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A mathematical entity consisting of a set of values (the carrier set) and a collection of operations that manipulate them. For example, the Integer abstract data type consists of a carrier set containing the positive and negative whole numbers and…

Signal processing is a discipline that deals with the extraction of information from signals. The devices that perform this task can be physical hardware devices, specialized software codes, or combinations of both. In recent years the complexity of…

Radar equipment carried by commercial and military aircraft. These aircraft use airborne radar systems to assist in weather assessment and navigation. Military systems also provide other specialized capabilities such as targeting of hostile aircraft…

A well-defined procedure to solve a problem. As such, an algorithm describes how to solve a problem (Fig. 1). The study of algorithms is a fundamental area of computer science. In writing a computer program to solve a problem, a programmer expresses…

Two-way radio communications by individuals as a leisure-time activity. Amateur, or “ham,” radio is defined by international treaty as a “service of self-training, intercommunications, and technical investigation carried on by amateurs; that is, by…

The process or result of the process whereby the amplitude of a carrier wave is changed in accordance with a modulating wave. This broad definition includes applications using sinusoidal carriers, pulse carriers, or any other form of carrier, the…

A device for moving the frequency of an information signal, which is generally at baseband (such as an audio or instrumentation signal), to a higher frequency, by varying the amplitude of a mediating (carrier) signal. The motivation to modulate may…

A device for recovering information from an amplitude-modulated (AM) electrical signal. Such a signal is received, usually at radio frequency, with information impressed in one of several forms. The carrier signal may be modulated by the information…

Radio communication employing amplitude modulation (AM) of a radio-frequency (RF) carrier wave as the means of conveying the desired intelligence. In AM, the amplitude of the carrier wave is made to vary in response to the fluctuations of a sound…

A computer or computational device in which the problem variables are represented as continuous, varying physical quantities. An analog computer implements a model of the system being studied. The physical form of the analog may be functionally…

A device for converting the information contained in the value or magnitude of some characteristics of an input signal, compared to a standard or reference, to information in the form of discrete states of a signal, usually with numerical values…

Modulation in which the instantaneous angle varies in proportion to the modulating waveform. When used in an analog manner, it is referred to as either frequency modulation (FM) or phase modulation (PM), depending upon whether the instantaneous…

Sea-level rise is caused by adding mass (water) and heat to the ocean. The Antarctic ice sheet represents a potentially large source of water. Knowing the speed and direction (velocity) at which the Antarctic ice sheet is flowing to the ocean is…

The device that couples the transmitter or receiver network of a radio system to space. Radio waves are used to transmit signals from a source through space. The information is received at a destination which in some cases, such as radar, can be…

A mathematical model of computing. The versatility of modern computers and their applications to the study of complex and dynamic systems, such as financial markets, cellular growth, and communication networks, raise questions about the ultimate…

The use of computers to automate decision tasks. A decision task is any task requiring the generation or selection of options. There is an increasing demand for autonomous systems that can perform various complex tasks without human control or…

The automatic control of the intermediate frequency in radio, television, or radar receivers, to correct for variations of the frequency of the transmitted carrier or the local oscillator in the receiver. For many reasons the frequency of the…

The automatic maintenance of a nearly constant output signal level of an amplifier circuit in the presence of a variable input signal level by adjusting its gain in inverse proportion to the input signal level. Automatic gain control (AGC) is also…

The collection, storage, and management of huge amounts of digital information. Databases falling into the realm of big data often begin in the hundreds of terabytes but can range up to petabytes (1015) or greater in size.The main characteristics…

Technologies that employ a distinctive, measurable biological or behavioral characteristic that can reliably distinguish one individual from another (biometric) for authentication, identification, and verification of individuals. Biometric…

Cameras in mobile phones or smartphones that can capture images and videos.The cellphone, the world’s favorite must-have gadget, has been with us for nearly a half-century, while experiencing continuous and often phenomenal improvements. Much of the…

