the base-2 numeral system or binary numeral system, which uses only two symbols: typically 0 (zero) and 1 (one).

Binary search algorithm

binary search, also known as half-interval search,[[22]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-Williams1976-22) logarithmic search,[[23]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-FOOTNOTEKnuth1998§6.2.1_("Searching_an_ordered_table"%29,_subsection_"Binary_search"-23) or binary chop,[[24]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-FOOTNOTEButterfieldNgondi201646-24) is a search algorithm that finds the position of a target value within a sorted array.[[25]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-FOOTNOTECormenLeisersonRivestStein200939-25)[[26]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-26)

Binary tree

Is a tree data structure in which each node has at most two children, which are referred to as the left child and the right child. A recursive definition using just set theory notions is that a (non-empty) binary tree is a tuple (L, S, R), where L and R are binary trees or the empty set and S is a singleton set.[[27]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-GarnierTaylor2009-27) Some authors allow the binary tree to be the empty set as well.[[28]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-Skiena2009-28)

Bioinformatics

Is an interdisciplinary field that develops methods and software tools for understanding biological data. As an interdisciplinary field of science, bioinformatics combines biology, computer science, information engineering, mathematics and statistics to analyze and interpret biological data. Bioinformatics has been used for [in silico](https://en.wikipedia.org/wiki/In_silico) analyses of biological queries using mathematical and statistical techniques.

Bit

(a portmanteau of binary digit)[[29]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-Mackenzie_1980-29) is a basic unit of information used in computing and digital communications. A binary digit can have only one of two values, and may be physically represented with a two-state device. These state values are most commonly represented as either a 0or1.

Bit rate

In telecommunications and computing, bit rate (bitrate or as a variable R) is the number of bits that are conveyed or processed per unit of time.[[30]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-30)

Blacklist

In computing, a blacklist or block list is a basic access control mechanism that allows through all elements (email addresses, users, passwords, URLs, IP addresses, domain names, file hashes, etc.), except those explicitly mentioned. Those items on the list are denied access. The opposite is a whitelist, which means only items on the list are let through whatever gate is being used. A greylist contains items that are temporarily blocked (or temporarily allowed) until an additional step is performed.

BMP file format

Also known as bitmap image file or device independent bitmap (DIB) file format or simply a bitmap, is a raster graphics image file format used to store bitmap digital images, independently of the display device (such as a graphics adapter), especially on Microsoft Windows[[31]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-bmp-31) and OS/2[[32]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-os2bmp-32) operating systems.

Boolean data type

Is a data type that has one of two possible values (usually denoted true and false), intended to represent the two truth values of logic and Boolean algebra. It is named after George Boole, who first defined an algebraic system of logic in the mid 19th century. The Boolean data type is primarily associated with conditional statements, which allow different actions by changing control flow depending on whether a programmer-specified Boolean condition evaluates to true or false. It is a special case of a more general logical data type (see [probabilistic logic](https://en.wikipedia.org/wiki/Probabilistic_logic))—logic need not always be Boolean.

Boolean expression

Is used expression in a programming language that produces a Boolean value when evaluated, that is one of true or false. A Boolean expression may be composed of a combination of the Boolean constants true or false, Boolean-typed variables, Boolean-valued operators, and Boolean-valued functions.[[33]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-33)

Boolean algebra

In mathematics and mathematical logic, Boolean algebra is the branch of algebra in which the values of the variables are the truth values true and false, usually denoted 1 and 0 respectively. Instead of elementary algebra where the values of the variables are numbers, and the prime operations are addition and multiplication, the main operations of Boolean algebra are the conjunction and denoted as ∧, the disjunction or denoted as ∨, and the negation not denoted as ¬. It is thus a formalism for describing logical relations in the same way that elementary algebra describes numeric relations.

Byte

Is a unit of digital information that most commonly consists of eight bits, representing a binary number. Historically, the byte was the number of bits used to encode a single character of text in a computer[[34]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-Buchholz_1962-34)[[35]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-Bemer_1959-35) and for this reason it is the smallest addressable unit of memory in many computer architectures.
[Booting](https://en.wikipedia.org/wiki/Booting)- is starting up a computer or computer appliance until it can be used. It can be initiated by hardware such as a button press or by software command. After the power is switched on, the computer is relatively dumb and can read only part of its storage called read-only memory. There, a small program is stored called firmware. It does power-on self-tests and, most importantly, allows accessing other types of memory like a hard disk and main memory. The firmware loads bigger programs into the computer's main memory and runs it.

Callback

Also known as a "call-after[[36]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-36) " function, is any executable code that is passed as an argument to other code that is expected to call back (execute) the argument at a given time. This execution may be immediate as in a synchronous callback, or it might happen at a later time as in an asynchronous callback.

Central processing unit

(CPU) is the electronic circuitry within a computer that carries out the instructions of a computer program by performing the basic arithmetic, logic, controlling and input/output (I/O) operations specified by the instructions. The computer industry has used the term "central processing unit" at least since the early 1960s.[[37]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-weik1961-37) Traditionally, the term "CPU" refers to a processor, more specifically to its processing unit and control unit (CU), distinguishing these core elements of a computer from external components such as main memory and I/O circuitry.[[38]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-kuck-38)

Character

In computer and machine-based telecommunications terminology, a character is a unit of information that roughly corresponds to a grapheme, grapheme-like unit, or symbol, such as in an alphabet or syllabary in the written form of a natural language.[[39]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-39)

Cipher

In cryptography, a cipher (or cypher) is an algorithm for performing encryption or decryption—a series of well-defined steps that can be followed as a procedure.

Class

In object-oriented programming, a class is an extensible program-code-template for creating objects, providing initial values for state (member variables) and implementations of behavior (member functions or methods).[[40]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-FOOTNOTEGammaHelmJohnsonVlissides199514-40)[[41]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-FOOTNOTEBruce20022.1_Objects,_classes,_and_object_types,_https://books.google.com/books?id=9NGWq3K1RwUC&pg=PA18-41) In many languages, the class name is used as the name for the class (the template itself), the name for the default constructor of the class (a subroutine that creates objects), and as the type of objects generated by instantiating the class; these distinct concepts are easily conflated.[[41]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-FOOTNOTEBruce20022.1_Objects,_classes,_and_object_types,_https://books.google.com/books?id=9NGWq3K1RwUC&pg=PA18-41)

Class-based programming

Or more commonly class-orientation, is a style of Object-oriented programming (OOP) in which inheritance occurs via defining [classes](https://en.wikipedia.org/wiki/Class_(computer_programming%29) of objects, instead of inheritance occurring via the objects alone (compare prototype-based programming).

