Glossary of computer science

Computer science
History Outline Glossary Category
v t e

This glossary of computer science is a list of definitions of terms and concepts used in computer science, its sub-disciplines, and related fields, including terms relevant to software, data science, and computer programming.

A

abstract data type (ADT)

A mathematical model for data types in which 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 from the point of view of an implementer rather than a user.

abstract method

One with only a

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]

abstraction

1.  In software engineering and computer science, the process of removing physical, spatial, or temporal details^[2] or attributes in the study of objects or systems in order to more closely attend to other details of interest;^[3] it is also very similar in nature to the process of generalization.

2.  The result of this process: an

object created by keeping common features or attributes to various concrete objects or systems of study.^[3]

agent architecture

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]

agent-based model (ABM)

A class of

complex systems, emergence, computational sociology, multi-agent systems, and evolutionary programming. Monte Carlo methods

are used to introduce randomness.

aggregate function

In

database management, a function

in which the values of multiple rows are grouped together to form a single value of more significant meaning or measurement, such as a sum, count, or max.

agile software development

An approach to

self-organizing and cross-functional teams and their customer(s)/end user(s).^[5] It advocates adaptive planning, evolutionary development, early delivery, and continual improvement, and it encourages rapid and flexible response to change.^[6]

algorithm

An unambiguous specification of how to solve a class of problems. Algorithms can perform calculation, data processing, and automated reasoning tasks. They are ubiquitous in computing technologies.

algorithm design

A method or mathematical process for problem-solving and for engineering

divide-and-conquer. Techniques for designing and implementing algorithm designs are also called algorithm design patterns,^[7]

such as the template method pattern and decorator pattern.

algorithmic efficiency

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.

American Standard Code for Information Interchange

(ASCII)

A character encoding standard for electronic communications. 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)

A set of

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

Also simply application or app.

media players, aeronautical flight simulators, console games, and photo editors. This contrasts with system software, which is mainly involved with managing the computer's most basic running operations, often without direct input from the user. The collective noun application software refers to all applications collectively.^[8]

array data structure

Also simply array.

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][10][11] The simplest type of data structure is a linear array, also called a one-dimensional array.

artifact

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)

Also machine intelligence.

human minds, such as "learning" and "problem solving".^[13]

ASCII

See American Standard Code for Information Interchange.

assertion

In computer programming, 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.

associative array

An associative array, map, symbol table, or dictionary is an

(key, value) pairs

, such that each possible key appears at most once in the collection. Operations associated with this data type allow:^[14][15]

• the addition of a pair to the collection
• the removal of a pair from the collection
• the modification of an existing pair
• the lookup of a value associated with a particular key

automata theory

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).

automated reasoning

An area of

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

The maximum rate of data transfer across a given path. Bandwidth may be characterized as network bandwidth,^[16] data bandwidth,^[17] or digital bandwidth.^[18][19]

Bayesian programming

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

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.^[20] The term benchmark is also commonly utilized for the purposes of elaborately designed benchmarking programs themselves.

best, worst and average case

Expressions of what the resource usage is at least, at most, and on average, respectively, for a given algorithm. Usually the resource being considered is running time, i.e. time complexity, but it could also be memory or some 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

A term used to refer to

statistical power, while data with higher complexity (more attributes or columns) may lead to a higher false discovery rate.^[21]

big O notation

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,^[22] Edmund Landau,^[23] and others, collectively called Bachmann–Landau notation or asymptotic notation.

binary number

In mathematics and

1 (one)

.

binary search algorithm

Also simply binary search, half-interval search,^[24] logarithmic search,^[25] or binary chop.^[26]

A search algorithm that finds the position of a target value within a sorted array.^[27]

binary tree

A

singleton set.^[28] Some authors allow the binary tree to be the empty set as well.^[29]

bioinformatics

An interdisciplinary field that combines

software tools for analyzing and interpreting biological data. Bioinformatics is widely used for in silico

analyses of biological queries using mathematical and statistical techniques.

bit

A basic unit of information used in computing and digital communications; a portmanteau of binary digit. A binary digit can have one of two possible values, and may be physically represented with a two-state device. These state values are most commonly represented as either a 0or1.^[30]

bit rate (R)

Also bitrate.