The process of converting scanned images of machine-printed or handwritten text (numerals, letters, and symbols) into a computer-processable format; also known as optical character recognition (OCR). Systems A typical OCR system (Fig. 1) contains…

A model for offering computing as a commonly purchased service (that is, a utility) for storing data and providing access to computing resources (for example, programs) via the Internet, instead of on a local computer. The notion of a “cloud” of…

An artificial device that circumnavigates the Earth, receiving and retransmitting radio-frequency signals to multiple points on Earth. The communications hardware includes antennas, receivers, signal processing, and power amplifiers. The performance…

An approach to designing intelligent systems using mathematical algorithms. It consists of the fields of neural networks, evolutionary computation, and fuzzy sets (Fig. 1). Computational intelligence has been used to enable self-driving cars and…

The practice of designing computer systems. Just as the architecture of a building describes its overall structural concept and principal features, the architecture of a computer system consists of a description of the overall layout and major…

The process of protecting against threats to computing systems. A threat is an event that can cause harm to computers, data or programs, or computations (Fig. 1). A failure of computer security occurs because of a vulnerability or weakness in a…

Complex systems in which computers play a major role. While complex physical systems and sophisticated software systems can help people to lead healthier and more enjoyable lives, reliance on these systems can also result in loss of money, time, and…

The evaluation of performance, from the perspectives of both developers and users, of complex systems of hardware and software. Modern computer-based information systems have become increasingly complex because of networking, distributed computing,…

Programmable computers integrated with electrically powered machines that perform household chores. Domestic robots, also known as home or service robots, are essentially programmable computers integrated with electrically powered machines that…

A burst of electromagnetic energy. In a military context—and the subject of this article—an electromagnetic pulse (EMP) is a transient electromagnetic signal produced by a nuclear explosion in or above Earth's atmosphere (Fig. 1). Though not…

The functions associated with managing the information assets of an enterprise, typically a business, company, or organization. Many companies are taking the view that information (see illustration) is an asset of the enterprise in much the same way…

The process by which information systems are designed, developed, tested, and maintained. The technical origins of information systems engineering can be traced to conventional information systems design and development, and the field of systems…

The field of engineering involving computer-based hardware and software systems, and communication systems, to enable the acquisition, representation, storage, transmission, and use of information. Information technology (IT) is critically dependent…

Any machine that can accomplish its specific task in the presence of uncertainty and variability in its environment. The machine's ability to monitor its environment and then adjust its actions based on what it has sensed is a prerequisite for…

Worldwide system of interconnected computer networks. The origins of the Internet can be traced to the creation of ARPANET (Advanced Research Projects Agency Network) as a network of computers under the auspices of the U.S. Department of Defense in…

Electromagnetic energy with wavelengths in free space ranging roughly from 0.1 to 100 cm, with corresponding frequencies ranging from 0.3 to 300 gigahertz (GHz). On the electromagnetic spectrum, microwaves represent the frequency band between radio…

Radio communication in which one or both ends of the communication path are movable. Mobile communications, also known as wireless communications, are conducted with transportable devices, such as cellular phones and tablet computers, that use radio…

A computer program that simulates the behavior of a set of neurons responsible for the mental activities of humans; also known as an artificial neural network (ANN). In humans and other animals, sets of a particular kind of cells, called neurons,…

The software component of a computer system that is responsible for managing and coordinating activities and sharing the resources of the computer. The operating system (OS) acts as a host for application programs that are run on the machine (see…

A receive-only radar used for search, tracking, surveillance, identification, guidance, and mapping. The techniques used are similar to those in radiometry; passive radar could be said to be a branch of radiometry. Military applications are quite…

An interactive technology intentionally designed for the purpose of changing users' attitudes or behaviors without coercion or deception. Persuasive technology melds the fields of psychology and information/communication systems. Researchers are…

The analysis and solution of problems by the use of mental processes. Cognitive psychology, which is a branch of psychology concerned with mental activities such as learning, memory, perception, and reasoning, seeks to understand the integral…