Class-orientation

Is a style of Object-oriented programming (OOP) in which inheritance occurs via defining [classes](https://en.wikipedia.org/wiki/Class_(computer_programming%29) of objects, instead of inheritance occurring via the objects alone (compare prototype-based programming).

Client

Is a piece of computer hardware or software that accesses a service made available by a server. The server is often (but not always) on another computer system, in which case the client accesses the service by way of a network.[[42]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-42) The term applies to the role that programs or devices play in the client–server model.

Cleanroom software engineering

Is a software development process intended to produce software with a certifiable level of reliability. The cleanroom process was originally developed by Harlan Mills and several of his colleagues including Alan Hevner at IBM.[[43]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-43) The focus of the cleanroom process is on defect prevention, rather than defect removal.

Closure

In programming languages, a closure (also lexical closure or function closure) is a technique for implementing lexically scoped name binding in a language with first-class functions. Operationally, a closure is a record storing a function[[a]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-44) together with an environment.[[44]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-45)

Cloud computing

Is shared pools of configurable computer system resources and higher-level services that can be rapidly provisioned with minimal management effort, often over the Internet. Cloud computing relies on sharing of resources to achieve coherence and economies of scale, similar to a public utility.

Code library

Is a collection of non-volatile resources used by computer programs, often for software development. These may include configuration data, documentation, help data, message templates, pre-written code and subroutines, classes, values or type specifications. In IBM's OS/360 and its successors they are referred to as partitioned data sets.

Coding

Computer programming is the process of designing and building an executable computer program for accomplishing a specific computing task. Programming involves tasks such as analysis, generating algorithms, profiling algorithms' accuracy and resource consumption, and the implementation of algorithms in a chosen programming language (commonly referred to as coding[[45]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-tumblr2014-46)[[46]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-tumblr1-47)). The source code of a program is written in one or more programming languages. The purpose of programming is to find a sequence of instructions that will automate the performance of a task for solving a given problem. The process of programming thus often requires expertise in several different subjects, including knowledge of the application domain, specialized algorithms, and formal logic.

Coding theory

Is the study of the properties of codes and their respective fitness for specific applications. Codes are used for data compression, cryptography, error detection and correction, data transmission and data storage. Codes are studied by various scientific disciplines—such as information theory, electrical engineering, mathematics, linguistics, and computer science—for the purpose of designing efficient and reliable data transmission methods. This typically involves the removal of redundancy and the correction or detection of errors in the transmitted data.

Cognitive science

Is the interdisciplinary, scientific study of the mind and its processes.[[47]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-48) It examines the nature, the tasks, and the functions of cognition (in a broad sense). Cognitive scientists study intelligence and behavior, with a focus on how nervous systems represent, process, and transform information. Mental faculties of concern to cognitive scientists include language, perception, memory, attention, reasoning, and emotion; to understand these faculties, cognitive scientists borrow from fields such as linguistics, psychology, artificial intelligence, philosophy, neuroscience, and anthropology.[[48]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-stanford1-49)

Comma-separated values

(CSV) file is a delimited text file that uses a comma to separate values. A CSV file stores tabular data (numbers and text) in plain text. Each line of the file is a data record. Each record consists of one or more fields, separated by commas. The use of the comma as a field separator is the source of the name for this file format.

Compiler

Is a computer program that transforms computer code written in one programming language (the source language) into another programming language (the target language). Compilers are a type of translator that support digital devices, primarily computers. The name compiler is primarily used for programs that translate source code from a high-level programming language to a lower level language (e.g., assembly language, object code, or machine code) to create an executable program.[[49]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-50)

Computability theory

Also known as recursion theory, is a branch of mathematical logic, of computer science, and of the theory of computation that originated in the 1930s with the study of computable functions and Turing degrees. The field has since expanded to include the study of generalized computability and definability. In these areas, recursion theory overlaps with proof theory and effective descriptive set theory.

Computation

Is any type of calculation[[50]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-51)[[51]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-52) that includes both arithmetical and non-arithmetical steps and follows a well-defined model, for example an algorithm. The study of computation is paramount to the discipline of computer science.

Computational chemistry

Is a branch of chemistry that uses computer simulation to assist in solving chemical problems. It uses methods of theoretical chemistry, incorporated into efficient computer programs, to calculate the structures and properties of molecules and solids.

Computational complexity theory

Focuses on classifying computational problems according to their inherent difficulty, and relating these classes to each other. A computational problem is a task solved by a computer. A computation problem is solvable by mechanical application of mathematical steps, such as an algorithm.

Computational model

Is a mathematical model in computational science that requires extensive computational resources to study the behavior of a complex system by computer simulation.[[52]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-53)

Computational neuroscience

(also known as theoretical neuroscience or mathematical neuroscience) is a branch of neuroscience which employs mathematical models, theoretical analysis and abstractions of the brain to understand the principles that govern the development, structure, physiology and cognitive abilities of the nervous system.[[53]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-Trappenberg_2002-54)[[54]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-55)[[55]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-56)[[56]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-57)

Computational science

(also scientific computing or scientific computation (SC)) is a rapidly growing multidisciplinary field that uses advanced computing capabilities to understand and solve complex problems. It is an area of science which spans many disciplines, but at its core it involves the development of models and simulations to understand natural systems.

Computer

Is a device that can be instructed to carry out sequences of arithmetic or logical operations automatically via computer programming. Modern computers have the ability to follow generalized sets of operations, called [programs](https://en.wikipedia.org/wiki/Computer_program). These programs enable computers to perform an extremely wide range of tasks.

Computer architecture

In computer engineering, computer architecture is a set of rules and methods that describe the functionality, organization, and implementation of computer systems. Some definitions of architecture define it as describing the capabilities and programming model of a computer but not a particular implementation.[[57]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-58) In other definitions computer architecture involves instruction set architecture design, microarchitecture design, logic design, and implementation.[[58]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-59)

Computer data storage

Often called storage or memory, is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers.[[59]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-60):15–16

Computer ethics

Is a part of practical philosophy concerned with how computing professionals should make decisions regarding professional and social conduct.[[60]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-BynumVeryShort-61)

Computer graphics

Are pictures and films created using computers. Usually, the term refers to computer-generated image data created with the help of specialized graphical hardware and software. It is a vast and recently developed area of computer science.