In telecommunications and computing, the number of bits that are conveyed or processed per unit of time.^[31]

blacklist

Also block list.

In

hashes, etc.), except those explicitly mentioned in a list of prohibited elements. Those items on the list are denied access. The opposite is a whitelist, which means only items on the list are allowed through whatever gate is being used while all other elements are blocked. A greylist

contains items that are temporarily blocked (or temporarily allowed) until an additional step is performed.

BMP file format

Also bitmap image file, device independent bitmap (DIB) file format, or simply bitmap.

A

graphics adapter), used especially on Microsoft Windows^[32] and OS/2^[33]

operating systems.

Boolean data type

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)—i.e. logic need not always be Boolean.

Boolean expression

An

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.^[34]

Boolean algebra

In mathematics and mathematical logic, the branch of algebra in which the values of the variables are the truth values true and false, usually denoted 1 and 0, respectively. Contrary to 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

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^[35][36] and for this reason it is the smallest addressable unit of memory in many computer architectures.

booting

The procedures implemented in starting up a

main memory. The firmware loads bigger programs into the computer's main memory

and runs it.

callback

Also a call-after function.^[37]

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)

The electronic circuitry within a

main memory and I/O circuitry.^[39]

character

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.^[40]

cipher

Also cypher.

In

decryption—a series of well-defined steps that can be followed as a procedure

.

class

In

objects, providing initial values for state (member variables) and implementations of behavior (member functions or methods).^[41][42] 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.^[42]

class-based programming

Also class-orientation.

A style of object-oriented programming (OOP) in which inheritance occurs via defining "classes" of objects, instead of via the objects alone (compare prototype-based programming).

client

A piece of

computer system, in which case the client accesses the service by way of a network.^[43] The term applies to the role that programs or devices play in the client–server model

.

cleanroom software engineering

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.^[44] The focus of the cleanroom process is on defect prevention, rather than defect removal.

closure

Also lexical closure or function closure.

A technique for implementing

function^[a] together with an environment.^[45]

cloud computing

Shared pools of configurable computer

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

A collection of

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^[46][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

The study of the properties of

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

The interdisciplinary, scientific study of the mind and its processes.^[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.^[49]

collection

A collection or container is a grouping of some variable number of data items (possibly zero) that have some shared significance to the problem being solved and need to be operated upon together in some controlled fashion. Generally, the data items will be of the same type or, in languages supporting inheritance, derived from some common ancestor type. A collection is a concept applicable to abstract data types, and does not prescribe a specific implementation as a concrete data structure, though often there is a conventional choice (see Container for type theory discussion).

comma-separated values (CSV)

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

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.^[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

Any type of calculation

model, e.g. an algorithm. The study of computation is paramount to the discipline of computer science

.

computational biology

Involves the development and application of data-analytical and theoretical methods,

bioengineering and biology to build computers

.

computational chemistry

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

A subfield of computational science which 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

A mathematical model in computational science that requires extensive computational resources to study the behavior of a complex system by computer simulation.^[55]

computational neuroscience

Also theoretical neuroscience or mathematical neuroscience.

A branch of

development, structure, physiology, and cognitive abilities of the nervous system.^{[56][57][58][59]}

computational physics

Is the study and implementation of numerical analysis to solve problems in physics for which a quantitative theory already exists.^[60] Historically, computational physics was the first application of modern computers in science, and is now a subset of computational science.

computational science

Also scientific computing and scientific computation (SC).

An interdisciplinary 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 computer models and simulations to understand complex natural systems.

computational steering

Is the practice of manually intervening with an otherwise autonomous

computational process

, to change its outcome.

computer

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. These programs enable computers to perform an extremely wide range of tasks.

computer architecture

A set of rules and methods that describe the functionality, organization, and implementation of

logic design, and implementation.^[62]

computer data storage

Also simply storage or memory.

A technology consisting of

data. Data storage is a core function and fundamental component of all modern computer systems.^[63]

^: 15–16

computer ethics

A part of practical philosophy concerned with how computing professionals should make decisions regarding professional and social conduct.^[64]

computer graphics

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

Also data network.

