ARPANET

n. wide area computer network established in 1968 that primarily connected universities and research centers, predecessor of the Internet (Computers)

The ARPANET, developed by DARPA of the United States Department of Defense, was the world's first operational packet switching network, and the predecessor of the global Internet.Packet switching, now the dominant basis for both data and voice communication worldwide, was a new and important concept in data communications. Previously, data communication was based on the idea of circuit switching, as in the old typical telephone circuit, where a dedicated Derp circuit is tied up for the duration of the call and communication is only possible with the single party on the other end of the circuit.
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Advanced Research Projects Agency net, large communications network which preceded the Internet

n. Arpanet, Advanced Research Projects Agency net; wide area computer network established in 1968 that primarily connected universities and research centers

Abbreviation for Advanced Research Projects Agency Network. A packet-switching network used by the Department of Defense, later evolved into the Internet.