Computer network

Or data network, is a digital telecommunications network which allows nodes to share resources. In computer networks, computing devices exchange data with each other using connections (data links) between nodes. These data links are established over cable media such as wires or optic cables, or wireless media such as WiFi.

Computer programming

Is the process of designing and building an executable computer program for accomplishing a specific computing task. Programming involves tasks such as analysis, generating algorithms, profiling algorithms' accuracy and resource consumption, and the implementation of algorithms in a chosen programming language (commonly referred to as coding[[45]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-tumblr2014-46)[[46]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-tumblr1-47)). The source code of a program is written in one or more programming languages. The purpose of programming is to find a sequence of instructions that will automate the performance of a task for solving a given problem. The process of programming thus often requires expertise in several different subjects, including knowledge of the application domain, specialized algorithms, and formal logic.

Computer science

Is the theory, experimentation, and engineering that form the basis for the design and use of computers. It involves the study of algorithms that process, store, and communicate digital information. A computer scientist specializes in the theory of computation and the design of computational systems.[[61]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-62)

Computer scientist

Is a person who has acquired the knowledge of computer science, the study of the theoretical foundations of information and computation and their application.[[62]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-63)

Computer security

cybersecurity[[63]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-64) or information technology security (IT security) is the protection of computer systems from theft or damage to their hardware, software or electronic data, as well as from disruption or misdirection of the services they provide.
[Computer vision](https://en.wikipedia.org/wiki/Computer_vision) –is an interdisciplinary scientific field that deals with how computers can be made to gain high-level understanding from digital images or videos. From the perspective of engineering, it seeks to automate tasks that the human visual system can do.[[64]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-65)[[65]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-66)[[66]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-67)

Concurrency

Refers to the ability of different parts or units of a program, algorithm, or problem to be executed out-of-order or in partial order, without affecting the final outcome. This allows for parallel execution of the concurrent units, which can significantly improve overall speed of the execution in multi-processor and multi-core systems. In more technical terms, concurrency refers to the decomposability property of a program, algorithm, or problem into order-independent or partially-ordered components or units.[[67]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-68)

Conditional

Conditional statements, conditional expressions and conditional constructs are features of a programming language, which perform different computations or actions depending on whether a programmer-specified boolean condition evaluates to true or false. Apart from the case of branch predication, this is always achieved by selectively altering the control flow based on some condition.

Continuation-passing style

In functional programming, continuation-passing style (CPS) is a style of programming in which control is passed explicitly in the form of a continuation. This is contrasted with direct style, which is the usual style of programming. Gerald Jay Sussman and Guy L. Steele, Jr. coined the phrase in AI Memo 349 (1975), which sets out the first version of the Scheme programming language.[[68]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-69)[[69]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-70)

Control flow

(or flow of control) is the order in which individual statements, instructions or function calls of an imperative program are executed or evaluated. The emphasis on explicit control flow distinguishes an [imperative programming](https://en.wikipedia.org/wiki/Imperative_programming) language from a [declarative programming](https://en.wikipedia.org/wiki/Declarative_programming) language.

Creative Commons

(CC), is an American non-profit organization devoted to expanding the range of creative works available for others to build upon legally and to share.[[70]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-71) The organization has released several copyright-licenses, known as Creative Commons licenses, free of charge to the public.

CSV

Comma-separated values.

Cyberbullying

Or cyberharassment, is a form of bullying or harassment using electronic means. Cyberbullying and cyberharassment are also known as online bullying.

Cyberspace

Is widespread, interconnected digital technology.

Data center

Or data centre, is a dedicated space used to house computer systems and associated components, such as telecommunications and storage systems. It generally includes redundant or backup components and infrastructure for power supply, data communications connections, environmental controls (e.g. air conditioning, fire suppression) and various security devices.[[71]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-NYT92212-72)[[72]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-ReferenceDC2-73)

Database

Is an organized collection of data, generally stored and accessed electronically from a computer system. Where databases are more complex they are often developed using formal design and modeling techniques.

Data science

Is an interdisciplinary field that uses scientific methods, processes, algorithms and systems to extract knowledge and insights from data in various forms, both structured and unstructured,[[73]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-74)[[74]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-75) similar to data mining. Data science is a "concept to unify statistics, data analysis, machine learning and their related methods" in order to "understand and analyze actual phenomena" with data.[[75]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-Hayashi-76) It employs techniques and theories drawn from many fields within the context of mathematics, statistics, information science, and computer science.

Data structure

Is a data organization, management and storage format that enables efficient access and modification.[[76]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-77)[[77]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-78)[[78]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-79) More precisely, a data structure is a collection of data values, the relationships among them, and the functions or operations that can be applied to the data.[[79]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-80)

Data type

Or simply type is an attribute of data which tells the compiler or interpreter how the programmer intends to use the data. Most programming languages support common data types of real, integer and boolean. A data type constrains the values that an expression, such as a variable or a function, might take. This data type defines the operations that can be done on the data, the meaning of the data, and the way values of that type can be stored. A type of value from which an expression may take its value.[[80]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-81)[[81]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-82)

Debugging

Is the process of finding and resolving defects or problems within a computer program that prevent correct operation of computer software or a system. Debugging tactics can involve interactive debugging, control flow analysis, unit testing, integration testing, log file analysis, monitoring at the application or system level, memory dumps, and profiling.

Declaration

In computer programming, a declaration is a language construct that specifies properties of an identifier: it declares what a word (identifier) "means".[[82]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-c11-83) Declarations are most commonly used for functions, variables, constants, and classes, but can also be used for other entities such as enumerations and type definitions.[[82]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-c11-83) Beyond the name (the identifier itself) and the kind of entity (function, variable, etc.), declarations typically specify the data type (for variables and constants), or the type signature (for functions); types may also include dimensions, such as for arrays. A declaration is used to announce the existence of the entity to the compiler; this is important in those strongly typed languages that require functions, variables, and constants, and their types to be specified with a declaration before use, and is used in forward declaration.[[83]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-84) The term "declaration" is frequently contrasted with the term "definition",[[82]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-c11-83) but meaning and usage varies significantly between languages.

Digital data

In information theory and information systems, is the discrete, discontinuous representation of information or works. Numbers and letters are commonly used representations.

Digital signal processing

(DSP) is the use of digital processing, such as by computers or more specialized digital signal processors, to perform a wide variety of signal processing operations. The signals processed in this manner are a sequence of numbers that represent samples of a continuous variable in a domain such as time, space, or frequency.

