In 1948 Claude Shannon laid the theoretical groundwork for communications networks by redefining information in terms of bits. A decade later, others such as Leonard Kleinrock and Paul Baran put those bits together in interesting ways, describing “packet switching” and distributed networks, basic technologies of a new government-funded network called ARPANET.

ARPANET went live in 1969 when Kleinrock’s lab at UCLA connected to Doug Engelbart’s lab at the Stanford Research Institute, and it grew quickly from there. Email, often called the first “killer application” of the Internet, dates from this early period, before the Internet actually existed. In 1971, Ray Tomlinson wrote the first applications for sending and receiving email, putting the well known @ in the address line.

In 1983 ARPANET reached out and joined hands with other existing networks, and the Internet was born. Simply put, the Internet is an immense grid of interconnected computers, the lines jammed in every direction with the constant flow of electromagnetic pulses. Turning this jumble of pulses into comprehensible messages is a problem that is solved by software.

One of the most visible and influential Internet software contributions is a collection of protocols and applications called the World Wide Web, written by Tim Berners-Lee in the early 1990s. The subsequent explosion of the Internet has been almost entirely because of the Web. Like the graphical user interface, the web appeals to people who have no interest in computers, who don’t care to see the code behind all the pictures, sound, and text.

The Internet has changed our relationship with computers. Before about 1995 the computer was considered a sophisticated tool. Now we’re apt to think of it as a communication medium, competing with television, radio, and newspapers on the one hand and the telephone and post office on the other.

Throughout history, civilization has thrived along lines of communication—trade routes, rivers, migratory paths, railroads, telegraph lines. Today the Internet connects the world. Its fantastic growth suggests that it strikes a chord in the human psyche. The World Wide Web has created an illusion called cyberspace. Hypertext takes us from here to there seamlessly, compressing and distorting the world. We are never completely sure where we are—and we are adapting to this new reality, creating an alternate geography. New software creates new habits almost overnight. Email, eBay, blogs, Google, instant messages. Everything is affected, all aspects of our lives. And the Internet is still new. The only certainty is that it will change the world in ways we cannot yet imagine.