A

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 Wi-Fi

.

computer program

Is a collection of

instructions^[65] that can be executed by a computer

to perform a specific task.

computer programming

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^[46][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

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.^[66]

computer scientist

A person who has acquired the knowledge of computer science, the study of the theoretical foundations of information and computation and their application.^[67]

computer security

Also cybersecurity^[68] or information technology security (IT security).

The protection of

electronic data, as well as from disruption or misdirection

of the services they provide.

computer vision

An interdisciplinary scientific field that deals with how computers can be made to gain high-level understanding from

human visual system can do.^[69][70][71]

computing

Is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes study of

information systems, information technology and software engineering.^[72]

concatenation

In

character strings end-to-end. For example, the concatenation of "snow" and "ball" is "snowball". In certain formalisations of concatenation theory, also called string theory, string concatenation is a primitive notion

.

Concurrency

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.^[73]

conditional

Also conditional statement, conditional expression, and conditional construct.

A feature of a

branch predication, this is always achieved by selectively altering the control flow

based on some condition.

container

Is a

class, a data structure,^[74][75] or an abstract data type

(ADT) whose instances are collections of other objects. In other words, they store objects in an organized way that follows specific access rules. The size of the container depends on the number of objects (elements) it contains. Underlying (inherited) implementations of various container types may vary in size and complexity, and provide flexibility in choosing the right implementation for any given scenario.

continuation-passing style (CPS)

A style of

Guy L. Steele, Jr. coined the phrase in AI Memo 349 (1975), which sets out the first version of the Scheme programming language.^[76][77]

control flow

Also flow of control.

The order in which individual

function calls of an imperative program are executed or evaluated. The emphasis on explicit control flow distinguishes an imperative programming language from a declarative programming

language.

Creative Commons (CC)

An American

non-profit organization devoted to expanding the range of creative works available for others to build upon legally and to share.^[78] The organization has released several copyright-licenses, known as Creative Commons licenses

, free of charge to the public.

cryptography

Or cryptology, is the practice and study of techniques for

digital currencies, computer passwords, and military communications

.

CSV

See comma-separated values.

cyberbullying

Also cyberharassment or online bullying.

A form of bullying or harassment using electronic means.

cyberspace

Widespread, interconnected digital technology.

D

daemon

In

syslogd is a daemon that implements system logging facility, and sshd is a daemon that serves incoming SSH

connections.

Data

data center

Also data centre.

A dedicated space used to house computer systems and associated components, such as telecommunications and data storage systems. It generally includes redundant or backup components and infrastructure for power supply, data communications connections, environmental controls (e.g. air conditioning and fire suppression) and various security devices.^[83]

database

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 mining

Is a process of discovering patterns in large

visualization, and online updating.^[84]

data science

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,^[89][90] 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.^[91] It employs techniques and theories drawn from many fields within the context of mathematics, statistics, information science, and computer science.

data structure

A data organization, management, and storage format that enables efficient access and modification.^[92][93][94] 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.^[95]

data type

Also simply type.

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.^[96][97]

debugging

The process of finding and resolving defects or problems within a

memory dumps, and profiling

.

declaration

In

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.^[99] The term "declaration" is frequently contrasted with the term "definition",^[98]

but meaning and usage varies significantly between languages.

digital data

In

information systems, the discrete, discontinuous representation

of information or works. Numbers and letters are commonly used representations.

digital signal processing (DSP)

The use of

continuous variable

in a domain such as time, space, or frequency.

discrete event simulation

(DES)

A model of 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.^[100] 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.

disk storage

(Also sometimes called drive storage) is a general category of storage mechanisms where data is recorded by various electronic, magnetic, optical, or mechanical changes to a surface layer of one or more rotating disks. A disk drive is a device implementing such a storage mechanism. Notable types are the hard disk drive (HDD) containing a non-removable disk, the floppy disk drive (FDD) and its removable floppy disk, and various optical disc drives (ODD) and associated optical disc media.

distributed computing

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.^[101] 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.^[101] Examples of distributed systems vary from SOA-based systems to massively multiplayer online games to peer-to-peer applications.

divide and conquer algorithm

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

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

Is the targeted subject area of a computer program. It is a term used in software engineering. Formally it represents the target subject of a specific programming project, whether narrowly or broadly defined.^[102]

Domain Name System (DNS)

A hierarchical and decentralized naming system for computers, services, or other resources connected to the Internet or to 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

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

download

In computer networks, to receive data from a remote system, typically a server^[103] 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.

