(Advanced Research Projects Agency NETwork) The research network funded by the U.S. Advanced Research Projects Agency (ARPA). The software was developed by Bolt, Beranek and Newman (BBN), and Honeywell 516 minicomputers were the first hardware used as packet switches. ARPAnet was launched in 1969 at four sites including two University of California campuses, the Stanford Research Institute and the University of Utah.

In late 1972, the ARPAnet was demonstrated at the International Conference on Computers in Washington, DC. This was the first public demonstration of packet switching.

TCP/IP Was Added
Over the next decade, ARPAnet spawned other networks, and in 1983 with more than 300 computers connected, its protocols were changed to TCP/IP. In that same year, the unclassified military Milnet network was split off from ARPAnet.

It Became the Internet
As TCP/IP and gateway technologies matured, more disparate networks were connected, and the ARPAnet became known as "the Internet" and "the Net." Starting in 1987, the National Science Foundation began developing a high-speed backbone between its supercomputer centers. Intermediate networks of regional ARPAnet sites were formed to hook into the backbone, and commercial as well as non-profit network service providers were formed to handle the operations. Over time, other federal agencies and organizations formed backbones that linked in.

The Big Shift
In 1995, commercial Internet service providers took control of the major backbones, and the Internet grew exponentially. See Internet.