Discrete event simulation

(DES) models the operation of a system as a discrete sequence of events in time. Each event occurs at a particular instant in time and marks a change of state in the system.[[84]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-85) Between consecutive events, no change in the system is assumed to occur; thus the simulation can directly jump in time from one event to the next.

Distributed computing

Is a field of computer science that studies distributed systems. A distributed system is a system whose components are located on different networked computers, which communicate and coordinate their actions by passing messages to one another.[[85]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-Coulouris-86) The components interact with one another in order to achieve a common goal. Three significant characteristics of distributed systems are: concurrency of components, lack of a global clock, and independent failure of components.[[85]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-Coulouris-86) Examples of distributed systems vary from SOA-based systems to massively multiplayer online games to peer-to-peer applications.

Divide and conquer algorithm

Is an algorithm design paradigm based on multi-branched recursion. A divide-and-conquer algorithm works by recursively breaking 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.

DNS

See *Domain Name System*.

Documentation

Software documentation is written text or illustration that accompanies computer software or is embedded in the source code. It either explains how it operates or how to use it, and may mean different things to people in different roles.

Domain Name System

(DNS) is a hierarchical and decentralized naming system for computers, services, or other resources connected to the Internet or a private network. It associates various information with domain names assigned to each of the participating entities. Most prominently, it translates more readily memorized domain names to the numerical IP addresses needed for locating and identifying computer services and devices with the underlying network protocols. By providing a worldwide, distributed directory service, the Domain Name System has been an essential component of the functionality of the Internet since 1985.

Double-precision floating-point format

Is a computer number format. It represents a wide dynamic range of numeric values by using a floating radix point.

Download

In computer networks, download means to receive data from a remote system, typically a server[[86]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-main-87) such as a web server, an FTP server, an email server, or other similar systems. This contrasts with uploading, where data is sent to a remote server. A download is a file offered for downloading or that has been downloaded, or the process of receiving such a file.

Edge device

Is a device which provides an entry point into enterprise or service provider core networks. Examples include routers, routing switches, integrated access devices (IADs), multiplexers, and a variety of metropolitan area network (MAN) and wide area network (WAN) access devices. Edge devices also provide connections into carrier and service provider networks. An edge device that connects a local area network to a high speed switch or backbone (such as an ATM switch) may be called an edge concentrator.

Event

Is an action or occurrence recognized by software, often originating asynchronously from the external environment, that may be handled by the software. Because an event is an entity which encapsulates the action and the contextual variables triggering the action we can use the acrostic mnemonic of an event as an "Execution Variable Encapsulating Named Trigger" to clarify the concept.

Event-driven programming

Is a programming paradigm in which the flow of the program is determined by events such as user actions (mouse clicks, key presses), sensor outputs, or messages from other programs or threads. Event-driven programming is the dominant paradigm used in graphical user interfaces and other applications (e.g., JavaScript web applications) that are centered on performing certain actions in response to user input. This is also true of programming for device drivers (e.g., P in USB device driver stacks[[87]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-88)).

Evolutionary computing

Is a family of algorithms for global optimization inspired by biological evolution, and the subfield of artificial intelligence and soft computing studying these algorithms. In technical terms, they are a family of population-based trial and error problem solvers with a metaheuristic or stochastic optimization character.

Executable

executable code or an executable file or executable program, sometimes simply referred to as an executable, causes a computer "to perform indicated tasks according to encoded instructions,"[[88]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-89) as opposed to a data file that must be parsed by a program to be meaningful. The exact interpretation depends upon the use - while "instructions" is traditionally taken to mean machine code instructions for a physical CPU, in some contexts a file containing bytecode or scripting language instructions may also be considered executable.

Exception handling

Is the process of responding to the occurrence, during computation, of exceptions – anomalous or exceptional conditions requiring special processing – often disrupting the normal flow of program execution. It is provided by specialized programming language constructs, computer hardware mechanisms like interrupts or operating system IPC facilities like signals.

Expression

An expression in a programming language is a combination of one or more constants, variables, operators, and functions that the programming language interprets (according to its particular rules of precedence and of association) and computes to produce ("to return", in a stateful environment) another value. This process, as for mathematical expressions, is called evaluation.

Fault-tolerant computer system

Are systems designed around the concepts of fault tolerance. In essence, they must be able to continue working to a level of satisfaction in the presence of errors or breakdowns.

Feasibility study

Aims to objectively and rationally uncover the strengths and weaknesses of an existing business or proposed venture, opportunities and threats present in the natural environment, the resources required to carry through, and ultimately the prospects for success.[[89]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-Justis-90)[[90]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-91) In its simplest terms, the two criteria to judge feasibility are cost required and value to be attained.[[91]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-92)

Filename extension

Is an identifier specified as a suffix to the name of a computer file. The extension indicates a characteristic of the file contents or its intended use.

Filter (software)

Is a computer program or subroutine to process a stream, producing another stream. While a single filter can be used individually, they are frequently strung together to form a pipeline.

For loop

A for-loop (or simply for loop) is a control flow statement for specifying iteration, which allows code to be executed repeatedly. Various keywords are used to specify this statement: descendants of ALGOL use "for", while descendants of Fortran use "do". There are other possibilities, for example COBOL which uses "PERFORM VARYING".

Formal methods

Are a particular kind of mathematically based technique for the specification, development and verification of software and hardware systems.[[92]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-butler-93) The use of formal methods for software and hardware design is motivated by the expectation that, as in other engineering disciplines, performing appropriate mathematical analysis can contribute to the reliability and robustness of a design.[[93]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-94)

Formal verification

Is the act of proving or disproving the correctness of intended algorithms underlying a system with respect to a certain formal specification or property, using formal methods of mathematics.[[94]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-95)

Functional programming

Is a programming paradigm—a style of building the structure and elements of computer programs—that treats computation as the evaluation of mathematical functions and avoids changing-state and mutable data. It is a declarative programming paradigm in that programming is done with expressions or declarations[[95]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-expression_style-96) instead of statements.

Game theory

Is the study of mathematical models of strategic interaction between rational decision-makers.[[96]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-Myerson-97) It has applications in all fields of social science, as well as in logic and computer science. Originally, it addressed zero-sum games, in which each participant's gains or losses are exactly balanced by those of the other participants. Today, game theory applies to a wide range of behavioral relations, and is now an umbrella term for the science of logical decision making in humans, animals, and computers.