E

edge device

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.

encryption

In

pseudo-random encryption key generated by an algorithm. It is possible to decrypt the message without possessing the key, but, for a well-designed encryption scheme, considerable computational resources and skills are required. An authorized recipient can easily decrypt the message with the key provided by the originator to recipients but not to unauthorized users. Historically, various forms of encryption have been used to aid in cryptography. Early encryption techniques were often utilized in military messaging. Since then, new techniques have emerged and become commonplace in all areas of modern computing.^[104] Modern encryption schemes utilize the concepts of public-key and symmetric-key.^[104]

Modern encryption techniques ensure security because modern computers are inefficient at cracking the encryption.

event

An action or occurrence recognized by software, often originating

handled

by the software. Because an event is an entity which encapsulates the action and the contextual variables triggering the action, the acrostic mnemonic "Execution Variable Encapsulating Named Trigger" is often used to clarify the concept.

event-driven programming

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^[105]).

evolutionary computing

A family of

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

Also executable code, executable file, executable program, or simply executable.

Causes a computer "to perform indicated tasks according to encoded

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.

executable module

execution

In computer and software engineering is the process by which a computer or virtual machine executes the instructions of a computer program. Each instruction of a program is a description of a particular action which to be carried out in order for a specific problem to be solved; as instructions of a program and therefore the actions they describe are being carried out by an executing machine, specific effects are produced in accordance to the

semantics

of the instructions being executed.

exception handling

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.

Existence detection

An existence check before reading a file can catch and/or prevent a fatal error.

expression

In a

mathematical expressions

, is called evaluation.

external library

F

fault-tolerant computer system

A system designed around the concept 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

An investigation which 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.^[107][108] In its simplest terms, the two criteria to judge feasibility are cost required and value to be attained.^[109]

field

Data that has several parts, known as a

database records, so called rows. Each record consists of several fields; the fields of all records form the columns

. Examples of fields: name, gender, hair colour.

filename extension

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)

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.

floating point arithmetic

In computing, floating-point arithmetic (FP) is arithmetic using formulaic representation of real numbers as an approximation to support a trade-off between range and precision. For this reason, floating-point computation is often found in systems which include very small and very large real numbers, which require fast processing times. A number is, in general, represented approximately to a fixed number of significant digits (the significand) and scaled using an exponent in some fixed base; the base for the scaling is normally two, ten, or sixteen. A number that can be represented exactly is of the following form:

${\displaystyle {\text{significand}}\times {\text{base}}^{\text{exponent}},}$

where significand is an integer, base is an integer greater than or equal to two, and exponent is also an integer. For example:

${\displaystyle 1.2345=\underbrace {12345} _{\text{significand}}\times \underbrace {10} _{\text{base}}\!\!\!\!\!\!^{\overbrace {-4} ^{\text{exponent}}}.}$

pair programming

An

programmers work together at one workstation. One, the driver, writes code while the other, the observer or navigator,^[158] reviews

each line of code as it is typed in. The two programmers switch roles frequently.

parallel computing

A type of computation in which many calculations or the execution of processes are carried out simultaneously.^[159] 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

Also formal argument.

In

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.

peripheral

Any auxiliary or ancillary device connected to or integrated within a computer system and used to send information to or retrieve information from the computer. An input device sends data or instructions to the computer; an output device provides output from the computer to the user; and an input/output device performs both functions.

pointer

Is an

dereferencing the pointer. As an analogy, a page number in a book's index could be considered a pointer to the corresponding page; dereferencing such a pointer would be done by flipping to the page with the given page number and reading the text found on that page. The actual format and content of a pointer variable is dependent on the underlying computer architecture

.

postcondition

In

assertions

within the code itself. Often, postconditions are simply included in the documentation of the affected section of code.

precondition

In

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.

primary storage

(Also known as main memory, internal memory or prime memory), often referred to simply as memory, is the only one directly accessible to the CPU. The CPU continuously reads instructions stored there and executes them as required. Any data actively operated on is also stored there in uniform manner.

primitive data type

priority queue

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.