The production of software through a progression of disciplined and controlled steps. As the need for complex, real-time, and life-critical software proliferates, there is a demand for an effective software development process that guarantees the…

A computer-generated environment that can be interacted with and experienced through ordinary human senses as if the environment were real. Virtual reality (VR) uses combinations of computer hardware and software to represent different aspects of…

A process of making physical objects directly from digital models, usually layer by layer; also known as additive manufacturing (AM). 3D printing has been hailed by many as the technology that will revolutionize how we live. As information…

A device that receives, processes, and presents information. The two basic types of computers are analog and digital. Although generally not regarded as such, the most prevalent computer is the simple mechanical analog computer, in which gears,…

Designing and writing a detailed sequence of operating instructions for a particular problem to be run on a computer; also known as programming. A computer is able to perform useful tasks only by executing computer programs. A programming language…

The hardware components, both internal and external, of a computer used to read (retrieve) or write (save) digital data. The ability to read and write data is an essential function of a computer and of the so-called von Neumann architecture…

A program or script that is loaded and executed on a computer without the knowledge of the user. A typical computer virus is a very small program, several kilobytes or less in size, constructed in a matter of hours or days. When executed, the virus…

A digital equivalent of paper banknotes. Just like paper banknotes, cryptocurrencies allow users to maintain privacy in digital commercial transactions while ensuring that value is transferred from one party to the other. Cryptocurrencies achieve…

The development of computational algorithms for the identification or extraction of patterns (structure) from large data sets. This is done in order to help reduce, model, understand, or analyze the data (Fig. 1). Tasks supported by data mining…

A software system for managing and controlling access to a database. In a database management system (DBMS), the mechanisms for defining its structures for storing and retrieving data efficiently are known as data management.A database is a…

The World Health Organization (WHO) is planning to recognize gaming disorder as a mental health disease in 2018. The 11th revision of the WHO's International Classification of Diseases (ICD), which is a major worldwide reference for epidemiological,…

The responsible use of computer and related resources with the objective of curbing the negative effects that the increasing use of computers and their associated technologies have on the Earth's limited natural resources. Green computing is part of…

An interdisciplinary field focused on the interactions between human users and computer systems, including the user interface and the underlying processes that produce the interactions. The contributing disciplines include computer science,…

The concept by which Internet or network connectivity, computing capabilities, and collection and exchange of data extend to everyday objects that are not computers. In the Internet of things (IoT), devices work with minimal human intervention to…

A branch of artificial intelligence (AI) based on the notion that machines (software applications) can learn from examples and can teach themselves how to solve specific problems without being programmed manually. Recent successes in artificial…

The different notations used to communicate instructions to a computer. A computer executes a sequence of instructions (a program) in order to perform some task. The set of instructions and the order in which they have to be performed is known as an…

Driverless cars operated via sensors, microprocessors, software, algorithms, and controllers; also known as autonomous cars and robotic cars. Most of the major automotive companies and some research organizations have developed working prototypes…

A set of instructions that causes a computer to perform one or more tasks. The set of instructions is often called a program or, if the set is particularly large and complex, a system. Computers cannot do any useful work without instructions from…

A handheld device that permits communication over a network between persons who are in different locations. A traditional telephone instrument, also called a set, contains a transmitter for converting the acoustic signals of a person's voice to…

An electronic display that allows a user to interact with a computer system by touching an area or areas on the display. Touch-screen displays have been in use for many years in ATMs, checkout registers, and other applications, but gained mass…

The advanced fifth-generation (5G) infrastructure, or International Mobile Telecommunications (IMT) for 2020 and beyond, defined as the ubiquitous ultrabroadband network supporting the Future Internet (FI), will be a revolution in the information…

A global network infrastructure, also known as the Internet of things (IoT), consists of a radio-frequency identification (RFID) system as an important component of a technology ecosystem in which physical objects are monitored, and their…