Garbage in, garbage out

(GIGO), describes the concept that flawed, or nonsense input data produces nonsense output or "garbage".

GIF

Graphics Interchange Format.

Gigabyte

Is a multiple of the unit byte for digital information. The prefix [giga](https://en.wikipedia.org/wiki/Giga-) means 109 in the International System of Units (SI). Therefore, one gigabyte is 1000000000bytes. The unit symbol for the gigabyte is GB.

Global variable

In computer programming, a global variable is a variable with global scope, meaning that it is visible (hence accessible) throughout the program, unless shadowed. The set of all global variables is known as the global environment or global state. In compiled languages, global variables are generally static variables, whose extent (lifetime) is the entire runtime of the program, though in interpreted languages (including command-line interpreters), global variables are generally dynamically allocated when declared, since they are not known ahead of time.

Graph theory

In mathematics, graph theory is the study of [graphs](https://en.wikipedia.org/wiki/Graph_(discrete_mathematics%29), which are mathematical structures used to model pairwise relations between objects. A graph in this context is made up of [vertices](https://en.wikipedia.org/wiki/Vertex_(graph_theory%29) (also called nodes or points) which are connected by [edges](https://en.wikipedia.org/wiki/Glossary_of_graph_theory_terms#edge) (also called links or lines). A distinction is made between undirected graphs, where edges link two vertices symmetrically, and directed graphs, where edges link two vertices asymmetrically.

Hard problem

Computational complexity theory focuses on classifying computational problems according to their inherent difficulty, and relating these classes to each other. A computational problem is a task solved by a computer. A computation problem is solvable by mechanical application of mathematical steps, such as an algorithm.

Hash function

Is any function that can be used to map data of arbitrary size to data of a fixed size. The values returned by a hash function are called hash values, hash codes, digests, or simply hashes. Hash functions are often used in combination with a hash table, a common data structure used in computer software for rapid data lookup. Hash functions accelerate table or database lookup by detecting duplicated records in a large file.

Hash table

In computing, a hash table (hash map) is a data structure that implements an associative array abstract data type, a structure that can map keys to values. A hash table uses a hash function to compute an index into an array of buckets or slots, from which the desired value can be found.

Heap

Is a specialized tree-based data structure which is essentially an almost complete[[97]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-98) tree that satisfies the heap property: if P is a parent node of C, then the key (the value) of P is either greater than or equal to (in a max heap) or less than or equal to (in a min heap) the key of C.[[98]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-99) The node at the "top" of the heap (with no parents) is called the root node.

Heapsort

Is a comparison-based sorting algorithm. Heapsort can be thought of as an improved selection sort: like that algorithm, it divides its input into a sorted and an unsorted region, and it iteratively shrinks the unsorted region by extracting the largest element and moving that to the sorted region. The improvement consists of the use of a heap data structure rather than a linear-time search to find the maximum.[[99]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-100)

Human-computer interaction

(HCI) researches the design and use of computer technology, focused on the interfaces between people (users) and computers. Researchers in the field of HCI both observe the ways in which humans interact with computers and design technologies that let humans interact with computers in novel ways. As a field of research, human–computer interaction is situated at the intersection of computer science, behavioral sciences, design, media studies, and several other fields of study.

IDE

Integrated development environment.

Imperative programming

Is a programming paradigm that uses statements that change a program's state. In much the same way that the imperative mood in natural languages expresses commands, an imperative program consists of commands for the computer to perform. Imperative programming focuses on describing how a program operates.

Incremental build model

Is a method of software development where the product is designed, implemented and tested incrementally (a little more is added each time) until the product is finished. It involves both development and maintenance. The product is defined as finished when it satisfies all of its requirements. This model combines the elements of the waterfall model with the iterative philosophy of prototyping.

Information space analysis

Is a deterministic method, enhanced by machine intelligence, for locating and assessing resources for team-centric efforts.

Inheritance

In object-oriented programming, inheritance is the mechanism of basing an object or class upon another object (prototype-based inheritance) or class (class-based inheritance), retaining similar implementation. Also defined as deriving new classes (sub classes) from existing ones (super class or base class) and forming them into a hierarchy of classes.

Input/output

Or I/O (or, informally, io or IO), is the communication between an information processing system, such as a computer, and the outside world, possibly a human or another information processing system. Inputs are the signals or data received by the system and outputs are the signals or data sent from it. The term can also be used as part of an action; to "perform I/O" is to perform an input or output operation.

Insertion sort

Is a simple sorting algorithm that builds the final sorted array (or list) one item at a time.

Instruction cycle

(also known as the fetch–decode–execute cycle or simply the fetch-execute cycle), is the cycle which the central processing unit (CPU) follows from boot-up until the computer has shut down in order to process instructions. It is composed of three main stages: the fetch stage, the decode stage, and the execute stage.

Integer

Is a datum of integral data type, a data type that represents some range of mathematical integers. Integral data types may be of different sizes and may or may not be allowed to contain negative values. Integers are commonly represented in a computer as a group of binary digits (bits). The size of the grouping varies so the set of integer sizes available varies between different types of computers. Computer hardware, including virtual machines, nearly always provide a way to represent a processor register or memory address as an integer.

Integrated development environment

(IDE), is a software application that provides comprehensive facilities to computer programmers for software development. An IDE normally consists of at least a source code editor, build automation tools, and a debugger.

Integration testing

(sometimes called integration and testing, abbreviated I&T) is the phase in software testing in which individual software modules are combined and tested as a group. Integration testing is conducted to evaluate the compliance of a system or component with specified functional requirements.[[100]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-101) It occurs after unit testing and before validation testing. Integration testing takes as its input modules that have been unit tested, groups them in larger aggregates, applies tests defined in an integration test plan to those aggregates, and delivers as its output the integrated system ready for system testing.[[101]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-102)

Intellectual property

(IP), is a category of property that includes intangible creations of the human intellect.[[102]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-103)[[103]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-104) There are many types of intellectual property, and some countries recognize more than others.[[104]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-105)[[105]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-106)[[106]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-107)[[107]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-108)[[108]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-109) The most well-known types are copyrights, patents, trademarks, and trade secrets.

Interface

Is a shared boundary across which two or more separate components of a computer system exchange information. The exchange can be between software, computer hardware, peripheral devices, humans, and combinations of these.[[109]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-HookwayInterface14-110) Some computer hardware devices, such as a touchscreen, can both send and receive data through the interface, while others such as a mouse or microphone may only provide an interface to send data to a given system.[[110]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-111)

Internal documentation

Computer software is said to have Internal Documentation if the notes on how and why various parts of code operate is included within the source code as comments. It is often combined with meaningful variable names with the intention of providing potential future programmers a means of understanding the workings of the code. This contrasts with external documentation, where programmers keep their notes and explanations in a separate document.