procedural programming

procedure

In

umbrella term callable unit is sometimes used.^[163]

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

A

set of instructions that produce various kinds of output. Programming languages are used in computer programming to implement algorithms

.

programming language implementation

Is a system for executing

computer programs. There are two general approaches to programming language implementation: interpretation and compilation.^[164]

programming language theory

(PLT) is a branch of computer science that deals with the design, implementation, analysis, characterization, and classification of programming languages and of their individual features. It falls within the discipline of computer science, both depending on and affecting mathematics, software engineering, linguistics and even cognitive science. It has become a well-recognized branch of computer science, and an active research area, with results published in numerous journals dedicated to PLT, as well as in general computer science and engineering publications.

Prolog

Is a

formal logic, and unlike many other programming languages, Prolog is intended primarily as a declarative programming language: the program logic is expressed in terms of relations, represented as facts and rules. A computation is initiated by running a query over these relations.^[168]

Python

Is an

programmers write clear, logical code for small and large-scale projects.^[169]

quantum computing

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.^[170]: I-5

queue

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

Also partition-exchange sort.

An

array

in order.

R

R programming language

R is a

statistical software^[172] and data analysis.^[173]

radix

Also base.

In digital numeral systems, the number of unique digits, including the digit zero, used to represent numbers in a positional numeral system. For example, in 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, and all other numbers are uniquely specified by positional combinations of these ten base digits; in the binary system that is the standard in computing, the radix is two, because it uses only two digits, 0 and 1, to uniquely specify each number.

record

A record (also called a structure, struct, or compound data) is a basic data structure. Records in a database or spreadsheet are usually called "rows".^{[174][175][176][177]}

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

Is a value that enables a program to indirectly access a particular

dereferencing

the reference.

reference counting

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.

relational database

Is a digital

E. F. Codd in 1970.^[178]

A software system used to maintain relational databases is a

better source needed

]

reliability engineering

A sub-discipline of

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.^[180] 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^[181]) is re-running functional and non-functional tests to ensure that previously developed and tested software still performs after a change.^[182] If not, that would be called a regression. Changes that may require regression testing include bug fixes, software enhancements, configuration changes, and even substitution of electronic components.^[183] 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^[184]).

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.^[185]

robotics

An interdisciplinary branch of

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.

round-off error

Also rounding error.^[186]

The difference between the result produced by a given

quantization error.^[188] When using approximation equations or algorithms, especially when using finitely many digits to represent real numbers (which in theory have infinitely many digits), one of the goals of numerical analysis is to estimate computation errors.^[189] Computation errors, also called numerical errors, include both truncation errors and roundoff errors.^[190]

router

A

internetwork (e.g. the Internet) until it reaches its destination node.^[191]

routing table

In

network host that lists the routes to particular network destinations, and in some cases, metrics (distances) associated with those routes. The routing table contains information about the topology of the network

immediately around it.

run time

Runtime, run time, or execution time is the final phase of a computer program's life cycle, in which the code is being executed on the computer's central processing unit (CPU) as machine code. In other words, "runtime" is the running phase of a program.

run time error

A

Type checking, register allocation, code generation, and code optimization are typically done at compile time, but may be done at runtime depending on the particular language and compiler. Many other runtime errors exist and are handled differently by different programming languages, such as division by zero errors, domain errors, array subscript out of bounds errors, arithmetic underflow errors, several types of underflow and overflow

errors, and many other runtime errors generally considered as software bugs which may or may not be caught and handled by any particular computer language.

search algorithm

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.

secondary storage

Also known as external memory or auxiliary storage, differs from primary storage in that it is not directly accessible by the CPU. The computer usually uses its input/output channels to access secondary storage and transfer the desired data to primary storage. Secondary storage is non-volatile (retaining data when power is shut off). Modern computer systems typically have two orders of magnitude more secondary storage than primary storage because secondary storage is less expensive.

selection sort

Is an

auxiliary memory

is limited.

semantics

In

platform, hence creating a model of computation

.

