The exchange of data between two devices over a communications medium. The development of data communications and networking technologies has had a profound impact on all aspects of modern life. Arguably, no other technology has affected more people in more ways. Data communications and networking has become a fundamental part of our day-to-day living. Internet commerce, banking, video streaming, and the ubiquitous social networks play a dominant role in many people’s lives. With the development of new technologies such as the Internet of Things and 5G cellular networks, the impact and importance of data communications and networking will continue to increase.

The process of transforming information from one representation to another smaller representation from which the original, or a close approximation to it, can be recovered. Data compression and decompression processes are often referred to as encoding and decoding. Data compression (Fig. 1) has important applications in the areas of data storage and data transmission. Besides compression savings, other parameters of concern include encoding and decoding speeds and workspace requirements, the ability to access and decode partial files, and error generation and propagation. See also: Data communications and networks; Data science

An Internet-based global naming and resolution system that provides for the precise identification, retrieval, and trading of digital items in the form of articles, books, images, bibliographies, supporting data, videos, charts, tables, audio, and other electronic files. Development of the digital object identifier (DOI®) system began in 1996 when content creators and technologists jointly recognized that information and entertainment objects could not be commercially distributed on the Internet unless there was a common system of unique identification for those objects. These early stakeholders envisioned an unambiguous, machine-readable identifier that could be used for all electronic communications and transactions involving content throughout its life cycle, including its creation, editing, publication, distribution, and archiving. Such an identifier would be especially critical for commercial transactions, from initial licensing through sales tracking, royalty computation, and financial reporting. See also: Internet; Information management

The path of information travel, usually from one electrical system to another, in which light acts as the information carrier and is propagated by total internal reflection through a transparent optical waveguide. An electrooptic modulator and an optoelectric demodulator are required to convert the electrical signals into light and back again at the transmit and receive ends of the link, respectively.

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 1969. ARPANET originally used 50 kilobits-per-second (kbps) public switched telephone network for communications before progressing to high-speed wired and optical communications. Today, the Internet connects myriad electronics—including computers, handheld devices, and objects such as appliances via the Internet of things—through high-speed wired and wireless networks around the world, and in a nonhierarchical manner unprecedented in the history of communications (Fig. 1). The Internet is a product of the convergence of media, computers, and telecommunications. It is not merely a technological development but the product of social, commercial, and political processes as well. From its origins in a nonindustrial, noncorporate environment and in a purely scientific culture, it quickly diffused into the world of commerce. While the Internet had a dramatic impact on the global economic and social order, it took almost 30 years to emerge as a major technological force. See also: Computer; Internet of things

Computer networks that usually cover a limited range, for example within the boundary of a building or a campus. A computer network is two or more computers that communicate with each other. The primary usage of local-area networks (LANs) is the sharing of hardware, software, or information across a network with a limited geography (Fig. 1) and usually on telecommunications lines and equipment owned and/or operated by the local-area network's organization. Resource sharing provided by local-area networks improves efficiency and reduces overhead. See also: Computer; Electronic mail; Multimedia technology

A software-controlled means of directing digitally encoded information in a communication network from a source to a destination, in which information messages may be divided into smaller entities called packets. Switching and transmission are the two basic functions that effect communication on demand from one point to another in a communication network, an interconnection of nodes by transmission facilities (see illustration). Each node functions as a switch in addition to having potentially other nodal functions such as storage or processing.

The evolving internet technologies for content sharing and collaborating among communities of online users. Since the advent of the Web 2.0—the more dynamic and interactive second generation of the World Wide Web—the term social media has become well-known but remains difficult to define. In fact, an internet search of this term produces varying results, such as "20 definitions of social media," "academic definitions of social media," "pragmatic definitions of social media," "legal definition of social media," and the like. Dictionary definitions of social media do not necessarily agree with definitions expressed by other sources, academic or not. So, it seems that the term social media, as it is used today, depends on the lens through which one is looking. This diversity of opinions makes it difficult to pin down an all-encompassing definition of social media (see figure). See also: Internet; Web 2.0; World Wide Web

The theory of circuits made up of ideal digital devices. Included in switching theory are the theories of circuits and networks for telephone switching, digital computing, digital control, and data processing. See also: Computer; Electrical circuit; Electronic switch; Electronics; Mobile communications; Telephone

The second generation of the World Wide Web (WWW), which is more dynamic and interactive than its predecessor, Web 1.0. Although the term Web 2.0 follows the trend to number the new releases or versions of software products, in reality the term is nothing more than a name for a set of Internet-based tools and how to use these tools to encourage users to participate and share opinions and resources, thus creating a colossal content online for other users (see illustration). In contrast with Web 1.0 where Internet users were “passive” in the sense that most of what the users did was to read static Web pages or pages that were rarely updated, Web 2.0 is a paradigm where a set of Internet-based tools and their use emphasize peers' social interaction and collective intelligence. This way, Web 2.0 not only helps users contribute to a Web site's content but also follow up with the Web site's latest content without even opening the actual Web page. Based on these features, Web 2.0 is commonly known as the wisdom Web, people-centric Web, participate Web, and read/write Web. Most Web 2.0 sites include a search engine that helps users locate the content other users have created. This technology has a more democratic approach than its predecessor, allowing all the citizens of the Web (webizens) to share and distribute their ideas and information. Although there are concerns about intellectual property, proprietary information, privacy, security, and control, Web 2.0 technologies can also help improve the collaboration and communication within the corporate environment and also across the multiple vertical industries. See also: Internet; World Wide Web