Internet

The Internet (portmanteau of interconnected network) is the global system of interconnected computer networks that use the Internet protocol suite (TCP/IP) to link devices worldwide. It is a network of networks that consists of private, public, academic, business, and government networks of local to global scope, linked by a broad array of electronic, wireless, and optical networking technologies.

Internet bot

Also known as a web robot, robot or simply bot, is a software application that runs automated tasks (scripts) over the Internet.[[111]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-112) Typically, bots perform tasks that are both simple and structurally repetitive, at a much higher rate than would be possible for a human alone. The largest use of bots is in web spidering (web crawler), in which an automated script fetches, analyzes and files information from web servers at many times the speed of a human.

Interpreter

Is a computer program that directly executes instructions written in a programming or scripting language, without requiring them previously to have been compiled into a machine language program.

Java

Is a general-purpose programming language that is class-based, object-oriented[[112]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-FOOTNOTEDECODER1-113)(although not a pure OO language[[113]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-114)), and designed to have as few implementation dependencies as possible. It is intended to let application developers "write once, run anywhere" (WORA),[[114]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-115) meaning that compiled Java code can run on all platforms that support Java without the need for recompilation.[[115]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-design_goals-116)

Kernel

When referring to an operating system, the kernel is the first section of the operating system to load into memory. As the center of the operating system, the kernel needs to be small, efficient and loaded into a protected area in the memory so as not to be overwritten. It can be responsible for such things as disk drive management, file management, memory management, process management, etc.

Library (computing)

Is a collection of non-volatile resources used by computer programs, often for software development. These may include configuration data, documentation, help data, message templates, pre-written code and subroutines, classes, values or type specifications.

Linear search

Or sequential search, is a method for finding an element within a list. It sequentially checks each element of the list until a match is found or the whole list has been searched.[[116]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-FOOTNOTEKnuth1998§6.1_("Sequential_search"%29-117)

Linked list

Is a linear collection of data elements, whose order is not given by their physical placement in memory. Instead, each element points to the next. It is a data structure consisting of a collection of nodes which together represent a sequence.

Linker

Or link editor, is a computer utility program that takes one or more object files generated by a compiler or an assembler and combines them into a single executable file, library file, or another 'object' file. A simpler version that writes its output directly to memory is called the loader, though loading is typically considered a separate process.[[117]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-118)

List

Or sequence, is an abstract data type that represents a countable 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 finite sequence; the (potentially) infinite analog of a list is a stream.[[118]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-119):§3.5 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.

Loader

Is the part of an operating system that is responsible for loading programs and libraries. It is one of the essential stages in the process of starting a program, as it places programs into memory and prepares them for execution. Loading a program involves reading the contents of the executable file containing the program instructions into memory, and then carrying out other required preparatory tasks to prepare the executable for running. Once loading is complete, the operating system starts the program by passing control to the loaded program code.

Logic error

In computer programming, a logic error is a bug in a program that causes it to operate incorrectly, but not to terminate abnormally (or crash). A logic error produces unintended or undesired output or other behaviour, although it may not immediately be recognized as such.

Logic programming

Is a type of programming paradigm which is largely based on formal logic. Any program written in a logic programming language is a set of sentences in logical form, expressing facts and rules about some problem domain. Major logic programming language families include Prolog, answer set programming (ASP) and Datalog.

Machine learning

(ML), is the scientific study of algorithms and statistical models that computer systems use to perform a specific task without using explicit instructions, relying on patterns and inference instead. It is seen as a subset of artificial intelligence. Machine learning algorithms build a mathematical model based on sample data, known as "training data", in order to make predictions or decisions without being explicitly programmed to perform the task.[[119]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-120)[[120]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-121)

Machine vision

(MV), is the technology and methods used to provide imaging-based automatic inspection and analysis for such applications as automatic inspection, process control, and robot guidance, usually in industry. Machine vision refers to many technologies, software and hardware products, integrated systems, actions, methods and expertise. Machine vision as a systems engineering discipline can be considered distinct from computer vision, a form of computer science. It attempts to integrate existing technologies in new ways and apply them to solve real world problems. The term is the prevalent one for these functions in industrial automation environments but is also used for these functions in other environments such as security and vehicle guidance.

Mathematical logic

Is a subfield of mathematics exploring the applications of formal logic to mathematics. It bears close connections to metamathematics, the foundations of mathematics, and theoretical computer science.[[121]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-122) The unifying themes in mathematical logic include the study of the expressive power of formal systems and the deductive power of formal proof systems.

Matrix

In mathematics, a matrix, (plural matrices), is a rectangular [array](https://en.wiktionary.org/wiki/array)[[122]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-123) (see irregular matrix) of numbers, symbols, or expressions, arranged in [rows](https://en.wiktionary.org/wiki/row) and [columns](https://en.wiktionary.org/wiki/column).[[123]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-124)[[124]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-125)

Memory

Computer data storage, often called storage, is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers.[[125]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-Patterson-126):15–16

Merge sort

(also commonly spelled mergesort), is an efficient, general-purpose, comparison-based sorting algorithm. Most implementations produce a stable sort, which means that the order of equal elements is the same in the input and output. Merge sort is a divide and conquer algorithm that was invented by John von Neumann in 1945.[[126]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-127) A detailed description and analysis of bottom-up mergesort appeared in a report by Goldstine and von Neumann as early as 1948.[[127]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-128)

Method

In object-oriented programming (OOP), is a procedure associated with a message and an object. An object consists of data and behavior. The data and behavior comprise an interface, which specifies how the object may be utilized by any of various consumers[[128]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-consumerdef001a-129) of the object.

Methodology

In software engineering, a software development process is the process of dividing software development work into distinct phases to improve design, product management, and project management. It is also known as a software development life cycle (SDLC). The methodology may include the pre-definition of specific deliverables and artifacts that are created and completed by a project team to develop or maintain an application.[[129]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-130)
[Modem](https://en.wikipedia.org/wiki/Modem)- (a portmanteau of modulator-demodulator) is a hardware device that converts data into a format suitable for a transmission medium so that it can be transmitted from one computer to another (historically along telephone wires). A modem modulates one or more carrier wave signals to encode digital information for transmission and demodulates signals to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded reliably to reproduce the original digital data. Modems can be used with almost any means of transmitting analog signals from light-emitting diodes to radio. A common type of modem is one that turns the digital data of a computer into modulated electrical signal for transmission over telephone lines and demodulated by another modem at the receiver side to recover the digital data.