sequence

In mathematics, a sequence is an enumerated collection of objects in which repetitions are allowed and order does matter. Like a set, it contains members (also called elements, or terms). The number of elements (possibly infinite) is called the length of the sequence. Unlike a set, the same elements can appear multiple times at different positions in a sequence, and order does matter. Formally, a sequence can be defined as a function whose domain is either the set of the natural numbers (for infinite sequences) or the set of the first n natural numbers (for a sequence of finite length n). The position of an element in a sequence is its rank or index; it is the natural number for which the element is the image. The first element has index 0 or 1, depending on the context or a specific convention. When a symbol is used to denote a sequence, the nth element of the sequence is denoted by this symbol with n as subscript; for example, the nth element of the Fibonacci sequence F is generally denoted F_n. For example, (M, A, R, Y) is a sequence of letters with the letter 'M' first and 'Y' last. This sequence differs from (A, R, M, Y). Also, the sequence (1, 1, 2, 3, 5, 8), which contains the number 1 at two different positions, is a valid sequence. Sequences can be

lists, the different names commonly corresponding to different ways to represent them in computer memory; infinite sequences are called streams

. The empty sequence ( ) is included in most notions of sequence, but may be excluded depending on the context.

serializability

In

isolation between transactions, and plays an essential role in concurrency control. As such it is supported in all general purpose database systems. Strong strict two-phase locking

(SS2PL) is a popular serializability mechanism utilized in most of the database systems (in various variants) since their early days in the 1970s.

serialization

Is the process of translating

methods

with which they were previously linked. This process of serializing an object is also called

unmarshalling

).

service level agreement

(SLA), is a commitment between a service provider and a client. Particular aspects of the service – quality, availability, responsibilities – are agreed between the service provider and the service user.

throughput; jitter

; or similar measurable details.

set

Is an abstract data type that can store unique values, without any particular order. It is a computer implementation of the mathematical concept of a finite set. Unlike most other collection types, rather than retrieving a specific element from a set, one typically tests a value for membership in a set.

singleton variable

A variable that is referenced only once. May be used as a dummy argument in a function call, or when its address is assigned to another variable which subsequently accesses its allocated storage. Singleton variables sometimes occur because a mistake has been made – such as assigning a value to a variable and forgetting to use it later, or mistyping one instance of the variable name. Some compilers and lint-like tools flag occurrences of singleton variables.

soft computing

software

Computer software, or simply software, is a collection of

data, such as online documentation or digital media

. Computer hardware and software require each other and neither can be realistically used on its own.

software agent

Is a computer program that acts for a user or other program in a relationship of agency, which derives from the Latin agere (to do): an agreement to act on one's behalf. Such "action on behalf of" implies the authority to decide which, if any, action is appropriate.^[197][198] Agents are colloquially known as bots, from robot. They may be embodied, as when execution is paired with a robot body, or as software such as a chatbot executing on a phone (e.g.

Asimo

).

software construction

Is a software engineering discipline. It is the detailed creation of working meaningful software through a combination of coding, verification, unit testing, integration testing, and debugging. It is linked to all the other software engineering disciplines, most strongly to software design and software testing.^[199]

software deployment

Is all of the activities that make a software system available for use.^[200]

software design

Is the process by which an agent creates a specification of a software artifact, intended to accomplish goals, using a set of primitive components and subject to constraints.^[201] Software design may refer to either "all the activity involved in conceptualizing, framing, implementing, commissioning, and ultimately modifying complex systems" or "the activity following requirements specification and before programming, as ... [in] a stylized software engineering process."^[202]

software development

Is the process of conceiving, specifying, designing,

bug fixing involved in creating and maintaining applications, frameworks, or other software components. Software development is a process of writing and maintaining the source code, but in a broader sense, it includes all that is involved between the conception of the desired software through to the final manifestation of the software, sometimes in a planned and structured process.^[203] Therefore, software development may include research, new development, prototyping, modification, reuse, re-engineering, maintenance, or any other activities that result in software products.^[204]

software development process

In

spiral development, rapid application development, and extreme programming

.

software engineering

Is the systematic application of engineering approaches to the development of software.^{[205][206][207]} Software engineering is a computing discipline.^[208]

software maintenance

In software engineering is the modification of a software product after delivery to correct faults, to improve performance or other attributes.^[209]

software prototyping

Is the activity of creating

prototyping as known from other fields, such as mechanical engineering or manufacturing

