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Cable
In telegraphy, an encased bundle of insulated copper or iron wires that conducts electrical signals. The first cables were developed to send telegraph messages under bodies of water.
Cablegram
A telegram transmitted via underwater cable.
Card Catalog
A set of index cards, kept in small wooden drawers, that refer to books in a library collection. Cards are typically sorted alphabetically by author, title, and subject, and often include descriptive information. Later replaced by computerized catalogs.
Carrier Pigeon
A domestic pigeon especially bred and trained to carry long-distance messages; a type of homing pigeon. Long before the invention of the telegraph, people used homing pigeons to carry short messages over hundreds of miles. The name carrier pigeon refers to a specific breed of large domestic homing pigeon. In the 19th and 20th centuries, carrier pigeons began to be bred for "show" and other types of homing pigeons, sometimes also referred to as "carrier pigeons," did the bulk of messengering.
Cathode Ray Tube or CRT
Device used in display screens, such as those in televisions or computer monitors. A CRT screen creates pictures by firing a stream of electrons (a "cathode ray") at a glass screen covered with a chemical film; the screen lights up where the electrons strike.
Cerf, Vinton (1943- )
Computer scientist best known as co-author (with Robert Kahn) of the TCP/IP protocols for inter-network communication.
Paper: "A Protocol for Packet Network Intercommunication" with Robert Kahn
Channing, Dr. William F. (1820-1901)
Boston physician, son of Unitarian minister, William Ellery Channing. In the 1850s, Channing, in collaboration with Moses G. Farmer, invented and developed the first electric fire alarm, an adaptation of the electromagnetic telegraph. First used in Boston in 1852, Channing's fire alarm was quickly adopted by other American cities. See fire alarm telegraph.
Chappe, Claude (1763-1805)
French engineer who developed the first workable optical telegraph. See optical telegraph.
Cipher Message
An encrypted message. In the 19th century, people often sent telegraph messages in code so that the contents could be kept confidential and as short as possible (one word, number, or collection of letters could substitute for an entire phrase). The compression of messages was vitally important to customers, because they were charged by the word.
Circuit
In electronics, a closed conductive path followed by an electric current; also a connected configuration of electrical or electromagnetic components or devices.
Circuit-switching
Method of transmitting information across a network typical of telephone systems. A message is transmitted through a circuit-switched network by establishing a single path from source to destination, as between two speakers on a telephone. This single path is kept open for the duration of the conversation. It is contrasted with packet-switching.
Code Book
A book of codes published so that telegraph operators, senders and recipients could keep telegraph messages short and confidential; see also cipher message.
Cold War
Worldwide power contest between the Soviet Union and the United States (and their allies) usually defined as lasting from 1947 to 1989.
Communications Decency Act of 1996
Part of the Telecommunications Act of 1996, the Communications Decency Act imposed restrictions on the distribution of pornographic and obscene material on the Internet. These restrictions were held to be unconstitutional violations of free speech by the Supreme Court in 1997.
Communications Technology
Any device or system that expedites the flow of information, for example, the electromagnetic telegraph and the Internet, but also others such as alphabetic writing systems and the printing press.
Communications Theory
A highly mathematical field of engineering created by Claude Shannon and devoted to the study of communications systems and networks. Closely related to information theory and very important for computer science, especially computer networking.
Compiler
Computer program that translates between machine language (1s and 0s) and more human-friendly (higher-level) programming languages, such as BASIC, PASCAL, or C.
Computer as a Communications Device, The
Paper: "The Computer as a Communications Device"
Author: J. C. R. Licklider
Joseph Carl Robnett Licklider was a psychologist interested in how humans interacted with machines — and in how humans could use machines to interact with each other. In his work on SAGE and at the Advanced Research Projects Agency (ARPA), "Lick" encouraged people to think of computers as tools for communication and collaboration.
Computer Virus
A computer program capable of reproducing itself. A virus is usually harmful to the computer it infects.
Cooke, William Fothergill (1806-1879)
English inventor who developed electric telegraphy. Cooke began his experiments in 1836. Soon afterward, he and Charles Wheatstone formed a partnership and in 1837 were granted their first patent (roughly the same time that Samuel F. B. Morse received his first patent). The Wheatstone-Cooke device, often called the "needle telegraph," employed electromagnetism, but operated on different principles than the Morse telegraph.
Cookies
Nickname given to small packages of information that are placed on a computer when one visits a Web site. Cookies are used by Web sites to identify visitors, enabling them to provide personalized services (such as remembering passwords, past purchases, and credit card numbers) as well as to gather personal information.
Cox, Donna (1949- )
Artist known for using computers to create complex animations and visualizations of scientific data.
Cyberspace
Term coined in the early 1980s by novelist William Gibson to describe the place where events take place online. Popularized in Gibson's novel, Neuromancer.
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