Natural language processing

(NLP), is a subfield of linguistics, computer science, information engineering, and artificial intelligence concerned with the interactions between computers and human (natural) languages, in particular how to program computers to process and analyze large amounts of natural language data. Challenges in natural language processing frequently involve speech recognition, natural language understanding, and natural language generation.

Number theory

Is a branch of pure mathematics devoted primarily to the study of the integers and integer-valued functions.

Numerical analysis

Is the study of algorithms that use numerical approximation (as opposed to symbolic manipulations) for the problems of mathematical analysis (as distinguished from discrete mathematics).

Numerical method

In numerical analysis, a numerical method is a mathematical tool designed to solve numerical problems. The implementation of a numerical method with an appropriate convergence check in a programming language is called a numerical algorithm.

Object

An object can be a variable, a data structure, a function, or a method, and as such, is a value in memory referenced by an identifier. In the class-based object-oriented programming paradigm, object refers to a particular instance of a class, where the object can be a combination of variables, functions, and data structures. In relational database management, an object can be a table or column, or an association between data and a database entity (such as relating a person's age to a specific person).[[130]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-Oppel-131)

Object code

Or object module, is the product of a compiler.[[131]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-132) In a general sense object code is a sequence of statements or instructions in a computer language,[[132]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-133) usually a machine code language (i.e., binary) or an intermediate language such as register transfer language (RTL). The term indicates that the code is the goal or result of the compiling process, with some early sources referring to source code as a "subject program."

Object-oriented analysis and design

(OOAD), is a technical approach for analyzing and designing an application, system, or business by applying object-oriented programming, as well as using visual modeling throughout the software development process to guide stakeholder communication and product quality.

Object oriented programming

(OOP), is a programming paradigm based on the concept of "objects", which can contain data, in the form of fields (often known as attributes or properties), and code, in the form of procedures (often known as [methods](https://en.wikipedia.org/wiki/Method_(computer_science%29)). A feature of objects is an object's procedures that can access and often modify the data fields of the object with which they are associated (objects have a notion of "this" or "self"). In OOP, computer programs are designed by making them out of objects that interact with one another.[[133]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-134)[[134]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-135) OOP languages are diverse, but the most popular ones are class-based, meaning that objects are instances of classes, which also determine their types.

Open-source software

(OSS), is a type of computer software in which source code is released under a license in which the copyright holder grants users the rights to study, change, and distribute the software to anyone and for any purpose.[[135]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-136) Open-source software may be developed in a collaborative public manner. Open-source software is a prominent example of open collaboration.[[136]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-Open_Collaboration-137)

Operating system

(OS), is system software that manages computer hardware, software resources, and provides common services for computer programs.

Optical fiber

Is a flexible, transparent fiber made by drawing glass (silica) or plastic to a diameter slightly thicker than that of a human hair.[[137]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-138) Optical fibers are used most often as a means to transmit light between the two ends of the fiber and find wide usage in fiber-optic communications, where they permit transmission over longer distances and at higher bandwidths (data rates) than electrical cables. Fibers are used instead of metal wires because signals travel along them with less loss; in addition, fibers are immune to electromagnetic interference, a problem from which metal wires suffer.[[138]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-139)

Pair programming

Is an agile software development technique in which two programmers work together at one workstation. One, the driver, writes code while the other, the observer or navigator,[[139]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-140) reviews each line of code as it is typed in. The two programmers switch roles frequently.

Parallel computing

Is a type of computation in which many calculations or the execution of processes are carried out simultaneously.[[140]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-141) Large problems can often be divided into smaller ones, which can then be solved at the same time. There are several different forms of parallel computing: bit-level, instruction-level, data, and task parallelism.

Parameter

In computer programming, a parameter or a formal argument, is a special kind of variable, used in a subroutine to refer to one of the pieces of data provided as input to the subroutine.[[b]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-142) These pieces of data are the values[[141]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-143)[[142]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-144)[[143]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-145) of the arguments (often called actual arguments or actual parameters) with which the subroutine is going to be called/invoked. An ordered list of parameters is usually included in the definition of a subroutine, so that, each time the subroutine is called, its arguments for that call are evaluated, and the resulting values can be assigned to the corresponding parameters.

Postcondition

In computer programming, a postcondition is a condition or predicate that must always be true just after the execution of some section of code or after an operation in a formal specification. Postconditions are sometimes tested using assertions within the code itself. Often, postconditions are simply included in the documentation of the affected section of code.

Precondition

In computer programming, a precondition is a condition or predicate that must always be true just prior to the execution of some section of code or before an operation in a formal specification. If a precondition is violated, the effect of the section of code becomes undefined and thus may or may not carry out its intended work. Security problems can arise due to incorrect preconditions.

Priority queue

Is an abstract data type which is like a regular queue or stack data structure, but where additionally each element has a "priority" associated with it. In a priority queue, an element with high priority is served before an element with low priority. In some implementations, if two elements have the same priority, they are served according to the order in which they were enqueued, while in other implementations, ordering of elements with the same priority is undefined.

Program lifecycle phase

Program lifecycle phases are the stages a computer program undergoes, from initial creation to deployment and execution. The phases are edit time, compile time, link time, distribution time, installation time, load time, and run time.

Programming language

Is a formal language, which comprises a set of instructions that produce various kinds of output. Programming languages are used in computer programming to implement algorithms.

Quantum computing

Is the use of quantum-mechanical phenomena such as superposition and entanglement to perform computation. A quantum computer is used to perform such computation, which can be implemented theoretically or physically.[[144]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-2018Report-146):I-5

Queue

Is a collection in which the entities in the collection are kept in order and the principal (or only) operations on the collection are the addition of entities to the rear terminal position, known as enqueue, and removal of entities from the front terminal position, known as dequeue.

Quicksort

(sometimes called partition-exchange sort) is an [efficient](https://en.wikipedia.org/wiki/Algorithm_efficiency) [sorting algorithm](https://en.wikipedia.org/wiki/Sorting_algorithm), serving as a systematic method for placing the elements of a [random access](https://en.wikipedia.org/wiki/Random_access) [file](https://en.wikipedia.org/wiki/Computer_file) or an [array](https://en.wikipedia.org/wiki/Array_data_structure) in order.