. A prototype typically simulates only a few aspects of, and may be completely different from, the final product.

software requirements specification

(SRS), is a description of a

non-functional requirements, and it may include a set of use cases

that describe user interactions that the software must provide to the user for perfect interaction.

software testing

Is an investigation conducted to provide stakeholders with information about the quality of the software product or service under test.^[210] Software testing can also provide an objective, independent view of the software to allow the business to appreciate and understand the risks of software implementation. Test techniques include the process of executing a program or application with the intent of finding software bugs (errors or other defects), and verifying that the software product is fit for use.

sorting algorithm

Is an

lexicographical order. Efficient sorting is important for optimizing the efficiency of other algorithms (such as search and merge algorithms) that require input data to be in sorted lists. Sorting is also often useful for canonicalizing

data and for producing human-readable output. More formally, the output of any sorting algorithm must satisfy two conditions:

1. The output is in nondecreasing order (each element is no smaller than the previous element according to the desired total order);
2. The output is a permutation (a reordering, yet retaining all of the original elements) of the input.

Further, the input data is often stored in an

array, which allows random access, rather than a list, which only allows sequential access

; though many algorithms can be applied to either type of data after suitable modification.

source code

In

assembler or compiler into binary machine code that can be executed by the computer. The machine code might then be stored for execution at a later time. Alternatively, source code may be interpreted

and thus immediately executed.

spiral model

Is a risk-driven software development process model. Based on the unique risk patterns of a given project, the spiral model guides a team to adopt elements of one or more process models, such as incremental, waterfall, or evolutionary prototyping.

stack

Is an abstract data type that serves as a collection of elements, with two main principal operations:

• push, which adds an element to the collection, and
• pop, which removes the most recently added element that was not yet removed.

The order in which elements come off a stack gives rise to its alternative name, LIFO (last in, first out). Additionally, a peek operation may give access to the top without modifying the stack.^[212] The name "stack" for this type of structure comes from the analogy to a set of physical items stacked on top of each other. This structure makes it easy to take an item off the top of the stack, while getting to an item deeper in the stack may require taking off multiple other items first.^[213]

state

In information technology and computer science, a system is described as stateful if it is designed to remember preceding events or user interactions;^[214] the remembered information is called the state of the system.

statement

In computer programming, a statement is a syntactic unit of an imperative programming language that expresses some action to be carried out.^[215] A program written in such a language is formed by a sequence of one or more statements. A statement may have internal components (e.g., expressions).

storage

Computer data storage is a technology consisting of

data. It is a core function and fundamental component of computers.^[63]

^: 15–16

stream

Is a sequence of data elements made available over time. A stream can be thought of as items on a conveyor belt being processed one at a time rather than in large batches.

string

In

arrays or other sequence (or list

) data types and structures.

structured storage

A NoSQL (originally referring to "non-SQL" or "non-relational")^[216] database provides a mechanism for storage and retrieval of data that is modeled in means other than the tabular relations used in relational databases. Such databases have existed since the late 1960s, but the name "NoSQL" was only coined in the early 21st century,^[217] triggered by the needs of Web 2.0 companies.^[218][219] NoSQL databases are increasingly used in big data and real-time web applications.^[220] NoSQL systems are also sometimes called "Not only SQL" to emphasize that they may support SQL-like query languages or sit alongside SQL databases in polyglot-persistent architectures.^[221][222]

subroutine

In

umbrella term callable unit is sometimes used.^[163]

symbolic computation

In

floating point numbers, while symbolic computation emphasizes exact computation with expressions containing variables

that have no given value and are manipulated as symbols.

syntax

The syntax of a computer language is the set of rules that defines the combinations of symbols that are considered to be correctly structured statements or expressions in that language. This applies both to programming languages, where the document represents source code, and to markup languages, where the document represents data.

syntax error

Is an error in the

program execution, and an interpreter's error messages might not differentiate syntax errors from errors of other kinds. There is some disagreement as to just what errors are "syntax errors". For example, some would say that the use of an uninitialized variable's value in Java code is a syntax error, but many others would disagree^[224][225] and would classify this as a (static) semantic

error.

system console

The system console, computer console, root console,

stderr

), but there may be system-specific interfaces, for example those used by the system kernel.