Radix

In digital numeral systems, the radix, or base, is the number of unique digits, including the digit zero, used to represent numbers in a positional numeral system. For example, for the decimal/denary system (the most common system in use today) the radix (base number) is ten, because it uses the ten digits from 0 through 9.

Recursion

Occurs when a thing is defined in terms of itself or of its type. Recursion is used in a variety of disciplines ranging from linguistics to logic. The most common application of recursion is in mathematics and computer science, where a function being defined is applied within its own definition. While this apparently defines an infinite number of instances (function values), it is often done in such a way that no infinite loop or infinite chain of references can occur.

Reference counting

Is a programming technique of storing the number of references, pointers, or handles to a resource, such as an object, a block of memory, disk space, and others. In garbage collection algorithms, reference counts may be used to deallocate objects which are no longer needed.

Reliability engineering

Is a sub-discipline of systems engineering that emphasizes dependability in the lifecycle management of a product. Reliability describes the ability of a system or component to function under stated conditions for a specified period of time.[[145]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-147) Reliability is closely related to availability, which is typically described as the ability of a component or system to function at a specified moment or interval of time.

Regression testing

(rarely non-regression testing[[146]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-148)) is re-running functional and non-functional tests to ensure that previously developed and tested software still performs after a change.[[147]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-149) If not, that would be called a [regression](https://en.wikipedia.org/wiki/Software_regression). Changes that may require regression testing include bug fixes, software enhancements, configuration changes, and even substitution of electronic components.[[148]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-150) As regression test suites tend to grow with each found defect, test automation is frequently involved. Sometimes a change impact analysis is performed to determine an appropriate subset of tests (non-regression analysis[[149]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-151)).

Requirements analysis

In systems engineering and software engineering, requirements analysis focuses on the tasks that determine the needs or conditions to meet the new or altered product or project, taking account of the possibly conflicting requirements of the various stakeholders, analyzing, documenting, validating and managing software or system requirements.[[150]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-152)

Robotics

Is an interdisciplinary branch of engineering and science that includes mechanical engineering, electronic engineering, information engineering, computer science, and others. Robotics involves design, construction, operation, and use of robots, as well as computer systems for their perception, control, sensory feedback, and information processing. The goal of robotics is to design intelligent machines that can help and assist humans in their day-to-day lives and keep everyone safe.

Search algorithm

Is any algorithm which solves the search problem, namely, to retrieve information stored within some data structure, or calculated in the search space of a problem domain, either with discrete or continuous values.

Technical documentation

In engineering, technical documentation refers to any type of documentation that describes handling, functionality and architecture of a technical product or a product under development or use.[[151]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-153)[[152]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-154)[[153]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-155) The intended recipient for product technical documentation is both the (proficient) end user as well as the administrator / service or maintenance technician. In contrast to a mere "cookbook" manual, technical documentation aims at providing enough information for a user to understand inner and outer dependencies of the product at hand.

Tree

Is a widely used abstract data type (ADT) that simulates a hierarchical tree structure, with a root value and subtrees of children with a parent node, represented as a set of linked nodes.

Type theory

In mathematics, logic, and computer science, a type theory is any of a class of formal systems, some of which can serve as alternatives to set theory as a foundation for all mathematics. In type theory, every "term" has a "type" and operations are restricted to terms of a certain type.

Upload

In computer networks, to upload is to send data to a remote system such as a server or another client so that the remote system can store a copy.[[154]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-156)

Uniform Resource Locator

(URL), colloquially termed a web address,[[155]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-FOOTNOTEW3C2009-157) is a reference to a web resource that specifies its location on a computer network and a mechanism for retrieving it. A URL is a specific type of Uniform Resource Identifier (URI),[[156]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-158)[[157]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-FOOTNOTERFC_39862005-159) although many people use the two terms interchangeably.[[158]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-FOOTNOTEJoint_W3C/IETF_URI_Planning_Interest_Group2002-160)[[c]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-163) URLs occur most commonly to reference web pages (http), but are also used for file transfer (ftp), email (mailto), database access (JDBC), and many other applications.

URL

Uniform Resource Locator.

User agent

Is software (a software agent) that is acting on behalf of a user, such as a web browser that "retrieves, renders and facilitates end user interaction with Web content".[[161]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-164) An email reader is a mail user agent.

User interface

(UI), in the industrial design field of human-computer interaction, is the space where interactions between humans and machines occur. The goal of this interaction is to allow effective operation and control of the machine from the human end, whilst the machine simultaneously feeds back information that aids the operators' decision-making process. Examples of this broad concept of user interfaces include the interactive aspects of computer operating systems, hand tools, heavy machinery operator controls, and process controls. The design considerations applicable when creating user interfaces are related to or involve such disciplines as ergonomics and psychology.

User interface design

Or user interface engineering, is the design of user interfaces for machines and software, such as computers, home appliances, mobile devices, and other electronic devices, with the focus on maximizing usability and the user experience. The goal of user interface design is to make the user's interaction as simple and efficient as possible, in terms of accomplishing user goals (user-centered design).

Variable

In computer programming, a variable, or scalar, is a storage location (identified by a memory address) paired with an associated symbolic name (an [identifier](https://en.wikipedia.org/wiki/Identifier_(computer_programming%29)), which contains some known or unknown quantity of information referred to as a [value](https://en.wikipedia.org/wiki/Value_(computer_science%29). The variable name is the usual way to reference the stored value, in addition to referring to the variable itself, depending on the context. This separation of name and content allows the name to be used independently of the exact information it represents. The identifier in computer source code can be bound to a value during run time, and the value of the variable may thus change during the course of program execution.[[162]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-165)[[163]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-166)

Virtual machine

(VM), is an emulation of a computer system. Virtual machines are based on computer architectures and provide functionality of a physical computer. Their implementations may involve specialized hardware, software, or a combination.

V-Model

In software development, the V-model[[164]](https://en.wikipedia.org/wiki/Glossary_of_computer_science#cite_note-167) represents a development process that may be considered an extension of the waterfall model, and is an example of the more general V-model. Instead of moving down in a linear way, the process steps are bent upwards after the coding phase, to form the typical V shape. The V-Model demonstrates the relationships between each phase of the development life cycle and its associated phase of testing. The horizontal and vertical axes represent time or project completeness (left-to-right) and level of abstraction (coarsest-grain abstraction uppermost), respectively.

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